Microcystic Epithelial Edema (MCE) of the cornea is a condition affecting the eye’s clear front surface. It involves fluid accumulation within the cornea’s layers, forming small, fluid-filled structures, which disrupts the cornea’s clarity.
The Nature of MCE Cornea
Microcystic epithelial edema refers to fluid buildup within the epithelial layer, the outermost protective surface of the cornea. This leads to tiny, blister-like microcysts, typically 15-50 µm in diameter. These microcysts can give the corneal surface a hazy or cloudy appearance.
Several underlying factors can lead to MCE. Elevated intraocular pressure (IOP), often associated with conditions like glaucoma, can impair the corneal endothelium’s ability to pump fluid. Inherited corneal dystrophies, such as Fuchs’ endothelial dystrophy, cause a progressive loss of endothelial cells, which maintain corneal hydration.
Chronic overwear or improper fit of contact lenses can also contribute to MCE by causing corneal hypoxia. This disrupts corneal cell metabolism and fluid regulation. Furthermore, complications following eye surgeries, particularly cataract extraction, can damage endothelial cells or induce inflammation. Corneal infections or inflammatory conditions like keratitis or uveitis can also cause MCE by damaging cells.
Identifying MCE Cornea
Individuals with MCE cornea often notice visual and ocular symptoms. Blurred or hazy vision is common, and is often more pronounced upon waking. This morning worsening occurs because lack of tear evaporation during sleep can increase corneal swelling. Patients may also experience glare or see halos around lights, particularly in bright conditions, due to light scattering.
Eye discomfort, a foreign body sensation, or mild pain can also accompany MCE, especially if microcysts rupture. An ophthalmologist typically diagnoses MCE cornea through a slit-lamp examination. The characteristic fluid-filled microcysts within the corneal epithelium can be clearly observed.
Additional diagnostic tools, such as corneal pachymetry, may measure corneal thickness, which can be increased due to edema. Advanced imaging techniques like corneal confocal microscopy can provide more detailed images and assess severity.
Treatment and Outlook
Treatment for MCE cornea primarily focuses on addressing the underlying cause. For elevated intraocular pressure, topical medications are often prescribed. If contact lens use is implicated, discontinuing lens wear or switching to a more appropriate type and schedule is advised.
Medical management often includes hypertonic saline drops or ointments. These solutions create an osmotic gradient that helps draw excess fluid out of the cornea, reducing swelling. Applying hypertonic ointment at night can be particularly helpful, as corneal edema tends to be more severe upon waking. Therapeutic soft contact lenses may be employed to provide comfort and protection.
For severe or chronic cases, particularly those associated with Fuchs’ endothelial dystrophy or significant endothelial damage, surgical interventions may be considered. Corneal transplantation procedures, such as Descemet’s Stripping Endothelial Keratoplasty (DSEK) or Descemet’s Membrane Endothelial Keratoplasty (DMEK), involve replacing the damaged inner layer with healthy donor tissue. These procedures restore the cornea’s ability to pump fluid effectively and improve vision. The overall prognosis depends significantly on successful identification and management of its root cause, with early intervention leading to more favorable outcomes.