Temporary keratoprosthesis

Abstract

FIELD: medicine.SUBSTANCE: temporary keratoprosthesis contains a lens and a cylindrical stem made of transparent optical glass. The lens has a radially convex surface and holes located on the periphery of the lens for fixing the keratoprosthesis on the cornea of the eye. In this case, the keratoprosthesis stem is made with annular parallel grooves on it, forming parallel annular protrusions on the surface of the stem along the height of the stem. The height of the stem is within 1.9–2.1 mm, the diameter of the stem is within 6.8–7.2 mm. The lens and the stem are made separately from each other and are fastened together so that the height of the lens with the stem is within 3.8–3.94 mm, and the diameter of the lens is within 9–11 mm.EFFECT: improving the optical qualities of the keratoprosthesis and the accuracy of visual control of its position during operations.3 cl, 4 dwg

Description

[0001] This invention relates to medical technology in the field of ophthalmology, specifically to devices for temporarily blocking a technological opening in a cloudy portion of the cornea during reconstructive surgery on the eyeball. The technical solution presented in this description relates to keratoprostheses designed to replace the cloudy portion of the cornea and perform reconstructive surgery on the eyeball.

[0002] Open eye injuries (OE) are a common occurrence, representing one of the most severe forms of visual injury in both peacetime and wartime. Patients with questionable and unfavorable prognoses for open eye injuries account for 36.7% and 30.2% of ophthalmological casualties, respectively. Penetrating keratoplasty is required in 9.2% of these cases. Given the severity of anterior and posterior eye injuries and the need for simultaneous vitreoretinal surgery, temporary keratoprosthetics are required in 47.1% of cases due to severe traumatic corneal changes and the impossibility of performing vitreoretinal surgery due to insufficient corneal transparency. However, the known models of temporary keratoprosthesis are only descriptive in nature and are not in serial production, and in the case of the production of keratoprostheses by the ETP of the Federal State Autonomous Institution Scientific and Technical Complex "Microsurgery of the Eye", their serial production has been suspended.

[0003] The Eckardt silicone temporary keratoprosthesis, manufactured by Dorc, has been discontinued. Commercially available polymethyl methacrylate keratoprostheses (OcularInstruments, USA or OpticlearOphthalmicLenses, India) are difficult to obtain and deliver. Furthermore, due to the material used for their manufacture, all of the above-mentioned commercially available models do not provide flawless, high-quality, and detailed fundus visualization. They have poor wear resistance, poor resistance to mechanical damage, and are intended for single use, resulting in a high final cost.

[0004] In connection with the above, the purpose of developing the temporary keratoprosthesis presented in this description is to ensure high-quality performance of combined vitreoretinal and optical-reconstructive surgery in case of combined damage to the anterior and posterior parts of the eyeball.

[0005] Taking into account the specifics of the vitreoretinal and optical-reconstructive stages of surgical intervention for combined damage to the anterior and posterior segments of the eyeball, the basic technical requirements for a new model of temporary intraoperative keratoprosthesis were formulated. The temporary keratoprosthesis had to meet the following criteria:

[0006] - to ensure the highest possible visualization of the fundus for the purpose of performing surgical interventions on the intraocular structures of the posterior pole of the eyeball due to the transparency of the material;

[0007] - ensure the simplest and least traumatic fixation to the episclera of the eyeball;

[0008] - ensure reliable sealing of the corneal trepanation hole, including in case of deformation of the eyeball during sanitation of the peripheral parts of the retina under conditions of scleropression and alternative values ​​of infusion for hemostatic purposes;

[0009] - ensure rapid sealing of the “open sky”;

[0010] - ensure repeated use of the keratoprosthesis, the possibility of its sterilization and extension of its service life.

[0011] At the same time, the keratoprosthesis must not have a toxic effect on surrounding tissues or cause inflammatory or allergic reactions in the patient undergoing surgery. To meet these requirements, a temporary intraoperative keratoprosthesis has been developed. Its design includes a transparent cover lens with an optical power and surface curvature radius close to that of the natural cornea, and an optical cylinder for fixation within the edges of the corneal trephine hole.

