Incidence and quantitative analysis of dissociated optic nerve fiber layer appearance: real loss of retinal nerve fiber layer?

PURPOSE: To assess the association between appearance of dissociated optic nerve fiber layer (DONFL) after internal limiting membrane (ILM) peeling and changes in the macular nerve fiber layer (NFL) area by spectral-domain optical coherence tomography (SD-OCT). METHODS: This study included 132 consecutive patients who had successfully undergone vitrectomy with ILM peeling for idiopathic epiretinal membrane or macular holes and had been followed up for ≥6 months. Two examiners evaluated macular 5-line raster horizontal SD-OCT images and categorized the patients on the basis of presence (group I) or absence (group II) of DONFL. The average macular NFL areas in both groups were measured using ImageJ at baseline and 1, 3, and 6 months after surgery. RESULTS: Among the 132 eyes of 132 patients, DONFL was noted in 42 (31.8%), 104 (78.8%), 106 (80.3%), and 106 (80.3%) eyes at 1, 3, and 6 months and at the last visit (12.8 ± 6.5 months) after surgery. These layers appeared most commonly between 1 and 3 months after ILM peeling. There was no significant difference in average macular NFL area between groups I and II (3453.4 ± 125.3 and 3513.0 ± 100.2 pixels, respectively) at 6 months after surgery (p = 0.56). CONCLUSIONS: Appearance of DONFL increased between postoperative months 1 and 3. Moreover, there was no significant difference in average NFL in terms of DONFL. Thus, appearance of DONFL might represent macular NFL rearrangement and reorganization rather than true mechanical damage to the NFL after ILM peeling.