Diseases of the cornea

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

Due to the fact that the cornea is part of the outer capsule of the eye, it is exposed to all unfavorable environmental factors.

[1], [2], [3]

Epidemiology

According to statistics, out of all patients who come to an outpatient clinic, every fourth person has 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 also reduced visual acuity. Diseases of the cornea are one of the main causes of blindness and vision.

[4], [5], [6], [7],

Causes of the diseases of the cornea

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

[8], [9], [10],

Pathogenesis

The peculiarities of the structure, anastomosing and innervation of the marginal loopy network of vessels around the cornea are explained by its rapid response to the development of the pathological process in sclera, conjunctiva, iris and ciliary body. In the conjunctival cavity, communicating through the tear ducts with the nasal cavity, there is always a microflora. The slightest trauma of the epithelium of the cornea is sufficient to open the entrance 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 slow.

[11], [12], [13], [14], [15], [16]

Symptoms of the diseases of the cornea

Point epithelial erosions are small, somewhat concave epithelial defects, stained with fluorescein, but they are not distinguishable when stained with Bengal pink. Point epithelial erosion is a nonspecific symptom of corneal diseases and can develop with various keratopathies. Localization of erosion can often indicate the etiology of the disease.

• upper limb: with spring catarrh, upper limbal keratoconjunctivitis, atony of eyelids and poorly selected contact lenses;
• section of the cornea between the edges of the eyelids (with open eyes); with dry eye syndrome, decreased corneal sensitivity and exposure to ultraviolet rays;
• at the lower limb: with diseases of the edge of the lower eyelid, lagophthalmus, rosacea keratitis, toxic effects of drops.

Epithelial epithelial keratitis is a typical sign of viral infections. Characteristic is the detection of granular, opalescent, swollen epithelial cells, visible without staining. These defects of the epithelium are well colored by Bengal pink, but badly by fluorescein.

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

Signs of threads:

• Thin, comma-shaped, mucous filaments lying on the epithelium are connected at one end to the surface of the cornea, the other end is free to move when blinking. At the location of the filament attachment, a subepithelial, semitransparent region of gray color can be detected.
• The filaments are well colored with Bengal pink, but not fluorescein, because fluorescein accumulates between cells, and Bengal pink stains dead and degenerate cells and mucus.

The causes of the development of threads:

Keratoconjunctivitis with dry eye syndrome, upper limbal keratoconjunctivitis, recurrent erosion syndrome, surgical eye interventions, lagophthalmia, decreased corneal sensitivity, herpes zoster ophthalmicus, acute cerebrovascular accident in the middle brain and essential blepharospasm.

Pannus - subepithelial ingrowth of fibrovascular tissue of limbus of inflammatory or degenerative genesis. The progressive pannus is characterized by the presence of infiltration along the course of the growing vessels. With regressive pannus, the vessels spread beyond the infiltrate.

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

Symptoms of corneal stromal infiltrates

• Focal, granular opacification of light gray color, most often in the anterior layers of the stroma, combined, as a rule, with hyperemia of the limbus or conjunctiva.
• Around the main focus is a corolla of less dense infiltration, where in some cases single inflammatory cells are discernible.

Causes of corneal stromal infiltrates

• Non-infectious (for example, sensitivity to antigens), arise when wearing contact lenses and marginal keratitis.
• Infectious keratitis caused by bacteria. Viruses, fungi and protozoa.

Symptoms of corneal stromal edema : optical cavities between stroma plates associated with increased corneal thickness, and reduced transparency due to structural disturbances in stroma architecture;

Causes of edema of the corneal stroma: disciform keratitis, keratoconus, Fuchs dystrophy and corneal endothelium damage as a result of surgical interventions.

Vascularization occurs with various diseases of the cornea. With biomicroscopy, venous vessels of the cornea are always distinguishable, but arterial vessels are difficult to see without fluorescent angiography. Deep vessels move away from the anterior ciliary vessels and go straight in the radial direction, disappearing at the limb, in contrast to the tortuous surface vessels that can be detected outside the limb. The emptied deep vessels of the cornea are discernible in reflected light in the form of "shadows" of blood vessels.

