Oculyzer with integrated pachymeter for detection of tear film lipid layer

Abstract

The invention relates to a device for corneal topography, in which there is an electrically controllable light diffusing screen for switching from a diffusing state to a transparent state and vice versa, and which is arranged along the path of the light beam that is then projected into the eye, thus enabling the execution of a corneal topography or an analysis of the lipid layer thickness of the eye depending on the state in which the screen is.

Description

Technical Field

[0001] This invention relates to the technical field of eye analysis / measurement equipment.

[0002] In particular, the present invention relates to an innovative integrated device for general ophthalmic analysis that allows for the performance of at least one corneal topography and / or at least one ocular lipid layer (also known as lipid layer thickness) analysis. Background Technology

[0003] Corneal topography has long been known. This type of examination is performed using a specific machine called a corneal topography instrument.

[0004] The examination is non-invasive and allows for the reconstruction of corneal curvature maps.

[0005] Figure 1A A corneal topography instrument of the prior art was described.

[0006] Therefore, a support frame (102', 60) is provided to support the light projection device 100.

[0007] The camera 300 is positioned behind the light projection device. A support is also present directly in front of the light projection device 100, allowing the patient to stably rest his / her chin and head on it for secure positioning, thus allowing the device to perform its function.

[0008] For illustrative purposes only, the eye 200 is schematically shown in front of the light projection device 100, and for the sake of brevity, additional supports for the chin and forehead are not shown.

[0009] In well-known configurations, the light projection device 100 may include a so-called Placidodisc 100, which is simply a flat disc or a disc made of a cone. Figure 1A The cone is shown and is backlit by multiple light sources 101.

[0010] The Placido disc provides multiple concentric circles formed within a cone, typically alternating between white and black circles. The white circles allow light to pass through, while the black circles block the light. In this way, the backlight 101 is precisely projected onto the eye placed on the opposite side in the form of these concentric circles, because the light will only pass through the white circles and be blocked by the black circles.

[0011] Figure 1A The light 102 passing through the white circle is schematically shown, and the image captured by the camera 300 through the axial hole in the Placidor disc 100 is also shown with arrow 103.

[0012] Therefore, the eye will reflect multiple concentric circles, or rings or discs (whichever you prefer), which represent alternating illumination 101 and black circles. The black circles are circles without light or that can be described as black (i.e., the unlit areas of the eye), because, as mentioned, they are produced by the obstruction of light.

[0013] In well-known variations, the placid disc can be directly replaced by a specific light source distribution arranged to project a pattern onto the eye, which performs a function similar to the ring of the placid disc.

[0014] Therefore, the patient stands in front of the device, resting his / her chin on the support, so that the light projection device is actually in front of the patient's eyes.

[0015] In this way, the concentric discs are reflected onto the eye (or the Placido disc, or in any case, a pattern related to the distribution of light) and then projected onto the surface of the anterior cornea.

[0016] Images of the eye are captured by camera 300 and processed using well-known software, allowing for the reconstruction of corneal topography.

[0017] therefore, Figure 1A The example shown is a backlit Placido disc with camera 300 positioned at the rear and eye 200 at the front. This also applies when the Placido disc is replaced with a solution where the light source distribution is directly visible on the surface.

[0018] Figure 1B The image shows concentric circles projected into the patient's eye during this examination, captured by a camera 300 positioned on the axis.

[0019] Obviously, in addition to corneal topography, other examinations may be needed, but these examinations are incompatible with corneal topography and therefore require specialized equipment.

[0020] One such case is, for example, the analysis of the lipid layer of the tear film, which is technically referred to as "lipid layer thickness".

[0021] This examination allows physicians to clearly see the actual presence of the lipid layer on the surface of the eye.

[0022] This type of inspection, in such Figure 1B The projection of concentric circles in the eye shown is inaccurate and complicated because the black circles represent unlit areas, making it impossible to detect the presence of lipid layers.

