Transient increase of retinal nerve fiber layer thickness after macular hole surgery.

We studied the changes in the thickness of the retinal nerve fiber layer (RNFL) after surgery for idiopathic macular hole (MH) using spectral-domain optical coherence tomography (SD-OCT). Twenty eyes of 20 consecutive patients who underwent vitrectomy to close a MH were studied. The peripapillary RNFL thickness was measured by SD-OCT before and at 1, 3, and 6 months after surgery. The mean overall thickness, the thickness of the four quadrants, and the thickness of each of the 12 clock hours of the RNFL were analyzed. The mean overall RNFL thickness before surgery was 93.3 ± 9.6 lm,and it increased significantly to 98.7 ± 7.4 lm at 1 month after surgery (P\0.05). The mean overall thickness then returned to the pre-surgery level at three and 6 months. The transient increase of RNFL thickness at 1 month after surgery was statistically significant in the superior, nasal, and inferior quadrants. The increase in the thickness of the nasal quadrants was maintained for up to 6 months. When the thickness of the individual 12 clock hours were analyzed, the transient increase of RNFL thickness at 1 month after surgery was significant at each of the 0­5 o'clock positions. The transient increase in the RNFL thickness after MH surgery may be caused by mild edema of the inner retinal layers caused by the MH surgery.

Relationship between retinal layer thickness and focal macular electroretinogram components after epiretinal membrane surgery.

PURPOSE: To study the effect of epiretinal membrane (ERM) removal on the function and structure of the retina, and to determine whether the functional changes were correlated with the changes in the thickness of different retinal layers. METHODS: Focal macular electroretinography (FMERG) and spectral-domain optical coherence tomography (SD-OCT) were performed on 17 eyes of 15 patients before and after ERM surgery. The parafoveal retina was divided into an inner layer, a middle layer, and an outer layer in the OCT images. The thickness of each layer was measured before and after the ERM surgery. The a-wave, b-wave, and oscillatory potentials (OPs) of the FMERGs were analyzed before and after the ERM surgery. RESULTS: The thickness of the inner and middle retinal layers was significantly reduced after surgery (by 39% and 23%, respectively). The mean amplitudes of the b-waves and OPs at 6 months postoperatively were significantly larger than those recorded preoperatively (by 21% and 61%, respectively). The ratios of the pre- to postoperative b-wave and OP amplitudes were correlated with the thickness reduction of the middle retinal layer (b-wave, r = -0.51, P < 0.05; OPs, r = -0.82, P < 0.01). CONCLUSIONS: The significant correlations between the reduction in the thickness of the middle retinal layer and increase in the amplitude of the b-waves and OPs suggest that the improvement of macular function after ERM peeling is due to the decrease in the thickness of the middle retinal layer.