Impact of Preoperative Ocular Hypotony on Refractive Predictability After Phacovitrectomy for Rhegmatogenous Retinal Detachment

Background/Objectives: Rhegmatogenous retinal detachment is a vision-threatening condition often treated with combined cataract surgery and vitrectomy, but accurate postoperative refractive prediction may be difficult when ocular anatomy is altered by preoperative hypotony. This retrospective comparative study evaluated the effect of preoperative ocular hypotony on refractive predictability and visual outcomes after combined phacovitrectomy for rhegmatogenous retinal detachment. Materials and Methods: Electronic medical records from Nagasaki University Hospital from 2010 to 2022 were reviewed. Among 731 eyes that underwent combined phacovitrectomy with sulfur hexafluoride gas tamponade for rhegmatogenous retinal detachment, 17 eyes with preoperative ocular hypotony (intraocular pressure ≤ 7 mmHg) that met the inclusion criteria were identified. Thirty-four eyes with normal intraocular pressure were selected as controls in a 1:2 ratio. Refractive outcomes were assessed through spherical equivalent and mean absolute error, and visual outcomes were evaluated through best-corrected visual acuity at baseline and 6 months postoperatively. Results: Mean absolute error was significantly higher in eyes with hypotony than in normotonic eyes (1.46 ± 0.95 diopters vs. 0.70 ± 0.81 diopters; p = 0.002; mean difference, 0.76 D; 95% CI, 0.21–1.31; Hedges’ g = 0.87). Target postoperative refraction within ±0.5 diopters was achieved in 23.5% of hypotonic eyes and 50.0% of normotonic eyes (p = 0.07), the corresponding proportions within ±1.0 D were 35.3% and 76.5%, respectively (p = 0.006). Best-corrected visual acuity improved significantly in both groups, but final visual acuity at 6 months was worse in hypotonic eyes (0.35 ± 0.31 vs. 0.09 ± 0.17 logarithm of the minimum angle of resolution; p < 0.001). Conclusions: Preoperative ocular hypotony in rhegmatogenous retinal detachment was associated with greater refractive prediction error and worse visual outcomes after phacovitrectomy.