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Contact lens-induced hypoxia triggers the cornea to undergo anaerobic respiration, resulting in a buildup of lactic acid that osmotically draws water into corneal cells, causing edema. [6] Two explanations have been proposed for contact lens-induced stromal thinning. It is thought that this edema may inhibit stromal tissue synthesis. [4]
Many cases are asymptomatic, however patients many have decreased vision, glare, monocular diplopia or polyopia, and noticeable iris changes. [2] [5] On exam patients have normal to decreased visual acuity, and a "beaten metal appearance" of the corneal endothelium, corneal edema, increased intraocular pressure, peripheral anterior synechiae, and iris changes.
Corneal opacification is a term used when the human cornea loses its transparency. The term corneal opacity is used particularly for the loss of transparency of cornea due to scarring. Transparency of the cornea is dependent on the uniform diameter and the regular spacing and arrangement of the collagen fibrils within the stroma.
Corneal hydrops is an uncommon complication seen in people with advanced keratoconus or other corneal ectatic disorders, [1] and is characterized by stromal edema due to leakage of aqueous humor through a tear in Descemet's membrane. [2]
As a progressive, chronic condition, signs and symptoms of Fuchs dystrophy gradually progress over decades of life, starting in middle age. Early symptoms include blurry vision upon wakening which improves during the morning, [2] as fluid retained in the cornea is unable to evaporate through the surface of the eye when the lids are closed overnight.
On slit-lamp examination, conjunctival injections, epithelial corneal edema, [3] small to medium-sized fine keratitic precipitates, aqueous cells and flare may also be noted. [4] Blurring of vision, eye pain and discomfort are the main symptoms. [4] Colored halos may occur due to elevated IOP. [5]
Whichever, it is always potentially serious and sometimes necessitates urgent treatment and corneal opacities are the fourth leading cause of blindness. Opacities may be keratic, that is, due to the deposition of inflammatory cells, hazy, usually from corneal edema, or they may be localized in the case of corneal ulcer or keratitis.
Treatment options include contact lenses and intrastromal corneal ring segments for correcting refractive errors caused by irregular corneal surface, [7] [8] corneal collagen cross-linking to strengthen a weak and ectatic cornea, [9] or corneal transplant for advanced cases.