[0023] More specifically, circular (or patterned) illumination makes the lipid layer visible in a discontinuous manner, precisely because it can only be seen where the light intensity is greater, i.e., where the rings (or circles or discs, depending on the case) are reflected, and not where the ring image is present. Therefore, the rings make viewing the lipid membrane difficult because they illuminate it discontinuously.

[0024] Therefore, specific equipment is needed to measure lipid layer thickness.

[0025] In particular, manufacturing a multifunctional device that can combine corneal mapping operations with lipid layer thickness measurement is complex because the obtained illumination can interfere with the accurate detection of the liquid layer.

[0026] Nevertheless, there are several solutions on the market that attempt to address the aforementioned technical issues, namely, to integrate the existence of the Placido disc for corneal analysis and the possibility of detecting so-called lipid layer thickness.

[0027] For example, Figure 2 The described known and commercially available solution features a classic topographic mapper 100, which includes a placid disc 101, supported as previously described by a load-bearing column 102' forming part of a support frame. The acquired eye images (see the screen on which the images are transmitted) are processed using specific software to enable accurate determination. The thickness of the lipid layer Although the reflection in the eye is due to the presence of the Placido disc and thus exists in the eye image, the solution is therefore imprecise and complex in all cases.

[0028] In another known solution, the plascid disk is formed in cone 500 (see [link]). Figure 3 The cone has a small acyclic region. Essentially, the rings are interrupted, and therefore not continuous, thus creating an acyclic region 501. This acyclic region 501 is projected into the eye (see region 502), and thus allows the presence of the lipid layer to be assessed in this region, as in a well-lit area. However, it is clear that even this solution has the limitation of allowing only a very limited view of the eye region. In particular, both the detection of the lipid layer and corneal topography are inaccurate.

[0029] Finally, in known and commercially available solutions, a removable opaque screen is used, which is then used as a light diffuser. It is well known that a light diffuser allows a beam of light to pass through it but deflects it in several different directions, resulting in uniform illumination and causing the true image to be lost. For example, if a beam of light representing a ring passes through a transparent screen, the beam passes through the screen undisturbed, maintaining its direction, and is projected into the eye. On the other hand, if the ring passes through a diffuser screen (which is opaque), the light is deflected in several directions, and the resulting light projected onto the eye will be uniform light illuminating the entire area, thus losing the conformation of the ring.

[0030] In view of this, the existing technical solution introduced here uses a diffuser screen that is removably applied in front of the Placidor disc (and is therefore opaque).

[0031] In particular, by placing such a diffuser in front of the Placido disk, the illumination of the concentric circle pattern that highlights the lipid membrane in a discontinuous manner is transformed into uniform illumination.

[0032] Therefore, when the device is no longer used as a corneal topography instrument, but as a device for detecting the lipid layer on the surface of the eye, it is sufficient to simply apply such a diffuser screen in front of the Placidor disc.

[0033] However, despite its proper functioning, this solution has a technical drawback: the diffuser screen exists as an accessory and must be applied when needed to cover the Placido disk.

[0034] In particular, when performing lipid layer assessment, a screen covering the Placido disk is applied, while when performing corneal mapping, the screen is removed and classic topography is performed.

[0035] Clearly, this is not a universal solution, also because the accessory, precisely because it is a separate component, may be lost or its quick connection system with the Plascido disk may fail.

[0036] In addition, assembly / disassembly takes time.

[0037] In addition, the following publications are known: US2014 / 104574, US2019 / 227327, US2008 / 204659, and US6447119. Summary of the Invention

[0038] Therefore, the object of the present invention is to provide a device that solves at least some of the above-mentioned technical defects.

[0039] In particular, the object of the present invention is to provide a device that enables both corneal topography measurement and tear film lipid layer measurement in a universal and functional manner, as well as in an accurate and rapid manner, without the need to disassemble or reassemble accessories, thereby giving the device itself versatility.

[0040] These and other objectives are achieved by this device, which is used to allow the execution of at least one corneal topography and / or lipid layer thickness analysis according to claim 1.

