Changes in the effective optical zone following hyperopic keratorefractive lenticule extraction

Objective: To evaluate the longitudinal changes in the effective optical zone (EOZ) following hyperopic keratorefractive lenticule extraction (KLEx) and investigate factors influencing the EOZ.

Patients and methods: This retrospective study included 27 patients who underwent hyperopic KLEx. According to the transition zone (TZ) sizes, they were divided into two groups: group A (21 eyes) with a 2.0-mm TZ and group B (10 eyes) with a 0 or 0.2-mm TZ. The programmed treatment zone (PTZ) was the sum of the programmed optical zone (POZ) and the TZ.. Changes in the EOZ were evaluated at the early (within 1 month postoperatively) and late (over 6 months postoperatively) postoperative stages. The effects of the surgical and corneal topographic parameters on EOZ were explored.

Results: A significantly higher postoperative spherical equivalent was found in group B than in group A (p = 0.002). The early and late EOZ diameters were 4.27 ± 0.20 mm and 4.04 ± 0.21 mm in group A, and 3.48 ± 0.29 and 3.12 ± 0.49 mm in group B, respectively. ΔEOZ/POZ and ΔEOZ/PTZ were significantly larger at the late than the early postoperative stage in both groups (p < 0.001), with a larger ΔEOZ/POZ value in group B than that in group A at both stages (p < 0.001). EOZ reduction was negatively associated with POZ at the late postoperative stage (ΔEOZ/POZ: p = 0.043; ΔEOZ/PTZ: p = 0.020).

Conclusions: The EOZ continued decreasing following hyperopic KLEx. A larger TZ and POZ would result in a larger postoperative EOZ.