Corneal diseases

Corneal diseases account for 25-30% of all eye diseases.

Since the cornea is part of the outer capsule of the eye, it is exposed to all adverse environmental factors.

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Epidemiology

According to statistics, every fourth patient coming to an outpatient appointment has a corneal disease. The social significance of corneal diseases is explained not only by the high frequency of development, but also by the duration of treatment, frequent relapses, and decreased visual acuity. Corneal diseases are one of the main causes of blindness and low vision.

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Causes corneal diseases

1. open position of the cornea (accessible to external factors);
2. anatomical and embryonic connection with the conjunctiva, sclera and vascular tract;
3. absence of vessels in the cornea and slow metabolism;
4. constant influence of the microflora of the cojunctival sac and lacrimal sac on the cornea.

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Pathogenesis

The peculiarities of the structure, anastomosis and innervation of the marginal looped network of vessels around the cornea explain its rapid response to the development of the pathological process in the sclera, conjunctiva, iris and ciliary body. The conjunctival cavity, communicating through the lacrimal ducts with the nasal cavity, always contains microflora. The slightest injury to the corneal epithelium is enough to open the entry gate for infection.

The cornea is easily involved in the pathological process and slowly emerges from it, since it has no vessels. All metabolic processes in the cornea are slowed down.

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Symptoms corneal diseases

Punctate epithelial erosions are small, slightly concave epithelial defects that stain with fluorescein but are not visible with rose bengal. Punctate epithelial erosions are a non-specific sign of corneal diseases and can develop with various keratopathies. The localization of erosions can often indicate the etiology of the disease.

• at the upper limbus: with vernal catarrh, upper limbal keratoconjugative...
• the area of the cornea between the edges of the eyelids (with open eyes); in case of dry eye syndrome, decreased sensitivity of the cornea and exposure to ultraviolet rays;
• at the lower limbus: for diseases of the edge of the lower eyelid, lagophthalmos, rosacea keratitis, toxic effects of drops.

Punctate epithelial keratitis is a typical sign of viral infections. It is characterized by the discovery of granular, opalescent, swollen epithelial cells, visible without staining. These epithelial defects stain well with rose bengal, but poorly with fluorescein.

Edema of the corneal epithelium is a sign of endothelial decompensation or a significant and rapid increase in intraocular pressure. The cornea loses its characteristic shine, and in severe cases, small (vesicles) and small (bullae) bubbles may appear.

Signs of threads:

• Thin, comma-shaped mucous threads lying on the epithelium are connected at one end to the surface of the cornea, the other end moves freely when blinking. At the point of attachment of the thread, a subepithelial translucent gray area can be found.
• The threads are stained well with rose bengal, but not with fluorescein, since fluorescein accumulates between cells, and rose bengal stains dead and degeneratively altered cells and mucus.

Reasons for the development of threads:

Keratoconjunctivitis in dry eye syndrome, superior limbal keratoconjunctivitis, recurrent erosion syndrome, ocular surgery, lagophthalmos, decreased corneal sensitivity, herpes zoster ophthalmicus, acute cerebrovascular accident in the midbrain, and essential blepharospasm.

Pannus is a subepithelial ingrowth of fibrovascular tissue of the limbus of inflammatory or degenerative origin. Progressive pannus is characterized by the presence of infiltration along the course of the ingrowing vessels. In regressive pannus, the vessels extend beyond the infiltrate.

Infiltrates are areas of active inflammation of the corneal stroma, consisting of accumulations of leukocytes and cellular detritus.

Signs of corneal stromal infiltrates

• Focal, granular opacity of a light gray color, most often in the anterior layers of the stroma, usually combined with hyperemia of the limbus or conjunctiva.
• Around the main focus there is a rim of less dense infiltration, where in some cases single inflammatory cells can be seen.

Causes of development of corneal stromal infiltrates

• Non-infectious (eg, sensitivity to antigens), occur when wearing contact lenses and marginal keratitis.
• Infectious keratitis caused by bacteria, viruses, fungi and protozoa.

Signs of corneal stromal edema: optical voids between the stromal plates associated with an increase in the thickness of the cornea, and a decrease in transparency due to a violation of the stromal architecture;

Causes of corneal stromal edema include dysciform keratitis, keratoconus, Fuchs dystrophy, and corneal endothelial damage due to surgery.

