RU2367379C1 - Keratoprosthesis and leukoma surgery therewith - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: group of inventions concerns ophthalmology and can be applied in treatment of severe (IV-V) keratoleukomas. A keratoprosthesis comprises a cylindrical optical element fixed within a hole of a support base. The latter is made of plate porous-permeable titanium nickelide of plate thickness decreasing radially from the centre out. Accordingly, porosity smoothly increases 30%-40% to 50-60%, and the primary pore size varies 100 mcm to 200 mcm. Solid curvature of the support base is congruent with eye cornea. The penetrating keratoprosthesis is single-stage. Trepanation of cornea and removal of crystalline lens is followed with installation of the keratoprosthesis along the visual eye axis to ensure contact of a concave surface of the support base with cornea. The keratoprosthesis is fixed with applying allosclera edges of which are sutured to sclera in oblique meridians.

EFFECT: rapid and effective integration of keratoprosthesis base and is surrounding tissues, reliable fixation of the optical element, and higher competence of treating cataracts in minimum corneal injuries.

3 cl, 5 dwg, 1 ex

Description

The invention relates to medicine, namely to ophthalmic surgery, and can be used in the treatment of cataracts of IV-V categories.

The visual system provides 80% of information about the outside world. With loss of vision, a person finds himself in a dramatic situation of helplessness and despair. The apple of the eye and the magical insight of the blind are bright folklore metaphors that symbolize the value of this sensory organ. Therefore, the relevance of the tasks of ophthalmology cannot be overestimated, despite the fact that eye diseases themselves do not pose a direct threat to human life.

The most vulnerable to the damaging effect is the anterior, optical zone of the eye. Mechanical injuries, widespread chemical and thermal burns, frostbite and radiation exposure cause clouding and a complete loss of the transparency of the cornea (eyesore). Severe illnesses lead to blindness and disability of the patient.

With mild degrees of the disease, therapeutic medical assistance is possible. There are drugs that help self-repair tissue. At the stage of scarring and late complications in the cornea (IV-V stage according to the classification of Filatov-Bushmich), effective help is possible only through surgical intervention. The technique of such operations is diverse and, according to the results, unequal. The most advanced methods are described and classified in the monograph [Puchkovskaya N.A., Yakimenko S.A., Nepomnyashchaya V.M. Eye burns. - M .: Medicine, 2001, p.196-256]. They are based on keratoprosthetics - replacing a defective cornea with optically transparent prostheses made of rock crystal, glass, celluloidin, acrylic, plexiglass and other materials. The search for optimal materials and techniques for implanting prostheses has been noted in the prior art since the late 18th century. Lamellar optical elements curved in the shape of the cornea were installed intralamellarly and fixed with support bases of gold, polyethylene, tantalum, and platinum. The disadvantages of these methods, due to the disadvantages of prostheses, are poor survival of the prostheses, which leads to inflammation and necrotization of the cornea, rejection of the prosthesis. Through prosthetics turned out to be more reliable when an extended cylindrical optical element penetrates through the trepanation hole the cornea, the anterior, posterior chambers, the lens and stands in the vitreous. Such an optical element performs the function of a light guide and a fixed focus lens. Recently, the concept of end-to-end prosthetics has become the main one, and the design search has focused most of all on the selection of suitable device materials.

Known keratoprosthesis Fedorov-Zuev [Fedorov S.N., Zuev V.K. End-to-end corneal prosthetics for burn sores // Vestn. ophthalmology. 1976. No. 4. S.39-44], containing a non-porous lamellar support base made of tantalum and an optical cylindrical element made of plexiglass brand "Dacryl". The optical element has a threaded connection with a sleeve, which is rigidly fastened to the base. The disadvantage of this device is the low survival rate due to imperfections in the basis. An impermeable base plate over a large area separates the front and back layers of the cornea, violating their anatomical and physiological relationship, trophic conditions and leading to the development of aseptic necrosis.

