Purpose:
To characterize a newly discovered retinal blinding disease of Chinese Crested Dogs (CCD) using clinical and laboratory methods in privately owned animals.
Methods:
Ophthalmic examination was performed in 123 1-10-year-old CCDs of both sexes, including indirect ophthalmoscopy, followed by full-field flash electroretinography (ERG) using a standardized protocol in 25 of the dogs anesthetized with dexmeditomidine. Four affected and one normal CCD, age 6-8 years, were euthanised and the eyes immersion fixed in 4% paraformaldehyde for immunohistochemistry, and in 2.5% glutaraldehyde for light- and electron microscopy.
Results:
In 32 CCDs, age 3-10 years, areas of circular donut shaped darkly pigmented lesions with a light-colored center were observed. They started in peripheral fundus, increased in number and expanded centrally, as observed in older affected dogs. ERG scotopic and photopic responses were normal in younger dogs with less severe clinical disease but a- and b-wave amplitudes became markedly reduced or non-recordable over time in clinically more severely affected animals. Morphology showed conglomerates of RPE65-positive retinal pigment epithelial (RPE) cells in the subretinal space and/or hypertrophy, detachment and migration of RPE cells into overlying neuro-retina. There were also areas of geographic atrophy with RPE and photoreceptor degeneration and dystrophic changes in choriocapillaris.
Conclusions:
The RPE and choriocapillaris appear primarily affected in the CCD disease with secondary degeneration of the photoreceptors. This spontaneous disease of CCDs has some similarities to human age related macular degeneration but not to generalized primary photoreceptor disorders such are progressive retinal atrophy of dogs or retinitis pigmentosa of humans.
Keywords: degenerations/dystrophies • retinal pigment epithelium • microscopy: electron microscopy