Ophthalmic instrument for crosslinking of the sclera of an eye

Abstract

An ophthalmic instrument (10) for crosslinking of the sclera (5) of an eye (1) is presented. The ophthalmic instrument (10) comprises a periocular arm (11) which extends from a proximal end (12) to a distal end (13) and which comprises a bend (14) to reach along at least part of an outer contour of the eye (1) with an inside face (15) of the periocular arm (11). An opening (16) is arranged through the inside face (15) at or near the distal end (13) of the periocular arm (11). A light delivery device (17) is arranged in the opening (16) of the periocular arm (11) to deliver light for local crosslinking of the sclera (5) of an eye (1) positioned adjacent to the inside face (15) of the periocular arm (11).

Description

[0001] OPHTHALMIC INSTRUMENT FOR CROSSLINKING OF THE SCLERA OF AN EYE

[0002]

[0001] The present disclosure relates to an ophthalmic instrument for crosslinking of the sclera of an eye. A periocular arm and a base member for such an ophthalmic instrument are also presented.

[0003]

[0002] Crosslinking of the sclera of the eye (also known as scleral crosslinking, SXL) is a procedure that is generally carried out in vivo on the eye of a patient. By crosslinking collagen fibres in scleral tissue, the sclera becomes harder or stiffer. Scleral crosslinking can be performed with the aid of a photosensitive crosslinker which is applied to scleral tissue and subsequently illuminated with light of an appropriate wavelength to activate the photosensitive crosslinker to chemically bind and crosslink collagen fibres in the scleral tissue. With a crosslinked collagen network, the scleral tissue exhibits a higher hardness or rigidity than untreated or native scleral tissue.

[0004]

[0003] Scleral crosslinking is generally only carried out on the exterior, visible parts of the sclera of the eye. It is much more difficult to perform scleral crosslinking on other parts of the sclera which lie deeper inside the eye socket, including posterior and / or retrobulbar parts of the sclera. The inventor has therefore developed an ophthalmic instrument for scleral crosslinking which can reach parts of the sclera that are usually hidden inside the eye socket.

[0005]

[0004] An ophthalmic instrument for crosslinking of the sclera of an eye is presented. The ophthalmic instrument comprises a periocular arm which extends from a proximal end to a distal end and which comprises a bend to reach along at least part of an outer contour of the eye with an inside face of the periocular arm. An opening is arranged through the inside face of the periocular arm, preferably at or near the distal end thereof. A light delivery device is arranged in the opening of the periocular arm to deliver light for crosslinking, preferably local crosslinking, of the sclera of an eye positioned adjacent to the inside face of the periocular arm.

[0006]

[0005] The bend of the periocular arm serves to follow the outer contour of the eye, or at least a part of said outer contour, so that the periocular arm can be positioned adjacent (or peripheral) to the sclera of the eye inside the eye socket. The inside of the bend is comprised by the inside face of the periocular arm. In other words, the inside of the bend forms at least a part of the inside face of the periocular arm. In addition to the bend, the periocular arm may comprise a straight part, preferably near or at its proximal end.

[0007]

[0006] The words ‘near the distal / proximal end’ mean nearer to the distal / proximal end than to the proximal / distal end. The distal end forms the tip of the periocular arm for introduction into the eye socket. The proximal end is connectable towards the ophthalmologist or operation robot for manipulation.

[0008]

[0007] The arrangement of the periocular arm with the light delivery device being arranged through the opening in the inside face allows local crosslinking of the sclera of the eye. The opening can define an aperture through which light is delivered by the light delivery device. A non-uniform scleral hardness may then be imparted by local crosslinking of the sclera. This is considered highly advantageous for treating disorders such as progressive myopia (further discussed below).

[0009]

[0008] In general, it is contemplated to arrange the opening at any position in the inside face of the periocular arm. Even multiple openings can be considered, though a single opening is preferred foraccurately delivering light for local crosslinking of the sclera. An opening at or near the distal end of the periocular arm has the advantage that crosslinking of the sclera can also be performed at deeper or more retrograde locations on the sclera, even including posterior parts of the sclera. The periocular arm may even reach behind the eye for crosslinking of retrobulbar parts of the scleral tissue. Such a periocular arm may be termed a retrobulbar arm suitable for retrobulbar scleral crosslinking. When the opening, preferably the single opening of the periocular arm, is arranged at or near the distal end or tip of the periocular arm, light can be delivered in a local, selective way to posterior parts of the sclera deep inside the eye socket with minimal disruption of surrounding tissue.

[0010]

[0009] The configuration with light delivery device arranged in the opening of the inside face of the periocular arm also allows light delivery straight onto the sclera, that is, with an incidence angle at or near 90° on the outer surface of the sclera. This is advantageous as refractive effects are minimized in such optical geometry. Further, back reflections of the light from the sclera and / or other optical signals from the sclera may be collected through the light delivery device to accurately monitor progress of crosslinking.

[0011]

[0010] The light delivery device may be or comprise a light source but may also be combined with a light source, in which case the light delivery device may merely deliver incident light to adjacent scleral tissue.

[0012]

[0011] Though a flexible periocular arm is also contemplated, a rigid periocular arm is preferred as this provides an ophthalmologist / surgeon or operation robot with feedback of the mechanical resistance during operative procedures. The rigidity of tissue touched by the periocular arm can be felt by the operating ophthalmologist / surgeon or can be assessed by force sensors in the operation robot. Since tissue, including the eyeball, is not rigid but has varying degrees of (elastic) flexibility, it is more difficult to accurately position the periocular arm when the periocular arm is flexible.

[0013]

[0012] Preferably, the periocular arm comprises a housing in which the opening is arranged. The housing may be rigid.

[0014]

[0013] A rigid periocular arm is preferably implemented with a rigid housing. The rigid housing then comprises the opening for the light delivery device.

[0015]

[0014] The housing may be hollow to accommodate various internal components, such as one or more than one light source, an optical waveguide, electrical conductors, etc. as described below.

[0016]

[0015] The outer surface of the periocular arm (e.g. formed by the housing) may generally be opaque for the light that is deliverable by the light delivery device. Said light is to be delivered only through the opening. In any case, the light delivery device is transparent in a functional bandwidth of the light used to effect scleral crosslinking, for example 315 - 485 nm.

[0017]

[0016] The periocular arm and / or its housing can be constructed from surgical grade materials, for example stainless steel, titanium and ceramics or appropriate synthetic materials such as a polyvinylchloride, a methacrylate or a silicone. The periocular arm or its housing may be provided with an external sheath or coating, for example to increase biocompatibility. The external sheath or coating can be of gold or any of the materials listed above. The external sheath or coating may be of an elastic material (e.g. arranged on a rigid housing) to reduce the risk of accidental damage tosurrounding tissue. For an elastic material, one of the appropriate synthetic materials such as a polyvinylchloride, a methacrylate or a silicone may be used.

