Abstract
Purpose: :
To identify RNFL thickness modification after ILM peeling and to correlate it to visual field (VF) changes and to the postoperative appearance of early transient edematous swelling of the arcuate RNFL (SANFL) and of later dissociated optic nerve fiber layer (DONFL).
Methods: :
interventional, prospective case series. 25 eyes of 25 patients (72.7±6.5 years), who underwent ILM peeling after staining with brilliant blue G for macular hole and epiretinal membrane, were included. Best corrected visual acuity (BCVA), intraocular pressure (IOP), autofluorescence (AF) and blue light images, spectral domain OCT (SD-OCT) of the macular region and of the RNFL, using the follow-up method (Spectralis HRA+OCT, Heidelberg Engineering, Heidelberg, Germany), were performed in both eyes before and 1, 3 and 6 months after surgery. VF (Humphrey central 30-2) was performed before surgery and after 6 months. Data were analyzed using Friedman, Wilcoxon, Mann-Whitney, Spearman and Fisher tests.
Results: :
BCVA, expressed in LogMAR, significantly improved after surgery (0.65±0.32 vs 0.32±0.29, p<0.001). No IOP and VF difference was found in the study eye during the follow up period and when compared to the fellow eye. SD-OCT images showed a significant increase of RNFL thickness in the superotemporal and inferotemporal sectors 1 month after surgery (130.2±24.7µm vs 140.8±27.3µm and 136.2±17.5µm vs 154.6±25.8µm; p<0.01 and p<0.001, respectively) and a progressive decrease until the 6th-month compared to basal values (113.9±18.9µm and 125.2±23.4µm, p<0.0001 and p<0.01, respectively). Temporal RNFL thickness was stable after 1 month (98.4±26.8µm vs 106.4±24.4µm, p>0.05), but progressivly decreased after 6 months (70.72±16.83µm, p<0.001). RNFL thickness was significantly different from fellow eyes, which did not show any modification during the 6 months. SANFL appearance, viewable on AF image as 3 to 5 hypofluorescent striae originating from the optic nerve head and running between the macula and the vascular arcades, was found in 17 patients (68%). DONFL appearance was found in 14 patients (56%). No correlation was found between RNFL thickness and neither VF nor SANFL or DONFL appearance.
Conclusions: :
The selective changes of temporal, superotemporal and inferotemporal optic disc areas could be due to a possible damage after ILM peeling. The postoperative 1st-month increase of superotemporal and inferotemporal RNFL thickness could be related to edematous swelling of arcuate RNFL also in patients without SANFL appearance on AF image. The 6th-month RNFL thickness reduction, without VF defects, could indicate an early damage to the arcuate RNFL, independently to DONFL appearance.
Keywords: vitreoretinal surgery • nerve fiber layer • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)