Short-term Postoperative Visual Acuity Decrease and Recovery after Ahmed Tube Shunt Procedure for Glaucoma

Purpose: To elucidate the vision loss and recovery course after the Ahmed tube shunt procedure 6 months postoperatively. To identify risk factors associated with significant vision loss. Design: Retrospective chart review. Participants: One eye of all adult patients who underwent an Ahmed glaucoma valve procedure from January 2008 to December 2017 with a minimum 6-month follow-up. Methods: Patients' preoperative and postoperative corrected visual acuity (CVA) were documented for 1 week, 1 month, 3 months, and 6 months postoperatively. Main Outcome Measures: Preoperative and postoperative CVA at various time points were compared using repeated-measures analysis of variance. The proportions of patients with mild (<3 lines of Snellen CVA loss), moderate (3-5 lines, inclusive), and severe (>5 lines) vision loss were calculated and compared using a chisquare test. Logistic regression analysis was conducted to identify risk factors associated with a loss of 3 or more lines of CVA 6 months after surgery. Results: A total of 375 patients were included, whose mean preoperative CVA was 0.76. At 1 week postoperatively, mean CVA worsened to 0.96 (P < 0.05), but recovered back to preoperative level by the third postoperative month (P > 0.05). In terms of any vision loss, 55.6% of patients had worse CVA than preoperation at 1 week postoperatively, including 23.5% who had 3 or more lines of vision loss; these proportions decreased to 39.2% (P < 0.001) and 9.3%, respectively, by 6 months postoperatively. The most common causes of significant vision loss were preexisting ocular conditions and cataract progression. Postoperative antimetabolite injection was associated with a lower risk of 3 or more lines of CVA loss 6 months postoperatively (odds ratio, 0.44; P = 0.023). Conclusions: After the Ahmed tube shunt procedure, the worst CVA occurred at 1 week postoperatively and mean CVA returned to the preoperative level by month 3 postoperatively. Approximately 40% of patients had any CVA loss compared with preoperation, and 9.3% of patients had 3 or more lines of CVA loss at month 6 postoperatively. Postoperative antimetabolite injection was associated with a lower risk of 3 or more lines of postoperative vision loss. (C) 2020 by the American Academy of Ophthalmology