Stereopsis and Outer Retinal Structure After Reduced-Fluence Photodynamic Therapy for Central Serous Chorioretinopathy: A 12-Month Study

Changes in binocular function after anatomical resolution of central serous chorioretinopathy (CSC) following reduced-fluence photodynamic therapy (RFPDT) remain unclear. We characterized 12-month stereopsis outcomes and the associated clinical and optical coherence tomography (OCT) factors. This retrospective single-center study included 51 eyes of 51 patients with unilateral CSC treated with RFPDT. Best-corrected visual acuity (BCVA), Titmus Stereo Test (TST), TNO stereotest (TNO), and central retinal thickness (CRT) were assessed at baseline and at 3, 6, and 12 months. Stereopsis (TST and TNO) was the primary longitudinal outcome; BCVA and CRT were secondary. Change over time was assessed with linear mixed-effects models. Associations of baseline and concurrent clinical and OCT factors with stereopsis were examined using Spearman correlation and multivariable linear regression. Improvements in TST, TNO, and BCVA were evident by 3 months (all P < 0.001), with no significant further change thereafter except a small BCVA gain by 12 months ( P = 0.006). At 12 months, abnormal stereopsis remained in 35% (TST) and 57% (TNO) of eyes. Larger baseline serous retinal detachment (SRD) area was independently associated with worse concurrent TST and TNO, but not with 12-month stereopsis. Greater 12-month outer retinal layer thickness (ORLT) was associated with better concurrent TNO in an adjusted model ( P = 0.029). In eyes with good baseline acuity, longer baseline photoreceptor outer segment (POS) length was the only independent predictor of better 12-month TST. Stereopsis improved during the 12 months following RFPDT but often remained abnormal, even in eyes with good BCVA. Different structural parameters were associated with stereopsis by disease stage—subretinal fluid extent during active disease and residual outer retinal structure after resolution—and in these good-acuity eyes, pre-treatment outer retinal structure predicted 12-month stereopsis. Together, these findings suggest that stereopsis may capture residual visual dysfunction that is not fully reflected by BCVA.