A prospective evaluation of photorefractive intrastromal cross‐linking for the treatment of low‐grade myopia

Abstract

Abstract Purpose To evaluate photorefractive intrastromal cross‐linking (PiXL) treatment for low‐grade myopia, comparing three treatment protocols. Methods Healthy individuals, 25.6 ± 3.6 years of age, with low‐grade myopia underwent epi‐on Pi XL with either: 4‐mm zone treated in high oxygen environment (4 mm‐ HIGH ; n = 15), 4‐mm/room air (4‐mm LOW; n = 6), or 6‐mm/high oxygen (6‐mm HIGH ; n = 6). Efficacy was determined by change in uncorrected visual acuity ( UCVA ), manifest refractive spherical equivalent ( MRSE ) and corneal curvature ( K mean ) over a 12‐month follow‐up. Safety was determined by best spectacle corrected visual acuity ( BSCVA ), corneal endothelial cell loss and registration of side‐effects. Results Twenty‐seven subjects were included. Due to insufficient effect with the 4‐mm LOW treatment and an unacceptable degree of initial light sensitivity/ocular irritation in the 6‐mm HIGH group, the inclusions to these treatments were stopped after inclusion of 6 patients in each group. The 4‐mm HIGH treatment showed a significantly larger improvement in UCVA (−0.45 ± 0.27 Log MAR ) and MRSE (+0.99 ± 0.44 D) at 1, 6 and 12 months compared with the 4‐mm LOW treatment (p < 0.05). At 12 months posttreatment, endothelial cell count and BSCVA were unaltered. More initial side‐effects were noted with the 6‐mm HIGH treatment, compared with the 4‐mm HIGH treatment (p < 0.05). Conclusion Epi‐on Pi XL may become a safe and effective non‐ablative treatment for low‐grade myopia. The effect is augmented by high oxygen environment and remains stable for 12 months. The initial ocular irritation is acceptable with a 4‐mm treatment zone. The present results justify further clinical studies on Pi XL , including refinements of the technique and long‐term results.