Effect of induced myopia on scleral mechanics and myofibroblast populations

Abstract

Abstract Purpose: Determine the effect of induced refractive error on a) ocular compliance and b) scleral contractile cell populations in guinea pig. Methods: One week old guinea pigs (n = 29) were monocularly deprived of form vision (MD) for 14 days. Cycloplegic refractive error was measured with an IR Optometer. Ocular compliance (change in length/mmHg change in IOP) of MD and control eyes was compared by raising the IOP to 50 mmHg for one hour in 8 anaesthetised animals. A‐scan ultrasound measures of axial length were taken every 10 minutes with raised IOP, and after returning IOP to 15 mmHg. Antibodies to DAPI and α‐smooth muscle actin (α‐SMA) were used to determine the total cell population and cell contractile potential respectively in MD and control sclera. Results: MD induced ‐4.06 ± 1.88 D of myopia, which was correlated with 169 ± 267 μm of vitreous chamber depth (VCD) elongation (n = 29; R2 = 0.37). Both deprived and control eyes showed negative creep compliance (eye shortening) over one hour of raised IOP, equivalent to 1.44 μm shortening per minute. On returning the IOP to 15 mmHg the VCD of the control eye was shorter than baseline by 92.86 ± 88 μm while the deprived eye remained 83.48 ± 37 μm longer than baseline (± SEM; n = 8). These differences were not statistically significant (p = 0.173). There was however an increase of 6% in the percentage of the total cell population positive for α‐SMA in myopic versus control sclera (p = 0.015; n = 7). Conclusions: Myopic and control eyes show similar negative creep compliance in vivo with raised IOP, and no difference in their elastic compliance response. However the α‐SMA positive cell population is increased in myopic sclera, suggesting a role in scleral remodelling.