Pellucid Marginal Degeneration Research Paper

Pellucid Marginal Degeneration is a rare corneal ectatic disorder(PMC). This bilateral, non-hereditary , idiopathic disorder is characterized by irregular astigmatism(Collagen cross-linking in the treatment of pellucid marginal degeneration)and thinning of the peripheral cornea in absence of inflammation, often affecting the inferior quadrant in a crescentic fashion. The disorder includes an area of corneal protrusion above the point of maximal thinning. This is the hallmark of the disorder and is what distinguishes it from Keratoconus.
Pathophysiology of Pellucid Marginal Degeneration
The exact aetiology of Pellucid Marginal Degeneration has not been ascertained. However it is thought to be secondary to collagen abnormalities. Intraocular
pressure is hypothesized to be the cause of the protuberance.(eyewiki)
Symptoms experienced by patients
Typically patients do not experience any specific symptoms. In rare instances patients may report sudden vision loss as well as excruciating pain. Thinning of the cornea leads to corneal perforation which is responsible for the pain the patient experiences.(Wikipedia ref 2)
Signs presented by patients
The most well known and most obvious sign of Pellucid Marginal Degeneration is inferior corneal thinning. Thinning usually occurs inferiorly a couple of millimeters away from the limbus. Although there is no pain or inflammation involved , it does lead to significant irregular astigmatism.( http://www.reviewofophthalmology.com/). Severely reduced uncorrected visual acuity is another sign. Typically spherocylinder lenses cannot be used to improve or correct this. Practically normal visual acuity. Against-the-rule astigmatism shown by keratometry and refraction. In advanced and very rare cases of Pellucid Marginal Degeneration raptures in Descemet’s membrane may lead to acute corneal hydrops. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3498565/)