Structural Analysis of the Optic Nerve Head in Healthy Eyes and in Eyes withGlaucoma

Overview

Purpose:
Assess the possibilities of structural analysis of the optic nerve head byHeidelberg Retina Tomograph (HRT) and its use in detection of glaucomatous changes of the optic nerve in particular. Indicate the topographical parametersthat are most influenced by glaucoma and are therefore vital in early diagnosis ofglaucomatous changes of the optic nerve.Patients and methods: Laser scanning tomography (HRT II) was used to examine68 healthy eyes (control group) and 42 eyes with open angle glaucoma (studygroup). All the examined subjects were older than 35 years of age. The analysisconcerned the following topographical parameters of the optic nerve head: discarea, cup area and rim area, cup volume, rim volume, cup/disc area ratio, meancup depth, maximum cup depth, mean retinal nerve fiber layer thickness (RNFL),RNFL cross sectional area, height variation contour and cup shape measure anddiscriminant functions used for classification of the optic nerve head findingaccording to F. S. Mikelberg and R. Burk. Statistical analysis was employed toascertain the significant difference in these topographical parameters for thehealthy eyes and the eyes with glaucoma. This method was used for both the wholeoptic disc and the 6 sectors of the optic nerve head. Another aim of the analysiswas also to find out the correlation between the topographical parameters andage.Results: Significant difference in the topographical parameters for thewhole opticdisc was spotted in the following parameters: rim volume, mean RNFL thickness,RNFLcross sectional area and discriminant functionFSM. Significant differenceswere also found in between individual sectors of the optic nerve head, except forthe upper temporal and upper nasal sector. The parameter, which varied mostfrequently between the groups, was rim volume. Significant correlations betweenage and topographical parameters were found forthe following parameters: rimarea, cup shape measure and mean RNFL thickness.Conclusion: Results of our study showed, that HRT is able to distinguish betweennormal and the pathological findings of optic nerve head according to topographicalparameters significantly different between the two examined groups. Theseparameters are important in the diagnosis of glaucoma and also in the follow-upof patients with open angle glaucoma.

Key words:
Heidelberg Retina Tomograph, structural analysis, topographicalparameters of the optic nerve head, open angle glaucoma