Postoperative demarcation lines in rhegmatogenous retinal detachment: what en-face imaging reveals about visual outcomes

Purpose: To investigate postoperative demarcation lines using en-face optical coherence tomography (OCT) after pars plana vitrectomy (PPV) for primary rhegmatogenous retinal detachment (RRD) and assess association with visual outcomes. Methods: Consecutive patients undergoing PPV for primary RRD with gas tamponade were prospectively enrolled. Postoperative demarcation lines on en-face OCT were defined as hyper-reflective lines following contour of previous detachment edge. Postoperative best-corrected visual acuity (BCVA) and metamorphopsia were analyzed in relation to location of demarcation lines (within the central 3-mm ETDRS zone vs. between 3 and 6 mm). A control group of patients treated with silicone oil (SO) was included for comparison. Results: A total of 31 eyes met inclusion criteria. En-face OCT identified postoperative demarcation lines in 30 eyes (96.7%). None were seen in 25 eyes after SO removal (p < 0.001). Ellipsoid zone (EZ) disruption at demarcation line was found in 21 eyes, persistent subretinal fluid (SRF) in 6 eyes, and outer retinal folds (ORF) in 3 eyes. Eyes with persistent SRF had longer interval between symptom onset and surgery compared with those showing EZ disruption or ORF (p = 0.025). Demarcation lines within central 3-mm ETDRS zone were significantly associated with greater horizontal metamorphopsia (B = 0.232, p = 0.003), whereas no significant association was found with postoperative BCVA (B = − 0.094, p = 0.280). Conclusions: En face OCT accurately detects postoperative demarcation lines, which may represent a previously overlooked factor influencing visual dysfunction after PPV for RRD with gas tamponade.