Fuchs dystrophy is a disease of the organ of vision, the cause of which is the death of cells of the posterior epithelium of the cornea. Clinically manifested by a decrease in visual acuity in the morning, photophobia, hyperemia, increased lacrimation, pain syndrome. Diagnosis of endothelial corneal dystrophy includes external examination, confocal microscopy, biomicroscopy, pachymetry, visometry. Symptomatic therapy is based on instillation of hypertonic saline solutions. Surgical tactics – through or layered keratoplasty.
H18.4 Corneal degeneration
Endothelial corneal dystrophy, or Fuchs dystrophy, is a pathological condition in ophthalmology characterized by trophic disorder followed by degeneration of the cornea. The first description of primary endothelial corneal dystrophy was presented by the Austrian scientist E. Fuchs at the beginning of the twentieth century. The researcher believed that the pathology develops due to a violation of regional blood supply or innervation, hormonal imbalance.
The disease can be primary or secondary, early or late. In the early variant, endothelial corneal dystrophy can be diagnosed in children under 3 years of age. The clinic of the late variant is observed in patients over the age of 45 years. Early dystrophy occurs with the same frequency among men and women. The late form of the disease is more common among females.
Primary endothelial corneal dystrophy is a genetically determined disease. An autosomal dominant type of inheritance with incomplete or high penetrance has been established. In the early form, a mutation of the COL8A2 gene occurs, in the late form – SLC4A11 or ZEB1. At the same time, 50% of patients develop the disease sporadically.
Less often, the trigger is the dysfunction of the mitochondria of endotheliocytes, which leads to their insufficiency. The pathological process is localized in the inner layer of the cornea, whose endotheliocytes subsequently cannot divide and regenerate. The etiological role of environmental factors and systemic pathologies in the development of this disease has not been established.
The most common cause of secondary endothelial corneal dystrophy is traumatic damage to the organ of vision. The iatrogenic factor is realized during surgical intervention. The chronic course of keratitis in the absence of timely treatment contributes to the degeneration of the cornea, which is caused by damage to the endothelium. In this pathology, the inflammatory process is not an etiological factor, but only a prerequisite for the development of endothelial corneal dystrophy in genetically compromised individuals.
Compensatory hyperfunction of endotheliocytes during the progression of the disease cannot ensure the removal of excess fluid and the maintenance of corneal transparency. This is due to the sweating of the watery moisture of the anterior chamber of the eye through defects in the endothelium into the stroma of the cornea. Pronounced swelling leads to endothelial corneal dystrophy. When the edema spreads to the outer layer, bullous keratopathy occurs. Surgical interventions on the cornea due to pronounced thinning of the endothelium are often complicated by edema, which exacerbates destructive processes.
Symptoms of Fuchs dystrophy
From a clinical point of view, there are primary and secondary forms of Fuchs’ dystrophy. The primary lesion of the cornea is congenital. The first manifestations of early dystrophy are found at birth or in early childhood, but this type of disease is extremely rare. The late variant of primary Fuchs endothelial dystrophy develops more often in people after 45 years. This type of pathology is characterized by binocular, but asymmetric course. Secondary dystrophy is an acquired disease in which there is a monocular lesion.
Depending on the severity of the pathology, the clinic of endothelial corneal dystrophy may be characterized by a latent course or manifestations of bullous keratopathy. The symptoms of the disease progress slowly, so it may take about 20 years from the moment the first signs appear to the formation of a detailed clinical picture.
The first stage
At the first stage of endothelial corneal dystrophy, morphological changes affect only the central parts of the cornea. At the same time, specific collagen formations (gutta) of a teardrop-shaped, warty and mushroom-shaped form appear. There are no complaints. The only symptom of the disease is a slight decrease in visual acuity in the morning.
