Functional Assessment of Aqueous Humor Outflow by Aqueous Angiography in Primary Open Angle Glaucoma.

Prcis: Evaluation of aqueous humor outflow (AHO) pathways shows a segmental pattern with the highest outflow in the nasal quadrant and least in the temporal quadrant in patients of primary open angle glaucoma (POAG).

Aim: To quantitatively evaluate circumferential peri-limbal aqueous humor outflow (AHO) pathways in patients of primary open angle glaucoma (POAG) using aqueous angiography (AA).

Methods: A cross-sectional, observational, single-centre study recruited patients between 45 and 80 years with POAG, controlled on antiglaucoma medications, along with visually significant age-related cataract, planned for phacoemulsification surgery. AA was performed using 0.1% indocyanine green (ICG) dye injected into the anterior chamber, just before the capsulorhexis step. Images of 30 eyes of 30 patients were analyzed at 60 seconds from the injection of ICG dye for angiographic signal intensity (ASI) in 4 quadrants (90 degree each), with each quadrant further divided into 2 sectors of 45 degree each (total 8 sectors), circumferentially along the limbus. ASI was assessed by estimating the mean gray value using Image J software and compared between quadrants, sectors, severity of POAG, males versus females, and right versus left eyes. Further, calculating the normalized flow for each of the quadrants and sectors for every image, a division into high-flow (HF), intermediate-flow (IF), and low-flow(LF) regions was done. The correlation and relation of ASI with age and severity of POAG were also assessed using appropriate statistical tests.

Results: The mean age of the patients was 60.5±6.32 years (range 48-71 y), with 20 males and 10 females. Out of the 30 eyes recruited, mild/moderate POAG was seen in 13 patients, and severe POAG was present in 17 patients. Nonuniform, segmental AHO pathways with the highest ASI were seen in the nasal quadrant [52.41(42.78-57.67)] followed by superior [43.34(34.75-53.48)], inferior [28.73(21.42-35.85)], and temporal quadrant [27.71(21.23-34.87)] ( P ≤0.0001). The highest percentage of HF, IF and LF regions were documented in the nasal (83.33%), superior (36.67%), and temporal (73.33%) quadrants, respectively. A negative correlation of ASI with age (using Spearman rank correlation coefficient) was seen ( r =-0.470, P =0.009) with linear regression of β=-1.354, P =0.008. In addition, ASI between mild/moderate versus severe POAG, males versus females and right versus left eyes were not statistically significant ( P >0.05).

Conclusion: Segmental AHO pathways were noted along the limbus with maximum ASI in the nasal quadrant (HF region) followed by superior (IF region), inferior, and temporal (LF region) quadrants in patients of POAG. Patterns were similar in mild/moderate versus severe POAG, males versus females and right versus left eyes. With increasing age, a decrease in ASI was documented.