[0041] This device includes: - At least one light projection device (100); - And it includes a screen (20) that covers at least a portion of the light projection device (100).

[0042] Therefore, in other words, the screen 20 is positioned to intercept at least a portion of the path of the light pattern emitted by the device 100, for example by placing the screen 20 in front of the device 100, and thus also as mentioned, by positioning the screen 20 to cover at least a portion of the light projection device.

[0043] In all the foregoing cases, according to the invention, the screen (20) is electrically controllable, thereby enabling selective changes from a transparent state to an opaque state and / or vice versa.

[0044] In this way, all the aforementioned technical defects were resolved.

[0045] Solutions for controllable screens (i.e., whose state can be controlled and thus switched from opaque to transparent and / or vice versa) allow for the permanent attachment of the screen to light projection devices, such as placid discs. For example, the fastening can be fixed and non-removable, thus making the device compact, versatile, and quick to use.

[0046] All operators only need to check the state of the screen, thus setting it to either opaque or transparent depending on the check to be performed.

[0047] Alternatively, the device can automatically switch the functions of screen 20 based on the type of inspection selected on the device in question (e.g., via a specific control panel) via a specific control.

[0048] When the screen is in a transparent state, the light beam is not deflected, so it is as if the screen does not exist. When the screen is switched to an opaque state, it acts as a diffuser, illuminating the relevant area with uniform diffuse light.

[0049] Depending on the examination to be performed, the screen can be placed in either a transparent or diffuser state. In the diffuser state, the lipid layer thickness can be examined because the screen 20 uniformly diffuses illumination from, for example, a projection of concentric discs relative to the Placido disc. In this way, the discs are invisible because they are transformed into diffuse and uniform light. Similarly, in the transparent state, normal corneal topography can be performed, allowing reflection from the concentric discs as they are faithfully projected.

[0050] Even with a removable screen (i.e., applied in a way that allows it to be removed when necessary), the screen can remain fixed in place to cover the light projection device (such as a Placid disc) for an extended period of time while the device is in use, so that it can then be removed when necessary (e.g., for maintenance or other reasons).

[0051] Therefore, whether the screen is permanently fixed or removable, in any case, once fixed, it will not interfere with the operation of the device when performing corneal topography, so it can remain in place without any problems and can be switched to allow for examination of lipid layer thickness.

[0052] The present invention also aims to use the screen (20) in an ophthalmic instrument that includes at least one light projection device (100) that projects a light pattern in use, such that the screen is positioned to intercept the path of at least a portion of the light pattern emitted by the light projection device (100).

[0053] According to the invention, the screen (20) is now electrically controllable to switch from an opaque state (in which the screen acts as a diffuser of light emitted by the light projection device (100) passing through it) to a transparent state (in which the screen allows light emitted by the light projection device (100) passing through it to pass through without any deflection) and / or vice versa.

[0054] Advantageously, in this way, the same ophthalmic instrument can have several functions at the same time.

[0055] For example, when the screen (20) is in the transparent state, the ophthalmic instrument can perform the function of a corneal topography instrument, and when the screen (20) is in the opaque state, the ophthalmic instrument is suitable for measuring lipid layer thickness.

[0056] More specifically, for example, when the light projection device 100 is a device adapted to project a luminescent pattern suitable for corneal topography measurement, such as a placid disc or the like, the ophthalmic instrument can perform the function of a corneal topography instrument.

[0057] In this case, when the screen (20) is placed in a transparent state that does not deflect the light pattern emitted by the light projection device 100, corneal topography measurement is possible.

[0058] Using the same ophthalmic instrument, when the screen (20) is placed in an opaque state such that the light pattern emitted by the light projection device is now diffused in the opaque state, it is now possible to measure the lipid layer thickness.

[0059] Advantageously, the screen (20) includes at least one layer of transparent material coated with an electrically switchable film so as to allow a transition from a transparent state to an opaque state and / or vice versa by means of electrical excitation.

[0060] Advantageously, the membrane may be a polymer of the PDLC or PNLC type.

