Corneal endothelial dystrophy affects the innermost layer of the cornea, the transparent front part of the eye. This layer, known as the endothelium, plays a direct role in maintaining the cornea’s clarity. When the endothelial cells do not function correctly, fluid can accumulate within the cornea, leading to swelling and a loss of transparency. This change in corneal clarity can progressively impair vision, causing it to become hazy or distorted over time. The condition typically progresses slowly, impacting an individual’s sight gradually.
Understanding the Cornea and Endothelium
The cornea serves as the eye’s outermost lens. It is a transparent, dome-shaped structure composed of several distinct layers, each with a specialized function. The innermost layer, the endothelium, is a single layer of cells lining the back surface of the cornea.
These endothelial cells are responsible for pumping excess fluid out of the corneal stroma. This pumping action maintains the cornea in a relatively dehydrated state, which is necessary for its transparency. Unlike many other cells in the body, corneal endothelial cells do not regenerate significantly if damaged or lost. A healthy density of these cells is maintained to ensure proper fluid balance.
Forms of Corneal Endothelial Dystrophy
Fuchs’ endothelial dystrophy being the most frequently encountered. This condition is characterized by the gradual deterioration of endothelial cells and the formation of small, wart-like deposits called guttata on Descemet’s membrane, located just beneath the endothelial layer. Guttata can disrupt the normal pumping function of the endothelial cells, leading to corneal swelling and blurred vision. Fuchs’ dystrophy typically affects both eyes, often showing greater severity in one eye compared to the other.
Posterior Polymorphous Corneal Dystrophy (PPCD) represents another form, where endothelial cells exhibit abnormal growth patterns, sometimes resembling epithelial cells. These cells can form vesicles, bands, or diffuse opacities on the posterior corneal surface, potentially leading to corneal edema and even glaucoma in some cases. Congenital Hereditary Endothelial Dystrophy (CHED) is a rare, inherited condition that presents at birth or in early infancy, causing significant corneal clouding due to widespread endothelial dysfunction. Both PPCD and CHED are genetic conditions, often inherited in an autosomal dominant or recessive pattern.
Recognizing the Signs and Symptoms
Individuals experiencing corneal endothelial dystrophy often notice a gradual onset of visual changes, often beginning with blurred vision. This blurring may be more pronounced upon waking in the morning and tends to improve throughout the day. The temporary morning blur occurs because fluid accumulates in the cornea overnight while the eyelids are closed, reducing the normal evaporation process. As the day progresses, the fluid may evaporate, leading to some clearing of vision.
Over time, as the condition advances, the blurred vision can become constant and more severe, no longer clearing during the day. People may also report experiencing glare or seeing halos around lights, particularly at night, which can make driving challenging. A feeling of grittiness or the sensation of a foreign body in the eye is also common, along with eye pain, especially if the corneal swelling leads to the formation of small blisters (bullae) on the surface that can rupture. The progression of these symptoms varies among individuals, but they typically worsen over years.
Diagnostic Approaches
Diagnosing corneal endothelial dystrophy begins with a comprehensive eye examination. This examination allows the clinician to assess overall eye health and visual acuity. A specialized instrument called a slit-lamp biomicroscope is then used to closely examine the cornea under high magnification. During this examination, the presence of guttata, which are small, distinct bumps on the back surface of the cornea, can be observed, along with any signs of corneal swelling or clouding.
Pachymetry measures corneal thickness, often using ultrasound or optical methods. An increase in corneal thickness can indicate fluid accumulation. Specular microscopy may also be utilized to capture images of the endothelial cell layer. This imaging allows for the counting of endothelial cells and an assessment of their size and shape, providing insights into the health and density of these cells.
Treatment Strategies
Treatment aims to manage symptoms and, in advanced cases, restore corneal clarity. Non-surgical approaches are often the initial step for milder symptoms. Hypertonic saline solutions, available as eye drops or ointments, can help draw excess fluid out of the cornea, reducing swelling and improving vision. Soft contact lenses may also be prescribed to act as a bandage, protecting the corneal surface from discomfort caused by epithelial blisters.
When vision significantly declines and conservative measures are no longer effective, surgical intervention becomes an option. Descemet’s Stripping Endothelial Keratoplasty (DSEK) and Descemet’s Membrane Endothelial Keratoplasty (DMEK) are modern partial-thickness corneal transplantation procedures. In DSEK, a thin layer of donor corneal tissue, including the endothelium, is transplanted, while DMEK involves transplanting an even thinner layer consisting almost entirely of Descemet’s membrane and the endothelial cells. These procedures replace the dysfunctional endothelial cells with healthy donor cells, which then begin pumping fluid, allowing the cornea to clear. Traditional penetrating keratoplasty (PKP), a full-thickness corneal transplant, is a less common option today for endothelial dystrophies but may be considered in complex cases where other corneal layers are also affected.