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Comparing stereometric parameters between Heidelberg Retinal Tomography 2 and 3 in Asian eyes: the Singapore Malay
Victor Koh1, Seng Chee Loon, Wan-Ling Wong
1Department of Ophthalmology, National University Health Systems, Singapore.
Purpose:
To examine the correlation and agreement of stereometric parameters between Heidelberg Retinal Tomograph version 2 (HRT-2) and HRT-3 in a normal Asian population.
Methods:
This was a population-based study using data from the Singapore Malay Eye Study. Participants underwent a standardized and complete ophthalmic examination. A confocal laser ophthalmoscope using HRT-2 was used to take retinal images by 2 trained operators. Disc contours were drawn by a single experienced ophthalmologist. Without modifying the contours, the exact images were then exported and analyzed with HRT-3 software. Paired t tests were used to compare mean differences, whereas interclass correlations and Bland-Altman plots were used to assess agreement and trend of Moorfields regression analysis parameters between HRT-2 and HRT-3.
Results:
A total of 2960 Malay participants [mean age, 58.3 y (SD 10.9); 50.5% female] were included. Average disc size was 2.15 μm. Interclass correlations and Bland-Altman plots showed good agreement between HRT-2 and HRT-3. However, global disc area, rim area, cup area, cup-disc area ratio, rim-disc area ratio, and rim volume were significantly different between HRT-2 and HRT-3, with all area and rim volume measurements using HRT-2 were approximately 4% larger compared with HRT-3. Analysis of HRT-2 and HRT-3 parameters from different sectors of the scans showed an inconsistent change in measurement values. Cup shape measurement was significantly different in the temporal region compared with the nasal region of the optic nerve head.
Conclusions:
There was good correlation between the 2 HRT versions and conversion equations were possible to calibrate HRT-3 parameters from HRT-2 measurements in Asian eyes. However, HRT-2 and HRT-3 showed significant differences in stereometric parameters. Further studies are needed to determine the impact of such differences and in comparative accuracy of HRT-2 versus HRT-3 for diagnosis and monitoring of glaucoma.