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Emilie van der Sande, Beerend Winkelman, Chris de Zeeuw, Caroline C W Klaver; Validation of lens-induced myopia protocols in C57BL/6 mice. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5867.
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© ARVO (1962-2015); The Authors (2016-present)
Murine models are widely used to study the relation between genetic and environmental factors in myopia development. Because inducing a substantial myopic shift in mice is more challenging than in other species, optimization of experimental protocols is needed to achieve maximal effect. Here, we aim to replicate previously described methods and further develop an efficient protocol for lens-induced myopia.
Myopia was induced in C57BL/6 mice by placing glass lenses (-30/-59/+37 D) in front of the left eye (OS) using head-mounted goggles, starting on P24/25 for the duration of 4 weeks; the right eye (OD) was used as control. Mice were housed on a 18h:6h light/dark-cycle (200 lux illuminance). Measurements were performed weekly in head-fixed and awake mice. Axial length (AXL) and vitreous chamber depth (VCD) was measured using SD-OCT, and refractive error (RE) was measured with eccentric IR photorefractometry (Schaeffel, 2004). A subset of mice was tested with and without 1% tropicamide eye drops. Pupils of all mice showed a ring pattern during photorefraction, indicative of a discontinuity in the lens between concentric zones of different focal lengths. RE was therefore based upon the close-to-linear gradient in the central part of the pupil.
In total, 57% of the mice developed a relative myopic shift in the challenged eye, of which 50% had an increased axial length. We observed considerable variation in the RE at P24/P25 (mean±SD: -7.6±9.8 D, OS-OD: mean abs.: +10.8 D). As a result of this variation, the group that received -30 D lenses did not show a relative myopic shift (OS-OD: RE: +6.21 D, AXL: -2.2 µm, VCD: +20.2 µm). In contrast, the absolute RE on P52 indicated myopia induction (mean±SD: OD: -4.5±3.4 D, OS: -16.6±2.4). The -59 D lens group showed a relative myopic shift and increased axial length (OS-OD: RE: -5.8 D, AXL: +14.1 µm, VCD: +18.9 µm). The group with positive powered lenses (+37 D) showed a relative hyperopic shift (OS-OD: RE: +7.3 D, AXL: +5.5 µm, VCD: +31.31 µm). Application of 1% tropicamide did not significantly affect RE (with-without: -0.9 ± 3.04 D, P=0.77).
A greater myopic phenotype was developed with -59 D lenses, compared to -30 D lenses. This study provides evidence that use of cycloplegic agents is not affecting the RE in mice. Lowering the variation in initial RE and AL using strict inclusion criteria will enhance consistency of the results.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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