[0012] The high incidence of combat-related eye injuries in ophthalmological casualties, with mine-blast injuries predominating, leads to an increase in the number of requests for specialized vitreoretinal and optical-reconstructive ophthalmic surgery. In cases of severe eye trauma with damage to the anterior and posterior segments, traumatic corneal changes can interfere with visualization of the posterior segment and reconstructive vitreoretinal surgery aimed at restoring the correct anatomical and topographic relationships of the posterior pole structures. This subsequently minimizes the possibility of a favorable functional outcome after the optical-reconstructive stage.

[0013] The temporary intraoperative keratoprosthesis is able to maintain the correct spherical shape of the eyeball during surgery due to the stability of intraocular pressure due to reliable sealing of the trepanation hole, provides excellent visualization of the posterior segment and high-quality implementation of all stages of vitreoretinal intervention in full, including bimanual manipulations.

[0014] A temporary intraoperative keratoprosthesis is known from patent documentation, made from an optically transparent biocompatible material, containing elements for suturing, wherein the keratoprosthesis is made in the form of a square plate with a thickness of 0.5 mm, and the elements for suturing are made in the form of a pair of arcuate through grooves with an indentation of 1-1.5 mm from each corner of the square plate (RU 12004 U1, 16.12.1990).

[0015] A temporary intraoperative keratoprosthesis is known, the body of which has a meniscus shape with a radius of curvature of the cornea, a thickness of 0.5 to 0.8 mm, a diameter of 6.0 to 10.0 mm, along the periphery of the convex surface of the body there is a protruding rim with a height of 0.2-0.3 mm and technical through channels directed at an angle from the convex surface of the body to its edge (RU 163774 U1, 10.08.2016).

[0016] A temporary keratoprosthesis is known, which is a lens transparent in the visible range with an optical power close to the optical power of the cornea of ​​the eye and has a mushroom shape, the length of the stem (trunk) of which is approximately equal to the thickness of the cornea of ​​the eye, and the radius of curvature of the surface of the cap is approximately equal to the curvature of the cornea of ​​the eye. The diameter of the cap is greater than the diameter of the stem. Moreover, for fixation of the keratoprosthesis on the surface of the eye, suturing holes are made on the periphery of the cap and at the maximum distance from its center for suturing the keratoprosthesis to the surface of the eye (Benner JD, Landers MB III. An infusion temporary keratoprosthesis for pars plana vitrectomy. Am J Ophthalmol. 1996; 122 (4): 579-580). A method for fixing a keratoprosthesis on the surface of the eye is provided, which consists of cutting out a round hole in the cornea of ​​the eye with a diameter slightly smaller than the diameter of the keratoprosthesis stem, and tightly inserting the keratoprosthesis stem into this hole.Next, the keratoprosthesis is sutured to the ocular surface through the suturing holes. This ensures a secure seal around the eye and secures the keratoprosthesis to its surface. Afterward, to restore the original shape, a fluid, specifically perfluorodecalin, is injected into the eye under positive pressure. It has been established that during keratoprosthesis placement, the stem traumatizes the surrounding ocular tissue. This leads to frequent swelling and postoperative complications. Furthermore, due to the large thickness of the keratoprosthesis, the visualized image has low resolution.

[0017] A temporary keratoprosthesis without a stem is known and is a lens transparent in the visible range with a curvature of the upper optical surface close to the curvature of the cornea, and an optical power close to the optical power of the cornea of ​​the eye. To fix the keratoprosthesis on the surface of the eye, suturing holes are made along its periphery, at the maximum distance from the center, allowing the keratoprosthesis to be sutured to the surface of the eye (Landerswide-fieldtrunkless TKR, OcularInstruments. Article "An Improved Temporary Keratoprosthesis". Retina Today, 2014, Vol. 9, No. 6, p. 42). A method for using a temporary keratoprosthesis without a stem is provided, which consists in cutting out the cornea in the form of a round hole with a diameter smaller than the diameter of the temporary keratoprosthesis. Next, through the suturing holes, the temporary keratoprosthesis is sutured to the surface of the eye so that it fits as tightly as possible to the tissues surrounding the hole in the cornea.After this, a fluid, specifically perfluorodecalin, is injected into the eye under positive pressure to restore its original shape. The disadvantage of this solution is that it does not provide a hermetic seal between the temporary keratoprosthesis and the ocular tissue. This disadvantage stems from the fact that, using suturing holes, it is virtually impossible to secure the temporary keratoprosthesis to the ocular surface without the filling fluid leaking through the gap between the surface of the temporary keratoprosthesis and the eye.