[0018]

[0017] The outer surface of the periocular arm (e.g. formed by the housing, external sheath or coating) preferably has a smooth outer surface suitable for ophthalmic surgery.

[0019]

[0018] Preferably, the inside face of the periocular arm comprises a radius of curvature in the range of 10 - 15 mm. The inside face is at least partly curved due to the bend. The radius of curvature may in particular be measured in the plane of the bend. The size of the human eyeball ranges from about 22 - 25 mm. The preferred radius of curvature of the bend of the periocular arm is advantageously chosen in the range of 10 - 15 mm, more preferably 11 - 13 mm. The bend may even be fixed, i.e. rigid, and the periocular arm can still be used for most (or practically all) patients.

[0020]

[0019] It is not necessary that the radius of curvature is constant throughout the bend. For example, a first radius of curvature at the distal end of the periocular arm may be smaller than a second radius of curvature at the proximal end of the periocular arm. Preferably, said first radius of curvature is in the above-mentioned range, while the second radius of curvature is above said range. The bend may, more generally, exhibit a radius of curvature, measured at the inside face of the periocular arm, that increases from the distal end towards the proximal end of the periocular arm. A larger radius of curvature towards the proximal end of the periocular arm may improve manoeuvrability of the periocular arm in the eye socket around the eyeball.

[0021]

[0020] The periocular arm, in particular the inside face, may comprise a bending angle in the range of 30 - 120°, preferably 40 - 100°, more preferably 75 - 115°, most preferably (90 ± 10)°. The bend of the periocular arm spans a certain bending angle, which can be defined as the circular arc along which the bend extends. The bend itself forms a curved surface on the inside face of the periocular arm, which may but need not be circular (i.e. the bend can form a circular arc on the inside face of the periocular arm). This is advantageous to follow the roughly circular outer contour of the sclera of the eye. It is preferred that the bend comprises or is formed by a circular arc in the above-mentioned ranges, which include angles suitable for reaching parts of the sclera that are usually difficult to access in vivo, such as periocular or even retrobulbar parts of the sclera. The periocular arm may form a retrobulbar arm when the bending angle is above 75°.

[0022]

[0021] Preferably, a cross-section of the periocular arm transverse to the inside face is less than 4.0 mm. This cross-section is defined as the thickness of the periocular arm. The width of the periocular arm is defined as the cross-section that is transverse to both the thickness as well as the longitudinal direction of the periocular arm. A thickness below 4.0 mm is desirable for easy insertion of the periocular arm between the rectus muscles of the eye. The width is preferably below 8 mm, more preferably below 6 mm or even below 4.0 mm. The width may correspond to the thickness.

[0023]

[0022] Preferably, the distal end of the periocular arm comprises a taper. Such a taper facilitates insertion of the periocular arm into the eye socket.

[0024]

[0023] The ophthalmic instrument may be formed by the periocular arm. However, the periocular arm may also form a component of an ophthalmic instrument, for example as part of an assembly for an ophthalmic instrument which also includes a base member.

[0024] The proximal end of periocular arm may comprise a mechanical connector for releasably connecting the periocular arm to a base member of the ophthalmic instrument. The mechanical connector can be implemented in various ways, e.g. as a bayonet fitting, a socket or a screw connection. When the base member is connected to the periocular arm via the mechanical connector, the base member may in particular extend in a longitudinal direction in extension of the proximal end of the periocular arm.

[0025]

[0025] The ophthalmic instrument may further comprise the base member connected or releasably connectable to the proximal end of the periocular arm. The base member may be a coupling piece or adapter for an operating robot or may in fact form part of the operating robot. Alternatively, the base member can be implemented as a handle for manually operating the ophthalmic instrument.

[0026]

[0026] The base member may be fixedly connected to the periocular arm. Alternatively, the base member may be releasably connected to (the proximal end of) the periocular arm, preferably by means of the mechanical connector of the proximal end of the periocular arm and a corresponding mechanical connector comprised by the base member, in particular a lengthwise or distal end thereof.

[0027]

[0027] Preferably, the base member is formed as a handle for manual operation of the ophthalmic instrument. The handle may have an elongate form, that is coupled or couplable to the periocular arm at a lengthwise end of the handle in line with the elongation direction of the periocular arm at its proximal end. The handle and periocular arm may thus be aligned for better manipulation of the ophthalmic instrument, in particular the distal end of the periocular arm, inside the eye socket.

[0028]

[0028] Alternatively, the base member can be formed as an adapter for coupling to an operation robot. For example, the base member may have a further (or second) electrical connector for receiving electrical power from the operation robot.

[0029]

[0029] The handle formed by the base member may comprise an exterior grip surface that is roughened for improved grip in the hands of the person (or apparatus) handling the ophthalmic instrument. Preferably, the exterior surface of the handle comprises grooves, in particular in the form of a raster pattern comprising two sets of grooves extending under a positive and negative inclination angle, respectively, relative to an elongation direction of the handle. Intersections of two sets of grooves provides groove crossings which further improve grip.

[0030]

[0030] The ophthalmic instrument may further comprise a light source (or a plurality of light sources) optically coupled or couplable to the light delivery device. The light source is preferably implemented as a light-emitting diode (LED) or a LED array. In practice, 3 V and 6 V LEDs were found useful for the ophthalmic instrument. The light source, e.g. the LED, may be configured to emit light with a wavelength in the range of 315 - 485 nm. Blue (485 - 450 nm), violet (450 - 380 nm) and / or ultraviolet light (especially ultraviolet A, 400 - 315 nm) are particularly useful for crosslinking with the aid of various photosensitive crosslinking agents, such as riboflavin or substances derived from riboflavin. For riboflavin, light of around 450 nm and / or ultraviolet A can be used to induce crosslinking of scleral tissue. The light source may then be referred to as a crosslinking light source.

[0031] The light source can be arranged at various positions in or at the ophthalmic instrument but may also be external to the ophthalmic instrument. When the light source is internal to the ophthalmic instrument, the light source may for example be arranged in the periocular arm or in the base member.

[0031]

[0032] The light source may be arranged in the periocular arm to emit light towards the light delivery device. The light delivery device may then be formed by an optical element, even as simple as an optical window. The optical element may be configured to diffuse or focus incident light onto adjacent scleral tissue.

[0032]

[0033] When the light source is arranged in the periocular arm, the housing of the periocular arm may accommodate the light source. The housing may fixedly hold the light source and the light delivery device to ensure mutual optical alignment.

[0033]

[0034] The light source can be arranged in the distal end of the periocular arm. The light source may then be positioned adjacent to the light delivery device. It can be advantageous to illuminate the sclera with only a short optical path between the light source and the illuminated scleral tissue.