[0061] Advantageously, a controller may be included, which is configured to automatically control the screen by controlling the transition of the screen from an opaque state to a transparent state and / or vice versa.

[0062] Advantageously, a manual switch (70) may be included as an alternative to or in combination with the controller.

[0063] Advantageously, the screen (20) can be fixed in a non-removable manner.

[0064] More particularly, preferably, the screen can be non-removably fixed to the light projection device (100).

[0065] Advantageously, alternatively, the screen (20) can be fixed in a removable manner.

[0066] In this case, it can preferably be attached to the light projection device (100) in a removable manner, for example.

[0067] Advantageously, the light projection device (100) may be a Placid disc comprising a plurality of concentric discs with backlight illumination.

[0068] Alternatively, advantageously, it can be a surface having multiple light sources arranged in a certain pattern.

[0069] Advantageously, the device may include a camera (300) arranged behind the light projection device (100), such that the device (100) is included between the camera and the screen.

[0070] Advantageously, the device (100) and the screen have holes coaxial with the camera.

[0071] Advantageously, in all configurations, the device for the purposes of this invention includes a support frame (102', 60).

[0072] Advantageously, in all configurations, the support frame supports the screen (20).

[0073] The present invention also aims to use the screen (20) in an ophthalmic instrument that includes at least one light projection device (100) that projects a light pattern in use, such that the screen is positioned to intercept the path of at least a portion of the light pattern emitted by the light projection device (100).

[0074] According to the invention, the screen (20) is electrically controllable to switch from an opaque state (in which the screen acts as a diffuser of light emitted by the light projection device (100) passing through it) to a transparent state (in which the screen allows light emitted by the light projection device (100) passing through it to pass through without any deflection) and / or vice versa.

[0075] Therefore, advantageously, when the screen (20) is in the transparent state, the ophthalmic instrument can perform the function of a corneal topography instrument, and when the screen (20) is in the opaque state, the ophthalmic instrument is suitable for measuring lipid layer thickness.

[0076] Therefore, advantageously, the object of the present invention is to use a device according to one or more of the foregoing features so as to enable the same device to perform at least one corneal topography and / or at least one lipid layer thickness analysis.

[0077] The present invention also aims to provide a method for performing at least one corneal topography and / or lipid layer thickness analysis, the method comprising the following steps: - Provides a light projection device (100) so that a light pattern can be projected during use; - Arrange at least one screen (20) to intercept at least a portion of the light pattern emitted by the light projection device during use, the screen being an electrically controllable screen capable of switching from a transparent state to an opaque state and / or vice versa by means of electrical control. Attached Figure Description

[0078] According to the invention, other features and advantages of the device will become more apparent from the following description of certain embodiments (given by way of example rather than limitation) with reference to the accompanying drawings, wherein: Figure 1A A corneal topography instrument according to the prior art is schematically shown; Figure 1B The concentric circles are shown as reflections in the eye and are precisely used for corneal topography. Figure 2 A prior art corneal topography instrument is shown, which allows for the acquisition of an eye image in which concentric placido discs are reflected, and then the image is analyzed using specific software to assess lipid layer thickness, in addition to corneal topography. Figure 3Other solutions in the prior art are shown, in which the concentric circles of the Plassid disk are interrupted to form a small region 501 without circles, in order to allow for proper detection of lipid layer thickness; Figure 4 and Figure 5 This represents a solution based on the invention for a screen that can control between light diffusion and transparency (e.g., using well-known smart film technology); Figure 6 This is a diagram of the device; Figure 7 and Figure 8 Other figures of the device are shown, in which the same reference numerals are retained for components identical to those in the prior art; in particular, the screen 20 according to the invention, which has two functions, namely: transparent (where it does not deflect light) and opaque (i.e., has a diffuser function, where it deflects light to produce uniform illumination); at last, Figure 9 An eye image viewed by the device according to the present invention is shown. Detailed Implementation

[0079] The object of this invention is a device for allowing the performance of at least corneal topography and / or lipid layer thickness analysis, said device comprising: At least one light projection device (100) is adapted to project a light pattern along a path; This includes a screen (20) positioned to intercept at least a portion of the path of the light pattern emitted by the light projection device (100). And the screen (20) is electrically controllable so that it can be selectively changed from a transparent state to an opaque state and / or vice versa.