[0018] To seal the gap between the temporary keratoprosthesis and the ocular surface, a keratoprosthesis is used. The keratoprosthesis consists of a lens transparent in the visible range with a curvature of the upper optical surface close to the curvature of the cornea and an optical power close to the optical power of the cornea. The lens is rigidly fixed to the surface of a ring whose diameter is greater than the diameter of the lens. The temporary keratoprosthesis is fixed to the ocular surface by suturing it so that the conjunctiva is sewn around the ring of the temporary keratoprosthesis with a purse-string suture, the thread of which is pulled so that a conjunctival fold forms on the surface of the ring around the lens (RU 2626373 C1, 26.07.2017). The positive effect is achieved due to the fact that the conjunctival fold formed on the surface of the thin suturing ring seals the gap between the surface of the temporary keratoprosthesis and the surface of the eye.

[0019] In established practice, optically neutral glass (RU 47692 U1, 10.09.2005) can be used as materials for the manufacture of keratoprostheses for performing vitreoretinal surgeries in the absence of a transparent cornea, or a hydrophobic acrylic material with a high refractive index obtained by polymerization of a mixture of monomers (RU 2728693 C1, 31.07.2020).

[0020] Keratoprostheses made of acrylic material do not fully meet the requirements of transparency and strength, and keratoprostheses made of neutral glass do not fully meet the conditions of their reliable fixation in the working position.

[0021] Of the known solutions, the closest to the keratoprosthesis presented in this description is a keratoprosthesis consisting of a lens transparent in the visible range with a curvature of the upper optical surface close to the curvature of the cornea and an optical power close to the optical power of the cornea of ​​the eye, wherein the lens is rigidly fixed to the surface of a ring whose diameter is greater than the diameter of the lens. Fixation of the temporary keratoprosthesis on the surface of the eye is achieved by its fixation in such a way that the conjunctiva is sewn around the ring of the temporary keratoprosthesis with a purse-string suture, the thread of which is pulled so that a conjunctival fold is formed on the surface of the ring around the lens (RU 2626373 C1, 26.07.2017 – prototype).

[0022] A mushroom-shaped temporary keratoprosthesis for vitreoretinal surgery on eyes with cloudy corneas is known. The keratoprosthesis is made of PMMA, a polymethyl methacrylate-based material. The material from which the keratoprosthesis is made has poor light transmittance, is easily damaged by mechanical stress, and is used as a single-use device for a single operation, which limits its shelf life.

[0023] The purpose of the development and creation of the temporary keratoprosthesis presented in this description is to ensure high-quality performance of combined vitreoretinal and optical-reconstructive surgery in case of combined damage to the anterior and posterior parts of the eyeball.

[0024] The technical result of the invention is to improve the optical qualities of the keratoprosthesis and the accuracy of visual control of its position during operations.

[0025] The technical result is obtained by a temporary keratoprosthesis containing a lens and a cylindrical stem made of transparent optical glass, the lens has a radial outwardly convex surface and openings located on the periphery of the lens for fixing the keratoprosthesis on the cornea of ​​the eye, while the stem of the keratoprosthesis is made with annular parallel grooves on it, forming parallel annular protrusions along the height of the stem on the surface of the stem, while the height of the stem is within 1.9-2.1 mm, the diameter of the stem is within 6.8-7.2 mm, the lens and the stem are made separately from each other and fastened together so that the height of the lens with the stem is within 3.8-3.94 mm, and the diameter of the lens is within 9-11 mm.

