Intraocular pressure measurement in the conscious rat

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74866/1/j.1600-0420.1999.770108.x.pd

Optic Disc Imaging in Conscious Rats and Mice

PURPOSE. To determine whether useful images of the optic discs of conscious rats and mice can be obtained by using a photo slit lamp and a modified Goldmann-type fundus contact lens. METHODS. Testing was performed with a photo slit lamp equipped with two 2x teleconverters and a digital camera through a Goldmann-type fundus contact lens that was fabricated for the rodent eye. RESULTS. Images of the rat and mouse optic discs were obtained that are comparable to those used by ophthalmologists to assess optic neuropathy in glaucoma, a key part of the standard of care and of clinical investigation of this disease. The cup in the optic disc image of these rodents is darker than the neural rim of the disc, rather than lighter, as it is in humans. CONCLUSIONS. In addition to the application of this imaging method to studies of the effect on optic disc cupping of induced increased intraocular pressure in rats and mice, by detecting and documenting the onset and the course of optic neuropathy, it should be valuable in identifying animal models of glaucoma, in studying neuropathogenic mechanisms, and in assessing the effects of experimental therapies. (Invest Ophthalmol Vis Sci. 2003;44:160 -163 3 However, a laboratory animal model of POAG is still not available. One factor in the delay was resolved by a reliable, noninvasive method for measurement of intraocular pressure (IOP) in conscious rats 4 and mice, 5 because increased IOP, also called ocular hypertension, is the most important risk factor in human POAG. Still missing for phenotypic assessment of a rodent mimic of this disease is a reliable method for documenting in the living animal the sine qua non of POAGits characteristic optic neuropathy. The present report describes a method for obtaining images of the optic disc in conscious rats and mice that are comparable to those routinely available to ophthalmologists for detecting the onset and monitoring the course of optic neuropathy in patients with POAG. This is a key part of both the current standard of care and of clinical investigation of this disease. 6 By obtaining documenting images of the optic discs over time in rodent models of POAG, changes in the discs' appearance that are comparable to those observed clinically in humans can be correlated with the histology and histochemistry of the optic nerve head. MATERIALS AND METHODS The experiments adhered to the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research, the tenets of the Declaration of Helsinki, and the guidelines of the University Committee on the Use and Care of Animals (UCUCA) of the University of Michigan. Optic disc images were obtained in Brown Norway rats (Harlan Sprague-Dawley, Indianapolis, IN) and in CS7 Black mice (Jackson Laboratories, Bar Harbor, ME). Initial experiments were performed under general anesthesia with intraperitoneal pentobarbital sodium (50 mg/kg). Subsequently, images were obtained in conscious, untrained rats and mice that were gently restrained in modified rat or mouse polyethylene cones (Decapicone; Braintree Scientific, Inc., Braintree, MA) as has been described for Goldmann applanation tonometry in awake mice. 5 Briefly, the apex of the cone was trimmed so that the animal's head could protrude until the cut edge of the cone crossed temporally midway between the eyes and ears. As in humans, the animals' pupils were dilated with drops of tropicamide (Mydriacyl 1%; Alcon Laboratories, Inc., Ft. Worth, TX), and their eyes were topically anesthetized with drops of proparacaine 0.5%. The animals were positioned at a photo slit lamp (900 P-BQ; Haag-Streit, AG, Köniz, Switzerland) on a Plexiglas platform supported by aluminum posts that fit into the holes for the chin-rest paper pins. Goldmann-Type Fundus Lens with Hruby Preset Lens-Type Holder A special Goldmann-type fundus contact lens The contact lens, with a minute drop of 2.5% methylcellulose on the contact area, was placed on the cornea. One person adjusted the animal's position until the disc came into view for the other person, the photo slit lamp operator. The Hruby lens-type holder supported the contact lens. Its control lever was used for alignment, adjusting light reflexes away from the disc by slight turning and tilting of the contact lens, and maintaining focus by avoiding the movement of these small animals that a finger-held contact lens can cause. Digital Image Acquisition This photo slit lamp has a mirror housing that incorporates a front surface mirror that swings into the optical path and closes its flash contact when its shutter release bar is activated. The photo slit lamp settings in this study included: Galilean power changer at 25x, mirror housing diaphragm at 3, slit illuminator spotlight diameter at 3 mm and filter at heat-absorbing, and light source flash at high. Attached to the mirror housing was the objective tube for monophotography, an adapter (model F; Nikon, Melville, NY), two teleconverters (TC-201 2x; Nikon) and the camera. A digital camera (FinePix S1 Pro; Fujifilm, Elmsford, NY) was used for the imaging. Its picture element is a 23.3 ϫ 15.6-mm chargecoupled device (CCD) with primary color filter with 3.4 megapixels in From th

Evolution of extensively drug-resistant tuberculosis over four decades: whole genome sequencing and dating analysis of Mycobacterium tuberculosis isolates from KwaZulu-Natal.

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A theory of entangled political economy, with application to TARP and NRA

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