Lateral elongation of flat irregular pigment epithelial detachment: A novel optical coherence tomography biomarker in polypoidal choroidal vasculopathy

Purpose: To explore novel Optical Coherence Tomography (OCT) biomarkers and precursor lesions in Polypoidal Choroidal Vasculopathy (PCV). Methods: This retrospective cohort study included 76 treatment naïve fellow eyes of PCV. Focus was given to analyse the various morphological changes in the clinically unaffected fellow retina during the follow-up period. Results: 11 fellow eyes (14.47%) developed disease activity in the form of Sub Retinal Fluid (SRF) or Intra Retinal Fluid (IRF) within a mean follow-up of 17 months. All 11 eyes (100%) showed the presence of flat irregular pigment epithelial detachment (FIPED) and a peculiar property of lateral elongation of FIPED during disease activity. A positive correlation with the disease progression was found for the same (P < 0.0001). The mean horizontal dimension of the flat irregular PED at the enrolment was 1984 ± 376u and the mean expansion of FIPED at SRF formation was 461 ± 152u. ICG taken at the time of disease activity in the fellow eye revealed branching vascular network (BVN) in 9 (81.8%) eyes, polyps in 7 (63.6%) eyes, a combination of both in 5 (45.4%) eyes. Type one BVN with interconnecting channels showed faster disease progression than type two BVN. Eye tracking ICG illustrated that BVN corresponded to the FIPED in OCT and polypoidal lesions developed at the end of expanding FIPED. Conclusion: Flat irregular pigment epithelial detachment with its characteristic property of lateral elongation may be considered as a precursor lesion for PCV and as a novel OCT biomarker for the disease activity. Fellow eyes with FIPED need close monitoring to identify development of disease activity at the earliest.