Correlation of confocal laser scanning tomography with planimetric photographic measurements of the optic disc in a normal South Indian population: the Vellore Eye Study.

ABSTRACT

PURPOSE: To compare the confocal laser tomographic scanning evaluation with photographic measurements of the optic nerve head in a South Indian population. METHODS: The prospective comparative clinical non-interventional epidemiologic study included 62 subjects (62 eyes) forming a population-based sample, selected randomly. Mean age was 47.2 +/- 8.9 years, mean refractive error measured was -0.17 +/- 1.10 diopter (range, - 4.50 to + 2.50 diopter). Confocal laser scanning tomographic images on Heidelberg Retina Tomograph (HRT) and colour optic disc photographs were morphometrically analysed and compared. Main outcome measures were morphologic optic disc parameters. RESULTS: The optic disc area measurements were significantly smaller (p < 0.001) in the HRT technique than in the photographic method. In contrast, the HRT as compared to the photographic measurements showed significantly (p < 0.001) larger values for the relative width and relative area of the neuroretinal rim. The differences in measurements between both methods were maximum in the nasal part (p < 0.001) of the optic disc and minimum in the temporal disc region. CONCLUSION: In normal eyes of South Indians, neuroretinal rim measurements by the HRT and expressed as percentage of disc size measurements are significantly larger than rim measurements on disc photographs.