The indicated drawback of the device also relates to a method of treating an eyesore - surgery, the technique of which is used when installing this prosthesis [Fedorov S.N., Zuev V.K. End-to-end corneal prosthetics for burn sores // Vestn. ophthalmology. 1976. No. 4. S.39-44]. The method includes two stages of the operation: at the first stage, the support basis with the plugged hole of the sleeve is intralamellarly explanted in the thorn, the second layers of the cornea above the hole are trepanized, the plug is removed and the posterior layers of the cornea are treated through the vacated hole. An optical cylindrical element is screwed into the keratoprosthesis sleeve.

Known more advanced keratoprosthesis with a modified design of the supporting base [Puchkovskaya NA, Yakimenko SA, Golubenko EA Long-term results of keratoprosthetics // Ophthalmological Journal. 1979. No. 7. S.388-391]. Openwork, with large gaps, the structure of the support base is more integrable with corneal tissue, but does not provide the desired result. The installation method of this prosthesis, like the previous one, includes two stages of the operation and intralamellar placement of the supporting base. Separation of the layers of the cornea violates the trophic tissue with the ensuing negative consequences.

Known, as a scientific attempt to study the survival of the base to the cornea, keratoprosthesis with a supporting base made of a nickel wire mesh [Moroz Z.I. et al. A new model of end-to-end keratoprosthesis for the treatment of corneal sore throats // Ophthalmic Surgery. 1994. No4. S.32-35]. The mesh structure of the support base, due to its elasticity, is more adaptive to the shape of the cornea, which increases the uniformity of pressure on it, reduces the possibility of pressure sores, necrosis and rejection. Nickel is not biologically inert enough, which is a significant drawback in this function; the sleeve-screw mounting of the optical element to the base is cumbersome and heavy for such a finely organized structure as the optical zone of the eye. The consequence of these technological shortcomings is the development in four cases of 32 operations of aseptic necrosis around the optical element. To install this keratoprosthesis, the above Fedorov-Zuev method is used with its inherent features and disadvantages.

Known keratoprosthesis for surgical treatment of cataracts of category IV-V, containing a plate support base of permeable-porous titanium nickelide, spatially curved in shape and curvature of the cornea of the eye, and a cylindrical optical element for broadcasting and focusing the light flux [RF Patent No. 1802703]. A hole is made in the center of the basis for placing an optical element in it. A keratoprosthesis is implanted in stages. At the first stage, the cornea of the eye is stratified to 2/3 of the depth and a basis is established in the formed pocket. The hole in the base is suppressed with a temporary insert and the corneal incision is sutured with a sealing suture. After 2-3 months - the integration time of the porous basis in the cornea - the outer layers of the latter trepan over the temporary liner, remove the liner and trepan the inner layers of the cornea. An optical cylindrical element on the thread is introduced into the support base.

The advantages of permeable-porous titanium nickelide provide, due to the high biocompatibility of the latter, greater operation viability. Keratoprosthesis is faster and more reliable than in previous analogues, integrates with tissue, less rejected.

The disadvantage of the device and method of surgical treatment of cataracts using the specified keratoprosthesis, is increased trauma to the cornea due to the formation of a "pocket", suture tissue destruction, two-stage operation.

By the greatest similarity of the technical essence with the proposed solution, of which the dominant similar feature is the basis material, these analogs of the device and method are taken as a prototype.

The technical result of the proposed group of inventions is to increase the viability of the treatment of walleye.

The specified technical result is achieved by the fact that in a keratoprosthesis containing a plate support base of permeable-porous titanium nickelide, spatially curved in shape and curvature of the cornea of the eye, with a hole in the center and a cylindrical optical element for transmitting and focusing the light flux placed in the hole, the thickness of the plate the support base gradually decreases by 20-50% in the radial direction from the hole to the periphery, the porosity of titanium nickelide increases from 30-40%, the advantageous time changes pore measures from 100 microns to 200 microns.

It is preferable to place the cylindrical optical element in the hole of the basis with a tight fit.

