Applicability of ISNT rule to retinal nerve fiber layer thickness by SD-OCT in normal subjects.

Aim: The usefulness of the Inferior>Superior>Nasal>Temporal (ISNT) rule for the neuroretinal rim (NRR) has been widely used in differentiating normal eyes from glaucoma, but only a few studies have assessed whether this classical ISNT rule applies to the retinal nerve fibre layer (RNFL). This study aimed to determine the applicability of the ISNT rule for the peripapillary RNFL thickness in normal eyes using Spectral Domain Optical Coherence Tomography (SD-OCT) and assess if variants of the ISNT rule apply.

Methods: A cross-sectional study was conducted on 120 eyes of 62 healthy subjects who fulfilled the study criteria.