Biomedical subjects

D C Coile

Publications and source records attributed to D C Coile.

5 recordsLinked to original sources

PubMed1992

Foveal dark adaptation, photopigment regeneration, and aging.

Foveal dark adaptation in 58 subjects and photopigment regeneration in 60 subjects from 10-78 years of age exhibit parallel slowing of recovery rate with increasing age, with significant correlation of the two functions among individuals. The data are suggestive of an initial slight decline in rate before age 50, followed by a greater decline occurring at different ages in different individuals. Longitudinal data for one subject from age 40-65 show an increase in pigment regeneration time constant consistent with this idea. Foveal sensitivity and photopigment density both decrease with increasing age and are significantly correlated among individuals, although sensitivity declines more with age than does photopigment density. In contrast to earlier proposals based upon the Rushton-Dowling equation, we found no universal constant of proportionality to relate log relative threshold to photopigment within our population.

Adolescent↗

PubMed1991

Experimental stray light in retinal densitometry.

The effects of stray light upon retinal pigment densitometric measurements were evaluated by adding specified amounts of stray light to fundus reflections. To allow for interpolations and extrapolations, a computer simulation was devised and validated against the empirical data. The results demonstrate that measured density is greatly decreased by increases in stray light but the time constant of pigment regeneration is little affected.

Computer Simulation↗

PubMed1989

Behavioral determination of critical flicker fusion in dogs.

Steady-state critical flicker-fusion frequencies (CFFs) were determined for four beagle dogs using the psychophysical technique of conditioned suppression. The CFFs obtained demonstrated that the dog can discriminate flicker at much faster rates than has been suggested by ERG data. In addition, dog rods may support the discrimination of flicker at much higher rates than can human rods. An indication of a psychophysical rod-cone break occurred at a luminance level intermediate to those previously reported in ERG CFF studies. This level is similar to that in the cat, but much higher than that in man. The high CFFs provide the first psychophysical evidence of a well-developed functioning cone system in the dog.

Animals↗

PubMed1988

Schematic eyes for domestic animals.

Schematic and reduced eyes for the horse, cow, sheep, pig, cat, and dog were calculated from optical parameter values obtained from the literature. Calculations were performed with the aid of a computer program using standard Gaussian equations and a homogeneous lens model. Calculated schematic eyes had refractive states within 1.5 D of emmetropia; retinal image sizes ranged from 0.22 (cat and dog) to 0.44 (horse) mm/deg. The cat eye presented here is more nearly emmetropic than a previously published cat schematic eye. The effects of altering refractive indices, radii of curvature, and thicknesses of refractive components upon refractive state and retinal image size are examined. The largest differences resulted from changes made to refractive indices of the lens and vitreous and to the vitreous depth.

Animals↗

PubMed1988

A BASIC computer program for schematic and reduced eye construction.

A simple computer program for calculating schematic and reduced eyes is presented. The user supplies distances from the front of the eye and radii of curvature of refractive surfaces (anterior and posterior cornea and lens), distance to retina, and refractive indices of ocular media (cornea, aqueous, lens, vitreous). These values are input to calculate the necessary parameters for construction of a schematic and reduced eye, using Gaussian formulae and assuming a homogenous lens. The program produces powers of optical components and of the whole eye, cardinal points of the eye, and estimates of refractive state and retinal image size. These values may be printed in tabular form or plotted to scale with a graphics plotter. The program simplifies construction of schematic eyes by allowing rapid recalculation of the eye after changing one or more input parameters.

Animals↗