Improving the consistency of the treatment of the eyesore is also achieved by using the method of surgical treatment of the eyesore by keratoprosthetics using a keratoprosthesis with a support base of permeable-porous titanium nickelide, molded along the curvature of the eye and supporting a cylindrical optical element located in its central hole. In contrast to the prototype method, a plate support base is mounted on the surface of the cornea and retentively fixed with a sclera allograft superimposed on top of the plate support base.

The attainability of the technical result of the invention, the device, is due to the manifestation of the properties of the distinguishing features characterizing the parameters of the support basis:

The varying thickness of the plate support base with its increase to the Central hole allows you to fix the cylindrical optical element without additional mounting sleeve and threaded connection, i.e. technically simple and operationally reliable.

One of the options for simple and reliable fastening of the optical element in the hole of the support base is a tight fit, which is performed with a negative difference between the hole diameters and the bore diameter of the optical element. A tight fit (the nature of the connection of parts) in the "hole-shaft" system is carried out in metals due to the elastic deformation of the material. Titanium nickelide is deformed according to the law of elastic deformation, which is several times larger than the elastic deformation of metals. This factor allows you to mount a keratoprosthesis - a lightweight and precision design - with the least mechanical effort, reducing the possibility of technological defects and errors. The surface of the hole rough at the cut of the porous material further contributes to preventing the migration of the optical element in the absence of additional fixing techniques. A decrease in the porosity and predominant pore size near the hole also contributes to the reliability of fixing the optical element by increasing the mechanical strength of the material in the central portion of the basis that carries the main load. The absolute values in the intervals of pore size and porosity are selected from the conditions of optimal integration of porous titanium nickelide and body tissues: cornea of the eye on the one hand, and allograft on the other. The latest data were obtained by the authors as the original result of studies of the biocompatibility of titanium nickelide.

Fast and successful integration of a porous implant (basis) with surrounding tissues, mechanically strong fixation of the optical element, i.e. a reduction in the risk of keratoprosthesis reposition is regarded as an increase in the viability of the treatment of leukemia, which in essence they are.

Theoretical calculations and experimental preparation of objects on animals served as a moral and technical prerequisite for their use in the clinic. A new set of features of the device and method indicate the compliance of the proposals with the criteria of the invention "inventive step".

The drawings show:

Figure 1. A photo of the patient’s eye before surgery.

Figure 2. Keratoprosthesis: a) lateral projection 1 - optical element; 2 - supporting basis; b) frontal projection of the support basis; 3 - hole.

Figure 3. The appearance of the keratoprosthesis in detail: 4 - a blank for the supporting base.

Figure 4. Keratoprosthesis installation scheme: 5 - cornea; 6 - allograft sclera; 7 - fixing sutures.

Figure 5. Photo of the patient’s eye after surgery.

The attainability of the technical result is confirmed by clinical examples of keratoprosthetics in the ophthalmology clinic of the Siberian State Medical University (Tomsk).

Example 1

Patient K., 24 years old, was admitted to the hospital with a diagnosis of post-burn leukoma of the cornea of the III degree and complicated cataract of the left eye, visual acuity - correct light perception. In the right eye: post-burn leukoma of the II degree, visual acuity - 0.04. An operation was performed on the left eye: cataract removal, end-to-end keratoprosthetics. In this case, a keratoprosthesis of the proposed design with the following characteristics was used: the supporting basis (prosthesis haptic) is made of permeable-porous titanium nickelide sheet (item 4, figure 3) with dimensions of 14 × 17 mm and a sheet thickness in the center of 2.2 mm, edges 1.5 mm. In the manufacture of a support base blank with the indicated variable sheet thickness, differential etching was used, which is proportional in time to the volume of material to be removed. In the center of the basis, along the edge of the hole (pos. 3, Figs. 2, 3), the porosity of the material is 35% and gradually increases to the edges to 60%, respectively, the predominant size of the permeable pores is from 100 to 200 μm. The changing characteristics of porosity were achieved in the process of porous ingot technology at the stage of forming (pressing) briquettes for synthesis by powder metallurgy methods [Medical materials and shape memory implants. Gunther V.E. et al. Tomsk: Publishing House of Tomsk State University, 1998. S.458-465]. The diameter of the hole 3 in the base is 4 mm. The radius of curvature of the inner spherical surface of the base is about 25 mm.

