Photorefractive Keratectomy In Myopia And Myopic Astigmatism Using A Sliding Scale Mmc Dose - A 10-Year Big Data Analysis.

To present the big data analytics of refractive outcomes of photorefractive keratectomy (PRK) performed for myopia and myopic astigmatism using a sliding scale of 0.02% mitomycin C and to compare the outcomes between mild, moderate, high and very high myopia.

IRB approved retrospective analysis of all cases of PRK in the refractive clinic at a tertiary referral centre in South India.

A retrospective review of consecutive eyes with myopia or compound myopic astigmatism undergoing PRK at our institute over the past ten years was done. A total of 27105 eyes from 11964 patients who underwent PRK between January 2013 and December 2022 were included in the study. They were subdivided into four groups based on the magnitude of myopia correction: low (0-3D), moderate (3-6D), high (6-9D), and very high (>9D). Measured outcomes included pre and postoperative uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, corneal haze, and complications. All patients underwent PRK with Mitomycin C 0.02% with a sliding scale of exposure time proportional to the refractive error corrected.

65% of eyes from the low myopia group, 58% in the moderate myopia group, 47% in the high myopia group and 27 % in the very high myopia group achieved UDVA of 20/20 at one-month post-PRK. This improved to 84%, 83%, 70%, and 48% at six months post-PRK and 89%, 85%, 72%, and 44% respectively at 12 months after surgery. At the end of 12 months, 99.9%, 100%, 99.6%, and 99.3% in mild, moderate, high, and very high myopia groups had UDVA of 20/40 or better. At 12 months, the mean postoperative logMAR UDVA was -0.02, -0.02, -0.04, and -0.12 in low, moderate, high and very high myopia groups. Of all these patients, only 12 eyes (0.04%) required repeat surgery for post-PRK haze.

This big data analysis shows that PRK provides excellent refractive outcomes and has been safe and stable for over a year, even in cases of high myopia. A sliding scale of Mitomycin C exposure appears to work well in preventing post-PRK haze even in high corrections.