“I’m not an ophthalmologist,” I demurred, “but I think her optic discs are abnormal.” It was subtle but the disc looked irregular and slightly puffy. There were no signs of retinal hemorrhage or detachment. Jamyang’s retinal blood vessels looked fine - not too big, not too small. The retinal blood supply comes from one large artery that radiates into smaller vessels around the optic disc. This is the optic disc, the beginning of the optic nerve that transports the information to the brain. The nerve fibers then bundle together in the center of the retina forming a flat white circle. The retina is a collection of rods and cones lining the back of the globe that collect visual information. A highly reflective area there, called the tapetum, acts like a mirror, which is why dogs’ eyes seem to glow in the dark when caught by headlights or other illumination. Imagine a layer of paint on the inside of the back half of the globe. Jamyang’s lenses were clear.Ĭhange the ophthalmoscope setting. Cataracts are opacifications in the lenses. Imagine the lens as a small flattened marble right behind the iris. Now look through the pupil to the back hemisphere. Jamyang’s looked normal, as did her iris.Ĭhange the ophthalmoscope setting. The front hemisphere is called the anterior chamber. The pupil is an adjustable hole in the middle of the iris. The iris is a membrane across the center of the globe, dividing it into front and back hemispheres. Time to examine the internal structures of her eyes.Īn ophthalmoscope is essentially a bright light with a magnifying glass that can be set to focus at different distances. Progressive retinal atrophy, sudden acquired retinal degeneration, tumors, or infectious diseases affecting the optic nerve or brain, glaucoma, retinal detachment, cataracts, toxins, hereditary conditions, auto-immune diseases. There is a long list of things that can cause partial or complete vision loss in dogs. “She’s not completely blind, but something is definitely wrong.” Jamyang continued to stare straight ahead. It’s instinctive to glance at something you see moving out of the corner of your eye, and most animals with normal vision will track the cotton’s path by moving their head down, or at least their eyes. Standing beside Jamyang, I pulled a small piece of cotton off a roll, then dropped it so that it fell silently past one eye. Her menace response was definitely reduced. Occasionally an animal is so distracted by their plight of being on the exam table that you literally have to stick your finger in their eye before they blink, but Jamyang was not that nervous. You want to be sure any reaction is the result of vision, not other senses. The goal is to suddenly threaten the eye, without making any sound, moving air, or touching the dog even slightly. In other words, I poked my finger at her eye. However, this reflex doesn’t rule out visual impairment. The responses seemed a little slow, but both eyes dilated and constricted as expected. I moved the light away, then back, watching her pupils. I shone the bright light directly in her face. Jamyang’s pupils were a bit dilated, but that could be anxiety, a common response at the veterinarian. “Let’s take a look,” I said, pulling my light closer. The reported behavioral changes are more often the result of deafness, arthritis, even senility, but not blindness. That cloudy appearance usually indicates a normal aging process called nuclear sclerosis that does not affect vision. People think the greyish haze in those older eyes means cataracts and assume their pups are going blind. Clients frequently complain of less acute senses in middle-aged dogs. “Jamyang doesn’t seem to be seeing well,” her owner commented as I began my exam. “This won’t take long,” I thought, rushing into the room disheveled, but looking forward to a cheerful, healthy pet visit. But first, Jamyang was here, a ten-year-old Labrador mix scheduled for a physical and vaccinations.
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