[0026] The leg has at least 3 grooves, each of which has the same width and depth within 0.19-0.21 mm, the distance between the centers of opposite lens holes is at least 9 mm with the diameter of each lens hole being no more than 1 mm.

[0027] The lens and the cylindrical stem are bonded together with transparent optical glue. The lens has a flat surface facing the stem, between which and the surface of the stem a right angle is formed. The lens and the stem of the keratoprosthesis are made of K-8 optical glass with a working range of the material within 365-2000 nm, with resistance to mechanical and thermal influences, as well as to the effects of carbon dioxide.

[0028] Figure 1 shows an enlarged view of the temporary keratoprosthesis.

[0029] Fig. 2 shows a fragment of a temporary keratoprosthesis in an enlarged view.

[0030] Fig. 3 shows a temporary keratoprosthesis installed in the cornea of ​​the eye.

[0031] In Fig.4 – view A in Fig.1.

[0032] The keratoprosthesis has a mushroom-shaped form in the side view (Fig. 1). In the first embodiment, the keratoprosthesis comprises a lens 1 made of optical glass and a stem 2 attached to it. The stem is manufactured separately from the lens and is connected to it with optical transparent adhesive. The stem 2 has a circular cross-section; in the top view (Fig. 4), the lens is predominantly circular. The second embodiment of the keratoprosthesis can be manufactured as a single monolithic piece, cast from glass in a mold, and have the same parameters as the first embodiment.

[0033] The lens has 3 openings on its periphery, located along the perimeter of the lens, and the leg 2 has grooves 4 made on its outer surface. The grooves are designed for a tighter fit of the keratoprosthesis into the opening of the cornea, the openings 3 of the lens are designed to fix the keratoprosthesis on the cornea of ​​the eye by known means.

[0034] The lens has a rounded surface 5 convex toward the stem, with a radius of 9-11 mm. The lens has a flat surface 6 facing the stem. A right angle is formed between surface 6 and surface 7 of the stem.

[0035] The keratoprosthesis is made from standard K-8 optical glass according to GOST 3514-94. It has a working range of 365–2000 nm and is resistant to mechanical and thermal stress, as well as carbon dioxide. This standard K-8 optical glass, used in laser technology, is preferably used, but other similar materials with the specified characteristics can be used in the manufacture of keratoprostheses.

[0036] Between the grooves 4 of the stem, annular projections 8 are located around the perimeter of the stem. The number of projections depends on the number of grooves. For a stem height of 2 mm and a diameter of 7 mm, the optimal number of grooves is three, each with an equal width and depth within the range of 0.19-0.21 mm, with the optimal value of these parameters being 0.2 mm. A chamfer 9 is provided at the end of the stem to facilitate insertion into the corneal opening. The ends of the lens and all its corners are rounded, including the internal angle between plane 6 and stem 2, as well as the rounded end of the lens.

[0037] The lens height with stem is between 3.8-3.94mm, with an optimal height of 3.87mm. The optimal lens diameter is 10mm, ranging from 9-11mm. The distance between the centers of the three opposite holes is at least 9mm, and the diameter of each hole is no more than 1mm.

[0038] In Fig. 3, position 10 shows the cornea of ​​the eye.

[0039] The temporary keratoprosthesis is used as follows. After excising the cloudy cornea 10 (Fig. 3) with a trephine to the required corneal opening diameter, the temporary keratoprosthesis is placed in the resulting opening, provided that the diameter of the keratoprosthesis corresponds to the diameter of the opening in the cornea. Threads (not shown) of interrupted sutures are then passed through the through holes 3 of the lens, and lens 1 is sutured to the cornea 10. This ensures that the lens fits snugly against the corneal episclera, ensuring a seal along the superior edge of the corneal trephine opening. The round, transparent stem of the keratoprosthesis, with grooves on its surface and annular projections 8 (Fig. 2), ensures tight fixation of the keratoprosthesis in the corneal burr hole, allowing for rapid opening and closing of the "open palate." The presence of annular projections 8 on the stem minimizes the possibility of external filtration of the infusion fluid by securing it to the lateral edges of the burr hole.

