Cross-Linking in PMD
Pellucid marginal degeneration (PMD) is member of the corneal ectasia family, such as keratoconus and post-LASIK ectasia. However, it differs from keratoconus in 3 essential ways:
- PMD usually starts later in life, usually at the age of 20 to 30 years
- It usually does not stop as people age, rather, it progresses slowly throughout life
- PMD occurs much further in the periphery of the cornea. As a result, the eyesight stays good for longer, and this unfortunately means that patients notice the disease later than with keratoconus.
How is it treated?
CXL can also be successfully used in PMD, but it is sometimes necessary to repeat CXL after 6 or 12 months.
Cross-linking in PMD is similar to keratoconus but with one important difference: the cornea needs to be irradiated in an “eccentric” (off-centred) pattern, which exposes corneal stem cells to UV light. It has been unclear for years whether it is possible to irradiate these stem cells with UV light without damaging them and causing serious consequences for the eye. Our research group has shown in a series of elaborate experiments that this is indeed possible.
In advanced cases, the cornea is so thin that a standard CXL can no longer be used. This is where our extensive experience of treating extremely thin corneas comes to bear.