[0034]

[0035] Alternatively, the light source can be arranged in the proximal end of the periocular arm. This arrangement may reduce the size of the distal end or tip of the periocular arm, which may further facilitate introducing the periocular arm into the eye socket and reaching posterior parts of the sclera. A reflective element may be positioned between the light source and the light delivery device to transfer or reflect light emitted by the light source to the light delivery device through the periocular arm, in particular the bend. The reflective element can be formed by one or more than one mirror and / or by surfaces or interfaces of an optical waveguide. The reflective element or optical wave guide may also be present when the light source is arranged in the base member (as discussed below).

[0035]

[0036] The periocular arm may further comprise a scleral indentation protrusion arranged on the inside face, preferably at or near the distal end. The scleral indentation protrusion protrudes from the inside face of the periocular arm and provides an indentation of the sclera when the periocular arm is positioned onto the eye. This indentation can be observed by the ophthalmologist / surgeon through the cornea of the eye and thereby aids this professional in positioning the periocular arm accurately, even before initiating the illumination for scleral crosslinking (a guide light source can also be omitted).

[0036]

[0037] The scleral indentation protrusion is preferably arranged in a positionally fixed relation with the light delivery device, or more preferably aligned with the light delivery device. For example, when the light source is arranged in the tip of the periocular arm, the scleral indentation protrusion may be aligned with the light source. Alignment of the scleral indentation protrusion with the light delivery device and / or the light source allows even more accurate positioning of the periocular arm and illumination of those parts of the sclera that are to be treated by scleral crosslinking. In an advantageous embodiment, the scleral indentation protrusion is comprised or formed by the light delivery device.

[0037]

[0038] In practice, it is preferred that the scleral indentation protrusion has a smooth outer surface to avoid scratching the eye, in particular the sclera onto which it is to be arranged. Preferably theouter surface of the scleral indentation protrusion is convex (i.e. convexly shaped). In a highly preferred embodiment, the scleral indentation protrusion is aligned with the light delivery device (or is comprised by the light delivery device) and has a convex outer surface, which aids in diffusing the crosslinking light over the sclera of the eye. When the crosslinking light is diffused, a larger yet localised area of (the posterior part of) the sclera can be treated with a single exposure, which may further reduce invasiveness of the treatment.

[0038]

[0039] Further, the periocular arm may comprise an electrical connector that is arranged at or near the proximal end and that is electrically coupled to the light source. Electrical conductors such as wires may be arranged in the periocular arm from the electrical connector to the light source. An external power source can be coupled to the electrical connector for powering the light source. The power source can be a mains connection but may also be a battery. For example, a battery can be arranged in the base member or handle of the ophthalmic instrument to which the periocular arm can be coupled.

[0039]

[0040] As an alternative, the light source may be arranged in the base member. The periocular arm can be made even smaller when the light source is arranged in the base member, i.e. external to the periocular arm.

[0040]

[0041] The ophthalmic instrument may further comprise a battery connected or connectable to the light source. It is preferred that such a battery is arranged in the base member, especially when implemented as a handle for manual operation. This avoids any cumbersome mains power cable and also improves the balance of the ophthalmic instrument in the hand of the ophthalmologist / surgeon. Both of these advantages facilitate accurate manipulation during operative procedures.

[0041]

[0042] When the ophthalmic instrument has the light source arranged in the periocular arm and the battery arranged in the base member, the ophthalmic instrument may further comprise a releasable electrical connector arranged for powering the light source when the base member is mechanically coupled, in particular in a releasable way, to the periocular arm. The electrical connector can also be provided in the base member when the light source is arranged in the base member. The battery (arranged in the base member) or an external power source may then be connected to the electrical connector of the base member to power the light source.

[0042]

[0043] Preferably, the electrical connector is arranged with the mechanical connector to ensure electrical contact when the mechanical connector is engaged. In this case, the periocular arm can be mechanically and electrically connected to the base member in one operation.

[0043]

[0044] The periocular arm may comprise an optical waveguide to guide light emitted by the light source to the light delivery device. In this case, it is preferred that the light source is arranged in the base member or near the proximal end of the periocular arm (e.g. in the periocular arm at or near the proximal end thereof). An optical element can be provided between the light source and the optical waveguide for coupling light emitted by the light source into the optical waveguide. For example, the optical element can be a lens or a fibre-optic coupler.

[0044]

[0045] The optical waveguide may be formed by or comprise a light pipe arranged to guide light towards the light delivery device. That is, the optical waveguide can be implemented as a light pipe(or light tube) with a reflective inner surface. Such light pipe can be formed by the housing having the reflective inner surface because of the material it is made of and / or because of a reflective coating. The housing may be hollow or may be filled with a transparent material (i.e. transparent at least for the light used for scleral crosslinking).

[0045]

[0046] Alternatively, the optical waveguide can be based on fibre-optic technology, including use of optical fibres which can be made from various glasses, polymers or photonic crystals. In this case, the optical waveguide may be formed by or comprise one or more than one optical fibre coupled to a fibre-optic in-coupler arranged at the proximal end of the periocular arm and coupled to the light delivery device. Preferably, the light delivery device is a fibre-optic out-coupler. Light emitted by the light source is launched into the optical fibres by means of the fibre-optic in-coupler. The optical fibre(s) then guide the light to the light delivery device, which may be provided in the form of a fibre-optic out-coupler. The fibre-optic out-coupler may provide enhanced collimation of the light for scleral crosslinking. An even smaller area of the sclera may then be specifically crosslinked.

[0046] Alternatively, when regular (non-fibre) optics are used, the light delivery device may comprise a refractive lens assembly to focus and / or collimate the light onto adjacent scleral tissue.

[0047]

[0047] A fibre-optic in-coupler is also termed a fibre-optic launcher. The light delivery device can be implemented as a fibre-optic out-coupler. It is noted that the in-coupler and out-coupler are termed as such seen in the optical path of illumination of the sclera. However, the fibre-optic arrangement may also serve to conduct light reflected or emitted from the sclera to a photosensor, which may be comprised by the ophthalmic instrument. In this case, the fibre-optic out-coupler and in-coupler function as in-coupler and out-coupler, respectively, for light coming from the sclera.

[0048]

[0048] The periocular arm and the base member may be fixedly connected but can also be provided as separate components for assembling into an ophthalmic instrument. The present disclosure therefore also provides an assembly for an ophthalmic instrument as disclosed herein. This assembly comprises the periocular arm as disclosed herein and the base member as disclosed herein. The proximal end of the periocular arm is mechanically, electrically and / or optically connectable to the base member, preferably to a longitudinal end of the base member.

[0049]

[0049] In other words, the proximal end of the periocular arm and the base member are mutually connectable in a mechanical, electrical and / or optical way. A mechanically connectable implementation is preferred when it is desirable to take apart the ophthalmic instrument, for example to exchange the periocular arm, the light source, the battery, etc. The periocular arm may for example be sterilized separately from the base member. In addition to being mechanically connectable, the periocular arm and the base member may also be configured to be electrically and / or optically contactable to each other, preferably via the same proximal end and longitudinal end, respectively. An optically connectable implementation is preferred when the base member comprises the light source. An electrically connectable implementation is preferred when the periocular arm comprises the light source, in which case the periocular arm and the base member may each comprise corresponding electrical connectors.

