A variant in the RBP4 gene causes multiple eye abnormalities due to a fetal serum vitamin A (retinol) deficiency. Vitamin A is needed to synthesize retinoic acid (RA), a potent molecule needed for the proper development of the eye and other tissues. The eye is the most sensitive among organs to reduced RA levels during the formation of the embryo.
Signs and symptoms
Affected dogs may have small or undeveloped eyes or other defects of the retina, iris, or optic nerve. Because their vision is impaired, this may cause dogs to often hesitate on stairs, bump into doorways or walls, have difficulty fetching toys, and be disoriented if the furniture is moved.
Microphthalmia may be observed at birth or as soon as the puppies open their eyes, and other changes may be noted on an ophthalmic exam at a few weeks of age, though they are present from birth.
Microphthalmia can be observed during a basic eye examination; however, a veterinary ophthalmologist may be needed for a comprehensive diagnosis of the more subtle changes.
There is no specific treatment for Microphthalmia.
What to do if your dog is at risk
- Owners should help affected dogs navigate their environments by keeping furniture in the same location in the home, ensuring they are on a leash in an unfamiliar territory outside, and training them to understand verbal commands.
This variant was first identified in the Soft Coated Wheaten Terrier.
Microphthalmia is transmitted as an autosomal recessive trait with penetrance determined by the maternal genotype.
RBP4 Exon 2 ‐ chr28
This health condition affects the following breeds
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