Fuchs Dystrophy is a progressive corneal disorder affecting the endothelium, the layer of cells responsible for maintaining the cornea’s fluid balance. These endothelial cells act like pumps, actively removing fluid to keep the cornea clear and transparent. When Fuchs Dystrophy causes these cells to deteriorate, the cornea swells, leading to cloudy vision. Diagnosis relies on observing specific cellular damage and measuring the resulting corneal swelling.
Recognizing Visual Symptoms
Diagnosis often begins when a patient reports specific changes in vision. A hallmark symptom is blurry or hazy vision that is noticeably worse upon waking up in the morning. This occurs because, during sleep, the natural evaporation of fluid from the cornea is reduced, allowing excess fluid to accumulate.
As the day progresses and the eyes remain open, the surface fluid evaporates, which can temporarily improve vision in the early stages. Patients may also experience increased glare sensitivity and see halos or starbursts around lights, particularly when driving at night. These visual disturbances result from light scattering caused by microscopic changes on the back surface of the cornea. Other symptoms include a reduced ability to see contrast and, in advanced cases, a gritty feeling in the eye.
Slit Lamp Examination
After discussing symptoms, the specialist performs a detailed examination using a slit lamp. This specialized microscope directs a narrow beam of light onto the cornea, providing a highly magnified, three-dimensional view of its layers. The most definitive visual sign the clinician looks for is the presence of corneal guttata.
Guttata are tiny, wart-like deposits of abnormal collagen that form on the inner layer of the cornea (the Descemet membrane) due to failing endothelial cells. They appear as small, dark spots against the light, often described as having a “beaten metal” appearance. The distribution and density of these guttata are noted, as their presence, especially in the central cornea, confirms the diagnosis of Fuchs Dystrophy.
In advanced stages, the slit lamp examination reveals signs of corneal edema, or swelling. The doctor may observe a fine, gray haze within the corneal tissue or vertical folds on the inner surface. These are indicators that the endothelial cells are failing to pump fluid out. Observing these physical signs of damage and fluid accumulation helps in staging the disease.
Confirmatory Measurement Tests
To confirm the diagnosis and determine disease severity, the clinician uses specialized, quantitative measurement tests. These tests provide data on the health and function of the corneal endothelium.
Pachymetry
Pachymetry is a non-invasive method used to measure the thickness of the cornea. A healthy central cornea typically measures around 545 micrometers. As Fuchs Dystrophy progresses, endothelial cells lose their pumping ability, causing excess fluid (edema) to build up. Increased corneal thickness correlates directly with this fluid accumulation and indicates a loss of functional capacity. Measuring the thickness provides an objective means to track disease progression.
Specular Microscopy
Specular microscopy is the most detailed way to evaluate the endothelial cells themselves. This non-contact instrument captures a high-magnification photograph of the cell layer, allowing for a precise count of cells per square millimeter. A normal adult eye typically has a density between 2,500 and 3,000 cells/mm². In Fuchs Dystrophy, this count declines, with fewer than 1,000 cells/mm² often indicating moderate to advanced disease.
The specular microscope also analyzes the shape and size of the remaining cells. It looks for signs of polymegathism (variation in cell size) and pleomorphism (variation in cell shape). These variations occur as healthy cells enlarge and change shape to compensate for those that have died, serving as an early indicator of endothelial stress.