Predicting Future Visual Field Loss with the Heidelberg Retina Tomograph (HRT) and Assessment of Optic Disc Photographs

Abstract

Abstract: : Purpose: To compare the sensitivity and specificity of two objective HRT classification tools and subjective assessment of stereoscopic optic disc photographs for predicting future visual field abnormality. Methods: 212 eyes with normal visual fields (VF) at baseline were followed longitudinally with HRT (Heidelberg Retina Tomograph, Heidelberg Engineering, Dossenheim, Germany), for 2 or more years (mean follow-up 5.2 years, range = 2.1 to 8.0 years). Of these eyes, 54 (25%) developed repeatable VF defects on 24-2 automated perimetry (full threshold and/or SITA) (convert group) and 158 (75%) eyes did not develop repeatable VF defects (non-convert group). We determined how many eyes from each group developed disc abnormalities based on 2 classification tools available in HRT software; 1) at least one repeatable inferior and/or superior disc sector outside of normal limits using the Moorfields Regression Analysis (MRA) or 2) at least one repeatable glaucomatous HRT Classification (HRTC) (according to Mikelberg). These data were compared to results from subjective masked assessment of simultaneous optic disc stereophotographs. Results: 20/54 (37%) convert eyes showed repeatable abnormal MRA results before they showed repeatable abnormal VF results (mean 4.4 years prior to VF conversion, range = 2.2 years to 7.7 years). 19/54 (35%) VF convert eyes were classified as abnormal using the HRTC (repeatable) and 32/54 (63%) were classified as abnormal based on disc photographs on or before the VF conversion date. 29/158 (18%, 82% specificity) non-convert eyes showed repeatable abnormal MRA results before their most recent VF test (mean 4.4 years prior to most recent VF, range = 0.3 years to 8.0 years). 50/128 (32%, 68% specificity) VF non-convert eyes were classified as abnormal using the HRTC and 90/128 (60%, 40% specificity) VF non-convert eyes were classified as abnormal based on disc photographs on or before their most recent VF test date. Conclusions: In our population, as a predictor of future VF abnormality, the Moorfields Regression Analysis was as sensitive and was more specific than HRT Classification. Subjective masked grading of optic disc photographs was more sensitive and less specific than both HRT-based techniques. It is possible that non-convert eyes classified as abnormal will develop VF loss with further follow-up.

Keywords: optic disc • imaging methods (CT, FA, ICG, MRI, OCT, RTA, S