Abstract:

Objective To evaluate the safety and effect of femtosecond-assisted intrastromal corneal cross-linking (F-CXL) for keratoconus. Design Prospective case series. Participants Twenty two patients (30 eyes) diagnosed as progressive keratoconus accepted F-CXL in Tongren Eye Center from Oct. 2015 to May. 2016. Methods All eyes were scheduled to receive the riboflavin-ultraviolet corneal collagen crosslinking using a femtosecond laser pocket under surface anesthesia objective measurements, including corneal topography, corneal pachymetry, demarcation line, corneal biomechanical property and endothelial cell count were evaluated preoperatively and at 1 day, 1 week, 1 month, 3 months, 6 months and 12 months postoperatively. Main Outcome Measures Best corrected visual acuity (BCVA), thinnest corneal thickness(TCT), corneal steep K-reading (Ks）、corneal flat K-reading (Kf), average K-reading (Avek), corneal central thickness (CCT)、corneal hysteresis (CH), corneal resistence factor (CRF), corneal endothelial cell count, demarcation line and images by confocal microscope. Results No serious complications happened during or after the surgery. However, some eyes experienced mild or moderate discomforts 1 day after surgery which were well relieved after 3 days. During 12-month follow-up, there was no significant increase in topographic parameters including Ks, Kf, Avek and reductions in CCT, CH, CRF. Desides, F-CXL performed the best from 3 months to 6 months postoperatively and then weakened gradually. Spearman analysis showed the preoperative Ks greater than 53.08 D was associated with more improvement in Ks but age, baseline BCVA and baseline TCT were found unrelated to the amount of change in Ks, Avek, Cyl and CCT. Corneal stromal demarcation line could be identified from 1 week in 18 eyes (60%) and then got more clear and intact, the mean depth of which was (302.56±31.02) μm at 3 months. In addition, corneal confocal microscopy revealed that activated keratocytes and newly-formed, compact collagen fibers could be observed after 1 month. During the follow-up, no significant reduction in corneal endothelium cell count proved the safety of this technique. Conclusion F-CXL is an effective and safe method to halt the advancement of progressive KC which is a solid preliminary basis of the combined surgery, despite further studies and close monitoring required.

Key words: keratoconus, intrastromal pocket, corneal cross linking