Impact of macular surgery on internal retinal layers: post-operative morphological and functional determinants

Purpose : To evaluate the impact of macular surgery on inner retinal layers and their morphological and functional modifications. Methods : This prospective study included 16 eyes of 15 consecutive patients who underwent vitreoretinal surgery for idiopathic epiretinal macular membrane or idiopathic macular hole. We excluded patients affected by inflammatory or vascular retinal diseases. Baseline and follow up evaluations at month 1, 3, and 6 included complete ophthalmological evaluation and instrumental examination. Functional evaluation was performed by ETDRS visual acuity, Amsler test and retinal sensibility and fixation (MP-1 microperimetry, NIDEK, Italy). Morphological evaluation was performed by autofluorescence imaging (AF) with Spectralis HRA2, (Heidelberg, Germany) and retinal layers analysis, in particular we examined Ganglion Cell Layer (GCL) and Retinal Nerve Fiber Layer (RNFL) as well as central retinal thickness (CRT) with SD OCT (Cirrus OCT, Zeiss USA). Statistical analysis was performed on collected data. Results : AF evaluation showed only at month 1 retinal pigment epithelium thin defects on macular region. Mean GCL thickness analysis showed a mean decrease from 40,4 ± 7,2 mm at baseline to 38,7 ± 4,6 mm at month 6 (p>0.05) as well as mean RNFL thickness from 15,8 ± 6,5 mm at baseline to 14,9 ± 1,7 mm at month 6 (p>0.05). Mean CRT changed decreased from 378,7 ± 89,6 mm at baseline to 254,7± 34,6 mm at month 6 (p<0.05). Mean visual acuity and retinal sensibility increased significantly from 0.68 ± 0.12 LogMAR and 8,4 ± 2,5 dB at baseline to 0,35 ± 0,16 LogMAR and 11,4 ± 1,5dB at month 6 (p<0.05). All patients reported a reduction in metamorphopsia, but 3 patients didn’t recover visual acuity, showing a central visual field blurring. Conclusions : A detailed OCT evaluation allows understanding the real modifications and the impact of the surgery on the whole macular structure. Central retinal thickness alone could not show the different behaviour of retinal cells, from Muller cells to ganglionar cells. GCL and RNFL thickness analysis show the effects of surgery on inner retinal layers. Retinal sensibility and visual acuity coupled really show the long term effectiveness of surgery.