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Timothy S Kern, Jie Tang, lingzhen Pan, Zhiqiang Li, Yubo Shen, Wen Zeng, Li Gong; Assessment of macular thickening in spontaneously diabetic rhesus monkeys. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3581. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
We assessed retinal thickness in a colony of spontaneously diabetic rhesus monkeys. Previous studies of primates have shown that the retinopathy that develops in diabetic primates is very similar to that which develops in diabetic patients. The purpose of this study was to determine if spontaneously diabetic rhesus monkeys develop retinal edema, and to investigate how quickly it developed.
A spontaneously diabetic of rhesus monkeys in the Primed Monkey Research Center in China were studied. Spectral domain OCT measurements and color fundus photographs were collected on 45 spontaneously diabetic primates (11-20 yrs of age) and 15 nondiabetic controls of similar age. The duration of diabetes was 1 to 7 years. Clinical chemistry data was collected on all animals annually. Retinal thickness was evaluated once by 2 methods using OCT: (1) at the fovea and 1.5mm on either side of it, and (2) using a point-counting method (52-point grid) to determine the fraction of macula that had thicknesses in different progressive thickness groupings (250-300μm, 301-350μm, 351-400μm, etc).
Fasting plasma glucose averaged 4.1±0.3 mmol/L and 5.9 ± 0.5 in nondiabetic and diabetic animals, respectively. Thickness of the retina in nondiabetic animals was 192±11μm at the fovea, and 307±15μm and 328±13μm 1.5mm from fovea on the temporal and nasal sides, respectively. We defined retinal thickening as thickness values that exceeded the normal mean by 2 standard deviations. Of 45 primates having diabetes for up to 7 years, 33% of them showed thicknesses ≥2 SD above the nondiabetic mean at the fovea and nasal retina (1.5mm from fovea). On the temporal side, 9% of diabetics showed thicknesses ≥2 SD above the nondiabetic mean. 22% of diabetics had ≥20% of the macula in the 351-400μm size class (potentially abnormal thickness), compared to 0% of the nondiabetics. Using less stringent thickness criteria, 62% of diabetics had ≥5% of the macula in the 351-400μm size class, compared to only 20% of the nondiabetics. Some diabetics had more severe edematous changes, and intraretinal hemorrhages and hard exudates were noted by ophthalmoscopy in some diabetics.
Some rhesus monkeys having spontaneous type 2 diabetes develop significant macular thickening within 7 years of diabetes, and so can serve as a pre-clinical model for studies related to early diabetic macular edema.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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