Refractive Outcomes of Topography-Guided Photorefractive Keratectomy With Simultaneous CXL for Keratoconus
Purpose
Evaluate refractive outcomes, efficacy and safety of simultaneous topography-guided photorefractive keratectomy (TG-PRK) with collagen cross-linking (CXL) for keratoconus (KC) using a neutralization technique and determine degree of hyperopic effect of CXL induced keratometric flattening after first year.
Methods
Epithelial removal by trans-epithelial laser, riboflavin 0.1% until aqueous staining, UV irradiation 370nm 8-15 minutes, 3mW/cm2 - 5.4 J/m2 , hypotonic riboflavin if less than 400um, bandage contact lens, standard post PRK management Degree of refractive correction based on residual stromal depth of 300 microns with target correction of -1.25 diopters (D). Symptom score (10 point) , uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), keratometry(K), efficacy, and safety were at 12 months.
Results
At 1 year result, 288 out of 464 eyes met all inclusion criteria. 144(50%) had UCVA of 20/40 or better. 49(17%) had UCVA of 20/25 or better. 147(51%) had BSCVA improved, 69(24%) gained 2 lines or more, 17(6%) lost 2 lines or more. Average symptom score improved from 6.7 to 4.2. Mean reduction of astigmatism was 1.69±1.78 diopters (D). Mean spherical equivalent reduced from -2.74±2.81D to -1.24±2.18D. Complications included 7 with delay in epithelial healing, 4 with subsequent haze, 4 sufficient to reduce BCVA more than 2 lines, with one undergoing keratoplasty. One developed herpetic keratitis recovering pre-operative BCVA after PTK.
Conclusion
Early satisfactory refractive outcomes were obtained with simultaneous topographically-guided PRK with CXL for keratoconus. Progressive hyperopia probably related to cross linking, sufficient to be visually significant, occurred in 4 eyes. At one year follow-up, half of the eyes achieved UCVA of 20/40 or better and more than half improved BSCVA.