En face OCT, a somewhat newer imaging protocol, may be a more accurate tool in pinpointing retinal nerve fiber layer (RNFL) defects than OCT deviation maps, a study in the Journal of Glaucoma reports. A team of Korean researchers found localized RNFL defects in en face images showed excellent topographic correlation with red-free photos, while OCT deviation maps frequently misidentified the defects.

The study included 70 localized RNFL defects that appeared in red-free photographs (red-free defect). The researchers overlaid en face images and OCT deviation and thickness maps and compared the angular locations and width of the red-free defects to the en face structural images (en face defect) and OCT RNFL deviation (deviation map defect) and thickness maps (thickness map defect).

Among 70 eyes with red-free defects, investigators reported the OCT deviation map misidentified 13 (18.6%) defects compared with one (1.4%) from the thickness map and zero in the en face image. Additionally, investigators found no significant differences among red-free defects, en face defects and OCT thickness map defects in the angular width and locations.

Researchers also observed significantly greater angular widths in the OCT RNFL deviation maps compared with the other imaging techniques. The study noted the correlation coefficients of angular width and locations between the red-free defect and en face defect were significantly higher than those between the red-free defect and OCT map defects.

“Localized RNFL defects detected in red-free photographs showed highest topographic correlation with defects detected in OCT en face images. En face structural images may aid in identifying the localized RNFL defects in glaucomatous eyes,” the researchers wrote in their paper.

Park JH, Yoo C, Kim YY. Localized retinal nerve fiber layer defect location among red-free fundus photograph, en face structural image, and Cirrus HD-OCT maps. J Glaucoma. October 17, 2019. [Epub ahead of print].