Purchase this article with an account.
M. F. Bird, M. L. Kisilak, M. C. W. Campbell; Optical Quality of the Rat Eye. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2759.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The optical quality of the rat eye is important to the imaging of the fundus and the delivery of light to the retina in this common animal model of ocular disease. We wished to quantify the optical quality, compare it with the predictions of a previously developed eye model and predict optimum pupil sizes for retinal imaging.
We measured the aberrations of the eyes of four female pigmented Long Evans rats (minimum age 240 days) using a modified Hartman Shack device. The rat was oriented so that the beam would be approximately along the optical axis. Measurements were taken with the animals lightly restrained and under sedation. Measured aberrations were compared to the predictions of an anatomically based eye model (developed for adult pigmented DA rats) in which the crystalline lens has a gradient of refractive index. This model predicts the monochromatic aberrations as a function of pupil size and field angle and the change in the point spread function (PSF) at differing focal planes. Fundus images were taken of five alert Sprague Dawley albino rats (breeders) with differing entrance pupil sizes using a confocal scanning laser ophthalmoscope. The quality of the images was assessed by calculating the image quality metric, entropy.
The measured aberrations increase with increasing pupil size. The models predict the experimentally observed increase of spherical aberration with pupil size. The amounts of spherical aberration are variable among rats and the GRIN eye model predicts values for one rat over which the largest range of pupil sizes were analyzed but underestimates the average across rats. In the symmetrical model, on axis, the only higher order aberration (HOA) is spherical aberration. However, other HOA are present experimentally. The root mean square HOA of the model 20 degrees off axis was closest to those measured. From the model, point spread functions were calculated as a function of pupil size. The pupil size predicted to give the smallest in focus PSF was consistent with the pupil which gave the fundus images with the best quality. This pupil was substantially smaller than the animal’s maximum dilated pupil.
The GRIN eye model gives predictions of aberrations within the range measured across animals. It also predicted the best pupil size for fundus imaging. In order to take advantage of the good f number of the rat eye, adaptive optical correction will be necessary. This would greatly improve image quality and would reduce the volume of the PSF, localizing the effects of light energy, including two photon interactions.
This PDF is available to Subscribers Only