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J.P. Dillon, I. Barbazetto, J. Liang, S. Chang, A. Spector, L. Zheng, J. Merriam; Oxygen Tension in the Rabbit Vitreous and Lens: Changes With Vitrectomy . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3501.
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Purpose: Oxygen is believed to be one of the potential causative agents for the development of nuclear cataracts following vitrectomy. The aim of this study was to determine the partial pressure of oxygen (pO2) in different compartments of the rabbit eye, and to describe the changes following vitrectomy using basal salt solution (Alcon) as a vitreous replacement. Methods: Rabbits (3.5-5.3kg) were anesthetized and oxygen tension was probed using a fiber-optic oxygen sensor (optode). Measurements were taken pre and post vitrectomy at several defined positions within the vitreous, the lens and the anterior chamber. A micromanipulator in conjunction with an operating room microscope was employed to ascertain the exact position of the probe within the eye. Follow-up measurements were performed 1 to 8 weeks after vitrectomy. The contra-lateral eye served as a control. Results:. Oxygen tension in the globe is asymmetrical with the lowest pO2 in the nucleus of the lens (ca 10 mmHg) and the highest pO2 close to the retinal surface (40-60 mmHg) depending on neighboring large vessels. The tension drops off rapidly to 20 mmHg some 0.5 mm from the retina. From that position to the posterior surface of the lens there is a shallow gradient of decreasing pO2. The region of the lens near the posterior capsule has a low oxygen tension close to the values of the vitreous directly behind the posterior capsule (12 mmHg), while the tension in the anterior part of the lens is about 2 times higher. Immediately following vitrectomy the pO2 in the BSS replacement varied from ca. 90 to 140 mmHg, and decreases over approximately 30 min. to levels that are 2-3 times that of normal vitreous. At 2-3 weeks post-vitrectomy the concentration in the lens is twice as high as in the contralateral non-vitrectomized lens. In addition there is no longer a gradient in the vitreous cavity, except close to the retina Conclusions: Oxygen tension in the posterior region of the lens is determined by that in the vitreous. Oxygen levels in the lens increase significantly after vitrectomy. Such changes in oxygen tension may contribute to nuclear cataract formation following surgery.
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