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A. Shakoor, M. Shahidi, R.D. Shonat, M. Mori, N.P. Blair; Changes in Chorioretinal Oxygen Tension Due to Inhibition of Nitric Oxide Activity . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3351.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Nitric oxide (NO) and NO synthase (NOS) are present in almost every tissue of the eye and produce a host of effects including regulation of ocular blood flow. An optical imaging system was developed to measure oxygen tension in the chorioretinal vasculatures and applied to investigate oxygen tension changes due to inhibition of NO activity. Methods: Our previously developed chorioretinal optical section phosphorescence imaging system was modified to provide quantitative measurements of oxygen tension separately in the retinal and choroidal vasculatures. A narrow laser line was projected at an angle on the retina after intravenous injection of an oxygen–sensitive probe (Pd–porphyrin) and phosphorescence emission was imaged. A frequency–domain approach was used to measure the phosphorescence lifetime by varying the phase relationship between the modulated excitation laser light and sensitivity of the imaging camera. Chorioretinal oxygen tension imaging and measurements were performed in 5 rats before (baseline) and during intravenous administration of Nω–nitro–L–arginine (Nω–NLA) which served as a non–selective NOS inhibitor. Results: Compared to baseline, a statistically significant decrease in choroidal oxygen tension with administration of Nω–NLA at infusion rates of 6, 10, and 16 mg/min was found (P < 0.03). A lack of statistically significant change in the retinal vasculature oxygen tension with the infusion of Nω–NLA at these rates was observed (P > 0.05). With increased Nω–NLA infusion rates between 1 and 5 mg/min, the choroidal oxygen tension decreased significantly (F = 47.59; P < 0.0001). With infusion of Nω–NLA at increasing rates between 6 and 14 mg/min, a lack of statistically significant change in the choroidal oxygen tension was demonstrated (F = 2.85; P = 0.1). Oxygen tension changes in the retinal vein (F = 1.49; P = 0.3), artery (F = 1.94; P = 0.2) and capillaries (F = 0.13; P = 0.9) with increased Nω–NLA infusion rates were not statistically significant. Conclusions: The results demonstrate the potential of our novel chorioretinal oxygen tension imaging technique for better understanding of choroidal and retinal oxygen dynamics in physiologic and pathologic states.
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