Vascularization is seen in various corneal diseases. Corneal venous vessels are always visible on biomicroscopy, but arterial vessels are difficult to see without fluorescein angiography. Deep vessels arise from the anterior ciliary vessels and run straight radially, disappearing at the limbus, in contrast to the tortuous superficial vessels that can be found beyond the limbus. Deserted deep corneal vessels are visible in reflected light as vessel "shadows."

1. Tears - result from corneal stretching, congenital trauma and keratoconus, which leads to rapid fluid leakage into the corneal stroma.
2. Folds (band keratopathy) can be caused by surgical trauma, ocular hypotony, inflammation and stromal edema.

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Forms

Among the various types of corneal pathology, the main place is occupied by inflammatory diseases (keratitis) and dystrophies. In addition, the cornea is subject to injuries and burns. Corneal tumors develop rarely.

The following forms of corneal diseases are distinguished:

• keratitis and its consequences;
• dystrophies;
• tumors;
• anomalies of size and shape.

Keratitis and its consequences account for 20-25% of outpatients.

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Diagnostics corneal diseases

The frontal view and details in the corneal section are documented as follows.

Corneal opacities (scars or other degenerative changes) are depicted in black.

Edema of the epithelium is indicated by thin blue circles, edema of the stroma is indicated by blue shading, folds of Descemet's membrane are indicated by wavy blue lines.

The hypopyon is represented in yellow.

Blood vessels are in red. The superficial vessel is a wavy lily starting beyond the limbus, and the deep vessel is in the form of a straight line, the beginning of which is indicated at the limbus.

Pigmentation in the form of rings (iron deposits and spindle Krukenbcrg) is depicted in brown.

To diagnose corneal diseases, the method of external examination and lateral illumination is used. Maximum information about the localization of the inflammation site, its depth, the nature of infiltration and the reaction of external tissues can be obtained by examining the light section of the cornea during biomicroscopy with sufficient magnification. The study of corneal sensitivity is of great importance. The cause of corneal damage may be inside the body. It must be established, and then treatment aimed at eliminating the cause of the disease, in combination with local therapy, will be most effective.

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Treatment corneal diseases

Antibacterial and anti-inflammatory agents:

1. Antibacterial drugs can be used for corneal infections after preliminary examination. Collagen films can be used to improve drug delivery. The film is shaped like a regular soft contact lens, is in a dehydrated form and requires rehydration before use.
2. Topical glucocorticoids are used to suppress inflammation and limit scarring, although inappropriate use may promote microbial growth. Corneal regeneration may also be inhibited, causing ulceration and perforation. Topical steroids are contraindicated in acute herpes simplex.
3. Systemic immunosuppressive drugs are used in some forms of severe peripheral corneal ulceration and thinning associated with systemic connective tissue disease.

Drugs that accelerate the regeneration of corneal epithelium:

In eyes with thin stroma, it is important to accelerate the process of epithelial regeneration, since stromal thinning progresses more slowly with intact epithelium.

1. Artificial tears and ointments should not contain potentially toxic (eg, benzalkonium) or corneal sensitizing (eg, thiomersal) preservatives.
2. Eyelid closure is an emergency measure in neuroparalytic and neurotrophic keratopathies, as well as in eyes with persistent epithelial defects.
   • Temporary eyelid adhesion using Blenderm or Transpore tapes.
   • Injection of CI botulinurn toxin into the levator palpebrae muscle to create temporary ptosis.
   • Lateral tarsorrhaphy or medial angle plastic surgery.
3. Bandage soft contact lenses improve healing by mechanically protecting the regenerating corneal epithelium under conditions of constant eyelid trauma.
4. Amniotic membrane grafting may be useful for closure of persistent, treatment-resistant epithelial defects.

Other methods of treating corneal diseases

1. Tissue adhesive (cyanoacrylate) is used to limit stromal ulceration and seal small perforations. The adhesive is applied to a synthetic wafer, which is then placed over the area of thinning or perforation and covered with a bandage contact lens.
2. Closure of a progressive and intractable ulcer with a Gundersen conjunctival flap is used in the case of a unilateral chronic process with a low probability of vision restoration.
3. Limbal stem cell transplantation is used in cases of their deficiency, such as chemical burns or cicatricial conjunctivitis. The donor tissue source may be a fellow eye (autotransplant) in case of unilateral pathology, another person's eye, or a cadaveric eye (allograft) if both eyes are involved.
4. Keratoplasty is performed to restore transparency to the cornea.