The cylindrical optical element (1, Fig. 2) is made of polymethylmethacrylate and has dimensions: total length 12 mm, diameter of the belt 8 mm, thickness 2 mm, length of the cylindrical part (legs) to the belt - 8 mm, protruding above the belt - 2 mm. The cylinder diameter is 5 mm, so that the difference between it and the diameter of the hole 3 is a negative value of 1 mm. The protruding (outer) end of the cylinder is formed convex, the inner - concave. In this case, the optical power of the element is equal to 54 diopters.

A keratoprosthesis during its assembly and in operation works, and the method is as follows.

The spherical shape of the support base is formed in hot form on a blank-matrix made by anthropometric measurement of the cornea of the diseased eye. Before the operation, the support base was sterilized in a dry heat cabinet at a temperature of 180 ° C. The optical element is sterilized in a 10% NaOH solution for 12 hours and in an antibiotic solution - 1 hour. In sterile conditions, both parts are combined with compression force until the base surface rests in the band of the optical element (figure 2).

Under general anesthesia, the conjunctiva is cut off from the limbus in a circular incision and separated from the sclera. The rectus muscles are taken on the threads of the holder. In oblique meridians of the eyeball, 16 mm from the limbus, fixation sutures are applied in 4 sectors to strengthen the sclera allograft at the end of the operation. A trephine (diameter 5 mm) is used to perforate the cornea and a clouded lens is removed through the hole formed.

The prepared keratoprosthesis is established by conducting the posterior portion of the optical element through an opening in the cornea before applying a basis on its surface (Fig. 4). The pre-prepared allograft sclera 6 is placed on top of the supporting base 2 and is fixed by tight tension to the fixation sutures in the oblique meridians. The operation is completed by the imposition of nodal sutures on the conjunctiva and the formation of a hole in the sclera allograft (Fig. 5).

The visual acuity of the operated eye in the early postoperative period was 0.4, normal adaptation of the prosthesis in the tissues of the eye and the state of vision were unchanged during 5 years of observation.

A similar methodology operated on 11 patients aged 24 to 65 years with burn dystrophic sore eyes. The initial visual acuity of the diseased eye in all patients is in the conditional category “light perception”. The state of the paired eye is from a sharpness of 0.04 to complete blindness and anophthalmos (lack of an eye). Visual acuity after surgery reached 0.01-0.09 in five patients, 0.1-0.4 in three patients, 0.8 in one patient and two patients remained the original for reasons not directly related to the operation. In one patient, six months later, a protrusion of half the area of the supporting base took place and he was reoperated.

The presented statistical results and follow-up of clinical observations indicate a relatively high consistency of operations. The device and method of its implementation does not lead to gross anatomical and physiological disturbances of the membranes of the eye, decay of the corneal tissue, rejection of the keratoprosthesis and the formation of a retrosthetic membrane. The readiness of the device and method for wide clinical use meets the criteria of the invention of "industrial applicability".

Claims (3)

1. A keratoprosthesis containing a plate support base of permeable-porous titanium nickelide, spatially curved in shape and curvature of the cornea of the eye, with a hole in the center and cylindrical optical elements placed in the hole for broadcasting and focusing the light flux, characterized in that the thickness of the plate support base gradually decreases by 20-50% in the radial direction from the hole to the periphery, porosity increases from 30-40 to 50-60%, the preferred pore size changes from 100 to 200 microns. 2. The device according to claim 1, characterized in that the optical element is placed in the hole of the plate support base with a tight fit. 3. The method of surgical treatment of cataract with keratoprosthetics using the keratoprosthesis according to claim 1, characterized in that the plate-shaped support base made of permeable-porous titanium nickelide with a cylindrical optical element mounted on it according to the curvature of the cornea is mounted onto the surface of the cornea and the allotrans are fixedly fixed sclera, superimposed on top of a plate support base.

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