[0050]

[0050] In addition to or instead of the (crosslinking) light source described so far, the ophthalmic instrument may also comprise an auxiliary light source in order to facilitate positioning of (the distalend of) the periocular arm in the eye socket. The position of the periocular arm in the eye socket can be monitored visually through the cornea of the eye. With the auxiliary light source, it can be observed even better. This light source thus acts as a guide for the ophthalmologist or surgeon and is therefore also termed a guide light source.

[0051]

[0051] The guide light source is preferably implemented as a LED which may form part of a LED array (e.g. also comprising the crosslinking light source, for example a switchable LED array configured to switch between wavelength ranges or colours). The guide light source may be configured to emit light with a wavelength in the visible range (usually 400 - 700 nm). This range may in particular differ from, i.e. does not overlap with, the wavelength range of light emitted by the crosslinking light source to ensure that the guide light source does not stimulate scleral crosslinking, or at least to an extend far below that of the crosslinking light source. Preferably, the guide light is configured to emit light with a wavelength in the range of 485 - 750 nm, more preferably 500 - 750 nm. Orange (590 - 625 nm) and / or red (625 - 750 nm) light are particularly comfortable for the patient, as well as for the operating surgeon, as these colours tend to have less blinding effects. The guide light source may be configured to emit light only intermittently, e.g. as pulses, for further comfort of patient and surgeon while maintaining sufficient visibility through the sclera and the retina for observation through the cornea of the eye.

[0052]

[0052] The guide light source may be arranged in the periocular arm to emit light through or from the inside face thereof. Preferably, the auxiliary or guide light source is optically coupled or couplable to the light delivery device. In such arrangement, light emitted by the guide light source coincides with light to be emitted by the crosslinking light source, which facilitates accurate positioning of the light delivery device of the periocular arm onto that part of the sclera which is to be crosslinked.

[0053]

[0053] In general, the auxiliary light source may be arranged in any position of the ophthalmic instrument disclosed for the crosslinking light source. For example, the guide light source can be arranged in the distal end or tip of the periocular arm adjacent to the light delivery device and / or optically behind the light delivery device (as seen from the inside face). As another example, the guide light source sensor can be arranged in the proximal end or in the base member, optically coupled to the reflector(s) or optical waveguide in the periocular arm to receive light coming from the sclera. Alternatively, the guide light source can be arranged in the opening together with the light delivery device or in a separate opening configured for the guide light source, which separate opening is preferably arranged near the opening for the light delivery device.

[0054]

[0054] It is noted that crosslinking and auxiliary light source need not be arranged at the same or similar position. However, an advantageous implementation involves a LED array comprising the crosslinking light source and the auxiliary light source, which LED array may preferably be arranged in the distal end of the periocular arm. Further, the auxiliary light source can be optically coupled or couplable to the waveguide described in relation to the crosslinking light source.

[0055]

[0055] The guide light source may be electrically coupled or couplable to the battery as disclosed for the crosslinking light source. It is particularly preferred that the guide light source can be switched on or off independently from the crosslinking light source. An auxiliary switch circuit may be provided for this purpose.

[0056] It is noted that the periocular arm may in fact form the ophthalmic instrument, even without additional components. In other words, the ophthalmic instrument may consist of the periocular arm.

[0056]

[0057] The present disclosure thus also provides a periocular arm as disclosed herein, in particular a periocular arm of or for an ophthalmic instrument as disclosed herein.

[0057]

[0058] The base member may also be provided as a separate component for an ophthalmic instrument. The present disclosure thus also provides a base member as disclosed herein, in particular a base member of or for an ophthalmic instrument as disclosed herein.

[0058]

[0059] The periocular arm and / or ophthalmic instrument can be used in operative procedures for crosslinking specific locations or parts of the sclera of the eye which are difficult to access in vivo.

[0059]

[0060] An operative procedure for scleral crosslinking can involve the following steps. The procedure can be performed manually or with the assistance of an operation robot. A photosensitive crosslinking agent (such as riboflavin or riboflavin-based substances) should be applied to the relevant tissue before illumination starts. The photosensitive crosslinking agent can be applied to the tissue by injection into the eye socket or by topical application via an eye bath, for example. Preferably, the crosslinking agent is locally applied by peribulbar injection or sub-Tenon injection.

[0060]

[0061] First, a conjunctival incision is made, for example in the superior temporal quadrant. This incision serves to separate the conjunctiva from the sclera and can be made near the scleral-corneal limbus. Next, the periocular arm of the ophthalmic instrument is introduced into the eye socket through this conjunctival incision. During the procedure, the periocular arm can be coupled to the base member, for example in the form of a handle for manual operation or in the form of (an adapter for) an operation robot, which robot may in turn be controlled by the ophthalmologist or surgeon.

[0061]

[0062] The periocular arm is now positioned to bring the light delivery device into to desired anatomical location for local crosslinking of the sclera, for example peripheral or posterior parts of the sclera. The position of the periocular arm can be monitored through the cornea, for example using an ophthalmoscope, which can be facilitated further by the optional guide light source.

[0062] Illumination for scleral crosslinking is then started at a predetermined intensity and for a predetermined duration using the crosslinking light source. During illumination, reflections or other optical signals can be collected through the light delivery device of the periocular arm to monitor the crosslinking process (e.g. by fluorescence from the riboflavin and / or by back reflections from the sclera measured via the photosensor).

[0063]

[0063] Finally, the periocular arm is withdrawn from the eye socket once crosslinking and optional monitoring thereof are completed.

[0064]

[0064] The ophthalmic instrument can in particular be used for locally crosslinking the posterior sclera, for example to prevent myopia or progression of myopia. When only the posterior sclera is reinforced by crosslinking (rather than the whole eyeball), the remainder of the sclera retains its original state and can continue to develop. In this way, the development of a physiologically round eyeball with minimal myopia is encouraged. The posterior sclera can be defined as those parts ofthe sclera that are nearer to the fovea than to the cornea, while posterior parts of the sclera are nearer to the cornea than to the fovea.

[0065]

[0065] A non-local, overall hardening of the sclera by indiscriminate crosslinking is believed undesirable for developing patients as it also slows down or even halts the regenerative potential that comes with the further development or growth of the eyeball as the patient matures. The development of an oblong shape of the eyeball as seen in myopia can be slowed or stopped by local crosslinking of the posterior sclera, for which an advantageously suitable ophthalmic instrument is presented here.

[0066]

[0066] Monitoring of the scleral crosslinking process as described above can be implemented with a photosensor. The ophthalmic instrument may thus further comprise a photosensor for monitoring crosslinking progress. The photosensor may be configured to detect an optical indicator of the crosslinking progress, such as fluorescence from the photosensitive crosslinking agent (e.g. riboflavin or a riboflavin-based substance), back reflections from illumination by the light source and / or changes in the absorption or reflection spectrum (e.g. in the ultraviolet, visible and / or infrared wavelengths).

