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, Miniature Schnauzers, Collies, and Toy Poodles are myopic, and in some breeds the degree of myopia increases with age. 3 , 4 Breeds with hyperopic refractive states include Australian Shepherds, Alaskan Malamutes, and Bouvier des Flandres. 3 A recent study

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in Journal of the American Veterinary Medical Association

In an emmetropic eye, light from an object viewed at a distance (> 6.1 m, in general) is focused accurately on the retina. In an ametropic eye, the image is focused in front of (myopia) or behind (hyperopia) the plane of the retina, which causes

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in American Journal of Veterinary Research

emmetropic. In a myopic eye, light from infinity converges in front of the retina. Myopia may be the result of excessive refractive power of the eye or abnormal elongation of the eye's axial length. Conversely, in a hyperopic eye, light from optical infinity

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in American Journal of Veterinary Research

that the mean resting refractive state of 240 dogs was within 0.25 D of emmetropia, and breeds predisposed to development of myopia were also found. A more recent study 1 of 1,440 dogs found the mean ± SD refractive state of all eyes examined was −0

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in American Journal of Veterinary Research

Abstract

Objective

To determine the effect of optical defocus (such as what develops in spontaneous myopia and subsequent to cataract extraction) on visual acuity in dogs.

Animals

3 young adult male Beagles.

Procedure

The effect of optical defocus on visual acuity was determined by sweep visual evoked potential, using a within-subjects/repeated measures design in which each dog served as its own control. Dogs were positioned so that the eye being tested was 60 cm in front of the video display, and the target was centered on the area centralis. To create ametropia relative to the video screen, a series of concave and convex spherical lenses were placed 1 cm in front of the eye, and sweep visual evoked potential acuities were obtained.

Results

Maximal acuity was 7.0 to 9.5 cycles/degree. Defocusing by 2.0 diopters reduces Beagle grating acuity approximately 1 octave. Mimicking aphakia resulted in a marked depression of acuity to 0.7 cycles/degree or less.

Conclusions

Even mild degrees of ametropia have appreciable impact on the resolving power of the canine visual system.

Clinical Relevance

Spontaneous myopia is encountered in dogs and may be associated with impaired visual performance attributable to a reduction in visual acuity. Previous reports indicate the possibility of myopia in dogs to have a heritable component. On the basis of our results, refractive correction of aphakia is advisable, and refractive screening of dogs with demanding visual tasks (eg, service dogs, field-trial Labrador Retrievers) is recommended. (Am J Vet Res 1997;58:414–418)

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in American Journal of Veterinary Research

Abstract

Objective—To follow the development of the refractive error in the eyes of ostrich chicks from age 0 to day 37 after hatching.

Animals—35 ostrich chicks.

Procedures—Spot retinoscopy was conducted to assess refractive error in ostrich chicks. Seventy eyes of 35 ostrich chicks were examined. Of these, 18 chicks were followed over time. At least 4 serial measurements (at 2- to 7- day intervals) were conducted in each of these chicks from day 1 to 37 after hatching. Seventeen additional chicks were examined on days 0, 3, 12, and 19 after hatching.

Results—Ostrich chicks were myopic at hatching, with a mean ± SD refractive error of −4.47 ± 0.15 diopters (D). The refractive error rapidly decreased during the first week of life, and by day 7 after hatching, chicks were slightly hyperopic, with a mean refractive error of 0.42 ± 0.12 D. After day 7, there were no significant differences in the mean refractive error.

Conclusions—The development of optics in the ostrich eye appears to be unique among animals and is characterized by myopia at hatching, rapid onset of emmetropia, and minimal variation in refractive error among chicks. (Am J Vet Res 2001;62:812–815)

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in American Journal of Veterinary Research

error was +0.33 ± 0.58 D. Emmetropia (refractive error between −0.5 D and +0.5 D) was detected in 6 (21.4%) horses, hyperopia was detected in 16 (57.1%) horses, and myopia was detected in 2 (7.1%) horses. Anisometropia (unequal refractive errors between

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in American Journal of Veterinary Research

refractive state was −0.06 ± 0.68 D ( Figure 1 ). Emmetropia (0 D) was present in 77 of 158 (48.7%) horses. Hyperopia, with a maximum value of +1.5 D, was present in 38 (24.1%) horses, and myopia, with a maximum value of −1.5 D, was present in 40 (25

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in American Journal of Veterinary Research

indicated hyperopia, at a mean ± SD value of 2.67 ± 1.64 D. The mean refractive error of untreated phakic eyes indicated myopia at −1.11 ± 1.13 D ( Figure 1 ). All treated pseudophakic eyes had a 41.5-D foldable acrylic IOL and a greater mean refractive

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in American Journal of Veterinary Research

about professional myopia have become reality. The profession has made some adjustments congruent with his aspirations, but has never adopted the structural changes that would take full advantage of its potential. It remains constrained by a system that

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in Journal of the American Veterinary Medical Association