“DISSOCIATED OPTIC NERVE FIBER LAYER APPEARANCE” AFTER INTERNAL LIMITING MEMBRANE REMOVAL IS INNER RETINAL DIMPLING

Abstract

To examine volume-rendered spectral-domain optical coherence tomography images in patients who had undergone vitrectomy, many of whom had internal limiting membrane removal to investigate a condition termed "dissociated optic nerve fiber layer appearance." Patients who had undergone vitrectomy for either macular hole or epiretinal membrane were evaluated. Spectral-domain optical coherence tomography B-scan images were acquired with the use of eye tracking at an interval of either 30 μm or 60 μm. These were registered and exported to a volume-rendering program, and the resultant volume-rendered images were evaluated. The images were graded for the presence of inner retinal abnormalities, and correlates were made to corresponding alterations seen in fundus photographs and B-scan spectral-domain optical coherence tomography images. There were 25 eyes of 24 patients with a mean age of 72.4 (± 7.3) years, 15 of whom were women. The primary preoperative diagnosis was macular hole in 10 eyes (40%) and epiretinal membrane in 15 eyes (60%). As part of the surgery, 18 eyes (72%) had planned peeling of the internal limiting membrane. Volume rendering showed that 13 eyes had pitting or dimples of the inner retinal surface that seemed to follow the course of the nerve fiber layer in the region of the macula. The inner retinal dimples occurred only in eyes that had internal limiting membrane peeling. Correlation of the volume-rendered images with B-scan spectral-domain optical coherence tomography showed focal areas of thinning of the ganglion cell layer with decreased reflectivity from the nerve fiber layer in the areas of the dimples. A high proportion of eyes with internal limiting membrane peeling develop inner retinal dimples that course along the path of the nerve fiber layer. The dimples seem to be the result of an interplay between trauma and healing processes constrained by nerve fiber layer and do not appear to be because of dissociation of optic nerve fibers. The true nature of the abnormalities induced should be investigated to evaluate the long-term risks and benefits of routine internal limiting membrane peeling.