Using OCTA to assess peripapillary RNFL vessel density

Seattle-Enhanced imaging provided by optical coherence tomography angiography (OCTA) is enabling research focusing on vascular dysfunction in glaucoma.

At ARVO 2016, investigators from the Hamilton Glaucoma Center, Shiley Eye Institute, University of California, San Diego, presented findings from using OCTA to assess peripapillary retinal nerve fiber layer (RNFL) vessel density in glaucomatous eyes.

Noting that the influence of anatomical alterations of the lamina cribosa on the vascular hemodynamics of the optic nerve has not been determined, the researchers sought to determine whether there was a difference in OCTA-measured peripapillary RNFL vessel density between eyes with and without a focal lamina cribosa defect.

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The study-which involved subjects with open-angle glaucoma who were enrolled in the Diagnostic Innovations in Glaucoma Study (DIGS)-was led by Robert N. Weinreb, MD, Distinguished Professor and Chairman, Department of Ophthalmology, and director of the Shiley Eye Institute and Hamilton Glaucoma Center, University of California, San Diego.

Identification of a focal lamina cribosa defect was based on imaging with a swept-source OCT platform, and a spectral-domain OCT system was used to measure RNFL thickness and circumpapillary vessel density. Circumpapillary vessel density was calculated as the percentage area occupied by actively flowing vessels in the OCTA-measured region.

All included OCTA images were first reviewed for good quality using the Shiley Eye Institute Imaging Data Evaluation and Analysis Reading Center protocol.

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A slight majority of eyes included in the study had focal lamina cribosa defects as identified on the serial horizontal B-scan images from swept-source OCT. Glaucoma severity was similar in eyes with and without focal lamina cribosa defects.

Compared with their unaffected counterparts, however, eyes with lamina cribosa defects had significantly lower values for mean circumpapillary vessel densities in the global area analysis and in half of the eight 45° sectors. The difference between groups was highest in the inferotemporal sector, followed by the superotemporal, inferonasal, and superonasal sectors.

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The two patient groups were also compared with respect to age and a variety of disease-related characteristics that included circumpapillary RNFL thicknesses in all areas, visual field mean deviation, pattern standard deviation, presence of optic disc hemorrhage, mean ocular perfusion pressure, and IOP.

However, there were no statistically significant differences between groups for any of those variables.