[0067]

[0067] Preferably, the photosensor is optically coupled or couplable to the light delivery device. The light delivery device then also acts as a light collection device for light coming from the sclera into the periocular arm. The photosensor may be arranged at any position indicated for the light source to use the same optical elements such as the optical waveguide. For example, the photosensor can be arranged in the distal end or tip of the periocular arm adjacent to the light delivery device and / or optically behind the light delivery device (as seen from the inside face). As another example, the photosensor can be arranged in the proximal end or in the base member, optically coupled to the reflector(s) or optical waveguide in the periocular arm to receive light coming from the sclera. Alternatively, the photosensor can be arranged in the opening together with the light delivery device or in a separate opening configured for the photosensor, which separate opening is preferably arranged near the opening for the light delivery device.

[0068]

[0068] When the optical path of the light source and the photosensor overlap, a beamsplitter may be arranged in this optical path to separate light incident from the sclera from light emitted towards the sclera.

[0069]

[0069] The base member may comprise an indicator configured to indicate a progression metric based on a detection signal provided by the photosensor. The indicator may be implemented as a visual indicator (e.g. an array of subsequent visual slots changing appearance with progression) and / or as an auditive indicator (e.g. as a timer with sound output). A processor can be arranged in communicative connection with the photosensor and the indicator to control these components and implement the desired functionality.

[0070]

[0070] These and other aspects are further explained using the following schematic figures, in which embodiments are illustrated by way of practical examples.

[0071] - FIG. 1 shows a frontal view of the eye of a patient, the eye being held open by an ocular speculum while a periocular arm of an ophthalmic instrument is arranged in the eye socket via the superior temporal quadrant.- FIG. 2 shows the cross-section indicated in FIG. 1 viewed from above, the periocular arm reaching past the eye to illuminate a posterior section of the sclera of the eye.

[0072] - FIG. 3 shows a perspective view of the distal end or tip of the periocular arm in retrobulbar arrangement.

[0073] - FIG. 4A-4B show the principle of scleral crosslinking in a schematic cross-section of the sclera, in which FIG. 4A illustrates the condition before and FIG. 4B after crosslinking.

[0074] - FIG. 5 shows a periocular arm for an ophthalmic instrument, which may conform to that shown in FIG. 2.

[0075] - FIG. 6-10 show various further examples of ophthalmic instruments including periocular arms and / or base members.

[0076] - FIG. 11-13 show further examples of the distal end or tip of the periocular arm.

[0077]

[0071] The following reference numbers are used throughout:

[0078] 1 eye

[0079] 2 eye socket

[0080] 3 ocular speculum

[0081] 4 cornea

[0082] 5 sclera

[0083] 6 retina

[0084] 7 fovea

[0085] 8 optic nerve

[0086] 10 ophthalmic instrument

[0087] 11 periocular arm

[0088] 12 proximal end

[0089] 13 distal end or tip

[0090] 14 bend

[0091] 15 inside face

[0092] 16 opening or aperture

[0093] 17 light delivery device

[0094] 18 housing

[0095] 19 taper

[0096] 20 mechanical connector

[0097] 21 base member

[0098] 22 longitudinal or distal end

[0099] 23 mechanical connector

[0100] 24 battery

[0101] 25 light source

[0102] 26 fibre-optic in-coupler

[0103] 27 optical waveguide

[0104] 28 optical element

[0105] 29 electrical connector30 electrical conductor

[0106] 31 electrical connector

[0107] 32 electrical switch

[0108] 33 photosensor

[0109] 34 auxiliary or guide light source

[0110] 35 scleral indentation protrusion

[0111] 36 groove

[0112] 51 episclera

[0113] 52 scleral stroma

[0114] 53 lamina fusca

[0115] 54 collagen fibres

[0116] 55 fibroblast cell

[0117] 56 crosslinking agent

[0118]

[0072] FIG. 1 shows an eye 1 in the eye socket 2 of a patient. Here, the right eye of a patient is schematically illustrated by way of example. The eye 1 is held open by means of an ocular speculum 3 which engages the upper eye lid and the lower eye lid. The anatomy of the human eye is generally known and further involves the cornea 4 and the sclera 5, both visible in FIG. 1. A cross-section through the dashed line of FIG. 1 is illustrated in FIG. 2, which also shows the retina 6, including fovea 7, and optic nerve 8 among other anatomically well-known features of the eye 1.

[0119]

[0073] FIG. 1 and 2 further show an ophthalmic instrument 10 in the form of or comprising a periocular arm 11 arranged in the eye socket 2. The ophthalmic instrument 10 or periocular arm 11 is configured for crosslinking of the sclera 5 of the eye 1.

[0120]

[0074] The periocular arm 11 extends from a proximal end 12 to a distal end 13 and has a bend 14 arranged between these two ends 12, 13. The periocular arm 11 is thereby configured to reach along at least part of an outer contour of the eye 1 , which outer contour is formed by the sclera 5. An inside face 15 of the periocular arm 11 faces the sclera 5. The inside face 15 comprises the inside of the bend 14.

[0121]

[0075] An opening or aperture 16 is arranged through the inside face 15 of the periocular arm 11. The opening 16 is in particular arranged at or near the distal end 13 of the periocular arm 11. Though only one opening 16 is illustrated, a periocular arm 11 with more than one opening 16 is also contemplated.

[0122]

[0076] A light delivery device 17 is arranged in the opening 16 to deliver light for local crosslinking part of the sclera 5 positioned adjacent to and facing the opening 16 in the inside face 15 of the periocular arm 11. In FIG. 2, posterior sclera 5 near the fovea 7 is illuminated with light emitted from the distal end 14 of the periocular arm 11. The emission of light is schematically illustrated with dots.

[0123]

[0077] FIG. 3 shows a perspective view of the distal end or tip 13 of the periocular arm in retrobulbar arrangement, which may conform to the arrangement of FIG. 2. The periocular arm 11 comprises a housing 18 in which the opening 16 is arranged. The housing 18 may in particular be rigid. A light delivery device 17 is arranged in the opening 16 and accommodated by the housing 18.

[0078] As optional features, a light source 25, a photosensor 33 and an auxiliary light source 34 are arranged behind the light delivery device 17 (as seen from the inside face 15 conform the illustrated point of view of FIG. 3). Other positions and arrangements of the optional light source 25, photosensor 33 and auxiliary light source 34 are contemplated as explained herein. In the illustrated example, the light source 25, the photosensor 33 and the auxiliary light source 34 are arranged adjacent to each other so that there is an overlap between their respective fields of view onto the same part of the scleral tissue being crosslinked.

