Author Block: Isabela Martins Melo  ¹, Aditya Bansal¹, Sumana Naidu², Paola Oquendo¹, Hesham Hamli¹, Wei Wei Lee¹, Rajeev Muni¹.  ¹St Michaels Hospital, ²University of Toronto.

Author Disclosure Block: I. Martins Melo:   None.  A. Bansal:   None.  S. Naidu:   None.  P. Oquendo:   None.  H. Hamli:   None.  W. Lee:   None.  R. Muni:   None.

Abstract Title: Stages of Rhegmatogenous Retinal Detachment: The Missing Link to Determine Urgency in Fovea-Involving Detachments?

Abstract Body: Purpose:   To describe the sequential morphological changes following rhegmatogenous retinal detachment (RRD), utilizing a novel, objective, and clinically relevant staging system based on swept-source optical coherence tomography (SS-OCT) and determine its association with the duration of fovea-off and postoperative visual acuity.   Study Design:   Prospective cohort study.   Methods:   49 consecutive patients with fovea-involving RRD presenting to St. Michael’s Hospital, Toronto, from January 2020 to April 2022, were assessed at baseline    with SS-OCT and ultra-widefield SS-OCT. Primary RRDs with breaks above 8 and 4 o'clock were included. Patients with vision loss ≥ 3 months, PVR ≥ grade B, demarcation line, and previous history of vitrectomy or other retinal pathology were excluded. The staging system was based on the assessment of outer retinal morphology on successive SS-OCT scans from the peripheral break to the most posterior aspect of the RRD, following its direction of progression.   Results:   Mean age was 61.2(SD±15.2) years and the mean presenting logMAR visual acuity was 1.09(SD±0.75). All stages observed on the HD51-line scan were reported. Outer retinal changes occurred in five reproducible stages: 1) separation of the neurosensory retina from the RPE (42/49, 85.7%); 2) thickening of photoreceptor inner (IS) and outer segments (OS)(45/49, 91.8%); 3) outer retinal corrugation (ORC) formation: 3a) low-frequency(44/49, 93.6%) and 3b) high-frequency ORCs(42/49, 85.7%); 4) loss of definition of ORCs with concurrent thickening of ISs and OSs (26/49, 53.1%); 5) patchy (moth-eaten) or complete loss of ISs and OSs(17/49, 34.7%). The mean duration of fovea-off in days by stage in the parafovea was 2 days(SD±1.4), 2.3 days(SD±1.2), 11.4 days(SD±8.1), and 12 days(SD±13.3) for Stage 3a, 3b, 4, and 5 respectively. There was a statistically significant association between increasing stage of RRD and longer duration of foveal involvement(p=0.001) and, most importantly, between increasing stage and worse visual acuity at 3 months post-operatively (p=0.011).   Conclusions:   For the first time in humans  in vivo , the progressive morphologic changes that occur in the detached outer retina were described, using a novel, reproducible OCT-based staging system. Increased stage of RRD was associated with a longer duration of fovea-off and worse visual acuity at 3 months postoperatively. Recognizing the progressive changes that occur in RRD may have future implications for adjunct pharmacological therapies and has the potential to provide a framework for studies that assess the urgency of repair based on presenting stage, allowing clinicians to thoroughly consider the status of the retina on presentation.