[Structural analysis of the optic nerve head in healthy eyes and in eyes with glaucoma]

Abstract

Purpose: Assess the possibilities of structural analysis of the optic nerve head by Heidelberg Retina Tomograph (HRT) and its use in detection of glaucomatous changes of the optic nerve in particular. Indicate the topographical parameters that are most influenced by glaucoma and are therefore vital in early diagnosis of glaucomatous changes of the optic nerve.

Patients and methods: Laser scanning tomography (HRT II) was used to examine 68 healthy eyes (control group) and 42 eyes with open angle glaucoma (study group). All the examined subjects were older than 35 years of age. The analysis concerned the following topographical parameters of the optic nerve head: disc area, cup area and rim area, cup volume, rim volume, cup/disc area ratio, mean cup depth, maximum cup depth, mean retinal nerve fiber layer thickness (RNFL), RNFL cross sectional area, height variation contour and cup shape measure and discriminant functions used for classification of the optic nerve head finding according to F. S. Mikelberg and R. Burk. Statistical analysis was employed to ascertain the significant difference in these topographical parameters for the healthy eyes and the eyes with glaucoma. This method was used for both the whole optic disc and the 6 sectors of the optic nerve head. Another aim of the analysis was also to find out the correlation between the topographical parameters and age.

Results: Significant difference in the topographical parameters for the whole optic disc was spotted in the following parameters: rim volume, mean RNFL thickness, RNFL cross sectional area and discriminant function FSM. Significant differences were also found in between individual sectors of the optic nerve head, except for the upper temporal and upper nasal sector. The parameter, which varied most frequently between the groups, was rim volume. Significant correlations between age and topographical parameters were found for the following parameters: rim area, cup shape measure and mean RNFL thickness.

Conclusion: Results of our study showed, that HRT is able to distinguish between normal and the pathological findings of optic nerve head according to topographical parameters significantly different between the two examined groups. These parameters are important in the diagnosis of glaucoma and also in the follow-up of patients with open angle glaucoma.