Three-dimensional OCT based guinea pig eye model: relating morphology and optics

Abstract

Custom Spectral Optical Coherence Tomography (SOCT) provided with automatic quantification and distortion correction algorithms was used to measure the 3-D morphology in guinea pig eyes (n = 8, 30 days; n = 5, 40 days). Animals were measured awake in vivo under cyclopegia. Measurements showed low intraocular variability (<4% in corneal and anterior lens radii and <8% in the posterior lens radii, <1% interocular distances). The repeatability of the surface elevation was less than 2 µm. Surface astigmatism was the individual dominant term in all surfaces. Higher-order RMS surface elevation was largest in the posterior lens. Individual surface elevation Zernike terms correlated significantly across corneal and anterior lens surfaces. Higher-orderaberrations (except spherical aberration) were comparable with those predicted by OCTbased eye models.

Crystalline lens gradient refractive index distribution in the guinea pig

“…Knowledge of the crystalline lens GRIN as reported here, will improve computer eye models of the guinea pig eye, such as those we described previously, where a comparison of experimental and predicted aberrations showed a discrepancy in the sign of the spherical aberration. Incorporation of the GRIN in eye models will allow realistic predictions of spherical aberration and increased accuracy in the estimation of the guinea pig posterior crystalline lens shape in vivo.…”

“…The indices of refraction of the cornea, aqueous and vitreous humors, and a hypothetical homogeneous crystalline lens (1.376, 1.3346 and 1.401 respectively) were obtained from the literature and a good correspondence between the spherical error predicted from the calculated optical power and the axial length obtained using geometrical measurements from OCT was found. However, optical aberrations were also characterised in vivo , and the spherical aberration measured and predicted in the same eyes was dramatically different (positive from the virtual ray tracing estimates, and negative from the experimental aberrometry measurements) . In that work, we hypothesised that the source of the discrepancy was the presence of a GRIN in the crystalline lens, not accounted for in the simulations.…”

Estimation of intraocular lens position from full crystalline lens geometry: towards a new generation of intraocular lens power calculation formulas

“…Using the trained parametric model and the information within the pupil, very realistic lenses are constructed in vivo with a small estimation error. This method was applied to study the changes of lens full shape parameters with accommodation 27 , in older patients with cataract 23 , and in animal models of myopia 30 .…”

Morphological changes of human crystalline lens in myopia

“…Furthermore, we have recently presented and validated a method to estimate the full shape of the crystalline lens from its central part [38]. This method was successfully applied to assess changes of the crystalline lens full shape with accommodation [39] and with age [40] in vivo, to improve the estimation of the intraocular position in a cataract surgery [41] and to quantify the crystalline lens in animal models of myopia [42].…”