Purpose: To assess the agreement between a digital stereo optic disc camera
(Discam) and a Heidelberg Retina Tomograph (HRT) when measuring normal and
glaucomatous optic discs.
Methods: The optic discs of 78 eyes of 39 persons (18
POAG, 7 NTG, 2 OH and 12 normal) were imaged with the Discam and the HRT. Two
observers independently drew the disc margins on the HRT mean topography images
and the disc and cup margins on the Discam images. The agreement between area
cup-disc ratio (ACDR) and the radial cup-disc ratio (RCDR) at various angles
were calculated using the intraclass correlation coefficient (ICC).
Results: 8 eyes were excluded due to poor image
quality. ACDR agreement in 26 eyes with clinically normal optic discs was fair
to substantial (ICC = 0.22 and 0.64, observer A and B respectively). RCDR
agreement was poor in observer A (ICC = -0.01 to 0.1) and fair to moderate in
observer B (ICC = 0.33 to 0.46). ACDR agreement from 44 eyes with glaucomatous
excavation was moderate (ICC = 0.44 and 0.52, observer A and B respectively).
RCDR agreement was poor to moderate in observer A (ICC = 0.2 to 0.47) and poor
to substantial in observer B (ICC = 0.14 to 0.69).
Conclusion: The agreement ranged from fair to
substantial for ACDR and poor to substantial for RCDR. There was substantial
variation in the agreement from the two observers. Measurements derived from
the HRT and the Discam do not appear to be interchangeable for clinical
purposes.