Alamouti B., Kapp A., Funk J.

Albert-Ludwigs-Universität Freiburg, Augenklinik

Objective: In three-dimensional optic disc tomography a reference plane is required to calculate optic disc rim or cup values. The position of the reference plane often depends on the retinal thickness at the temporal disc margin. Originally it was assumed that the retinal thickness at the temporal disc margin is independent of age. We wanted to check this hypothesis using optical coherence tomography. Additionally we wanted to determine the reproducibility of the OCT-measurements in this area.
Methods: 104 eyes of 101 healthy volunteers were included in our study. Three OCT-Scans were performed on each eye. The scans were aligned vertically and placed at the temporal edge of the optic disc. For each eye, the thickness of the whole retina as well as the thickness of the retinal nerve fiber layer were calculated together with their coefficients of variation. Thereafter retinal thickness and nerve fiber layer thickness were correlated to age.
Results: The mean retinal thickness was 249 +/-22 µm. The mean retinal nerv fiber layer thickness was 109 +/-22 µm. The mean coefficients of variation were 3.7% (total retinal thickness) and 8.2% (nerve fiber layer thickness). Both the total retinal thickness and the nerve fiber layer thickness were significantly correlated to age (total retina: y = -0,471 x + 267,382 , p<0,0001, nerve fiber layer : y = -0,375 x +124,207 , p<0,0001).
Conclusions: Using OCT scans the total retinal thickness can be calculated with high reproducibility (coefficient of variation = 3.7%). The reproducibility of nerve fiber layer thickness measurements is clearly lower (coefficient of variation = 8.2%). Both the total retinal thickness and the nerve fiber layer thickness significantly decrease with age. This must be considered when follow-up examinations of the optic disc topography are performed.

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