Purpose
To describe the use of swept source optical coherence tomography (SS-OCT) as a clinically relevant tool for the preoperative en face evaluation of epiretinal membranes (ERM) and the integrity of the underlying retinal nerve fiber layer (RNFL).
Methods
SS-OCT images were captured in 9 eyes with ERMs diagnosed with clinical exam and spectral domain optical coherence tomography (SD-OCT). The SS-OCT device had a laser wavelength centered at 1060 nm with an acquisition speed of 100,000 A-scans/sec. 3 x 3 x 3 mm raster scans of the fovea were obtained (512 A-scans/B-scan; 512 B-scans/cube). SD-OCT scans were acquired over 6 x 6 mm (512 A-scans/B-scan; 128 B-scans/cube). En face images were created using 4mm summed voxel projections (slabs) centered on the internal limiting membrane and then moved posterior to the RNFL. Similar slabs were used to compare en face images from SD-OCT scans.
Results
En face images of ERMs could be obtained in all 9 eyes of 8 patients with diagnosed ERMs. The mean age was 68 years (range 47-88), visual acuity ranged from 20/20 to 20/200, and 4 had additional macular pathology on clinical examination (1 with fibrotic bands, 1 with vitreoretinal adhesions and microcystic edema, 1 with drusen and geographic atrophy, and 1 with a lamellar macular hole). Appearances of these membranes included plaques and radiating folds. With the overlying ERM and macular pathology, clear en face images of the underlying RNFL could also be acquired in 7 of 9 eyes (78%).
Conclusions
SS-OCT is a novel method for generating en face images of ERMs. Compared with SD-OCT en face images, SS-OCT could more clearly identify the plaques and folds of ERMs and underlying defects in the RNFL. Such images could be clinically useful for surgical planning and assessment of the integrity of the underlying RNFL. Larger studies, including pre and post operative imaging, will be necessary to evaluate post operative changes in the RNFL and the correlation of appearance on SS-OCT with visual outcomes.