Evaluation of safety and efficacy of different protocols of collagen cross linking for keratoconus

Introduction: Collagen cross-linking is a well-established modality that could stop the keratoconus from progressing. Off late, newer protocols have been suggested for progressive keratoconus, which include the use of hypoosmolar riboflavin for thinner corneas and the use of accelerated CXL protocol to reduce the effective treatment time. Objective: To assess the safety and efficacy of different protocols of conventional CXL, hypoosmolar CXL and accelerated CXL in patients with keratoconus. Materials & methods: It was a prospective, interventional study with minimum of 12 months follow-up. Patients were divided into 3 groups; conventional CXL, CXL using hypotonic riboflavin and accelerated CXL group. Primary outcome measures - For efficacy, Sim Kmax and Sim Kmin (Progression (Kmax > +1 D), stabilization (Kmax +1 D to -1 D) and regression (Kmax > -1 D). For safety - endothelial count evaluation (decrease >10% amounted to compromise the safety of the procedure). Secondary outcome measures - BCVA and adverse events. Results: 32 eyes underwent isotonic CXL treatment. Pre-treatment and post-treatment BCVA were 0.16 +/- 0.15 and 0.10 +/- 0.11 log MAR; specular counts 2782.81 +/- 307.25 (cells/ mm2) and 2708.5 +/- 263.27 (cells/ mm2) (p=0.05); KMax values 55.31 +/- 4.12 D and 53.9 +/- 3.77 D (p=0.0001). 16 eyes underwent hypotonic CXL treatment. Pre-treatment and post-treatment BCVA were 0.15 +/- 0.13 log MAR and 0.14 +/- 0.14; specular count 2701.19 +/- 243.25 (cells/ mm2) and 2713.5 +/- 369 (cells/ mm2) (p= 1) and KMax values 54.74 +/- 7.44 D and 52.74 +/- 6.76 D (p = 0.002). 15 eyes underwent accelerated CXL treatment. Pre-treatment and post-treatment BCVA were 0.16 +/- 0.15 and 0.10 +/- 0.12 log MAR; specular counts 2967.53 +/- 356.48 and 2893.07 +/- 336.55 (cells/ mm2) (p = 0.78) and KMax values 55.19 +/- 5.46 D and 54.24 +/- 5.33 D (p = 0.337). Conclusion: All three protocols appeared safe and efficacious as therapeutic regimen for progressive keratoconus.