Pellucid Marginal Degeneration - PMD
Pellucid Marginal Degeneration (PMD) is a similar condition to keratoconus in that the cornea thins but this area of thinning is located at the inferior part of the cornea and much more peripherally. This causes
PMD differs from keratoconus in that the age of onset is generally higher. Patients generally present in there late 20's onwards as opposed to their early teens in KC. A reason for this is that in most cases patients can achieve reasonable vision with glasses as the affected area of cornea is very low, ie below the visual axis. This means that the part of the cornea that is used to see through, the centre, is relatively unharmed. As the condition progresses, however, the cornea will distort so much that the central area is significantly affected and some form of therapy is needed.