Abstract
Purpose :
To measure 3-D eye morphology and ocular aberrations in guinea pig eyes to understand the relationships between cornea and crystalline lens geometry in this model, the sources of refractive errors, optical aberrations and potential accommodation.
Methods :
Guinea pigs (3 eyes) were measured in vivo at 30 days of age in two conditions: awake and under cyclopegia (1% cyclopentolate). Custom spectral anterior segment OCT provided with automatic quantification and distortion correction algorithms was used to measure corneal and crystalline lens radii and surface elevations (described by Zernike coefficients), anterior chamber depth (ACD), lens thickness and vitreous chamber depth. OCT- ocular aberrations were estimated by using multi-surface computational ray tracing in ZEMAX. Total aberrations were measured using a custom-developed Laser Ray Tracing. OCT-based aberrations and LRT-aberrations were compared for 3-mm pupils (with respect to the pupil center).
Results :
Measurements showed very low intrasubject/intersubject variability (on average: 0.06/0.12 mm in lens radii, 0.05/0.08 mm in interocular distances; 0.48 µm/1.76 µm surface Zernike coefficients; 0.04/0.10 in wave aberration Zernike coefficients). On average, the individual dominant surface term was astigmatism (72%, anterior cornea; 82%, anterior lens). Higher-order RMS surface elevation was larger in the posterior than in the anterior lens (x1.46, p<0.05). There was strong significant correlation in surface elevation Zernike terms (p<0.0001) across all anterior segment surfaces: anterior cornea vs posterior cornea (r=+0.94), anterior cornea vs anterior lens (r=+0.94), anterior lens vs posterior lens (r=-0.93). Cycloplegia showed changes in anterior and posterior corneal astigmatism (H/V astigmatism) and posterior lens high-order irregularities (vertical coma), and produced a defocus shift towards more positive values (1.9 D, OCT-aberrometry; 1.8 D, LRT-aberrometry).
Conclusions :
3-D OCT is a reproducible technique to evaluate in vivo the full 3-D anterior segment biometry allowing quantitative eye models relating morphology and optics in animal models for myopia.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.