[Influence of anterior chamber depth on optic disc measurements with OCT and HRT 3]

The aim of this study was to investigate the influence of the anterior chamber depth (ACD) on the measurement of the optic nerve head size with OCT and HRT 3.

100 pseudophakic eyes of 100 patients were enrolled in this prospective study. The measurement of the optic nerve head was performed with the optical coherence tomography (Stratus OCT, Carl Zeiss Meditec Inc., Dublin, CA) and the confocal laser scanning tomography (Heidelberg retina tomograph, HRT 3, Heidelberg Engineering, GmbH, Dossenheim, Germany). Bland and Altman plots were used to examine the agreement between the parameters of the two techniques. The relationship between the optic nerve head size and the ACD was analysed by linear regression.

Optic disc size measurement with the OCT and the HRT 3 showed no significant difference (p = 0.638). Measurement of the optic disc size with the OCT was significantly correlated with the ACD (- 0.234; p = 0.016). The optic disc size decreases with increasing values of the ACD. There was no influence of the ACD on the measurement of the optic disc size with the HRT 3 (r = 0.128; p = 0.193).

While the optic disc size measured by OCT decreased with increasing ACD, the measurement with the HRT 3 turned out to be independent of the ACD. The OCT may underestimate the optic disc size in lower ACD. This may result in reduced agreement between the two devices.