One-year outcome of bilateral randomised prospective clinical trial comparing photorefractive keratectomy (PRK) with mitomycin C (MMC) and laser in situ keratomileusis (LASIK).

We read with great interest the article by Wallau and Campos, who compared the 1-year outcome of photorefractive keratectomy (PRK) with mitomycin C (MMC) and laser in situ keratomileusis (LASIK) in a bilateral randomised prospective clinical trial. The authors concluded that Wavefrontguided PRK with 0.002% MMC is more effective than wavefront-guided LASIK for correction of moderate myopia, which is consistent with previous studies. We would like to make the following comments. The authors have conducted a bilateral randomised control trial; however, there is no mention of whether the postoperative evaluations were masked or not, as this could introduce an element of bias. The authors claim that there is a statistically significant difference in the uncorrected visual acuity (UCVA) with a UCVA better than 20/12.5 in the PRK+MMC group versus the LASIK group, with 52% of the eyes in the former group achieving >20/12.5 UCVA as compared with 31% in the latter. However, it is not clear why the authors have selected ‘supranormal’ UCVA for the cut-off rather than normal vision (20/20). It would be useful to know how many in each group had a UCVA of 20/20. A satisfaction questionnaire was administered to all patients; however, these data have not been analysed, and it would be interesting to know which eye the patient preferred and, in retrospect, which procedure the patient would opt for, given a choice. It is also not clear who was administering the questionnaire, as this could also introduce an element of bias. The authors could have provided the confidence intervals (CIs) for the wavefront measurements as well as the contrast sensitivity, as they mention a statistically significant difference between the two groups. The corneal hysteresis (CH) and corneal resistance factor (CRF) were measured postoperatively but not preoperatively. However, the CIs of the mean corneal hysteresis between the LASIK (8.55 (8.14 to 8.68)) group and the PRKeMMC (8.11 (7.9 to 8.26)) groups overlap, thereby casting doubt on the clinical and statistical significance of the same. The authors also fleetingly mention that postoperative pachymetry was significantly lower in the PRKeMMC group compared with the LASIK group. However, no details were given. In conclusion, although this study is a good attempt at comparatively analysing the outcome of LASIK and PRKeMMC, limitations such as an absence of masking, absence of details such as a patient satisfaction questionnaire, preoperative CH andCRF data, and overlapping of the CI of the mean do exist.