Abstract
Abstract: :
Purpose: The common marmoset, Callithrix jacchus, is an animal model in studies of emmetropization. The refractive development of the marmoset eye depends on visual experience, so knowledge of the optical quality of the eye is important. We used a clinical Shack-Hartmann wavefront sensor to measure the optical aberrations of marmoset eyes. Methods: Twelve eyes of six marmosets (mean age = 107 days) were used. Spherical equivalent refractions ranged from +1.58 D to +5.28 D (mean = +3.43 D; s.d. = 0.89 D), as measured by an infrared PowerRefractor (Multichannel Systems). Using a Complete Ophthalmic Analysis System (Wavefront Sciences), wavefront measurements were made with the eyes cyclopleged and the animals under general anesthesia. Since lid retractors were used, rigid plano corneal contact lenses were placed on the eye to ensure integrity of the anterior surface. The live video image of the eye was used to align the subject prior to each measurement. Captured images were analyzed when the centroid patterns were centered and alignment was judged to be good by inspection of the video frame. Approximately 5 images per eye were analyzed. Wavefront error was expressed as a seventh-order Zernike polynomial expansion. The RMS wavefront error for third-order and higher terms was used as an overall estimate of optical quality. This metric excludes the contribution from piston, tilt, defocus and astigmatism. Results: The mean pupil diameter of the 12 eyes was 2.96 mm (s.d = 0.23 mm). Although the contact lens could have affected refraction during measurements, the refractions determined from the wavefront sensor were correlated with the values from the PowerRefractor (r=0.67, p=0.02) and the mean refractions from the two instruments were not significantly different. The overall mean RMS wavefront error for third-order and higher terms was 0.29 um (s.d.=0.10 um). There was a tendency for higher-order wavefront error to increase with increasing hyperopia; this trend was stronger when each eye's lowest RMS value was used (r=0.56, p=0.06) than when each eye's mean RMS value was used (r=0.46, p=0.14). Conclusions: In this preliminary study it appears that the higher-order aberrations of the marmoset eye are fairly low, which is consistent with the high density of retinal cones and ganglion cells observed in this species. The wavefront aberrations are, however, higher than those observed in humans with the same pupil size (Howland, Ophthal. Physiol. Opt., 2002). In future studies we plan to examine emmetropes and myopes to determine further the relationship of high order optical aberrations and refractive error in this experimental species.
Keywords: optical properties • animal model • emmetropization