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M. Ali Shariati, Gun Ho Lee, Yaping Liao, Stanford School of Medicine; Thinning of the Optic Nerve in Aging and after Ischemia: An Imaging Study Using Spectral-Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3231.
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Anterior Ischemic Optic Neuropathy (AION) is caused by ischemia at the optic nerve head and is the most common acute optic neuropathy in patients older than 50 years old. We used spectral-domain optical coherence tomography (SD-OCT) to study anatomic changes during normal aging and following photochemical thrombosis model of AION.
We induced optic nerve head ischemia following rose bengal injection in adult mice using a frequency doubled Nd: YAG laser with low intensity light (400 μm diameter, 50 mW, 1 second duration, 15 spots). We performed circular (12°) and posterior pole (30° H x 25° V) scans and serially measured retinal thickness. With circular scans, we measured the Ganglion Cell Complex (GCC), which included the combined thickness of the retinal nerve fiber layer, ganglion cell layer, and inner plexiform layer. We also performed posterior pole analysis to measure total retinal thickness. Statistical significance was calculated using Student’s t-test.
Using OCT circular scan and manual segmentation, we found there was an aging associated 1.6 µm decrease in the thickness of GCC in one-year-old mice compared with three-months-old mice (three-months: 76.2 ± 0.2 µm, N = 79 eyes; one-year: 74.6 ± 0.3 µm, 2% reduction, N = 72 eyes; P < 0.0001). This thinning of the GCC layer was more prominent after AION. Three-weeks after AION, there was an 8 µm thinning of the GCC (baseline: 74.9 ± 0.9 µm; 3-week AION: 66.6 ± 1.0 µm, 11% reduction; P < 0.0001). Posterior pole analysis showed significant optic disc thinning following AION (baseline: 236.3 µm; AION: 190.9 ± 2.9 µm; 19% reduction, N = 40; P < 0.0001) but no change associated with aging (three-months: 246.7 ± 5.4 µm, N = 380 measurements in 94 eyes; one-year: 249.2 ± 1.0 µm, N = 280 measurements in 70 eyes; P = 0.7).
OCT quantifications of the ganglion cell complex and the optic disc thickness revealed both measurements decreased following AION, while only the ganglion cell complex thinned with aging. After AION, there was initial swelling followed by significant thinning of the ganglion cell complex over 3 weeks. This pattern of change was similar to that of humans but at a more rapid time scale. OCT study of the AION model enabled detail analysis of the retinal and optic disc changes that occur after optic nerve, which may be useful in determining possible therapeutic interventions.
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