Quantitative and objective topometrical analysis of drusen of the optic nerve head with the Heidelberg retina tomograph (HRT)

Abstract

Optic nerve head drusen (ONHD) are one of the most frequent causes for congenital swelling of the optic nerve head. Visual field and retinal nerve fiber layer defects are reported in cases of ONHD. The Heidelberg Retina Tomograph (HRT) allows a 3-dimensional topometric analysis of the optic nerve disc and measurement of the peripapillary mean retinal nerve fiber layer. A total of 18 eyes from 9 patients with sonographically confirmed drusen were analyzed with the HRT. Data were compared to a control group of 18 eyes from 9 matched healthy individuals. Statistical analyses were performed by using ANOVA (univariate). All patients with ONHD underwent a computerised visual field test (30 degrees, Octopus 101). Due to a bad reliability factor of over 10 in the visual fields by 4 out of 18 eyes, only measurements from 14 eyes were included in the study. We correlated visual field and HRT parameters and calculated the Pearson's correlation coefficient (r). We found a significant difference in the measured parameter mean retinal nerve fiber layer (RNFL) thickness ( p<0.05) between the two groups. In the ONHD group a negative correlation coefficient was found between the peripapillary mean RNFL thickness and the loss variance (r=-0.50, p=0.03) as well as between the peripapillary RNFL cross-sectional area and the loss variance (r=-0.47, p=0.04). The HRT is able to detect a peripapillary RNFL thinning in cases with ONHD. The mean RNFL thickness correlated with the loss variance. The HRT should be used to perform a quantitative and objective topometric analysis in cases with ONHD.