Identifying Optic Disc Topographic Parameters That Predict Mode of Progression

Abstract

Purpose:: Worsening of the optic disc often occurs earlier than the achromatic visual field in glaucoma suspect eyes and eyes with early glaucoma. The current study seeks to identify optic disc topographic parameters, as measured by Heidelberg Retinal Tomograph (HRT), that predict the appearance of earliest sign of glaucomatous damage at the level of visual field vs. optic disc.

Methods:: Glaucoma suspect eyes (including eyes with ocular hypertension) meeting the following inclusion criteria: ≥2 years of follow-up, ≥5 available visual fields, and normal visual fields at the beginning of follow-up were included from the Diagnosic Innovations in Glaucoma Study (DIGS) database at Hamilton Glaucoma Center, UCSD. Eligible eyes were required to have optic disc photographs (ODP) and reliable visual fields (VF) within 6 months of each other at baseline with an HRT image available within a year of the baseline ODP. VF abnormality during follow-up was defined as development of a repeatable abnormal PSD (p <0.05) or a GHT outside normal limits on 3 consecutive VFs. Optic disc worsening was determined through consensus evaluation of disc stereophotographs by 2 masked trained graders and adjudication by a third grader in case of disagreement. Progressing eyes were divided into 2 groups according to the modality by which initial evidence of progression was ascertained (ODP vs. VF). Baseline HRT‘s stereometric parameters were compared in the 2 groups. Multivariate logistic regression was applied to detect potentially discriminating variables.

Results:: A total of 47 eyes (47 patients) progressed after a mean (± SD) follow-up of 7.7 ± 3.1 years (range: 2.0-12.1 years). The mean linear c/d ratio in the study sample was 0.56 ± 0.16. Twenty-six eyes (55%) progressed based on VF findings and 21 eyes (45%) progressed according to optic disc findings. In univariate and multivariate analyses, none of the explored baseline HRT’s stereometric parameters (disc area, rim area, retinal nerve fiber layer cross-sectional area, cup shape measure, and maximum cup depth) were found to be predictive of whether the earliest sign of glaucoma progression occurred at the level of the VF vs. optic disc (p >0.35 for all parameters in the model).

Conclusions:: Findings on baseline HRT do not predict whether the first evidence of progression will occur at the level of the visual field as opposed to the optic disc.

Keywords: clinical (human) or epidemiologic studies: risk factor assessment • optic disc • visual fields