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W.R. Elliott, R.D. Glickman, H. Zwick, H. Rentmeister–Bryant; Morphological Changes Associated With Changes in Retinal Electrophysiology After Acute Laser Lesion in the Rat Snake Eye . Invest. Ophthalmol. Vis. Sci. 2005;46(13):280.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Utilizing the rat snake model, we previously reported a variety of effects of laser retinal injury including cellular immune responses, oxidative stress, and antioxidant treatment. We reported elsewhere the effects of acute laser injuries on retinal function, assessed with the pattern–evoked electroretinogram (PERG). Here we use the scanning laser ophthalmoscope (SLO), and associated methodologies, to characterize the retinal sequelae of laser injuries. Methods: A Rodenstock SLO (model 101), with acousto–optic modulator, was the imaging device, the stimulus platform for PERG, and the means for aligning the eye for laser exposures. Subjects were Great Plains ratsnakes (Elaphe guttata emoryi) anesthetized with a ketamine / xylazine cocktail for all procedures. Damaging laser exposures were produced with 50 mW, 10 msec exposures from a Nd:VO4 diode–pumped solid–state laser, mounted on, and coaxial with, the SLO’s imaging axis. The beam was shaped to produce a 50 micron retinal spot size, resulting in lesions approximately 75–100 µm in diameter. Exposures were placed in a linear array spaced 250 microns apart. Lesions were followed using direct imaging, with detection of oxidative and immune responses using specific fluorescent probes. Results:The photoreceptor matrix can be directly imaged in the small eye with the SLO, permitting observation of morphological changes in the retinal lesions over time. The photoreceptors affected are more reflective than normal cells in the first 24 hours after exposure. Within 1 hr after exposure, activated leucocytes are attracted by the damaged tissue, and begin to infiltrate the tissue surrounding the lesion. For 1–3 days, oxidation sensing probes, directly imaged by the SLO, show an oxidative process occuring in the lesion. Treatment of the exposed animals with N–acetylcysteine (NAC) reduced the apparent size of the lesion. Conclusions: The SLO is capable of directly imaging the photoreceptor matrix in the snake eye and pathological changes may be observed as they develope. The images of the retinal photoreceptor layer revealed a distinct pattern of responses after laser exposures. Two weeks post exposure, most of the cells which show this pathology are no longer seen in cSLO images. The mechanism of this cell death appears to have an oxidative stress component, which appears to be amenable to treatment.
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