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Jessica Fragola, Leandro Teixeira; Microphthalmia with multiple ocular abnormalities in 11 horses: a novel syndrome. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1725.
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© ARVO (1962-2015); The Authors (2016-present)
To report the clinicopathological features of a previously unrecognized ocular syndrome in horses characterized by bilateral microphthalmia with severe anterior segment dysgenesis, cartilaginous and glandular choristomatous ocular differentiation, aphakia, and retinal dysplasia.
22 globes from 11 neonatal equines diagnosed with congenital blindness secondary to microphthalmia were identified in the archives of the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW). Globes were formalin-fixed, paraffin-embedded, and sections were stained with H&E. Patient signalment, clinical history, and gross and histopathological lesions were reviewed and summarized.
All affected animals were euthanized for congenital blindness shortly after birth. 6/11 animals were female and 2/11 were male; the sex of 3/11 animals is unknown. Affected breeds included Thoroughbred (3/11), Standardbred (1/11), Paint (1/11), Rocky Mountain Spotted Horse (1/11), Quarter Horse (1/11), Arabian cross (1/11) and unknown (3/11). The malformation was bilateral in all cases. All globes were small, aphakic, and exhibited poorly defined corneal tissue, choristomatous differentiation of the anterior segment, and retinal dysplasia. In all globes the corneal stroma blended with or was replaced by skin-, conjunctiva-, or sclera-like tissue often containing sebaceous glands or hair follicles. The anterior uveal tract, anterior chamber, and posterior chamber were poorly formed or absent in all globes and replaced by choristomatous tissue. The choristomas presented cartilage in 21/22 eyes, gland in 18/22 eyes, and myxomatous and/or dense connective tissue in 22/22 eyes. All eyes exhibited some degree of retinal dysplasia, characterized by disorganization of retinal layers and/or rosettes, and 19/22 globes exhibited partial or diffuse retinal detachment.
This investigation describes a novel ocular syndrome in horses characterized by bilateral microphthalmia and aphakia associated with multiple ocular abnormalities. Given the predominance of anterior segment lesions, a defect during the embryological development of the lens placode is suspected. A specific genetic mutation and the role of toxic and/or infectious agents is yet to be determined. Increasing recognition and better understanding of this novel syndrome may help contribute to the understanding of the pathogenesis of microphthalmia with aphakia.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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