Purpose
To study the variability of the stereometric parameters of optic disc between the Heildelberg Retina Tomograph III (HRT III) and Three-Dimensional Optical Coherence Tomography (3D OCT) in normal subjects and in patients with Primary Open Angle Glaucoma (POAG).
Methods
This cross-sectional study included 18 eyes of normal patients and 35 eyes of POAG patients. Each patient underwent an HRT III examination and 3D OCT Topcon-1000 on the same day. All the examined subjects were older than 47 years. Excluded from the study were eyes with disc area higher than 2.43mm2, hazy media, refractive anomalies (myopia higher than 5 diopters or astigmatism higher than 2 diopters) and eyes with other diseases rather than POAG.The analysis concerned the following topographical parameters of the optic nerve: disc area, cup area, rim area, cup volume, rim volume, cup/disc area ratio and linear cup/disc ratio. The means of the variables were calculated for the HRT III and 3D OCT in both groups. A T-test was used to compare the HRT III against 3D OCT.
Results
In normal eyes there was a significant difference (p= <0.001) of cup area, cup volume, rim volume, cup/disc ratio and linear cup/ratio between the HRT III and the 3D OCT. In POAG eyes there was a significant difference (p= <0.003) of disc area, cup area, cup/disc area ratio and linear cup/disc ratio. In both groups the 3D OCT overestimate the stereometric parameters of the HRT III.
Conclusions
There is a great variability of the stereometric parameters of optic disc between the Heildelberg Retina Tomograph and Three-Dimensional Optical Coherence Tomography in normal subjects and in patients with Primary Open Angle Glaucoma.