Quantification of the thickness of the retinal nerve fibre layer. A comparison of laser scanning ophthalmoscopy, polarimetry and optical coherence tomography of eyes from healthy patients and patients with primary open angleglaucoma

Purpose. To evaluate the thickness of the retinal nerve fiber layer (RNFL) in healthy eyes and in eyes of patients with primary open angle glaucoma us ing the Heidelberg retina tomograph (HRT), the nerve fibre analyser (NFA) a nd the optical coherence tomograph (OCT). Methods. In this prospective cohort study, 40 normal eyes and 86 eyes of ag e-matched glaucoma patients were compared by confocal scanning laser tomogr aphy using the HRT, scanning laser polarimetry (NFA) and optical coherence tomography (OCT). The RNFL thickness was measured in the superior, inferior , nasal and temporal regions as well as the total circumference. Results. All three methods revealed a statistically significant difference between normal and glaucomatous eyes with respect to the mean RNFL thicknes s in the inferior and superior regions (p <0.001). The mean RNFL thickness in the superior region was 329 mum (HRT), 87 mum (NFA) and 94 mum (OCT) in healthy volunteers compared to 275 mum (HRT), 72 mum (NFA) and 82 mum (OCT) in the patient group. In the inferior region, it was 323 mum (HRT), 87 mum (NFA) and 93 mum (OCT) in healthy subjects versus 240 mum (HRT), 74 mum (N FA) and 83 mum (OCT) in glaucoma patients. Cut-off points to differentiate between normal and glaucomatous eyes could not be defined. There was no dif ference in the RNFL thickness of right and left eyes. Conclusions. In RNFL thickness measurements using HRT, NFA and OCT, glaucom a patients showed a significantly thinner RNFL in the superior and inferior areas compared to healthy volunteers. These results confirm the known hist ological and fundus photographic findings of RNFL thinning near the optic d isc in glaucoma patients. Although RNFL thickness cannot be used to diagnos e glaucoma in individual patients due to the high interindividual differenc es,the quantitative assessment of RNFL thickness may complement the diagnos tic armamentarium as a sensitive parameter for diagnosing and monitoring gl aucomas.