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Dietmar Link, Clemens Strohmaier, Bernd U. Seifert, Herbert A. Reitsamer, Walthard Vilser; Retinal Vessel Analysis in the Rat Eye with a Novel Non-Contact Fundus Camera. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2887.
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To measure retinal vessel behavior in rats non-contact in real-time.
We designed a non-contact flood-illumination fundus camera for the rat using the optical system design software ZEMAX. The optical pathways were implemented in a mechanical framework composed of standard components. For illumination we adapted a liquid light guide and a 50W Xe-lamp. For retinal vessel imaging at a maximum contrast the illumination spectrum was filtered to 560nm±15nm. Imaging and dynamic vessel analysis (DVA) was performed utilizing a 0.5'' B/W CCD camera (752x582 pixels, 25 frames per second) and the IMEDOS DVA software tool. The measurements were done on anesthesized rats in mydriatic eyes. To ensure homogenous fundus illumination and stable measuring conditions head and eye movements were minimized by a stereotactic fixation.
With a working distance of 15mm and a 30° field of view we performed in-vivo real-time fundus imaging and dynamic retinal vessel analysis in Brown Norway rats. For testing functionality of the experimental optical setup and reliability of the measurement we executed one baseline vessel diameter measurement recording a 7-minute sequence for one vein and one artery in the same rat. The vessel diameter means and standard deviations were ascertained to be 45µm±0.27µm (±0.61%) for the vein and 32µm±0.27µm (±0.86%) for the artery.
We build up a applicable non-contact flood-illumination fundus camera for the rat. Fundus imaging as well as retinal vessel analysis was demonstrated on Wistar albino rats and Brown Norway rats respectively. In albino rats the illumination light level required is 10% of that in the Brown Norway rats. Intended improvements apply to an increase of light transmission in both illumination and imaging path to minimize the light exposure of the rat.
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