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Li Qin Jiang, Frank Schaeffel, Ke Li Long, Jia Qu; Disruption Of Emmetropization And High Susceptibility To Form Deprivation In Albino Guinea Pigs. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6288.
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To compare refractive development and emmetropization in albino and pigmented guinea pigs.
Distributions of refractive state were examined in a large sample of 145 albino and 150 pigmented guinea pigs. Ignoring potential effects of the small eye artifact, albino (A) and pigmented (P) guinea pigs were divided into two groups, hyperopic (H) and myopia (M), just based just the signs of the refractions that were provided by an infrared photorefractor. Thereafter, eye development was separately followed in 10 randomly selected animals from each of the four groups (AM, AH, PM, PH) from 2 weeks to 10 weeks of age. This included measurements every other week of refractions, corneal curvatures (modified conventional keratometer) and ocular biometry (A-scan ultrasound). In addition, deprivation myopia was induced in 36 age-matched albino (18AH and 18AM) and 36 pigmented (18PH and 18PM) guinea pigs by diffusers that were worn from 2 to 6 weeks of age. Finally, sclera fibril diameters were compared in normal-sighted and myopic animals, using transmission electron micropscopy (TEM).
There was a clear difference in the average refractions in albino and pigmented animals (-2.32±5.71D versus 1.60±5.64D, t=5.929, p<0.01, unpaired t test). Myopia was more common in albino animals: 96 (66.2%) were myopic (AM) and 49 (33.8%) hyperopic (AH), whereas only 52 (34.7%) pigmented animals were myopic (PM) and 98 (65.3%) hyperopic (PH). Different from PM, AM did not show any recovery from myopia. With diffusers, AH became more myopic (-7.61±2.71 D and -11.17±2.55 D after 2 and 4 weeks, respectively) than PH (-4.48±1.46 D and -8.28±2.13 D after 2 and 4 weeks, respectively, p<0.01, two-factor ANOVA). Deprivation myopia could still be induced in PM (-1.64±1.44 D and -5.17±1.88 D after 2 and 4 weeks, respectively, p<0.01) but not in AM. TEM studies showed that scleral fibril diameters were smaller in myopic animals, both albino and pigmented.
Albino guinea pigs show limited emmetropization - no recovery from spontaneous myopia (which occurred in 66% of the animals) and lack of susceptibility to deprivation myopia. However, deprivation myopia could still be induced in hyperopic albinos and was even higher than in pigmented animals. The distinct effects of albinism on emmetropization will help to learn more about the mechanism of emmetropization - given that albinos and pigmented animals had comparable spatial vision which implies that gain changes in the emmetropization feedback loops must be responsible.
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