Abstract
Purpose :
Few studies have explored reasons for vision loss after Ahmed Glaucoma Valve (AGV) insertion, especially among minorities. We hypothesized that in a Latino and Black population, eyes with both preoperative split fixation and a postoperative hypertensive phase (SFHP) were more likely to lose visual acuity (VA) 1 year after AGV surgery.
Methods :
We reviewed charts of eyes followed for 12 months from Latino or Black patients who received standalone or combined AGV surgery (with phacoemulsification and/or cyclodestructive lasers). We excluded eyes with previous tube shunts and eyes missing visual field data or Snellen VA. A single surgeon conducted all procedures in the Bronx, NY from 2014-2019. Split fixation (SF) described <10 dB sensitivity in any of the four paracentral quadrants of the Humphrey 24-2 visual field. Hypertensive phase (HP) was defined as an IOP reading > 21 mmHg within the first 3 postop months after reduction of IOP to less than 22 in the first week, without tube malfunction. We used logistic regression to test the effect of SFHP on VA loss of two lines or more by 12 months. We considered 8 covariates: SF alone, HP alone, preop IOP, age, sex, race, diabetes, and systemic hypertension. Sterling IRB deemed this study to be exempt.
Results :
Of 241 eyes from 186 patients, VA loss of 2+ lines occurred in 52 (21.6%). Univariate regression revealed that SFHP eyes were 5.96 times more likely (95% CI=3.06-11.79; p<0.0001) to experience this outcome. Of the 8 covariates, only preop IOP and HP alone modified the odds ratio by >10% when added. HP increased the OR by 53.3%, while preop IOP decreased the OR by 10.6%. In the model including SFHP, SF alone, HP alone, and preop IOP, SFHP eyes were 7.99 times more likely to have lost 2+ lines by 1 year (95% CI=2.92-25.95; p=0.0001).
Conclusions :
SFHP moderately to greatly increased the odds of vision loss after AGV surgery in Latino and Black patients. HP alone and preop IOP were true confounders. In theory, SF may signify a severe glaucoma with fragile retinal nerve fibers, enabling a postoperative IOP spike to extinguish central vision. The confounding effect suggests that a hypertensive phase may even harm eyes without SF. Our findings indicate that prospective studies on controlling HP in severe glaucoma to protect vision may be warranted.
This is a 2021 ARVO Annual Meeting abstract.