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Y. Shui, N.M. Holekamp, D.C. Beebe; Oxygen Levels in Human Eyes Before and After Vitrectomy . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3022.
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Purpose: Vitrectomy is associated with a high incidence of nuclear cataracts within two years after surgery. We proposed that increased levels of oxygen reach the lens during and after vitrectomy and that increased exposure of the lens to oxygen contributes to nuclear cataract formation (Harocopos, Shui, et al., submitted). This is the initial report of a study designed to measure the levels of oxygen in the vitreous chamber before, immediately following, and at longer times after vitrectomy. Methods: Oxygen was measured in consenting patients who were undergoing vitrectomy during retinal surgery. The oxygen supply to the patients during vitrectomy, anesthesia conditions, and ocular and surgical histories were recorded. Oxygen measurements were made using an Oxylab pO2TM 21 gauge optical oxygen sensor (optode; Oxford Optronix, Oxford, UK). Two locations were selected for oxygen measurements, just posterior to the lens and in the center of the vitreous chamber. Oxygen was measured twice for each patient: before vitrectomy (infusion off) and immediately after finishing the vitrectomy (infusion on). Data were analyzed using Student’s t-test. Results: Data are reported for 47 participants, 20 male and 27 female. Average age was 65.6 ± 14.1 years. Average oxygen tension measured under lens and in the center of the vitreous body was 11.2 ± 4.9 and 8.9 ± 4.9 mmHg (P < 0.0001; paired t-test) before and 72.4 ± 18.5 and 78.6 ± 16.1 mmHg after vitrectomy (P < 0.001). Insufficient data are available for measurements made at longer times after vitrectomy. Interestingly, a subset of 14 patients with proliferative diabetic retinopathy (PDR) showed significantly lower oxygen levels than non-diabetics in the center of vitreous chamber before vitrectomy (7.1 vs. 9.7 mmHg, P < 0.05). Breathing oxygen during surgery markedly increased the oxygen tension in the vitreous. No side effects were observed during or after this study as a consequence of making the oxygen measurements. Conclusions: Oxygen optodes provide a sensitive and safe way to measure oxygen levels in the human eye. Oxygen levels are significantly higher near the lens than in the central vitreous. Immediately after vitrectomy, oxygen levels increase significantly in the eye, presumably from the oxygen in the perfusion fluid. Elevated oxygen levels may increase the risk of post-vitrectomy nuclear cataract. The retinal hypoxia that is associated with PDR is reflected in a decrease in oxygen levels in the vitreous body.
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