Pellucid Marginal Corneal Degeneration is an uncommon condition causing thinning of the lower part of the cornea. This non-inflammatory condition is often confused with keratoconus as it causes similar distortion of the cornea and requires complex contact lens designs, typically in the form of scleral lenses, to give the best quality of vision. Innovative Eye Care specialises in managing patients with Pellucid Marginal Corneal Degeneration and other ectatic conditions.
Pellucid marginal corneal degeneration (PMCD) was first investigated in 1957. It is not believed to be heriditary but a range of other eye conditions may be present in family members.
Patients will often present in their 2nd to 5th decade of life with blurred vision due to the irregularity of their cornea. Often against-the-rule astigmatism is present and contributes to the blur seen.
In PMCD the stroma (collagen) of the cornea is abnormal and thin but the other parts of the cornea are unaffected and function normally. This degeneration can progress slowly over time, but will only very rarely progress to the point of perforating the cornea.
PMCD is best managed with large diameter scleral contact lenses that will vault over the affected area of cornea and still provide a regular front surface for vision. In severe cases a corneal graft may be needed to restore functional vision. Collagen cross-linking is a surgical procedure used in some progressive cases to prevent further worsening of the condition. See our keratoconus page for more information about this.
CAPTION: A corneal topography of a patient with PMCD showing the irregular steepening of the lower part of the cornea giving a typical 'crab-claw' appearance.