Choroidal Thickening Drives Surgical Failure in RRD with Choroidal Detachment: a Geometric Model for Predicting Silicone Oil Underfill and Guiding Steroid Use

Rhegmatogenous retinal detachment with choroidal detachment (RRD-CD) poses persistent surgical challenges, and the role of perioperative steroids remains controversial. This study developed a geometric model quantifying the mechanical impact of choroidal thickening on vitreous cavity dimensions, and to provide a mechanistic rationale for silicone oil (SO) underfill and retinal re-detachment in RRD-CD. A spherical geometric model quantified the effects of choroidal thickness changes (Δr) on vitreous cavity volume (ΔV) and the surface area of the inner choroidal boundary (RPE–Bruch’s membrane complex) (ΔS). We retrospectively reviewed clinical data from 23 patients with RRD-CD and selected three representative cases to illustrate the model’s predictions as proof-of-concept. The model predicts that a 1-mm uniform increase in choroidal thickness—assuming global, uniform thickening as a theoretical upper-bound scenario—reduces vitreous cavity volume by approximately 1.65 mL (23