Corneal dystrophy (degeneration)

Corneal dystrophy (degeneration, keratopathy) is a chronic disease that is based on a violation of general or local metabolic processes.

The nature of corneal dystrophy may be different: family-hereditary factors, autoimmune, biochemical, neurotrophic changes, trauma, consequences of inflammatory processes, etc. The initial link of the lesion may remain unknown. Primary and secondary corneal dystrophies are distinguished.

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Familial hereditary corneal dystrophy

Primary corneal dystrophies are usually bilateral. Among them, the main place is occupied by familial and hereditary degenerations. The disease begins in childhood or adolescence, progresses very slowly, as a result of which it can remain unnoticed for a long period of time. The sensitivity of the cornea gradually decreases, there are no signs of eye irritation and inflammatory changes. During biomicroscopic examination, very delicate opacities in the central part of the cornea are initially detected, having the appearance of small nodules, spots or stripes. Pathological inclusions in the cornea are most often located in the superficial layers of the stroma, sometimes subepithelial. The anterior and posterior epithelium, as well as the elastic membranes of the cornea do not change. The peripheral parts of the cornea may remain transparent, there are no newly formed vessels. By the age of 30-40, a decrease in vision becomes noticeable, the corneal epithelium begins to change. Periodic listening to the epithelium causes pain, photophobia, and blepharospasm.

Different types of hereditary corneal dystrophies differ from each other mainly by the shape and location of focal changes in the cornea. Nodular, spotted, lattice and mixed dystrophies are known. The hereditary nature of these diseases was established at the beginning of the last century.

In Ukraine and Russia, this pathology is rare (less common than in other European countries).

Treatment of familial hereditary dystrophies is symptomatic. Vitamin drops and ointments, drugs that improve corneal trophism are prescribed: balarpan, taufon, adgelon, emoxipin, etaden, retinol, solcoseryl gel, actovegin; multivitamins are taken orally. Conservative treatment does not stop the progression of the disease. In case of significant vision loss, layer-by-layer or penetrating keratoplasty is performed. The best optical result is achieved by penetrating corneal transplantation. Familial hereditary dystrophy is the only type of corneal pathology that recurs in the donor transplant. 5-7 years after the operation, single nodules or stripes of delicate opacities appear on the periphery of the transparent transplant, the same as those in the patient's own cornea. Their number slowly increases, and vision gradually deteriorates. After 10-15 years, a repeat corneal transplant has to be performed, which in most cases takes well, providing high visual acuity.

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Epithelial (endothelial) corneal dystrophy

Epithelial (endothelial) corneal dystrophy (synonyms: edematous, epithelial-endothelial, endothelial-epithelial, bullous, deep dystrophy) can be either primary or secondary. For a long time, the cause of this disease remained unknown. At present, no one doubts the fact that primary edematous corneal dystrophy occurs when the barrier function of the single-row layer of posterior epithelial cells fails, caused by dystrophic changes in the cells or a critically small number of them (less than 500-700 cells in 1 mm ² ).

Mirror biomicroscopy allows us to detect subtle initial changes when the cornea is still transparent and there is no edema. They can also be diagnosed with regular biomicroscopy if you carefully examine the back surface of the cornea in a thin light section. Normally, the cells of the back corneal epithelium are not visible because they are very small. When the number of cells decreases significantly, the remaining cells flatten and stretch to cover the entire back surface of the cornea. The size of the cells increases by 2-3 times, so they can already be seen with biomicroscopy. The back surface of the cornea becomes similar to misted glass. This phenomenon is called drop cornea (cornea guttata). Currently, there are no ways to radically change this condition, but early diagnostics of the precursors of an impending disease allows for the correct planning of treatment of the associated pathology, for example, choosing the method of cataract extraction that is most sparing to the posterior surface of the cornea, refusing to insert an artificial lens (or finding the right model) and, what is very important, entrusting the operation to the most experienced surgeon. By eliminating or reducing the trauma to the cells of the posterior corneal epithelium, it is possible to postpone the development of edematous dystrophy for several months or years.

