Pachymetry Fluctuations During Corneal Crosslinking (CXL) Dr. Arthur Cummings1 Dr. Eugene Ng2 1) Wellington Eye Clinic, Dublin, Ireland 2) Royal Victoria Eye and Ear Hospital, Dublin, Ireland No financial disclosures ASCRS, Boston 2010

Corneal collagen crosslinking is a widely used treatment modality for keratoconus Current protocols recommend 400 microns of pre-treatment corneal thickness due to potential endothelial damage in thinner corneas

However, there are no studies looking at intra-procedural pachymetry during CXL. Medio-Cross (Riboflavin 0.1%, Dextran 500 20%) is supposed to be isotonic. We report intra-procedural pachymetry (at 5 minute intervals) using Medio-Cross during CXL

Results 15 consecutive patients who underwent CXL also had intra-procedural pachymetry measurements at 5 minute intervals. All patients had pre-operative pachymetry of >400 microns on both optical and ultrasound pachymetry.

A wide variation in the loss of corneal thickness was noted (15-36%). Results Medio-Cross instillation Pre-op Post epithelium 5 mins 10 mins 15 mins 20 mins Pre UVA Pachy Removal A wide variation in the loss of corneal thickness was noted (15-36%). Hypotonic Riboflavin added

Discussion Corneal “desiccation” may have accentuated “thinness” of the cornea as measured by ultrasound pachymetry (speed of sound in denser medium). The safe level of corneal thickness throughout the procedure (as measured by ultrasound pachymetry) needs to be defined if endothelial damage is to be avoided.

Discussion It is possible that the variable effect of Medio-Cross on corneal thickness may be related to the varying effect of CXL efficacy. The effects of hypotonic riboflavin (apart from increasing corneal thickness) may provide a false sense of safety The relative efficacy of CXL where hypotonic riboflavin is used is unknown.