[0124]

[0079] A schematic cross-section of the sclera 5 is presented in FIG. 4A, before crosslinking, and in FIG. 4B, after crosslinking.

[0125]

[0080] The sclera 5 comprises various layers of tissue, of which the two main layers are: episclera 51 , which is an outer layer comprising connective tissue and blood vessels, and scleral stroma 52, which is an inner layer comprising connective tissue and fibroblasts. The latter is strongly adherent to the underlying layer lamina fusca 53. The sclera 5 is a dense connective tissue comprising collagen fibres 54, here illustrated in the scleral stroma 52. Further, it comprises fibroblast cells 55 which produce elastic fibres.

[0126]

[0081] Scleral crosslinking involves the application of a photosensitive crosslinking agent 56, such a riboflavin or substances derived from riboflavin, to the sclera 5. Once the photosensitive crosslinking agent is applied to the tissue and has sufficiently impregnated the sclera 5, the sclera 5 is illuminated at the location which is to be crosslinked. The photosensitive crosslinking agent 56 is activated by the light and binds to various collagen fibres 54, thereby crosslinking these and solidifying the collagen network at these locations in the sclera 5. Residual photosensitive crosslinking agent 56 is removed by the body over time and metabolized.

[0127]

[0082] When using the ophthalmic instrument 10 and / or periocular arm 11 as disclosed herein, crosslinking can be performed specifically for a part of the sclera 5 that is exposed to the opening or aperture 16 from which the crosslinking light is delivered to the sclera 5.

[0128]

[0083] FIG. 5 shows another schematic exterior view of a periocular arm 11 in more detail. This periocular arm 11 otherwise conforms to that of FIG. 2. Various reference lines and angles are indicated to further explain the geometry of the periocular arm 11.

[0129]

[0084] The inside face 15 of the periocular arm 11 comprises a radius of curvature r, which is selected in the range of 10 - 15 mm to conform to the dimension of normal human eyes. Here, the bend 14 is such that the inside face 15 follows the path of a circular arc.

[0130]

[0085] Reference line Y indicates the longitudinal direction of the periocular arm 11 at the proximal end 12. Reference line x is perpendicular to reference line y in the same plane as the page of the drawing. The periocular arm 11 is bent in the xy-plane and angle A is measured in this plane.

[0131]

[0086] Further, the bend 14 of the periocular arm 11 spans a bending angle A of about 105°. The opening or aperture 16 is positioned at the distal end or tip 13 of the periocular arm and is centred at a bending angle A of 90°. In this arrangement, illumination can be cast through the opening 16 onto the posterior sclera of the eye.

[0132]

[0087] Various other bending angles A are contemplated and are also illustrated in FIG. 8A, 9 and 10, at about 75°, 88° and 94°, respectively. In general, the periocular arm 11 , in particular theinside face 15 thereof, may comprises a bending angle in the range of 30 - 120°, preferably 40 -100°, more preferably 75 - 115°, most preferably (90 ± 10)°. The closer the angle is to 90°, the more suitable the periocular arm 11 is for reaching all the way to the back of the eye 1 for crosslinking of the posterior sclera 5. A smaller angle may be more suitable for reaching peripheral parts of the sclera 5 which lie less deep into the eye socket 2.

[0133]

[0088] Further, FIG. 5 indicates a thickness t, which is defined as the cross-section of the periocular arm 11 which is transverse to the inside face 15 and preferably also transverse to the elongation direction of the periocular arm 11. The thickness may in this example be measured in the xy-plane and along the direction of the radius of curvature r in the bend 14 of the periocular arm 11 or along the x-direction in the straight part of the periocular arm 11 near the proximal end 12. It is preferred that the thickness is less than 4.0 mm (note that the figures are only schematic and not to scale though the angles are realistic).

[0134]

[0089] The distal end 13 of the periocular arm here comprises a taper 19. The proximal end 12 of the periocular arm 11 is provided with a mechanical connector 20. The mechanical connector 20 serves to releasably connect the periocular arm 11 to a base member 21. The periocular arm 11 and the base member 21 may be assembled to form an ophthalmic instrument 10. Examples of the base member 21 are illustrated in FIG. 6, 7, 8B and 8C.

[0135]

[0090] FIG. 6 and 7 each illustrate an ophthalmic instrument 10 which includes both a periocular arm 11 and a base member 21. However, all of the illustrated periocular arms 11 and base members 21 can be provided as separate devices.

[0136]

[0091] The base member 21 , preferably via its longitudinal or distal end 22, is releasably connectable to the proximal end 12 of the periocular arm 11. To this end, the distal end 22 of the base member 21 is provided with a mechanical connector 23 configured to connect with the mechanical connector 20 arranged at the proximal end 12 of the periocular arm 11. Various implementations of these mechanical connectors 22, 23 are contemplated, including a bayonet lock, a screw thread connection, a snap-lock and a plug-and-socket connector.

[0137]

[0092] As illustrated in FIG. 6, 7 and 8C, the base member 21 can be formed as a handle for manual operation of the ophthalmic instrument 10. These base members 21 also include a battery 24. FIG.

[0138] 8B shows a base member 21 which may be used as an adapter for an operation robot (not illustrated). In other embodiments, e.g. as illustrated in FIG. 10 and 13, the base member 21 or handle can be comprised by the ophthalmic instrument 10, in particular when the base member is fixed to the periocular arm.

[0139]

[0093] The periocular arms 11 of FIG. 6 and 7 are illustrated with an emphasis on the internal components, the exterior (e.g. the housing 18) being indicated with dashed lines.

[0140]

[0094] In FIG. 6, the periocular arm 11 is to cooperate with an external light source 25, here arranged in the base member 21. Another example of such arrangement is presented in FIG. 8A. Alternatively, the light source 25 can be arranged in the periocular arm 11 , for example as illustrated in FIG. 7 or 9 and may be configured to emit light towards the light delivery device 17. In any case, the light source 25 is optically coupled or couplable to the light delivery device 17.

[0095] The example of FIG. 6 employs fibre-optic technology to guide the light emitted by the light source 25 to the light delivery device 17. The periocular arm 11 here comprises a fibre-optic incoupler 26, illustrated in the proximal end 12 of the periocular arm 11 , and an optical waveguide 27 in the form of one or more than one optical fibre extending from the fibre-optic in-coupler 26 to the light delivery device 17, which is here implemented as a fibre-optic out-coupler. The base member 21 comprises an optical element 28 such as a focussing lens to cast light from the light source 25 into the fibre-optic in-coupler 26 of the periocular arm 11.

[0141]

[0096] In an alternative embodiment which is not illustrated, the optical element 28 can be arranged in the periocular arm 11 to receive light emitted by the light source 25 arranged in the base member 21 when the base member 21 is coupled to the periocular arm.

[0142]

[0097] In FIG. 7, the light source 25 is arranged in the distal end 13 of the periocular arm 11. In this case, light emitted by the light source 25 may directly enter the light delivery device 17, for example for collimation or focussing onto adjacent scleral tissue. The light source 25 is here implemented as a LED array.