The presence of the symptom of corneal droplet does not mean the onset of the disease (the cornea is transparent and not thickened), but it is evidence that the functional capabilities of the cells of the posterior corneal epithelium are close to the limit. The loss of a small number of cells is enough to form non-closing defects. This can be facilitated by infectious diseases, contusions, injuries, especially abdominal surgeries.

In cases where gaps appear between the cells of the posterior corneal epithelium, intraocular fluid begins to saturate the corneal stroma. The edema gradually spreads from the posterior layers to the entire cornea. Its thickness in the center can increase almost 2 times. At the same time, visual acuity is significantly reduced due to the fact that the fluid moves the corneal plates apart, as a result of which their strict order is disrupted. Later, edematous dystrophy spreads to the anterior corneal epithelium. It becomes rough, swells in the form of bubbles of various sizes, which easily peel off from the Bowman's membrane, burst, exposing the nerve endings. A pronounced corneal syndrome appears: pain, foreign body sensation, photophobia, lacrimation, blepharospasm. Consequently, dystrophy of the anterior epithelium is the final stage of edematous corneal dystrophy, which always begins with the posterior layers.

The condition of the posterior corneal epithelial cell layer is usually the same in both eyes. However, corneal edematous dystrophy develops first in the eye that was subjected to trauma (domestic or surgical).

Treatment of edematous corneal dystrophy is initially symptomatic. Decongestants are prescribed instillations (glucose, glycerin), as well as vitamin drops and agents that improve corneal trophism (balarpan, glecomen, carnosine, taufon). When the swelling reaches the corneal epithelium, antibacterial agents in the form of drops and ointments are necessarily added, as well as an oil solution of tocopherol, solcoseryl gel, actovegin, vitamin ointments that improve epithelial regeneration. Ointment preparations and therapeutic contact lenses serve as a kind of bandage for the cornea, protect open nerve endings from external irritations, and relieve pain.

Low-energy laser stimulation of the cornea with a defocused beam of a helium-neon laser gives a good therapeutic effect.

Conservative treatment provides only a temporary positive effect, so it is repeated periodically as the condition of the cornea worsens.

A radical method of treatment is penetrating subtotal keratoplasty. The donor transplant remains transparent in 70-80% of cases, provides the possibility of improving visual acuity and has a therapeutic effect on the remaining edematous rim of the patient's own cornea, which may be translucent, but its surface becomes smooth, the edema disappears. After 1-2 months, the corneas of the donor and recipient have the same thickness.

Long-term epithelial (endothelial) corneal dystrophy is usually combined with dystrophic changes in the retina, so even with ideal transparency of the donor transplant, one cannot count on the highest possible visual acuity: it is in the range of 0.4-0.6.

Secondary epithelial (endothelial) corneal dystrophy occurs as a complication of eye cavity surgeries, injuries or burns.

The clinical manifestations of primary and secondary edematous corneal dystrophy are very similar, but there are also significant differences. Usually one eye is affected. The underlying cause of the edema is always traceable - domestic, industrial or surgical trauma. The main difference is that corneal edema occurs in a limited area corresponding to the place of contact with the traumatic agent, and around this area there are healthy cells of the posterior corneal epithelium, capable of replacing the defect.

Through a defect in the posterior epithelial cell layer, intraocular fluid penetrates into the corneal stroma. Local edema gradually reaches the superficial layers and the anterior epithelium. In cases where the pathological focus is not in the center of the cornea, visual acuity may decrease slightly. When bullous dystrophy of the anterior epithelium occurs, irritation of the eyeball in the sector of the pathological focus, pain, photophobia, lacrimation, and blepharospasm occur.

Treatment is the same as for primary corneal dystrophy. The swelling begins to decrease after 7-10 days, when the corneal wound heals. In the secondary form of dystrophy, complete healing of the lesion and disappearance of the swelling are possible. This requires a different period of time - from one to several months, depending on the density of cells and the area of damage to the posterior epithelium, as well as on the rate of healing of the general corneal wound.

If a foreign body, such as the supporting element of an artificial lens, periodically touches the back surface of the cornea, the swelling increases and the pain increases, despite any treatment measures. In this case, it is necessary to either fix the lens (sew it to the iris) or remove it if its design is imperfect.

