Abstract
Purpose: :
To examine whether loss of retinal nerve fiber layer (RNFL) thickness measured by spectral-domain optical coherence tomography is correlated with progression of optic disc damage in glaucoma.
Methods: :
38 eyes from 38 patients (members of the Erlangen Glaucoma Registry, NTC00494923) with open angle glaucoma were included in the study. All patients received a detailed standardized glaucoma examination and were investigated by spectral-domain optical coherence tomography (Spectralis OCT, Heidelberg Engineering, Germany) measuring peripapillary RNFL thickness. All patients were examined in annual intervals over a period of at least three years with three successive OCT scans at each visit. Progressive changes of optic disc morphology between visit 1 and 4 were assessed by masked comparison of optic disc photographs. On the basis of morphological optic disc changes, the patients were classified into group 1 (no progression) and group 2 (progression). Longitudinal loss of RNFL thickness was compared between these groups.
Results: :
Mean peripapillary RNFL thickness decreased in group 1 (no progression) by 0.59 µm within 1 year, 2.35 µm within 2 years, and 3.32 µm within 3 years follow-up. In group 2 (progression), the loss of mean RNFL thickness was significantly higher by 2.97 µm within 1 year (p=0.038, Mann-Whitney U test), 4.99 µm within 2 years (p=0.02), and 6.38 µm within 3 years (p=0.011). The loss of mean RNFL thickness exceeded the intrasession variability (mean 1.47 ± 0.6 µm) of three measurements at the same date in 48.0% of patients in group 1, and 92.3% in group 2 after three years follow-up. Regarding all study patients, the sensitivity for detection of progression by OCT was 44% after 3 years at a specifity of 93%.
Conclusions: :
Longitudinal measurements of RNFL thickness show a more pronounced reduction of RNFL thickness in patients with progression of optic disc changes than in patients without progression. This may indicate a higher sensitivity of OCT for early glaucomatous changes compared to the assessment of optic disc morphology. Intrasession variability may mask minor changes in RNFL thickness.
Keywords: optic disc • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)