Objective: To investigate the changes of refraction and ocular biometric parameters in form deprived myopia, and try to find the effective duration to induce significant myopic shift in C57BL/6 mice.
Methods: It was an experimental study. Seventy-four C57BL/6 mice, approximately 23 days old, were divided into three groups randomly: FD (Form-deprivation), Recovery and Normal control groups. FD group was treated with diffuser worn on one eye for 2 weeks (n = 12), 3 weeks (n = 20) and 4 weeks (n = 18), respectively. In Recovery group, diffusers were removed after 4 weeks form deprivation, and vertical meridian refraction and other biometric parameters were performed immediately on 4(th) and 7(th) day. The same measurements were performed in the normal control group at the same time-points. Refraction was measured by photoretinoscopy and corneal radius of curvature (CRC) was measured by a modified keratometry. Corneal thickness (CT), anterior chamber depth (ACD), lens thickness (LT), vitreous chamber depth (VCD), and axial length (AL) were measured by optical coherence tomography (OCT) with focal plane advancement.
Results: The FD eyes were approximately -0.85 D more myopic compared to the fellow and the normal control eyes after 2 weeks form deprivation (P > 0.05). After 3 weeks form deprivation, treated eye had a obvious myopic shift (about -4.27 D) compared to fellow eye, with increased vitreous chamber depth and axial length, however, there was no statistic difference among FD eye, fellow eye and control eye. And after 4 weeks form deprivation, treated eyes were induced significant myopic shift (about -5.22 D) compared with the fellow eye. The difference in refraction of form-deprived and fellow eyes was significantly correlated with the difference in vitreous chamber depth and axial length, which indicate that the induced myopia was mainly axial. The relative myopia shifted rapidly diminished in 4 days after removing the diffuser, followed by a slower recovery. A complete refraction recovery occurred by 7 days after removal of the diffuser compared to the fellow and normal control eyes (P > 0.05).
Conclusion: Form deprivation myopia can be induced in C57BL/6 mice, but it required longer period than other animals; A complete recovery occurred by 7 days after removal of the diffuser.Optical Coherence Tomography is a useful instrument to measure mouse eye dimension.