Fixed (constant) contact of the lens support element does not cause corneal edematous dystrophy and does not require its removal unless there are other reasons for this. With fixed contact, when the lens support is enclosed in the corneal and iris scar, new damage to the posterior corneal epithelium no longer occurs, unlike the situation with periodically repeated contacts.

Secondary edematous corneal dystrophy may occur in an eye with an artificial lens, where there is no contact between the lens body or its supporting parts and the cornea. In this case, removing the lens does not provide a therapeutic effect, but, on the contrary, will be an additional trauma for the diseased cornea. The lens should not be "punished" if it is "not to blame" for the occurrence of corneal edema. In this case, the cause of secondary edematous dystrophy should be sought in the trauma of the operation itself.

Recovery may occur under the influence of the above treatment measures, but a more or less dense opacity always remains at the site of the edema. In severe cases, when edematous dystrophy affects the entire cornea or its center and conservative therapy does not give a positive result for a long time, penetrating subtotal keratoplasty is performed, but not earlier than 1 year after surgery or eye injury. The less thickened the cornea, the more hope for a favorable outcome of the operation.

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Band-shaped corneal dystrophy (degeneration)

Band corneal dystrophy (degeneration) is a slowly increasing superficial clouding in blind or visually impaired eyes.

Band-shaped corneal dystrophy develops several years after severe iridocyclitis, choroiditis in eyes blinded by glaucoma or severe trauma. Opacities arise against the background of altered sensitivity of the cornea, decreased mobility of the eyeball and decreased metabolic processes in the eye. With increasing atrophy of the muscular apparatus, involuntary movements of the eyeball (nystagmus) appear. Opacities are located superficially in the area of Bowman's membrane and the anterior epithelium. The corneal stroma and posterior layers remain transparent. Changes begin on the periphery of the cornea at the inner and outer edges and, slowly increasing, move to the center within the open eye slit in the form of a horizontally located band. Above, where the cornea is covered by the eyelid, it always remains transparent. Opacities are distributed unevenly, there may be islands of a transparent surface of the cornea, but over time they also close. Band-like degeneration is characterized by the deposition of calcareous salts, so the surface of the cornea becomes dry and rough. If such changes have been going on for a long time, thin plates of keratinized epithelium, impregnated with salts, can be rejected on their own. The raised salt outgrowths injure the mucous membrane of the eyelid, so they must be removed.

Coarse opacities and salt deposits in the cornea are formed against the background of pronounced general trophic changes in the blind eye, which can lead to subatrophy of the eyeball. There are known cases when calcareous deposits were formed not only in the cornea, but also along the vascular tract of the eye. Ossification of the choroid occurs.

Such eyes are subject to removal with subsequent cosmetic prosthetics. In eyes with residual vision, superficial keratectomy (cutting off the cloudy layers) is performed within the optical zone of the cornea (4-5 mm). The exposed surface is covered with epithelium growing from the undamaged upper part of the cornea, and can remain transparent for several years if the patient regularly instills drops that maintain corneal trophism and applies ointments that prevent keratinization of the epithelium.

Ribbon-shaped corneal dystrophy in children, combined with fibrinous-plastic iridocyclitis and cataracts, is characteristic of Still's disease (Still's syndrome). In addition to the triad of eye symptoms, polyarthritis, enlargement of the liver, spleen, and lymph glands are noted. After a course of anti-inflammatory treatment for iridocyclitis, cataract extraction is performed. When corneal opacities begin to cover the central zone, a decision is made to perform keratectomy. Treatment of the underlying disease is performed by a therapist.

Corneal marginal dystrophy (degeneration)

Marginal corneal dystrophy (degeneration) usually occurs in both eyes, develops slowly, sometimes over many years. The cornea becomes thinner near the limbus, forming a crescent-shaped defect. Neovascularization is absent or slightly expressed. With pronounced thinning of the cornea, its sphericity is disrupted, visual acuity decreases, areas of ectasia appear, due to which there is a risk of perforation. Conventional drug treatment gives only a temporary effect. A radical method of treatment is marginal layer-by-layer corneal transplantation.

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