[0143]

[0098] In the illustrated embodiment, the periocular arm 11 also comprises an electrical connector 29 that is electrically coupled to the light source 25. The electrical connector 29 is here arranged at or near the proximal end 12 by way of example, and electrical conductors 30 run through the periocular arm 11 to power the light source 25. With the battery 24 arranged in the base member 21 , the base member preferably also comprises an electrical connector 31 arranged for powering the light source 25 via the electrical connector 29 of the periocular arm 11. The electrical connectors 29, 31 may be arranged to electrically connect when the base member 21 is mechanically connected to the periocular arm 11 by means of the matching mechanical connectors 20, 23.

[0144]

[0099] The base member or handle 21 of FIG. 6 and 7 also includes an electrical switch 32, here illustrated as a manual operable button, to start and stop powering the light source 25 and thereby start and stop illumination. The electrical switch 32 can also be implemented under the control of a processor (not illustrated) for automated control of dosage of light, for example in time and / or intensity. The same processor may be coupled to the photosensor 33 for controlling the electrical switch 32 based on the received detection signal and may also be coupled to the indicator for indicating crosslinking progression as discussed above.

[0145]

[0100] FIG. 8A-8C show an assembly for an ophthalmic instrument 10 comprising a periocular arm 11 in FIG. 8A, a first base member 21 in FIG. 8B and a second base member 21 in FIG. 8C. The periocular arm 11 may be coupled to either of these base members 21. Further, the periocular arm 11 of FIG. 6 may also be coupled to these base members 21. This illustrated the variability of the assembly by exchanging periocular arms 11 and / or base members 21.

[0146]

[0101] In this example, the light source 25 is arranged in the base member 21. An optical element 28 is provided to transmit or focus light emitted by the light source 25 into the periocular arm 11. The periocular arm 11 comprises an optical waveguide 27 in the form of a light tube, here formed on or by the reflective interior surface of an opaque housing 18. The wave guide 27 guides lightemitted by the light source 25 to the light delivery device 17, here arranged at the distal end 13 of the periocular arm 11 and through the opening 16.

[0147]

[0102] The base member 21 of FIG. 8B is formed as an adapter for an operation robot and comprises an electrical connector 29 for powering the light source 25. This base member 21 is configured to be connected to an external power source, such as may be provided by an operation robot.

[0148]

[0103] The base member 21 of FIG. 8C is formed as a handle for manual operation and may conform to the handle of FIG. 6.

[0149]

[0104] FIG. 9 shows a periocular arm 11 in which the light source 25 is arranged in the proximal end 12 of the periocular arm 11. This example further comprises an electrical connector 29 arranged at the proximal end 12 for supplying power to the light source 25 once the periocular arm 11 is coupled to a base member 21 , e.g. the base member 21 of FIG. 7 with the battery 24. The electrical connection can be implemented here in the same way as explained in relation to FIG. 7. Alternatively, the periocular arm 11 of FIG. 9 can be electrically connected to another external power source.

[0150]

[0105] The periocular arm 11 of FIG. 9 further comprises a waveguide 27 in the form of a light tube which may be similar as explained in relation to FIG. 8A. The periocular arm 11 of FIG. 9 spans a larger bending angle A than the periocular arm 11 of FIG. 8A and may consequently be used for local crosslinking of parts of the sclera which lie deeper into the eye socket 2.

[0151]

[0106] FIG. 10 shows another example of the ophthalmic instrument 10. This ophthalmic instrument 10 also comprises the periocular arm 11 extending from the proximal end 12 to the distal end or tip 13 and comprising the bend 14 to reach along at least part of the outer contour of the eye with the inside face 15 of the periocular arm 11. The opening 16 is arranged through the inside face 15 at or near the distal end 13. The light delivery device 17 is arranged in the opening 16 to deliver light for local crosslinking of the sclera of an eye positioned adjacent to the inside face 15 of the periocular arm 11.

[0152]

[0107] In this example, the ophthalmic instrument 10 also comprises the optional base member 21 , which is here fixed to the periocular arm 11. The proximal end 12 of the periocular arm 11 and the distal end 22 of the base member 21 are adjacent and can even coincide. In particular, the periocular arm 11 and the base member 21 can be formed by a housing 18, preferably rigid, which may integrate both the periocular arm 11 as well as the base member 21.

[0153]

[0108] The base member 18 is here provided in the form of an elongate handle comprising an exterior grip surface formed by two sets of grooves 36 arranged in the outer surface of the base member 21. The two sets of grooves 36 are here arranged as a spiral running along the handle with a positive and a negative inclination angle, respectively, which results in groove crossings that further improve grip, in particular when handling the ophthalmic instrument 10 wearing surgical gloves.

[0154]

[0109] Various measurements are indicated in FIG. 10 byway of example for a practical implementation of the ophthalmic instrument 10: a thickness of the tip 13 is 3.5 mm, a diameter of the base member 21 is 5.0 mm, and a bending angle A between the proximal end 12 of theperiocular arm 11 and a proximal end or start of the tip 13 is 70°. The bending angle A all the way to the end of the tip 13 is about 94°. The handle portion of the base member 21 has a diameter of 5.5 mm to allow for the grooves 36.

[0155]

[0110] A detail of the tip 13 of FIG. 10 is shown in FIG. 11. The example of FIG. 10 and 11 also includes a light source 25 (e.g. a 3 V or 6 V LED) that is arranged in the distal end or tip 13 of the periocular arm 11 behind the light delivery device 17. To this end, the tip 13 is hollow to accommodate the light source 25. Further, an electrical conductor 30 runs through the ophthalmic instrument 10 from the light source 25, through the periocular arm 11 and the base member 21 to power the light source 25 by an external power supply. Alternatively, a battery 24 can be provided, e.g. as explained with the other examples.

[0156]

[0111] The tip 13 of FIG. 11 presents a light delivery device 17 in the form of a transparent window. The example of FIG. 12 and 13 includes a scleral indentation protrusion 35 and may otherwise be the same as the example of FIG. 10 and 11. The scleral indentation protrusion 35 is arranged in alignment with the light delivery device 17, in particular also with the light source 25 which is preferably arranged behind the light delivery device 17. When observing through the cornea (see the dashed arrow in FIG. 13), an indentation of the sclera may be observed at the location where the periocular arm 11 is (gently) pressed onto the eye 1. This readily presents itself as an inward buckling of the eye 1 when the scleral indentation protrusion 35 is pressed onto the eye 1. The operating surgeon or other professional user of the ophthalmic instrument 10 may then accurately determine the position of the periocular arm 11 behind the eye 1 before starting scleral crosslinking of the intended parts of the sclera 5.

