Bacillary Layer Detachment in Rhegmatogenous Retinal Detachments

Authors: Isabela Martins Melo  , Aditya Bansal, Wei Wei Lee, Paola Oquendo, Hesham Hamli, Rajeev Muni.  St Michaels Hospital.

Author Disclosures: I. Martins Melo:   None.  A. Bansal:   None.  W. Lee:   None.  P. Oquendo:   None.  H. Hamli:   None.  R. Muni:   None.

Abstract Body: 

Purpose:   To describe bacillary layer detachment (BALAD) and related abnormalities of the foveal bouquet in rhegmatogenous retinal detachment (RRD) and assess their impact on photoreceptor recovery and full-thickness macular hole (FTMH) formation, using optical coherence tomography (OCT).        

Study Design:   Prospective cohort study.   

Methods:   93 consecutive patients with fovea-off RRD, presenting to St. Michael’s Hospital from January 2020 to April 2022, were assessed at baseline for structural abnormalities in the fovea using high-definition OCT scans.   

Results:   59% (13/22) were male with a mean age of 63.3(±8.6). Mean baseline logMAR visual acuity was 1.35 (±0.36) with a duration of fovea-off of 6.4 days (±5.6) and RRD extent of 5.4 (±2.6 SD) clock hours. 23.7% (22/93) of patients had evidence of BALAD and associated abnormalities. The BALAD consisted of splitting within the photoreceptor inner segment (IS) myoid zone at the foveal bouquet, forming an intra-retinal cavity of variable height (mean 108.9μm±59.5). The posterior aspect of the BALAD was delineated by a hyperreflective band, with a mean maximum thickness of 125μm±49 and a mean lateral extension of 615μm±226. 86.4%(19/22) of patients had foveal BALAD, 15.8%(3/19) of which had clear cleavage planes extending from the outer nuclear layer into the myoid zone, and 14%(3/22) had an inner lamellar hole with a residual bridge of photoreceptor remnants (all of which progressed to FTMH). When assessing baseline features that could have contributed to the BALAD in RRD, all patients had cystoid macular edema and prominent outer retinal corrugations (ORCs) at baseline. Among patients with gradable OCT at 3 months, 80% (12/15) had ellipsoid zone discontinuity, which persisted in 41% (5/12) at 1 year.   

Conclusions:   This is the first observation of BALAD in RRD and the first study to describe its proposed pathophysiology. We hypothesize that horizontal and centrifugal tractional forces applied to the central foveal bouquet-Muller cell scaffold, due to hydration, lateral expansion, and change in the elasticity of the outer retina, with subsequent development of ORCs, may be responsible for the formation of BALAD. Further insult to the anterior border of the BALAD space from adjacent cystic changes in the outer nuclear layer may result in instability of the Müller cell plait making it susceptible to further disruption. BALAD and associated structural abnormalities may represent a possible pathophysiological basis for FTMH formation in RRD.