Abstract
Purpose: :
To determine the susceptibility to induction of refractive errors by form deprivation in albino compared with pigmented mice.
Methods: :
Two mouse strains derived from equivalent genetic background [C57BL/6J] were used in this study: C57BL/6J pigmented (n=14) and B6(Cg)-Tyrc-2j/J albino (n=14) mice. Form deprivation was induced by left eyelid suture after natural eye opening. After 4 weeks of form deprivation, followed by a period of form vision in a subgroup (n=11), refraction and biometry were determined using infra-red Power Refractor and AC Master interferometry, respectively. Left (deprived) eye minus right eye measurements were computed. Comparisons were made using nonparametric Wilcoxon signed ranked and rank sum tests. All the procedures were conducted in accordance with ARVO animal research policy and current legislation, after approval by the corresponding institutional ethics committees.
Results: :
Form deprivation induced transient relative mean hyperopia of 5.23 D [95% confidence interval, CI=2.96 to 7.51], p=0.02 (intereye axial length difference, IAL= -0.058 [-0.083 to -0.033] p<0.01), and subsequent mean myopia of -3.84 D [-0.79 to -6.89], p=0.019 (IAL= -0.032 [-0.073 to 0.008] p=0.106), considering all mice. Relative myopia in pigmented mice was of -5.79 D [0.80 to -12.38], p=0.07, (IAL= -0.003 [-0.055 to 0.048] p=0.8), whereas in albino mice relative induced myopia was -2.21 D [-5.81 to 1.37], p=0.17, (IAL -0.056 [-0.12 to 0.013] p=0.09). Transient hyperopia and myopia induced in albino mice were not significantly different from those induced in pigmented mice (p=0.49 and p=0.126, respectively).
Conclusions: :
Albino mice are equally susceptible to refractive changes than pigmented mice, at least with the timing and number of animals used. Transient hyperopia is paralleled by axial length changes, but induced myopia is not, due to technical limitations in measurements or contribution of other optical factors.
Keywords: myopia • plasticity • hyperopia