Short-term Changes in Ocular Surface pH after 23-gauge Microincision Vitrectomy Surgery

Purpose: This study aimed to investigate changes in ocular surface pH after 23-gauge microincision vitrectomy surgery. Methods: This retrospective study included 42 patients who underwent 23-gauge microincision vitrectomy. Best-corrected visual acuity and intraocular pressure were measured. Fundus examination, color fundus photography, and spectral-domain optical coherence tomography were performed. Chemosis was evaluated once a day after surgery, and the ocular surface pH was measured using a microelectrode on the day before surgery and every day up to day 5 after surgery. Results: A total of 42 eyes in 42 patients were examined. The average age was 63.7 years. The indications for surgery included epiretinal membrane in 14 eyes (33.3%), vitreous hemorrhage in 11 eyes (26.2%), macular hole in 11 eyes (26.2%), and rhegmatogenous retinal detachment in six eyes (14.3%). Although the mean ocular surface pH increased from 7.12 ± 0.04 to 7.55 ± 0.04 on the first day after surgery (p < 0.001), it gradually decreased to 7.41 ± 0.03 from the second day postoperatively (p < 0.001). It was subsequently measured as 7.33 ± 0.04 on the third day (p < 0.001) and 7.23 ± 0.03 on the fourth day (p < 0.001) postoperatively. On the fifth postoperative day, the ocular surface pH further decreased to 7.15 ± 0.03 (p = 0.152) and recovered to the preoperative state. A statistically significant correlation was found between the change in ocular surface pH and the chemosis grade (p = 0.001). Conclusions: After 23-gauge microincision vitrectomy surgery, the ocular surface pH shifted temporarily in the alkaline direction within a physiological range correlated with chemosis and intravitreal tamponade usage.