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  • Author or Editor: Simon M. Petersen-Jones x
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Abstract

Objective—To develop an allele-specific polymerase chain reaction (ASPCR)-based diagnostic test for the mutation in the cyclic guanosine monophosphate phosphodiesterase alpha subunit gene (PDE6A) that causes the rcd3 form of progressive retinal atrophy (PRA) in Cardigan Welsh Corgis.

Animals—1 affected homozygote, 1 unaffected carrier, 1 genotypically normal dog, and 500 unknown- PRA status Cardigan Welsh Corgis.

Procedure—Control blood samples were collected from Cardigan Welsh Corgis of known PRA status (ie, affected homozygote, unaffected carrier, and a genotypically normal dog) for test development. Test blood samples were collected from 500 Cardigan Welsh Corgis of unknown PRA status. Genomic DNA was used as a template in ASPCR. One pair of primers was designed to specifically amplify only the mutant allele, and another set to amplify only the wildtype allele. The PCR conditions were adjusted to ensure each reaction was 100% specific.

Results—The PCR conditions were identified so that each ASPCR only amplified the allele it was designed to amplify. Of the 500 Cardigan Welsh Corgis tested using the newly developed ASPCR, 457 were homozygous for the normal allele (genotypically normal), 43 were heterozygous (phenotypically normal carriers), and none were homozygous for the mutant allele.

Conclusion and Clinical Relevance—A rapid, ASPCR diagnostic test able to detect the PDE6A gene mutation responsible for the rcd3 form of PRA in Cardigan Welsh Corgis was developed. The test provides a useful service for Cardigan Welsh Corgi breeders and will enable them to prevent the birth of homozygote mutant dogs. (Am J Vet Res 2000;61:844–846.

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in American Journal of Veterinary Research

Abstract

Objective

To compare corneal thickness, intraocular pressure, and optical corneal diameter in Rocky Mountain Horses with cornea globosa and those with clinically normal corneas.

Animals

129 Rocky Mountain Horses.

Procedure

Ultrasonic pachymetry was used to measure corneal thickness. Applanation tonometry was used to measure intraocular pressure. A Jameson caliper was used to measure optical corneal diameter.

Results

The central and temporal peripheral portions of the cornea were significantly thicker in horses with cornea globosa than in horses with clinically normal corneas, but corneal thicknesses in the dorsal, ventral, and medial peripheral portions of the cornea were not significantly different between groups. There were no differences in corneal thickness between male and female horses or between right and left eyes. However, there was a positive correlation between age and corneal thickness. Intraocular pressure was not significantly different between horses with cornea globosa and those with clinically normal corneas, or between right and left eyes, or male and female horses. Optical corneal diameter for horses with cornea globosa was not significantly different from diameter for horses with clinically normal corneas, but optical corneal diameter was positively correlated with age.

Conclusions and Clinical Relevance

Cornea globosa in Rocky Mountain Horses is not associated with increased intraocular pressure. Corneal thickness and optical corneal diameter increase with age in Rocky Mountain Horses. (Am J Vet Res 1999;60:1317–1321)

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in American Journal of Veterinary Research

Abstract

Objective—To investigate the duration of dark-adaptation time required for recovery of electroretinographic responses after fundus photography or indirect ophthalmoscopy in dogs.

Animals—6 dogs.

Procedure—Initially, scotopic-intensity series of electroretinograms (ERGs) were recorded after 20 minutes of dark adaptation. The fundus of the left eye of each dog was photographed (n = 10) or examined via indirect ophthalmoscopy for 5 minutes with moderate- (117 candela [cd]/m2) or bright-intensity (1,693 cd/m2) light; ERGs were repeated after a further 20 or 60 minutes of dark adaptation (6 procedures/dog).

Results—Following 20 minutes of dark adaptation after fundus photography, the b- and a-wave amplitudes were reduced in response to brighter stimuli, compared with pretest ERGs; after 60 minutes of dark adaptation, ERG amplitudes had recovered. Following 20 minutes of dark adaptation after indirect ophthalmoscopy (moderate-intensity light), significantly lower b-wave amplitudes were recorded in response to 2 of the brighter flash stimuli, compared with pretest ERGs; after 60 minutes of dark adaptation, ERG amplitudes had recovered. Following 20 minutes of dark adaptation after indirect ophthalmoscopy (bright-intensity light), all ERG amplitudes were significantly decreased and implicit times were significantly decreased at several flash intensities, compared with pretest ERGs; after 60 minutes of dark adaptation, ERG amplitudes and implicit times had returned to initial values, except for b-wave amplitudes recorded in response to dimmer stimuli.

Conclusions and Clinical Relevance—Results suggest that at least 60 minutes of dark adaptation should be allowed before ERGs are performed in dogs after fundus photography or indirect ophthalmoscopy. (Am J Vet Res 2005;66:1798–1804)

Full access
in American Journal of Veterinary Research