Comparative study of 27G vs 25G vitrectomy for idiopathic epiretinal membrane

Abstract

Objective To evaluate the effect of 27G pars plana vitrectomy (PPV) and 25G PPV on idiopathic epiretinal membrane (IMEM). Methods Thirty-eight eyes of 38 patients with IMEM were enrolled into this retrospective and comparative study. Eighteen eyes were treated with 27G PPV (group A), 20 eyes underwent 25G PPV (group B) voluntarily. The best corrected visual acuity (BCVA), intraocular pressure (IOP), slit-lamp microscope, indirect ophthalmoscopy, fundus color photograph, ocular coherence tomography (OCT) and counting of corneal endothelial cells (CEC) were examined before the surgery. BCVA results were converted to the logarithm of the minimum angle of resolution (logMAR) visual acuity. There was no statistically significant difference between two groups in terms of BCVA, IOP, foveal macular thickness (FMT), the counting of CEC and CEC hexagon rate before the surgery (t=1.627, 0.860, 0.293, 1.238, 0.697; P>0.05). All operations were performed by the same doctor. Operation time for vitrectomy and peeling membrane was recorded. BCVA, IOP, OCT, FMT, counting of CEC and the improvement of metamorphopsia were observed on 1, 7 days and 1, 3 months after PPV. Results The mean operation time for vitrectomy in group A and B were (6.7±2.8), (10.5±3.3) min, respectively. The mean operation time for vitrectomy in group A was significantly longer than that in group B (t=3.084, P<0.05). The mean operation time for peeling membrane in group A and B were (10.2±5.2), (11.0±5.9) min, respectively. There was no statistically significant difference between two groups in terms of the time for peeling membrane (t=1.970, P=0.187). On 1, 7 days and 1, 3 months after PPV, the difference of BCVA (t=1.463, 0.683, 0.961, 1.226; P=0.833, 0.509, 0.699, 0.744) and IOP (t=1.314, 1.262, 0.699, 1.116; P=0.763, 0.721, 0.534, 0.712) between two groups were not statistically significant. On 1 day after PPV, there were 2 eyes and 5 eyes with <9 mmHg (1 mmHg=0.133 kPa) IOP in group A and B. On 7 days and 1, 3 months after PPV, the difference of FMT between two groups were not statistically significant (t=1.257, 1.368, 1.437; P=0.735, 0.745, 0.869). On 3 months after PPV, the difference of CEC between two groups were statistically significant (t=2.276, P<0.05); the difference of hexagon rate between two groups were not statistically significant (t=1.473, P=0.889). Conclusion The efficacy of 27G PPV for IMEM appears similar to 25G PPV. But 27G PPV has a shorter operating time for vitrectomy, a more stable IOP and a minimal damage to CEC. Key words: Vitrectomy; Surgical procedures, minimally invasive; Macula lutea; Membranes; Comparative effectiveness research