Comparing predictability between eyes after bilateral laser in situ keratomileusis - A theoretical analysis of simultaneous versus sequential procedures

Objective: To compare the predictability of laser in situ keratomileusis (L ASIK) between eyes of individuals to determine whether the refractive resul t of the first eye is useful in improving fellow eye outcomes. Design: Single-center case series. Participants: One surgeon and 196 eyes of 98 patients. Intervention: All patients received sequential bilateral LASIK. The mean ti me between procedures was 11.6 days. Attempted corrections ranged from 2.30 to 12.00 diopters (D). Main Outcome Measures: Predictability (achieved minus attempted correction) , postoperative manifest refraction, and theoretical postoperative manifest refraction, using a proposed attempted correction on the second eye based on first eye results, were analyzed. Results: At 1 week, 1 month, and 3 months, predictability of the first oper ated eye was correlated with predictability of the fellow eye (1 week: mean 1st = 0.33 D, mean 2nd = 0.33 D, Pearson coefficient = 0.46, P < 0.0005; 1 month: mean 1st = 0.028 D, mean 2nd = -0.020 D, Pearson coefficient = 0.43 , P < 0.0005; 3 months: mean 1st = -0.22 D, mean 2nd = -0.12 D, Pearson coe fficient = 0.52, P ( 0.0005). At the 3-month follow-up of the second eye, c omparing the actual distance from emmetropia with that calculated using a t heoretical proposed attempted correction based on the first eye refraction, distance from emmetropia was closer in the theoretical correction group. T his finding was stronger in patients with preoperative myopia less than 5.5 D (P = 0.03). For this group, 93% of patients in the proposed attempted co rrection group would fall within 1.0 D of emmetropia compared to 80% found in the actual outcomes. Conclusions: The refractive predictability between the two eyes of an indiv idual after LASIK is correlated. Theoretically, therefore, one may be able to achieve correction closer to emmetropia in the second eye by applying th e refractive predictability results from the first operated eye. In this st udy, using a theoretical proposed attempted correction in the second eye ba sed on the first eye outcome, we have shown that better outcomes in the sec ond eye are possible, particularly in low myopes. Thus, it may be advantage ous to perform bilateral LASIK sequentially rather than simultaneously, usi ng predictability outcomes from the first operated eye in planning fellow e ye treatment. Moreover, waiting approximately 1 week was found to be potent ially as effective as waiting longer periods of time between treatments. Fu rther studies are necessary to better assess the actual clinical significan ce of these findings.