To Study The Results Of Cross-Linked Bowman' Membrane Lenticule As Onlay Technique In Moderate To Severe Keratoconus.

To evaluate the clinical outcome of strengthened (by cross -linking, using standard riboflavin and UVA radiation exposure) Bowman lenticule as onlay  transplantation, a new surgical technique to reduce and stabilize ectasia in moderate keratoconus. Improvement in best corrected visual acuity, corneal thickness and keratometric stability was assessed pre and post operatively at 6 months. Any complications regarding healing were also evaluated.

Institutional Prospective, nonrandomized interventional study. 6 patients with moderate keratoconus underwent cross - linked Bowman lenticule onlay implant and the results evaluated and compared pre and postoperatively for parameters like best corrected visual acuity (BCVA) using ETDRS chart, keratometry and thickness using Scheimpflug-based corneal tomography. The results were assessed at 6 months. 

6 patients (4 males and 2 females) who were suitable (fit in tests and inclusion criteria) were enroled and underwent surgery. Bowman lenticule (9.5 mm diameter) was extracted using standard technique from therapuitic grade donor cornea and cross- linked using accelarated technique with UVA and riboflavin. The corneal bed of recipient patient is then prepared by debriding epithelium (central 8 mm) and a peripheral recess is then created underneath the epithelal rim 360 degrees. The lenticule is then placed as onlay and its periphery is tucked -in beneath epithial rim. A bandage contact lens is then placed.      

Complete epithelization was obsereved in all 6 patients in 1 week time. The entire lenticule becomes embodied. BCVA improved upto 2 lines from preoperative values and remained stable (or  improved) at 6 months in all patients. Pachymetry values improved from preoperative values and remained stable at 6 months. Maximum keratometry decreased on average from 90.2±9.0 diopters (D) to 70.5±4.5 D (P < 0.001) at 1 month after surgery and remained stable thereafter uptill 6 months. The lenticule onlay seems to have a gripping effect on cornea. One patient had epithelial misalignment at 12 'o clock position which was corrected 3 day post opertaively.      

The use of strengthened (cross - linked) lenticule as onlay device is a very easy surgical technique and can prove a very handy surgery for mild to moderate keratoconus with minimal intervention.