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Flora Hui, Phillip A Bedggood, Christine T Nguyen, Zheng He, Selwyn M Prea, Rebecca L Fish, Rachel Gurrell, Algis J Vingrys, Bang V Bui; Quantitative spatial and temporal analysis of fluorescein angiography in rat retina. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2096.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a method of quantifying fluorescein angiography dynamics across the rat retina.
Sodium fluorescein (1%, 0.07ml, 1.05ml/min) was administered via the femoral vein in anesthetized (60:5 mg/kg ketamine:xylazine) adult Long-Evans rats (n=10, 336.4±11.0g) and angiography dynamics recorded (Micron III, Phoenix Labs) at up to 30 frames/sec. After image registration (MATLAB), each pixel’s luminance profile was analysed to return the time constant to reach half rise (50% of maximum fluorescence) and half fall (50% decay). Data (average ± SEM) were compared across blood vessel types as a function of eccentricity from the optic nerve head and between quadrants (superior, inferior, nasal & temporal). To demonstrate utility of the method, fluorescein leakage was induced by Nd:YAG laser photocoagulation (532nm, 800mWx0.5s, size 100μm, n=4). Fluorescein angiography was conducted at baseline and 30 minutes post-laser.
Fluorescein angiography luminance profiles show a rapid increase followed by an exponential-like decay, in order of arterial, capillary and venous phases. With increasing retinal eccentricity between 286±10 to 921±38μm, half rise of arteries (from 6.9±0.1 to 7.0±0.1s, p=0.03) and capillaries (7.1±0.1 to 7.2±0.1s, p<0.01) became slower, which was not the case for veins (7.8±0.1 to 7.7±0.2s, p=0.17). Half fall of veins was faster (13.2±0.4 to 13.0±0.4s, p=0.04) towards the periphery, whereas arteries (11.0±0.4 to 10.9±0.4s) and capillaries were not (10.6±0.2 to 10.5±0.3s). Quadrant analysis showed no significant differences between quadrants in the half rise/half fall for any vessel type. Following laser photocoagulation luminance profiles in affected areas exhibited two phases. The first phase reached 81±5% of maximum fluorescence, with a half rise that was slower compared to baseline (9.8±0.3 to 7.1±0.2s, p=0.01). This was followed by a second phase that did not reach maximal brightness until 40±6s. Fluorescence was slow to decay and at 1 minute after fluorescein injection was 82±4% relative to max fluorescence, compared to pre-treatment (26±1%, p<0.01).
This analysis enables the quantification of spatial and temporal fluorescein angiography dynamics in normal and laser-injured rat retina. Subtle changes in spatial and temporal characteristics of vascular leakage are detected, that may be missed using conventional static, qualitative fluorescein angiography analysis.
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