Although OCT thickness maps are useful, researchers in South Korea have demonstrated that OCT en face images may show more details of retinal nerve fiber layer (RNFL) abnormalities that are difficult to see using previously available methods. They discovered that around half of diffuse RNFL defects identified in red-free photographs in their cohort appeared as localized defects in OCT en face images.

Out of the 209 study eyes diagnosed as having diffuse defects based on the red-free photographs, 50.72% appeared as localized defects in the en face images, while 37.32% were diffuse defects and 11.96% had no defects at all. Logistic regression analysis revealed that eyes with greater mean deviation and thicker inferior RNFL would be included in the no defect and localized defect groups based on OCT en face images, rather than in the diffuse defect group.

“Although the en face image provides more details regarding the RNFL, we cannot conclude that red-free fundus photography can be completely replaced by analysis of reflectance intensity in OCT en face images to detect diffuse RNFL defect,” the researchers noted. “Instead, information from en face images can supplement red-free fundus images and/or OCT RNFL thickness maps.”

Lim AB, Park JH, Jung JH. Characteristics of diffuse retinal nerve fiber layer defects in red-free photographs as observed in optical coherence tomography en face images. BMC Ophthalmol. January 8, 2020. [Epub ahead of print].