1. Gaps - as a result of stretching the cornea, congenital trauma and keratoconus, which leads to a rapid inflow of fluid into the stroma of the cornea.
2. The folds (banded keratopathy) can be caused by surgical trauma, eye hypotension, inflammation and edema of the stroma.

[17], [18]

Forms

Among the various types of pathology of the cornea, the main place is occupied by inflammatory diseases (keratitis) and dystrophy. In addition, the cornea is exposed to injuries and burns. Tumors of the cornea develop rarely.

The following forms of corneal diseases are distinguished:

• keratitis and their consequences;
• dystrophy;
• tumors;
• anomalies of quantities and shapes.

Keratites and their consequences account for 20-25% of outpatients.

[19], [20], [21]

Diagnostics of the diseases of the cornea

The front view and details in the corneal cut are documented as follows.

The opacities of the cornea (scar or other degenerative changes) are depicted in black.

Edema of the epithelium - blue thin circles, edema of the stroma - blue hatching, folds of the Descemet's membrane - wavy blue lines.

Hypopion is represented in yellow.

Blood vessels - in red. The surface vessel is a wavy lily that starts outside the limb, and a deep vessel - in the form of a straight line whose origin is denoted by the limb.

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

For the diagnosis of diseases of the cornea use the method of external examination, side lighting. The maximum information about the localization of the inflammation focus, the depth of its occurrence, the nature of infiltration and the reaction of external tissues can be obtained by studying the light cut of the cornea with biomicroscopy with sufficient magnification. It is important to study the sensitivity of the cornea. The cause of the defeat of the cornea can be inside the body. It needs to be established, and then treatment aimed at eliminating the cause of the disease, combined with local therapy will be most effective.

[22], [23]

Treatment of the diseases of the cornea

Antibacterial and anti-inflammatory agents:

1. Antibacterial drugs can be used for corneal infections after preliminary studies. Collagen films can be used to improve the delivery of the drug. The film resembles a conventional soft contact lens, is in a dehydrated form and requires rehydration before use.
2. Local glucocorticoids are used to suppress inflammation and scarring, although their inappropriate use can support microbial growth. It is also possible to suppress the regeneration of the cornea, provoke ulceration and perforation. Local steroids are contraindicated with simple herpes in the acute phase.
3. Systemic immunosuppressive drugs are used in some forms of severe peripheral ulceration of the cornea and its thinning associated with systemic involvement of connective tissue.

Preparations that accelerate the regeneration of the corneal epithelium:

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

1. Artificial tears and ointments should not contain potentially toxic (eg, benzalkonium) or corneal-enhancing preservatives (for example, thiomersal).
2. Closing of the eyelids is an extraordinary measure for neuroparalytic and neurotrophic keratopathies, as well as in the eyes with persistent epithelial defects.
   • Temporary gluing of eyelids by means of tapes Blenderm or Transpore.
   • Injection of toxin CI. Botulinurn in m. Levator palpebrae in order to create a temporary ptosis.
   • Lateral tarsorphia or plastic medial angle of the eye.
3. Bandage soft contact lenses improve healing, mechanically protecting the regenerating epithelium of the cornea in the conditions of permanent traumatization for centuries.
4. The transplantation of the amniotic membrane may be appropriate to close the persistent, non-susceptible epithelial defect.

Other methods of treating cornea diseases

1. Adhesive tissue adhesive (cyanoacrylate) is used to limit stromal ulceration and close small perforations. The glue is applied to a synthetic plate, which is then applied to the area of thinning or perforation and covered with a bandage contact lens.
2. Closure of progressive and non-treatable ulcers with a conjunctival flap of Gundersen is used in a unilateral chronic process with a low probability of restoring vision.
3. Transplantation of limbal stem cells is used in case of their deficiency, for example, with chemical burn or cicatrizing conjunctivitis. The source of the donor tissue can be a paired eye (autograft) with one-sided pathology, another person's eye, or a cadaver (allograft), when both eyes are involved in the process.
4. Keratoplasty is performed to restore the transparency of the cornea.