PURPOSE. To study the test retest variability of stereometric parameters on Heidelberg Retina Tomograph II (HRT II).
METHOD. HRT-II stereometric parameters from 5 consecutive images were obtained for 50 eyes (26 normal, 24 glaucoma) of 50 cases. Test-retest variability was studied using 3 different statistical methods. The effect of age, diagnosis, cupping, visual acuity and refractive error on test-retest variability on HRT II was analyzed.
RESULTS. Using coefficient of variance, intraclass correlation coefficient and Cronbach’s alpha the test-retest variability was found to be lowest for mean cup depth, cup area, cup/disc area ratio, vertical cup/disc ratio and rim/disc area ratio, in that order. The average baseline variability in Moorfields Regression Analysis was a one level change in 2 sectors. Test-retest variability had a significant correlation with age (r=0.33,p=0.019) and visual acuity (r=-0.46,p=0.005). As compared to eyes with astigmatism less than 1D (mean coefficient of variance=6.4+4.9), the test-retest variability was higher (p= 0.044) in eyes with astigmatism more than 1D (mean coefficient of variance=20.0+22.6).
CONCLUSIONS. The test retest variability of HRT II stereometric parameters is comparable to the one reported for HRT. Eyes with uncorrected astigmatism more than 1D and poor visual acuity may not be suitable for follow up using HRT-II stereometric parameters.