Background:   To assess the agreement between the Heidelberg Retina Tomograph and Cirrus spectral-domain optical coherence tomography (Cirrus HD-OCT [Carl Zeiss Meditec, Dublin, CA, USA]) when measuring optic disc parameters.

Methods:   Prospective, cross-sectional study. Methods:   A total of 96 glaucoma patients and 21 normal subjects were analysed. Methods:   Optic nerve head measurements, including disc area, rim area, cup-to-disc ratio and cup volume were obtained using both the Cirrus HD-OCT and Heidelberg Retina Tomograph 3 (Heidelberg Engineering GmbH, Heidelberg, Germany). Methods:   Bland-Altman plots were used to evaluate the agreement between each of the optic disc parameters.

Results:   Although Cirrus HD-OCT values were smaller than Heidelberg Retina Tomograph 3 values for the disc and rim areas, overall the Cirrus HD-OCT and Heidelberg Retina Tomograph 3 measurements were highly correlated (r = 0.657 to 0.821). As compared with Heidelberg Retina Tomograph 3, disc and rim areas tended to be minimized by Cirrus HD-OCT, especially when there were large disc and rim areas, although there was no relationship between the discrepancy and the level of measurement of the cup-to-disc ratio. The optical coherence tomography overestimated the Heidelberg Retina Tomograph-determined cup volume, especially when there were large cup volumes.

Conclusions:   Bland-Altman analyses revealed that with the exception of the cup-to-disc ratio, there was poor agreement between the Cirrus HD-OCT and Heidelberg Retina Tomograph 3 morphometric measurements. In addition, with the exception of the cup-to-disc ratio, the optic nerve head measurements could not be directly compared between the Cirrus HD-OCT and Heidelberg Retina Tomograph 3.