Blood Partial Pressure of Oxygen is Lower in the Optic Disk of Monkeys with Experimentally Induced Glaucoma

Abstract

Abstract: : Purpose: Blood flow is reduced in the optic disk of monkeys with experimentally induced glaucoma (Percicot, ARVO Abstract, 1996). Our aim was to study in the same model the partial pressure of oxygen (pO₂) of the blood perfusing the optic disk. Methods: Six years prior the measurements, six monkeys (∼ 8 kg) had had an argon laser trabeculum photocoagulation (ALP) in one eye resulting in a chronic elevation of the intraocular pressure (IOP). In both control and ALP eyes, two-dimensional maps of the blood pO₂ were recorded with the phosphorescence quenching by O₂ technique. The IOP and disk excavation were also measured by tonometry and scanning ophthalmoscopy, respectively. Results: Both IOP and cup/disk ratio were significantly higher (paired t-test, p < 0.001) in ALP eyes (47 ± 9 versus 15 ± 3 mmHg and 0.8 versus 0.2, respectively). pO₂ measurements were successful in 5 monkeys. In the control eye, blood pO₂ was 57 ± 6, 56 ± 7 and 41 ± 12 mmHg in capillaries of the ONH cup, ONH rim and in the retinal veins, respectively. In the corresponding vessels of the ALP eyes, blood pO₂ was 22, 24 and 36 % lower, respectively. This decrease was statistically significant in the retinal veins (paired t-test, p < 0.01). Conclusion: Combined with a reduced blood flow, the decrease of the blood pO₂ observed in the ALP eyes suggests an altered oxygen delivery to the ONH tissue in monkeys with experimentally induced glaucoma.

Keywords: 506 pathology: experimental • 498 optic disc • 428 hypoxia