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Clarke Nelson, Joseph Kao, Steven L Bernstein; A New Model of Rat NAION. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3860.
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© ARVO (1962-2015); The Authors (2016-present)
The current model of rodent non-arteritic anterior ischemic optic neuropathy (rNAION) is useful for revealing mechanisms potentially associated with human clinical pathology. The current model (Bernstein et al., IOVS, 2003), however, exhibits variability in degree of severity and rarely, retinal ischemia using current induction conditions. Our goal was to generate a more uniform animal model without ischemia using a novel dye coupled with laser excitation to determine its efficacy in rNAION induction.
Male Sprague Dawley rats (320 – 420 g) were utilized in an IACUC-approved protocol. Anesthetized animals were intravenously injected with modified indocyanine green (mICG) dye that serves as an efficient triplet photosensitizer at a dose of 10 mg/kg. We utilized infrared laser (Oculight SLx; IRIS medical) emission at 805 nm wavelength (300µm spot size), transmitted through a custom plano-convex contact lens, attached to a Haag-Streit slit lamp, using the appropriate adapter and custom fiber optic cable. We initially evaluated the ability of the slit lamp adapter to enable focused infrared light to the eye. We also compared laser with dye and laser alone as the inductive agent to both the optic nerve (ON) and peripheral retina using a slit lamp and SD-OCT.
When using laser alone at energies ranging from 100 to 2000 mW applied to the central and peripheral retina, no surface damage, scarring, retinal ischemia, or edema were noted on fundoscopic exam. SD-OCT revealed no changes to the retinal image. In contrast, laser combined with mICG, at both 1000 and 1400 mW laser powers focused on the ON generated a pattern consistent with the previous rodent NAION model, but without any retinal vascular dilatation. On SD-OCT, the mICG-induced rats revealed retinal detachment if laser power was applied to both the ON and the peripheral retina. Central ON induction resulted in widening of the ON shadow and retinal nerve fiber layer opacification suggestive of anterior ischemia and edema.
mICG dye coupled with infrared laser exposure has yielded promising results in generating rNAION without apparent retinal ischemia. Further work is ongoing to determine the repeatability and robustness of this new model and determine the most effective treatment approach.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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