Use of sequential Heidelberg retina tomograph images to identify changes at the optic disc in ocular hypertensive patients at risk of developing glaucoma

Aim-To determine if global and segmental changes in optic disc parameters o f sequential Heidelberg retina tomograph (HRT) images develop in individual ocular hypertensive (OHT) patients without white on white visual field def ects. Methods-Patients and normal controls were recruited from a prospective ocul ar hypertension treatment trial. The subject groups consisted of 21 OHT pat ients who had converted to early glaucoma on the basis of visual field crit eria (24-2 program on the Humphrey perimeter), 164 OHT subjects with normal visual fields, and 21 normal controls. Sequential HRT images 16-21 months apart were obtained for each subject and segmental optic disc parameters we re measured to determine if any change had occurred. From the analysis of s equential HRT images of the 21 normal eyes we established normal limits of interimage variation. Individual discs in each group showing changes above the 95% limit of normal variability were then sought. Results-Several segmental and global optic disc parameters were found to sh ow significant change in the converter group before confirmed visual field change, confirming our previously published results. Individual optic disc analysis using the 95% limit of normal variability data demonstrated glauco matous change in 13 out of 21 converter eyes. 47 of the 164 OHT eyes with n ormal visual fields showed change in global and segmental parameters in a " glaucomatous" direction above the level expected for normal variability. Th e parameters which changed most frequently in the OHT eyes were: global cup volume (6.7% of discs), inferonasal cup volume (11%), inferotemporal cup v olume (8.5%), and superotemporal cup area (7.3%). Conclusions-We have identified change in a subset of ocular hypertensive pa tients which could predate the development of glaucomatous visual field los s. The HRT could be of value in the sequential follow up of those suspected of having glaucoma by identifying eyes at risk of developing glaucoma. How ever, further refinement of the technique is required to eliminate some of the inherent variability of the analysis method described, and to increase the ability to detect at risk individuals.