Fuchs’ Endothelial Dystrophy
Fuchs endothelial dystrophy is characterized by an asymmetrical, bilateral, slowly progressive edema of the cornea in elderly patients. When inherited, the transmission is autosomal dominant. The root cause of the condition is a slowly progressive formation of guttate lesions between the corneal endothelium and the Descemet membrane. These wartlike, anvil-shaped or mushroom-shaped excrescences are said to be abnormal elaborations of basement membrane and fibrillar collagen by distressed or dystrophic endothelial cells. As the lesions enlarge, the covering endothelial cells initially become stretched, and they eventually fall off. Examples are shown in the images below.
Growth of cornea guttata progresses from the center of the cornea to the periphery. As the endothelial cells fall, the remaining cells enlarge to cover the gap. With the reduced number of endothelial cells, the pump function suffers. Endothelial cell attrition rises with increasing number and size of the guttate lesions. Cornea guttata may be discovered accidentally or when specular endothelial microscopy is performed to find out the cause of the visual disturbance.Studies have indicated the possibility of associated anterior stromal changes in the form of keratocyte depletion in this condition.
Fuchs endothelial dystrophy passes through 3 clinical stages. These stages evolve over a period of 2 or 3 decades. The changes are bilateral but usually asymmetric.
This stage is cornea guttata. It occurs in the fourth or fifth decade of life. Slit lamp examination by specular reflection may show cornea guttata in the central part of the corneal endothelium. Examples are shown in the images below.
Some pigment dusting also may be seen. The excrescences of corneal guttata increase in number and may become confluent, resulting in a beaten metal appearance of the endothelial surface. The condition spreads from the center toward the periphery.
The patient usually has no complaints at this stage. Some very observant patients notice that the quality of their 20/20 vision is not the same as before. A slit lamp examination of the endothelium leads to the diagnosis.
This stage is characterized by increasing visual and other problems, caused by incipient edema of the corneal stroma initially and later the epithelium. The patient sees halos around lights and also experiences blurred vision and glare. Tiny droplets of corneal epithelial edema (bedewing) are best seen using retroillumination. The epithelial microcysts later coalesce and form bullae; hence, the name bullous keratopathy. The bullae rupture and expose the cornea to the danger of infectious keratitis. The patient experiences foreign body sensation and pain. Corneal sensitivity is reduced by the destruction of the epithelial nerve endings.
Slit lamp examination shows typical changes quite early. The posterior corneal lamellae are first to become edematous. They cause wrinkling in the Descemet membrane, termed striae. Epithelial edema is seen later.
In this stage, subepithelial connective tissue and pannus formation along the epithelial basement membrane are present. The periphery of the cornea becomes vascularized. A reduction of bullae formation occurs. The epithelial edema is reduced, so that the patient is more comfortable. However, the stromal edema remains. The epithelial layer is strengthened by the underlying pannus and fibrous tissue.
No medical treatment is known to prevent or stop the formation of cornea guttata. Hyperosmotic drops and ointment and bandage contact lenses may help for a time. Once the vision becomes adversely affected, a penetrating graft is advised at the convenience and the need of the patient. A deep lamellar endothelial graft is new, potentially effective alternate technique. The results of surgery in Fuchs endothelial dystrophy are excellent in most cases.