OBJECTIVE: To elucidate the vision loss and recovery course after 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 Ahmed glaucoma valve procedure from January 2008 to December 2017 with a minimum of six-month follow-up. METHODS: Patients’ preoperative and postoperative corrected visual acuity (CVA) were documented for postoperative 1 week, 1 month, 3 months and 6 months. MAIN OUTCOME MEASURES: Pre- and postoperative CVA at various time points were compared using repeated measures ANOVA. The proportions of patients with mild (less than 3 lines of Snellen CVA loss), moderate (3–5 lines, inclusive), severe (more than 5 lines) vision loss were calculated and compared using a Chi-squared 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 postoperative 1 week, 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 pre-operation at postoperative 1 week, 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 postoperative 6 months. The most common causes of significant vision loss were pre-existing ocular conditions and cataract progression. Postoperative anti-metabolite injection was associated with a lower risk of 3 or more lines of CVA loss 6 months postoperatively (OR 0.44, p = 0.023). CONCLUSIONS: After Ahmed tube shunt procedure, worst CVA occurred at 1 week postoperatively and mean CVA returned to preoperative level by the third postoperative month. About 40% of patients had any CVA loss compared to pre-operation, while 9.3% of patients had 3 or more lines of CVA loss at the 6th postoperative month. Postoperative anti-metabolite injection was associated with a lower risk of 3 or more lines of postoperative vision loss.