The second stage
At the second stage, the number of endotheliocytes decreases, corneal edema develops, single bulls appear. The sensation of a foreign body is replaced by a decrease in the sensitivity of the cornea due to degeneration of nerve endings. Specific symptoms of this stage of endothelial corneal dystrophy are represented by photophobia, hyperemia of the eyes, decreased visual acuity in the morning, followed by recovery in the evening. This is due to the fact that due to closed eyes during sleep, moisture evaporation from the cornea is not properly carried out, which leads to the deposition of fluid. During the day, the evaporation of moisture helps to reduce puffiness and resume visual functions.
The prolonged course of endothelial corneal dystrophy causes a slowly progressive decrease in visual acuity. With the spread of the pathological process to the epithelial layer and the appearance of bullous changes, patients complain of a foreign body sensation and increased tearing. Pain syndrome, accompanied by severe discomfort in the eye socket, develops with the rupture of bullae in patients with bullous keratopathy.
The third stage
At the third stage, fibrous tissue is synthesized along the epithelium of the basement membrane, followed by the formation of a pannus. The general condition improves somewhat, but the progression of endothelial corneal dystrophy further leads to the appearance of epithelial erosions, ulcers of microbial genesis and vascularization of the central part of the cornea.
Diagnosis of endothelial corneal dystrophy is based on the results of external examination, special ophthalmological studies and genodiagnostics. External examination reveals clouding of the cornea, conjunctival injection of blood vessels is possible. Crucial data is obtained using:
- Confocal microscopy of the cornea. It is the gold standard in the diagnosis of this pathology. In addition to a detailed image of the endothelium, the density of cells and their average diameter per unit area are measured. The degree of reduction in the size and number of cellular elements in endothelial corneal dystrophy depends on the severity of the disease. Specific formations (gutta) in the form of dark-colored droplets with a bright central part and near-cellular localization are also revealed. At the beginning of development, the gutta dimeter is smaller than the endotheliocyte, later they merge and look like large spots.
- Biomicroscopy. During biomicroscopy with a slit lamp, local zones of degeneration of the endothelial layer, swelling are visualized. When the edema spreads to the outer layer, specific bulls are detected on the surface of the cornea, which indicates the development of bullous keratopathy.
- Pachymetry. The thickness of the cornea is determined by the method of pachymetry. Degenerative processes in endothelial corneal dystrophy lead to its thinning (less than 0.49 mm), but with the appearance of edema, its thickness may exceed the reference values (0.56 mm).
- Visometry. With the help of visometry, the degree of visual acuity reduction is measured. In order to obtain a reliable result and indirectly determine the severity of edema, patients with endothelial corneal dystrophy are recommended to conduct studies in the morning and evening.
Treatment of Fuchs dystrophy
Symptomatic therapy of endothelial corneal dystrophy includes instillation of hypertonic saline solutions in order to reduce swelling. The removal of excess fluid from the cornea improves visual acuity. In order to relieve pain, oral administration of analgesics or their instillation is indicated. Only soft contact lenses or glasses can be used to correct visual acuity. Also, in the treatment of endothelial corneal dystrophy, corneal cross-linking is used, which is based on photopolymerization of stroma fibers using the combined action of a photosensitizing drug and ultraviolet radiation.
Severe course of endothelial corneal dystrophy, accompanied by a marked decrease in visual acuity, severe thinning of the cornea according to pachymetry and low cell density per unit area according to confocal microscopy results, is an indication for keratoplasty. An end-to-end surgical intervention is indicated for a total dystrophic process. Layered keratoplasty is recommended for patients in case of damage to one or more layers of the cornea. At the same time, the descemet membrane is often transplanted together with the endothelium.
Prognosis and prevention
The prognosis for early diagnosis and treatment is favorable for life and work capacity. The absence of therapy can lead to complete loss of vision and disability of the patient. Specific measures for the prevention of endothelial corneal dystrophy have not been developed, since the disease is genetically determined. Non-specific preventive measures are reduced to the prevention of traumatic injuries in genetically compromised individuals, screening in newborns, timely diagnosis and treatment of ophthalmic pathology. All patients with an established diagnosis of endothelial corneal dystrophy need to be examined by an ophthalmologist 2 times a year.