Retinal nerve fibre layer imaging compared with histological measurements in a human eye.

PURPOSE

A feasibility study comparing retinal nerve fibre layer (RNFL) thickness values obtained with imaging devices against RNFL thickness measurements obtained histologically in a human eye.

DESIGN

A single patient scheduled for orbital exenteration, who still possessed a healthy functioning eye.

METHODS

Before surgery, the eye was imaged using optical coherence tomography (OCT) and scanning laser polarimetry (SLP). After orbital exenteration, the globe was sectioned, and 100 equidistant RNFL thickness measurements were obtained for each of four concentric rings centred on the optic disc, with diameters of 3.0, 3.5, 4.0, and 4.5 mm.

RESULTS

RNFL thickness was found to be inversely related to the distance from the centre of the optic disc along each radial meridian. Peripapillary RNFL thickness was found comparable for histology, OCT, and SLP. RNFL thickness measured histologically confirmed a 'double hump' pattern, peaking at the superior and inferior poles. Histologically derived RNFL thickness (microm), at 3.0 and 3.5 mm diameter ring ranged between 30-135 and 25-115 respectively. In comparison, the 3.0 mm diameter GDx data ranged between 25 and 100, and the 3.4 mm diameter OCT data between 40 and 175.

CONCLUSIONS

Imaging data appear qualitatively similar when compared to the histologically derived data. Quantitative differences may be partly due to scaling differences and histological artefacts. The histological analysis approach demonstrated in this study can potentially serve to validate imaging-derived data, as well as help improve our understanding of RNFL loss in glaucoma.