Changes in the effective optical zone following hyperopic keratorefractive lenticule extraction

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

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.

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).

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