Long-Term Reproducibility of Axial Length after Combined Phacovitrectomy in Macula-sparing Rhegmatogenous Retinal Detachment

There is a myopic shift in the final measured spherical equivalent following combined phacovitrectomy compared to the predicted postoperative value. This change in myopia is known to be associated with gas tamponade, but it also occurs in patients who do not have gas tamponade, and even when vitrectomy is performed in the pseudophakic eye. In this study, we focused on the long-term reproducibility of axial length after combined phacovitrectomy in patients with macula-sparing rhegmatogenous retinal detachment. Before surgery, one year after surgery, and two years after surgery, bilateral axial lengths were measured using partial interferometry. To confirm whether axial lengths changed after surgery, we conducted confidence analyses using the intraclass correlation coefficient (ICC), coefficient of variation (CV), and test–retest standard deviation (TRTSD). The preoperative mean axial length was 25.03 ± 1.69 mm in the affected eyes and 24.96 ± 1.70 mm in the fellow eyes. The ICC, CV, and TRTSD were 0.97, 0.45, and 0.114 in affected eyes and 0.98, 0.66, and 0.167 in fellow eyes, respectively, which shows a high level of reproducibility. Prediction errors for postoperative spherical equivalents measured using partial interferometry were −0.41 ± 0.67 diopters (p = 0.001), respectively, which shows a remarkable myopic shift. Correlation analyses indicated that this myopic shift was significant in eyes with a shallower anterior chamber and a thicker lens. In macula-sparing RRD patients, the axial length showed excellent long-term reproducibility two years after vitrectomy, cataract surgery, and gas tamponade. The myopic shift after surgery was therefore caused by factors that may have affected the intraocular lens position, such as preoperative anterior chamber depth and lens thickness, rather than a change in the axial length.