[Visual impact of sub-tenon's anesthesia during surgery for retinal detachment]

Objective: To investigate the visual impact and influence factors of sub-Tenon's anesthesia in retinal detachment patients during pars plana vitrectomy (PPV) or combined phacoemulsification and PPV surgery. Methods: In this prospective case series study, 104 consecutive patients who underwent PPV or combined phacoemulsification and PPV under sub-Tenon's anesthesia between October 2012 and December 2013 were enrolled. Intraoperatively, the patients were asked whether they could see the light of the operating microscope or not at 5 minutes after sub-Tenon's anesthesia, and at the end of phacoemulsification, core vitreous removal, peripheral vitreous removal and the whole surgery, with their contralateral eyes being covered tightly and no photobleaching. The best corrected visual acuity and visual evoked potentials were examined and compared with each other preoperatively and at 1.5 months and 3 months postoperatively. Chi-square test was used to compare the detection rate of amaurosis between different modus operandi and whether covered contra-lateral eye. Student-t test was used to compare the difference of age and preoperative BCVA between the patients with or without experienced amaurois. Lastly, BCVA between different times were tested by one-way ANOVA analysis. Results: Without covering the contralateral eyes, the incidence of no light perception in various surgical steps was 0%, while it was 72.1%(75/104), 93.8%(75/80), 96.2%(100/104), 96.2%(100/104) and 86.5%(90/104) at the five timepoints, respectively, when the contralateral eyes were covered tightly. The incidence was 51.9%(54/104), 85.0%(68/80), 85. 6%(89/104), 84.6%(69/104) and 66.3%(88/104), respectively, after photobleaching was excluded. Approximately 95.2%(99/104) of patients reported no light perception at least once, 54.5%(54/99) reported no light perception 5 minutes after sub-Tenon's anesthesia, and 30.3%(30/99) recovered light perception when the surgery was finished. All eyes recovered to at least light perception on the first postoperative day. The best corrected visual acuity and visual evoked potentials at 1.5 months and 3 months postoperatively were significantly better than those before surgery. The BCVA was 1.75±0.78 preoperative, 0.96±0.63 1.5 months after operation, and 0.92±0.57 3 months after operation. There was a significant statistical difference between preoperative BCVA and postoperative BCVA (F=50.61, P<0.01) . In patients without waveform detection preoperatively, PVEP waveform could be found in 43.6% and 61.4% of the pactients at 1.5 months and 3 months after operation respectively. In those had certain waveform preoperatively, PVEP amplitudes rise significantly after surgery (t(1.5)=-2.69, t(3)=-2.97, P<0.05) . Conclusions: No light perception was detected in various surgical steps of vitrectomy under sub-Tenon's anesthesia in most patients. The blocking of optic nerve conduction may be caused by sub-Tenon' s anesthesia. Photobleaching can also have some effect. The incidence of no light perception during the surgery was not correlated with preoperative visual acuity, age and gender. Moreover, the effect was transient and harmless to visual function.(Chin J Ophthalmol, 2017, 53: 332-337).