Changing the way you see the world.

Pellucid Marginal Degeneration commonly referred to as PMD or even just Pellucid, is an extremely rare degenerative corneal eye condition. The Term Pellucid Marginal Degeneration was first coined by an ophthalmologist named Schalaeppi in 1957. Pellucid Marginal Degeneration by definition is a bilateral thinning in the periphery of the cornea, that is not inflammatory, however unilateral cases have been reported.

A little more information about Pellucid Marginal Degeneration is that it is actually unknown how many instances of PMD there actually occur every year. PMD is extremely rare; however the main contributing factor to the unknown instance count is greatly due to its confusion with keratoconus, which is another more common eye disorder.

Keratoconus is sometimes confused with PMD because it is also a degenerative eye disorder, however in keratoconus patients there are changes within the cornea that cause it to thin and change to a more cone shape instead of the normal gradual cure that normal eyes have.

Most literature states that Pellucid Marginal Degeneration is not painful, and that no symptoms actually accompany the condition other than the obvious visual deterioration. The lack of pain however has not been the case for me. You can read more about my struggle with PMD here.

Early signs of PMD are virtual non-existent. When the eye is exampled by an optometrist or an ophthalmologist, the patients corneal thickness appears normal in the center, also showing an intact central epithelium. However the inferior cornea exhibits a peripheral band of thinning. When a patient has PMD there is a high astigmatism, along with horizontal bow ties, and inferior peripheral thinning between the 7 and 4 o’clock meridian. Here is a picture of that.

Thinning of the inferior cornea.

Pellucid Marginal Degeneration has had no identifiable factors linking reace, sex, or age. Almost all reported cases however have been early in life between the ages of 20 – 40. No known cause for the disease has been found. The most common element that leads to the discovery of PMD in a patient is the rapid visual decline due to the irregular corneal shape. This always will lead to a very bad astigmatism, and therefore creates extremely distorted vision. Overtime the deterioration and distortion will become more sever.

Due to the changes in the shape of the eye Pellucid rules patients out for many different types of eye surgeries such as refractive surgery, LASIK surgery, and PRK surgery. Another interesting point to note about PMD is that visual aids such as glasses do not work for pellucid due to the changed shape of the eye, vision will still be distorted.