Three-dimensional Nature of Retinal Nerve Fiber Layer Defects

Objective: To demonstrate the 3-dimensional nature of wedge-shaped retinal nerve fiber layer (RNFL) losses. To study the impact of training glaucoma fellows in this identification technique by evaluating their rate of RNFL loss detection on stereo disc photographs. Methods: Wedge-shaped RNFL defects were identified in stereo disc photographs of early-glaucoma patients. The 3-dimensional nature of RNFL defects and overlying retinal blood vessel contour changes were identified. Four glaucoma fellows were given stereo-photographs to identify the presence or absence of RNFL defects. After training in identification of RNFL defects by noting their 3-dimensional nature and overlying blood vessel contour changes, the same set of photographs were reevaluated by the fellows. We determined whether there was a difference between the before and after assessments in the probability of a correct response for each of the fellows. Results: Loss of retinal thickness in the form of grooves and the resulting 3-dimensional nature of the RNFL defects were visualized on stereoscopic examination. Overlying retinal blood vessels coursed into and out of the RNFL defects. Three case examples of such wedge-shaped RNFL defects are presented. For each fellow, the proportion of RNFL defects correctly identified after training was greater than the proportion before training (P < 0.001). Conclusions: Identifying the 3-dimensional nature of wedge-shaped RNFL defects may improve rate of detection of RNFL defects during clinical examination.