Cup-disc area ratio correlation with visual field defects using the Heidelberg Retina Tomograph (HRT) and a digital stereo optic disc camera (Discam)

Velota CT Sung, Anna Bhan and Stephen A Vernon

Department of Ophthalmology, Queen's Medical Centre, University Hospital, Nottingham, UK

Purpose:  To compare the correlation of area cup-disc ratios (ACDR) measured by the HRT and the Discam with visual field global indices in eyes with glaucoma.

Methods: Forty-eight eyes from 24 glaucoma patients had  optic disc images taken by the HRT and the Discam. The mean deviation (MD) and corrected pattern standard deviation (CPSD) from Humphrey Field Analyser were correlated (Pearson’s correlation coefficient) with the ACDR of the HRT mean topography and Discam stereo images. Two observers independently drew the disc margin on the HRT images and the disc and cup margins on the Discam images produced two sets of data.

Results: Images of 6 eyes were excluded because of poor image quality. Forty-two eyes (29 POAG,13 NTG) were analysed. In both observer's data, the HRT ACDR was significantly correlated with the MD (p<0.001) and the CSPD (p<0.01). The Discam ACDR was significantly correlated with the MD (p<0.05) but not with the CPSD. In POAG group, the HRT ACDR was significantly correlated with the MD (p<0.01) and the CPSD (p<0.05). In NTG group, the HRT ACDR was significantly correlated with the MD (p<0.05) but not with the CPSD. There was no significant correlation between the Discam ACDR and the MD or CPSD in both POAG and NTG subgroups.

Conclusion: In both subgroups of glaucoma there was better correlation between the HRT ACDR and the MD and CPSD than with the Discam ACDR. The HRT ACDR may be a better indicator of the degree of glaucomatous optic nerve head damage.