Performance of the crystalline lens in the accommodated eye of myopia

Abstract

Purpose: Accommodation of the eye is performed by deformation of the crystalline lens, and deficiency of the accommodation is believed to be a factor associated with myopia development. However, the lens performance during accommodation in the myopic eyes has not been well investigated. The purpose of this study was to measure optical and structural changes in the accommodated lens of myopic eyes.

Methods: A custom developed Hartmann-Shack wavefront sensor, integrated with a custom developed spectral domain optical coherent tomography (SD-OCT) system, was used to measure accommodative responses (AR) for 17 young adults (aged 21 to 39 yrs old, Rx from -0.75 D to -8.50D with a mean of -4.50±2.44D). The wavefront sensor measured Zernike aberrations up to 7^th order for the right eye when accommodative stimulation (AS) was presented for the same eye at 0.0, 2.0, 4.0 and 6.0D with a Badal system. The 840nm SD-OCT system, co-axially aligned with the wavefront sensor, was used to image the cornea and the lens.

Results: When accommodating 6D, the mean accommodative changes were 5.40±0.48D in refractive power and -0.03±0.04micron in spherical aberration. With 6D accommodation, the mean anterior chamber depth (ACD) was shortened by 0.28±0.06mm while the lens thickness (LT) was thicken by 0.313±0.07mm, and thus resulting in a backward movement of the posterior lens surface of 0.04±0.04mm. The mean anterior lens radius changed from 12.68±1.91mm at 0D to 8.99±1.69mm at 6D of accommodation. Whereas, the mean posterior lens surface was more curved. It ranged from 6.90±1.09 mm in radius at 0D to 6.30±1.02mm at 6D accommodation. There was a significant correlation between the LT change and the ACD change (R² = 0.76, p<0.001).<br />

Conclusions: Compared to a forward movement of the lens in the accommodated eye of emmetropia, as we reported in last ARVO, the lens moves backward more in the accommodated eye of myopia. The relatively more backward movement of the lens might contribute to the deficiency of accommodation in myopic eye and thus be associated with myopia development.