[0080] Figure 6-8 The solution according to the present invention is shown. Components identical to those in the prior art are numbered using the same reference numerals.

[0081] Therefore, a support frame (102', 60) was installed.

[0082] It consists of a base 60 from which a column (102') rises.

[0083] The light projection device 100 is fixed to the column (102').

[0084] For example, it can take the form of a cone that forms a placid disc, as mentioned above, or in an alternative form, such as a flat backlit surface or a surface with a light distribution placed in front.

[0085] Even in the case of a cone forming a Placido disk, there is a light distribution 101, however, it is placed behind the disk and thus forced to pass through concentric disks, which alternately allow light to pass through and block light, as discussed in the prior art.

[0086] As described in the prior art, camera 300 is located behind and coaxial with light projection device 100. Therefore, the device has an aperture coaxial with the camera to enable the acquisition of images of eye 200.

[0087] According to the present invention, screen 20 is now provided as follows, which is electrically controllable, thereby enabling it to switch from a transparent state to a light-diffusing (and therefore opaque) state.

[0088] Figure 7 The image shows light rays projected by light source 101 and passing through the cone, indicated as ray 102. These are non-deflected rays because, as... Figure 7 As illustrated, screen 20 is controlled to be in a transparent state.

[0089] on the other hand, Figure 8 The screen 20 is shown to be controlled to switch to diffuser state (i.e., opaque).

[0090] exist Figure 7 In its transparent state, the screen appears to be non-existent, and (in the case of the Placido disc) the ring is precisely as... Figure 1B The image is projected into the eye; exist Figure 8 In this case, screen 20 is electrically switched to a diffuser, thereby producing uniform light scattering. This results in a larger area of ​​the eye being uniformly illuminated, meaning that concentric rings are no longer seen in the reflecting eye, thus allowing for good measurement of the lipid layer.

[0091] Figure 4 The image shows magnified details of the Placido disc.

[0092] According to the present invention, such as Figure 4 As shown, screen 20 now exists, which is in Figure 4 It appears as an emulsion in the image.

[0093] exist Figure 4 In the image, the concentric disk portion covered by the screen is slightly obscured by the screen, which is in a cloudy state and thus acts as a diffuser as described above.

[0094] Figure 4 Also shown is a rod (30'), which is part of the device and is well known to serve as a support for the patient's forehead, which is placed in front of the placido disc together with an additional support 30 for the chin.

[0095] Figure 5This shows that screen 20 is actually transparent.

[0096] Basically, when a patient is to undergo an eye examination, he / she stands in front of the device, rests his / her forehead on the bar 30' and his / her chin on the support 30, thus actually facing his / her eyes toward the backlit Placido disc.

[0097] When the placido disc (or a general light-emitting device) is illuminated, the light pattern of the device is projected onto the eye, for example, as shown in the image. Figure 1B The concentric circles shown are captured by the camera and can be viewed on the screen.

[0098] According to the present invention and as indicated above, by being able to remove the screen from an opaque state ( Figure 4 or Figure 8 Switch to transparent state ( Figure 5 or Figure 7 And vice versa, operators (such as doctors) can now control screen 20.

[0099] In the milky state (see...) Figure 4 or Figure 8 The screen acts as a light diffuser, thus projecting uniform light into the eye.

[0100] In this state, the operator (e.g., a physician) can accurately assess the thickness of the lipid layer because there are no concentric discs in the eye; instead, there is a large area with uniform illumination.

[0101] When the screen is made transparent, such as Figure 5 or Figure 7 In the middle, it's as if the screen doesn't exist, therefore the image is actually... Figure 1B The image, because the light is not deflected, accurately reflects the pattern emitted from the light projection device 100.