[0157]

[0112] As can be seen in the examples of FIG. 10 and 13, the radius of curvature of the inside face 15 of the periocular arm 11 may be larger at the proximal end 12 than at the distal end 13. In particular, the radius of curvature at the distal end 13 may be close to that of the eye 1 while it is larger at the proximal end 12 to be at a (small) distance from the eye 1 , which is advantageous for manoeuvrability of the ophthalmic instrument 10 inside the eye socket and for reducing risk of damaging surrounding tissue, including more anterior parts of the sclera 5.

[0158]

[0113] In summary, the illustrated examples emphasize various embodiments of an ophthalmic instrument according to the present invention in which:

[0159] - the periocular arm 11 comprises the light source 25 near or at the distal end 13, with the optional base member 21 comprising the battery 24 (e.g. as in FIG. 7);

[0160] - the periocular arm 11 comprises the light source 25 near or at its proximal end 12 and the optical waveguide 27 for guiding emitted light to the light delivery device 17, with the optional base member 21 comprising the battery 24 (e.g. as in FIG. 9); and

[0161] - the periocular arm 11 comprises the optical waveguide 27 to guide light emitted from the light source 25 arranged in the base member 21 to the light delivery device 17, wherein the base member 21 optionally further comprises the battery 25 (e.g. FIG. 6 and 8A).

[0162]

[0114] In general, the ophthalmic instrument may comprise a battery for powering the light source and / or any other electrical components of the ophthalmic instrument 1 such as the processor, photosensor 33 and indicator. Preferably, the battery 24 is arranged in the base member 21. Thebase member 21 may be fixedly connected to the periocular arm 11 in any embodiment to provide an ophthalmic instrument 10 in which periocular arm 11 and base member 21 are integrated.

[0163]

[0115] These examples merely serve to illustrate the concept of the present invention without limiting the scope of protection requested, which is solely defined by the following claims.

Claims

CLAIMS1. An ophthalmic instrument for crosslinking of the sclera of an eye, the ophthalmic instrument comprising:- a periocular arm which extends from a proximal end to a distal end and which comprises a bend to reach along at least part of an outer contour of the eye with an inside face of the periocular arm, wherein an opening is arranged through the inside face at or near the distal end; and- a light delivery device arranged in the opening of the periocular arm to deliver light for local crosslinking of the sclera of an eye positioned adjacent to the inside face of the periocular arm.

2. The ophthalmic instrument of claim 1 , wherein the periocular arm comprises a rigid housing in which the opening is arranged.

3. The ophthalmic instrument of claim 1 or 2, wherein the inside face of the periocular arm comprises a radius of curvature in the range of 10 - 15 mm.

4. The ophthalmic instrument of any previous claim, wherein the inside face of the periocular arm comprises a radius of curvature that is larger at the proximal end than at the distal end, wherein the radius of curvature at or near the distal end is preferably in the range of 10 - 15 mm.

5. The ophthalmic instrument of any previous claim, wherein the periocular arm, in particular the inside face, comprises a bending angle in the range of 30 - 120°, preferably 40 - 100°, more preferably 75 - 115°, most preferably (90 ± 10)°.

6. The ophthalmic instrument of any previous claim, wherein a cross-section of the periocular arm transverse to the inside face is less than 4.0 mm.

7. The ophthalmic instrument of any previous claim, wherein the distal end of the periocular arm comprises a taper.

8. The ophthalmic instrument of any previous claim, wherein the proximal end of the periocular arm comprises a mechanical connector for releasably connecting the periocular arm to a base member of the ophthalmic instrument.

9. The ophthalmic instrument of any previous claim, further comprising the base member connected or releasably connectable to the proximal end of the periocular arm.

10. The ophthalmic instrument of claim 9, wherein the base member is formed as a handle for manual operation of the ophthalmic instrument.

11. The ophthalmic instrument of claim 10, wherein the handle comprises grooves forming a raster pattern, preferably comprising two sets of grooves extending under a positive and negative inclination angle, respectively, relative to an elongation direction of the handle.

12. The ophthalmic instrument of any previous claim, further comprising a light source optically coupled or couplable to the light delivery device.

13. The ophthalmic instrument of claim 12, wherein the light source is arranged in the periocular arm to emit light towards the light delivery device.

14. The ophthalmic instrument of claim 13, wherein the light source is arranged in the distal end of the periocular arm.

15. The ophthalmic instrument of claim 13, wherein the light source is arranged in the proximal end of the periocular arm.

16. The ophthalmic instrument of any of the claims 13- 15, wherein the periocular arm comprises an electrical connector that is arranged at or near the proximal end and that is electrically coupled to the light source.

17. The ophthalmic instrument of claim 12, wherein the light source is arranged in the base member.

18. The ophthalmic instrument of any of the claims 12- 17, further comprising a battery connected or connectable to the light source.

19. The ophthalmic instrument of claim 18 with the light source arranged in the periocular arm and the battery arranged in the base member, further comprising a releasable electrical connector for powering the light source when the base member is mechanically coupled to the periocular arm.

20. The ophthalmic instrument of any of the claims 12- 19, further comprising an auxiliary light source optically coupled or couplable to the light delivery device and configured to emit visible light through the sclera for observation via the cornea of the eye.

21. The ophthalmic instrument of claim 18, wherein the light source is configured to emit light with a wavelength in the range of 315 - 485 nm and the auxiliary light source is configured to emit light with a wavelength in the range of 485 - 700 nm.

22. The ophthalmic instrument of any previous claim, wherein the periocular arm further comprises a scleral indentation protrusion arranged on the inside face of the periocular arm, in particular at or near the distal end thereof.

23. The ophthalmic instrument of claim 22, wherein the scleral indentation protrusion is aligned with and / or formed by the light delivery device, and preferably comprises a convex outer surface.

24. The ophthalmic instrument of any previous claim, wherein the periocular arm comprises an optical waveguide to guide light emitted by the light source and / or auxiliary light source to the light delivery device, wherein the light source and / or auxiliary light source is preferably arranged at or near the proximal end of the periocular arm or in the base member.

25. The ophthalmic instrument of claim 24, wherein the optical waveguide is formed by a light tube arranged to guide light towards the light delivery device.

26. The ophthalmic instrument of claim 24, wherein the optical waveguide is formed by one or more than one optical fibre coupled to a fibre-optic in-coupler arranged at the proximal end of the periocular arm and coupled to the light delivery device, wherein the light delivery device is a fibreoptic out-coupler.

27. The ophthalmic instrument of any previous claim, further comprising a photosensor optically coupled or couplable to the light delivery device and configured to detect an optical indicator of crosslinking progress.

28. An assembly for an ophthalmic instrument according to any previous claim, the assembly comprising the periocular arm and the base member as defined in any previous claim, wherein the proximal end of the periocular arm is mechanically, and preferably also electrically and / or optically, connectable to the base member.

29. A periocular arm of or for an ophthalmic instrument according to any previous claim.

30. A base member of or for an ophthalmic instrument according to any of the claims 1 - 28.

Images