Dissociated optic nerve fiber layer-like appearance indicating an internal limiting membrane defect associated with an epiretinal membrane: two case reports

BACKGROUND: We report for the first time a way to predict the 2-dimensional extension of an internal limiting membrane (ILM) defect by detecting the area with dissociated optic nerve fiber layer (DONFL)-like spots in the preoperative optical coherence tomography (OCT) en-face images. CASE PRESENTATIONS: Case 1 was a 67-year-old man with metamorphopsia and decreased vision in his right eye. His best-corrected visual acuity (BCVA) was 20/100, with a pterygium, a moderate nuclear cataract, and an epiretinal membrane (ERM). Case 2 was a 73-year-old man with metamorphopsia and decreased vision in his left eye. His BCVA was 20/25, with a moderate nuclear cataract and an ERM. Both patients underwent simultaneous cataract surgery and pars plana vitrectomy with ERM and ILM peeling. Brilliant Blue G staining, performed before ERM and ILM peeling, revealed an unstained area. A careful evaluation of the area showed that it was not covered by either the ERM or ILM. A postoperative evaluation of the preoperative OCT images obtained from these cases showed DONFL-like low-brightness spots in the ILM defect area on the OCT en-face images. CONCLUSIONS: OCT en-face images may indicate the area of the ILM defect. To avoid iatrogenic damage to the retinal nerve fiber layer by touching/pinching it with forceps, detecting areas with DONFL-like spots in the preoperative OCT en-face images may be useful to predict an ILM defect.