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

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.

Retrospective chart review.

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.

Patients' preoperative and postoperative corrected visual acuity (CVA) were documented for 1 week, 1 month, 3 months, and 6 months postoperatively.

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 chi-square 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.

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).

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.