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Brent A. Bell, Charles Kaul, Mary E. Rayborn, Joe G. Hollyfield; Baseline Imaging in Mice to Screen for Pre-existing Retinal Abnormalities. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1733.
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Fundus imaging was performed in several strains of wild-type and knockout mice to pre-screen for retinal abnormalities prior to use in protocols designed to generate retinal lesions. The failure to exclude mice with retinal changes could potentially alter conclusions about experimental study outcomes.
Imaging was performed in mice ranging from 2-14 months of age. The strains investigated included C57BL/6J, BALB/c, compliment knockouts C3, C4, factor B, factor H, and SOD1 in C57BL/6J background. Mice were anesthetized with 90mg/kg of sodium pentobarbital administered IP. Mydriasis was induced with 2 µl of 0.5% Tropicamide/Phenylephrine combination drops. Eyes were kept hydrated with balanced saline solution. Retinal imaging was performed using confocal scanning laser ophthalmoscopy (SLO), spectral-domain optical coherence tomography (OCT) and contact fundus imaging (CFI). After imaging eyes received ophthalmic antibiotic ointment to prevent corneal dehydration.
A routine was developed for obtaining baseline fundus images of mice. Each mouse required approximately 25 minutes to complete with both SLO and OCT imaging. Data from over 450 mice have been obtained to date. The use of multiple imaging systems, with up to six separate imaging modalities, permitted comprehensive screening for retinal abnormalities. Numerous abnormalities were detected in each mouse strain with varying prevalence. The percentage of abnormalities observed in young (<4 months) mice were as follows: wild-type C57BL/6J (1.5%), factor B-/- (2.4%), C3-/- (4.8%), factor H-/- (5.6%), SOD1+/+, -/- (14.3%), C4-/- (17.1%), and BALB/cAnNTac (3.3%), BALB/cJ (100%). The numbers obtained in older (6-14 months) mice was as follows: wild-type C57BL/6J (5.9%), factor H-/- (0%), C3-/- (4.7%), SOD1+/+, -/- (7.7%), factor B-/- (8.3%), and C4-/- (13.6%).
Retinal abnormalities exist to varying degree in presumably normal mice that can be detected using SLO, OCT and CFI imaging. This study underscores the importance of prescreening mice using one or more of the various small animal fundus imaging modalities commercially available to avoid enrolling mice with pre-existing fundus abnormalities in protocols designed to generate retinal lesions.
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