Authors: David J. Mathew, Izhar Livne-Bar, Darren Chan, Yvonne M. Buys, Graham E. Trope, Marisa Sit, Becca Flitter, Karsten Gronert, Jeremy M. Sivak.

Author Disclosure Block: D.J. Mathew: None. I. Livne-Bar: None. D. Chan: None. Y.M. Buys: None. G.E. Trope: None. M. Sit: None. B. Flitter: None. K. Gronert: None. J.M. Sivak: None.

Abstract Body:

Purpose: To identify the aqueous humor (AH) lipidomic profile in glaucomatous eyes compared to those without glaucoma

Study Design: Prospective comparative study

Methods: AH samples from eyes with and without glaucoma underwent lipidomic analyses using liquid chromatography-mass spectrometry (LC-MS). The glaucoma samples were obtained from 60-80-year-old primary open angle glaucoma patients undergoing a glaucoma surgery with or without cataract surgery and the control samples were obtained from patients undergoing routine cataract surgery. Patients with diabetes mellitus, systemic inflammatory disease, uveitis, retinopathy and age-related macular degeneration were excluded. From each eye, 100 μL of AH was collected using a 30 Gauge needle mounted on a 1-mL syringe, introduced into the anterior chamber anterior to the limbus, prior to any surgical intraocular entry. The samples were snap frozen on dry ice and transported for lipidomic analyses of a panel of 40 polyunsaturated fatty acids (PUFA), metabolites and lipid mediators. All participating patients signed an informed consent form and the study was approved by the University Health Network and Kensington Eye Institute Research and Ethics Boards.

Results: AH was collected from 16 and 18 eyes with and without glaucoma, respectively. The mean age was 68.7±6.4 years for the glaucoma group and 71.0±4.7 years for the control group (p=0.25). The mean preoperative intraocular pressure 14.1±3.1 and 15.2±1.6 mmHg for the glaucoma and control groups, respectively (p=0.24). The cup-to-disc ratios were 0.9±0.1 and 0.3±0.1 for the glaucoma and control groups, respectively (p<0.001). All 16 glaucoma eyes received prostaglandin analogue eye drops prior to surgery; 15 were on beta-blocker eye drops. There were statistically significant differences between glaucomatous and control eyes for arachidonic acid (1328.0±322.0 vs 643.1±130.6, p=0.001), lipoxin A₄ (0.79±0.14 vs 0.32±0.10, p=0.01) and 12-hydoxyeicosapentanoic acid (0.35±0.17 vs undetected, p=0.04). Substantial levels, but no significant differences, were identified for docosahexanoic acid (212.0±46.33 vs 131.1±22.36, p=0.11), eicosapentanoic acid (6.21±1.40 vs 3.76±0.32, p=0.08), prostaglandin E₂ (2.83±1.92 vs undetected, p=0.13) and prostaglandin D₂ (2.43±1.49 vs 0, p=0.09). All other analytes were below detection limits.

Conclusions: Increased levels of lipid mediators are present in glaucomatous eyes. Arachidonic acid metabolites may be modulated in response to anti-glaucoma drops and play a role in glaucoma pathogenesis.