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S. K. Gardiner, C. A. Johnson, S. Demirel; Cup Size Measured With the Heidelberg Retinal Tomograph (HRT) Predicts Subsequent Functional Change in Early Glaucoma Better Than Rim Area. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4901.
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In this study, we aim to use HRT to predict the rate of subsequent functional change in glaucoma. In particular, we ask which features of an HRT scan are most predictive of more rapid functional change.
Data were taken from an ongoing longitudinal study of subjects with ocular hypertension or early glaucoma. 118 subjects were included who have undergone a sequence of at least 6 annual visits, including standard automated perimetry (SAP) and HRT; the most recent 6 such visits were used. The eye with most rapid functional loss for each subject was selected for analysis. Linear regression models were constructed to predict the SAP Mean Deviation (MD) in Year 1, based on HRT parameters from Year 1 together with the subject's IOP and treatment status at that date. Further regression models were constructed to predict their subsequent rate of change in MD over Years 2-6, based on the MD in Year 1 in addition to the same baseline parameters as before. For each model, the correlation between the actual value and the value predicted by the regression was calculated.
The correlation between the subjects' predicted and actual baseline MD was higher using Rim Area as a predictor (correlation = 0.584) than when using Cup Area (0.431) or Cup Volume (0.440); when comparing the correlations, p<0.001 in each case. By contrast, the subsequent rate of change in MD was better predicted by the models using Cup Area (correlation = 0.411) or Cup Volume (0.403) than when using Rim Area (0.192). When comparing these correlations, p=0.021 and 0.031 respectively.
Functional status is better correlated with rim area than cup size when measured on the same date. However, the cup size parameters are more predictive than rim area of subsequent functional change.
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