Safety, Efficacy, and Pachymetry Variation During and After CXL in Thin Keratoconic Corneas With Different Protocols
Narrative Responses:
Purpose
To study central corneal pachymetry variations, safety and efficacy during and following collagen cross linking (CXL) treatment using different protocols for Keratoconus patients with thin corneas.
Methods
Collagen cross linking was done in 28 eyes of patients having progressive keratoconus with thin corneas with pachymetry below 425 microns and these patients were followed up over a period of 6 to 12 months and beyond. Different protocols of (conventional and accelerated) CXL were used in these eyes by using riboflavin solutions (isotonic and hypoosmolar) with and without dextran and with standard and accelerated flash CXL protocols (with and without epithelium on) with different methods of riboflavin soak. Intraoperative Central Corneal Thickness (CCT) measurements using ultrasound pachymetry were performed per-operatively during the procedure.
Results
We found a significant intra-op pachymetry variation ranging from 248μ to 632μ in all the protocols except transepithelial CXL. This correlated well with transient corneal oedema seen in 4 patients. Efficacy of the CXL procedure was seen to be maintained in all the protocols at six months but was equivocal in transepithelial CXL and when corneal thickness increased beyond 600μ intraoperatively. No significant complications were seen other than corneal haze which was seen in all patients and transient corneal oedema in 4 patients that resolved with time. Two patients developed sterile corneal infiltrates that resolved over two weeks.
Conclusion
CXL is a relatively safe and effective procedure even in thin keratoconic corneas with modified CXL protocols. However Intraop pachymetry has a bearing on safety and efficacy of CXL procedure and should be done routinely as an added safety precaution in CXL procedure for all protocols.