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F Schaeffel, E Burkhardt; Measurement of Refractive State and Deprivation Myopia in a Black Wildtype Mouse . Invest. Ophthalmol. Vis. Sci. 2002;43(13):182.
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Purpose:The mouse eye has a bright retinal image (f/number about 0.9) but low optical quality (see figure; visual acuity about 0.5 cyc/deg, Prusky et al Vision Res 2000; 40: 2201-2209) which may render emmetropization unneccessary. However, because its genome is largely sequenced, the mouse would be an attractive model to study the biochemical and genetical basis of myopia. We have investigated how precisely it can be refracted and whether deprivation myopia can be induced. Methods:An eccentric infrared photorefractor (Schaeffel et al, OPO 1999; 19:180-192) was used with a 100 mm lens and extension rings to refract from a distance of 60 cm. For refractions, mice were cyclopleged with tropicamide but not anesthetized, and were restrained only by grabbing their tails. Little plastic hemispherical occluders were monocularly glued to the fur on day P25 and left attached for 10 days. Results:(1) Lenses ranging from +10 to -10D, held in front of the eyes for calibration, changed the slopes in the pupil according to: slope = lens power (D)*0.1197+0.6401 (n=32 measurements in 2 mice, R=0.8122). The data suggest a measurement variability of about +4D. (2) In occluded eyes, hyperopia declined from +12.8+-3.6 to +6.1+-2.1D, in the fellow eyes from 11.3+-3.1 to 5.1+-2.6D (4 animals). In untreated mice of the same strain, refractions were +15.9+-3.2 (day 31) and 16.6+-4.3D (day 36, n= 6). (3) Pupil sizes (under cycloplegia) changed from 1.87+-0.11 (day 25) to 2.07+-0.12 mm (day 36). Conclusion:(1) Unexpectedly, the mice could be refracted with a variability that translates into only +-16µm variability in axial length (total axial length about 3.3 mm). (2) Mice became more myopic from the occluders in 10 days (p<0.001 compared to untreated animals) but refractions in both eyes appeared to be tightly coupled. It has still to be found out whether this is deprivation myopia. (3) Derived from the increase in pupil size, the eyes grew by about 10% over the treatment period. View OriginalDownload SlideView OriginalDownload Slide
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