[0040] After the necessary surgical procedures are carried out in the eye cavity and completed, the keratoprosthesis is removed, and a penetrating donor corneal graft is placed in the trepanation hole of the cornea of ​​the eye and sutured to the cornea of ​​the eye.

[0041] The presented keratoprosthesis has a high light transmittance of about 92%, is not subject to deformation and scratching, and increases its service life indefinitely by reusing it after removal, disinfection, and treatment in a special solution, which significantly reduces the costs incurred in cases of using single-use keratoprostheses made of polymeric materials.

[0042] The technology for producing keratoprostheses from two simple parts that can be connected and have a simple shape has been significantly simplified. These parts are easy to process and, after being connected, form a more complex keratoprosthesis in the form of a mushroom in the side view.

[0043] Keratoprostheses with increased light transmission made from the specified glass significantly facilitate the surgeon’s work in terms of visibility of the process, which contributes to improving the quality of installation of the keratoprosthesis in the opening of the cornea of ​​the eye.

[0044] The choice of material for the keratoprosthesis is based on the high transparency of the optical glass, which guarantees the best possible visualization of intraocular structures during surgery compared to known polymeric alternatives (polymethyl methacrylate, polycarbonate, or silicone). The optical power and surface curvature of the temporary keratoprosthesis, which match the natural cornea, ensure high-quality fundus detail. Furthermore, the inertness of the optical glass with these properties guarantees the absence of toxic, allergic, or inflammatory effects on the tissues of the operated eye surrounding the temporary keratoprosthesis. The optical glass of the keratoprosthesis used is highly uniform, retains its shape well, and is easily processed, allowing the temporary keratoprosthesis to be shaped to the required size.The mechanical properties of heat and light resistance, as well as the high transparency of the selected keratoprosthesis material, ensure the maximum possible functionality of the temporary keratoprosthesis. Furthermore, the selected keratoprosthesis material has excellent optical and physicochemical properties, ensuring excellent medical performance, contributing to the clinical safety of the procedure and increasing the service life of the temporary keratoprosthesis.

[0045] During testing of the temporary intraoperative keratoprosthesis, it was demonstrated that the proposed model reduced the time needed for placement and centering of the prosthesis relative to the corneal surface due to improved visualization of the fundus and control through the lens and stem of the keratoprosthesis. Simplicity and reliability of fixation were also achieved, with minimal trauma to the tissues of the operated eye, along with rapid opening and closing of the "open palate" during the specified stages of the surgery. Furthermore, the temporary keratoprosthesis ensured complete sealing of the eyeball and visualization of the retina at all stages of the vitreoretinal procedure. During retinal periphery sanation with scleropression and achievement of alternative infusion values ​​of 60-80 mmHg to achieve hemostasis, external filtration of the infusion fluid along the edges of the corneal burr hole was not observed.

Claims

1. A temporary keratoprosthesis comprising a lens and a cylindrical stem made of transparent optical glass, the lens having a radially convex outward surface and openings located on the periphery of the lens for fixing the keratoprosthesis on the cornea of ​​the eye, while the stem of the keratoprosthesis is made with annular parallel grooves on it, forming parallel annular projections along the height of the stem on the surface of the stem, while the height of the stem is within 1.9-2.1 mm, the diameter of the stem is within 6.8-7.2 mm, the lens and the stem are made separately from each other and fastened together so that the height of the lens with the stem is within 3.8-3.94 mm, and the diameter of the lens is within 9-11 mm.

2. A temporary keratoprosthesis according to paragraph 1, characterized in that at least 3 grooves are made on the stem, each of which has the same width and depth within the range of 0.19-0.21 mm, the distance between the centers of oppositely located openings of the lens is at least 9 mm with the diameter of each opening of the lens no more than 1 mm.

3. A temporary keratoprosthesis according to claim 1, characterized in that the lens and the cylindrical stem are fastened together with transparent optical glue, the lens has a flat surface facing the stem, between which and the surface of the stem a right angle is formed, and the lens and stem of the keratoprosthesis are made of K-8 optical glass with an operating range of the material within 365-2000 nm, with resistance to mechanical and thermal influences, as well as to the effects of carbon dioxide.

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