[0102] Thanks to this solution, the screen applied to the light projection device 100 (e.g., a Placido disc) can also be a permanent screen, i.e., fixed in place without removal.

[0103] With the help of controls, such as buttons, operators can easily switch between opaque and transparent screen states as needed.

[0104] Of course, a removable screen solution cannot be ruled out.

[0105] For example, it can be applied in a removable manner using screws or magnets, so it can remain in place as needed and then be easily removed, for example, for maintenance, replacement or other reasons.

[0106] In view of this, in a preferred solution of the present invention, the screen is manufactured according to a technology called polymer-dispersed liquid crystal and abbreviated as PDLC or also known as "smart film".

[0107] This technology is well-known and is widely used, for example, in the furniture industry, where windows in homes are made of glass incorporating this technology, allowing them to become opaque or transparent depending on the homeowner's needs and his / her time and preferences.

[0108] It is an electro-optic liquid crystal film.

[0109] PDLC technology confines liquid crystal molecules within microdroplets, which are then distributed within a polymer compound deposited between two surface-conductive polyester films. By applying an electric field, the molecules alter the optical properties of the films in response to incident light.

[0110] An electric field is applied to align the liquid crystal molecules in an ordered manner. Therefore, light can pass through the film undisturbed (the light is not deflected by the molecules), appearing transparent to our eyes. In this respect, the PDLC film acts as a filter capable of producing electrically controllable haze.

[0111] By removing the electric field, the liquid crystal molecules return to a disordered / random state. Light is then repeatedly deflected (scattered) by the molecules, preventing our eyes from reconstructing an image of the object behind the film (in a semi-transparent state).

[0112] Then, simply apply this film to the glass and apply electrical contacts to generate an electric field, and control the opaque or transparent state with a simple on / off switch.

[0113] Activating the electric field, i.e., setting the switch to "on", produces a transparent state, while deactivating the electric field, i.e., setting the switch to "off", produces a milky or semi-transparent state, causing the screen to cover the image by partially blurring it.

[0114] In a variation of the invention, the device can automatically control the screen to transition from transparent to opaque based on the inspection to be performed, for example, by inputting the inspection to be performed from the device's control panel or otherwise selecting the device's operating mode. Therefore, manually activated controls are not required.

[0115] In a variant, the polymer film may be of the PNLC type, where PNLC stands for "polymer network liquid crystal". These are the reverse of the aforementioned PDLC, also known as reverse PDLC.

[0116] More specifically, PNLC is transparent when there is no electrical excitation, but becomes opaque when there is electrical excitation.

[0117] therefore, Figure 6A cone 100, representing a placid disc and supported by a frame, is depicted. The frame may include a vertical support 102' resting on a base 60, as is well known in the art.

[0118] like Figure 6 As shown, screen 20 is therefore positioned to cover at least a portion of the concentric disk. Therefore, the screen is preferably circular so that it can fit the circular periphery of the cone. Figure 6 As shown, the diameter of screen 20 allows it to fit inside a cone so that it covers multiple concentric disks.

[0119] This also applies to situations where the light diffuser is not conical but has a flat surface, where the screen still covers a portion of the light diffuser 100, or is even placed at a certain distance from the device.

[0120] Clearly, the diameter can be chosen as needed, for example, such that the diameter of screen 20 can be equal to or slightly smaller than the diameter of the largest base of the cone (in the case of the cone instance). Obviously, the larger the diameter of the screen, the more concentric disks can be obscured or generally become opaque.

[0121] therefore, Figure 6 A switch 70 is depicted, which is connected to the screen 20 so that the electric field can be activated and deactivated, thereby changing the state to opaque or transparent as needed.

[0122] As mentioned, the switching can also be automatic.

[0123] In all configurations, screen 20 naturally has a through-hole coaxial with the camera to clearly allow the camera to capture images of eye 200.

[0124] As mentioned, in a preferred solution of the present invention, the screen 20 may be fixed in a non-removable manner.

