In dogs, the lens of the eye is normally clear and transparent, allowing light to pass through and reach the retina at the back of the eye, where visual information is processed, explains Antje Joslin, DVM, co-owner of Tolleson Animal Clinic in Tolleson, Arizona, and veterinary consultant for Dogtopia, a dog daycare center with hundreds of locations across the U.S. and Canada.
Cataracts occur when protein fibers in the lens of the eye clump together, causing the normally clear lens to become cloudy, Dr. Joslin adds. These clumped proteins can interfere with the passage of light to the retina, which can cause blurred vision and, in more severe cases, partial or complete blindness.
Dog cataracts develop in stages:
– Incipient: A small, early-stage cataract that affects less than 15% of the lens. They’re often pinpoint-sized and don’t affect the dog’s vision.
– Immature: At this stage, the cataract has expanded to cover between 15% and 99% of the lens. Vision is noticeably affected but not completely lost, and the degree of impairment can vary.
– Mature: The cataract now covers the entire lens, resulting in severe vision loss or complete blindness. Dogs with mature cataracts may only be able to detect light and dark.
– Hypermature: As the cataract progresses, the lens begins to shrink, and the lens capsule may appear wrinkled. This stage often triggers inflammation in the eye, known as lens-induced uveitis.