[0125] Alternatively, it can still be removable and reusable, for example, by using quick-release devices such as magnets or snap-fit ​​elements, screws, etc.

[0126] The device thus created is therefore capable of performing at least corneal topography and lipid layer thickness assessment.

[0127] Clearly, the same device can be further equipped to perform at least one or more other operations besides those described above: Pupil tracing; Meibomian gland analysis; River of Tears (tear meniscus) Tear film breakup time; Red eyes; Fluorescein / staining.

Claims

1. An apparatus for allowing the performance of at least corneal topography and / or lipid layer thickness analysis, the apparatus comprising: - At least one light projection device (100) adapted to project a light pattern along a path; - And it includes a screen (20) which is placed to intercept at least a portion of the path of the light pattern emitted by the light projection device (100); The screen (20) is characterized in that it is electrically controllable so as to be able to selectively change from a transparent state to an opaque state and / or vice versa, and wherein the screen (20) comprises at least one layer of transparent material coated with an electrically switchable film so as to allow the transition from a transparent state to an opaque state and / or vice versa by means of electrical excitation.

2. The device according to claim 1, wherein, The membrane is a PDLC or PNLC type polymer.

3. The device according to one or more of the preceding claims, wherein, Includes a controller configured to automatically control the screen by controlling the transition of the screen from a milky state to a transparent state and / or vice versa, or, as an alternative to or in combination with the controller, includes a manual switch (70).

4. The device according to one or more of the preceding claims, wherein, The screen (20) is fixed in place; preferably it is fixed in place to the light projection device (100).

5. The device according to one or more of claims 1 to 3, wherein, The screen (20) is removably fixed; preferably, it is removably fixed to the light projection device (100).

6. The device according to one or more of the preceding claims, wherein, The light projection device (100) is a placid disc comprising a plurality of concentric discs with backlight illumination, or a surface having a plurality of light sources arranged according to a certain pattern.

7. The device according to one or more of the preceding claims, comprising a camera (300) arranged at the rear relative to the light projection device (100) such that the device (100) is included between the camera and the screen, preferably the device (100) and the screen having holes coaxial with the camera.

8. The device according to one or more of the preceding claims, the device comprising: - Supporting frame (50, 60); -In particular, the light projection device (100) is fixed to at least a portion of the frame (102', 60) so that it can project the predetermined light pattern.

9. Use of a screen (20) in an ophthalmic instrument comprising at least one light projection device (100) for projecting a light pattern in use, the screen being positioned to intercept at least a portion of the path of the light pattern emitted by the light projection device (100), and the screen (20) being electrically controllable to switch from an opaque state to a transparent state and / or vice versa, wherein in the opaque state the screen acts as a diffuser of the light emitted by the light projection device (100) and passing through the screen, and in the transparent state the screen allows the light emitted by the light projection device (100) and passing through the screen to pass through without deflection, and wherein, The screen (20) includes at least one layer of transparent material coated with an electrically switchable film, thereby allowing a transition from a transparent state to an opaque state and / or vice versa by means of electrical excitation.

10. The use according to claim 9, wherein, The membrane is a PDLC or PNLC type polymer.

11. The device according to one or more of claims 1 to 8 is used for performing at least one corneal topography and / or at least one lipid layer thickness analysis with the same device.

12. A method for manufacturing an apparatus suitable for performing at least corneal topography and / or lipid layer thickness analysis, the method comprising the steps of: - Provides a light projection device (100) so that a light pattern can be projected during use; - Provide at least one screen (20) to intercept at least a portion of the light pattern emitted by the light projection device in use, the screen being an electrically controllable screen capable of switching from a transparent state to an opaque state and / or vice versa by means of electrical control, and wherein the screen (20) comprises at least one layer of transparent material coated with an electrically switchable film, thereby allowing a transition from a transparent state to an opaque state and / or vice versa by means of electrical excitation.

13. The method according to claim 12, wherein, The membrane is a PDLC or PNLC type polymer.

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