How Aging Affects Dog Eyes
Elizabeth Adkins, DVM, MS, DACVO
Changes that occur with age can affect the entire body, including the eyes. As dogs age their eyelid skin becomes thinner and less elastic. For most dogs this is not a deleterious effect but any eyelid injuries in older dogs will heal more slowly than similar injuries in young dogs. Some dogs develop entropion (eyelids rolling in toward the cornea) as they age. Generally entropion is considered to be a young dog disease; however, it can affect older dogs too. Some dogs will need surgical correction of their entropion if the eyelid skin and fur is rubbing the cornea and causing irritation or corneal ulcers (defects on the surface of the cornea). Other dogs may need topical lubricant therapy to reduce the irritation to the corneal surface and other dogs may not need any treatment for this problem. In general entropion is uncommon in shiba inus. The statistics from the canine eye registration foundation (CERF) indicate that 1719 shibas were examined from 2000-2007 and 6 of these dogs had entropion. It is possible that this number is higher since the age-related entropion would probably develop after the dogs are no longer breeding and no longer getting a CERF examination. Some dogs develop dry eye with age. Other names for dry eye are keratoconjunctivitis sicca or KCS. This condition is due to low tear production and can cause severe discharge, redness and corneal ulcers. Treatment includes lubricants and medications to stimulate tear production. I have only seen one shiba with dry eye and there are no statistics on dry eye from CERF since this condition is not part of the CERF examination.
The corneas may become cloudy with age. This can be the result of cellular loss and changes within the cornea. Some dogs will develop lipid and mineral deposits in their corneas with age. This condition is called corneal dystrophy or corneal degeneration. The mineral deposits can cause corneal ulcers. Any underlying diseases (low thyroid function, high cholesterol) present in these dogs that could contribute to the deposits should be treated appropriately. Any resulting corneal ulcers should be treated by your veterinarian. The CERF data from 2000-2007 indicates that 13 shibas were diagnosed with corneal dystrophy.
Atrophy of the iris muscle is a very common change in older dogs. Iris atrophy reduces a dog’s ability to constrict their pupils so these dogs may seem light sensitive in bright sunlight. Also, more “eye shine” (light reflection from the back of the eye) may be noticed at night in these dogs.
Probably the most obvious age-related changes in dog eyes affect their lenses. Around six years of age or older you may notice a grayish cloudiness deep in the dog’s eyes. This occurs in all dogs (and in humans) and is called nuclear sclerosis or lenticular sclerosis. As we age our lens continues to grow but must fit in a very small space within the eye. As a result the fibers in the center of the lens become more densely packed. This is the condition that causes humans to need reading glasses. There is no treatment for this condition and you may notice that dogs with nuclear sclerosis cannot see as well up close as they did when they were young. Cataracts are another condition that can occur as dogs’ age. Small cataracts may not affect the dog’s vision much but large cataracts can cause blindness. Large cataracts can appear as a white marble inside the eye. Some cataracts can be surgically removed. For the 1719 shibas that had CERF examinations from 2000-2007 221 were diagnosed with some type of cataract. The vast majority of these cataracts were considered “significance unknown” by the examiner.
Lastly age can affect the retina causing retinal degeneration. In most dogs with mild age-related retinal degeneration you may not observe any vision changes. Age-related retinal degeneration differs from generalized retinal degeneration (also called progressive retinal atrophy or PRA) in that PRA is considered inherited and in most dogs PRA will cause progressive and complete blindness. According to the 2000-2007 statistics from CERF 6 shibas were diagnosed with generalized PRA and PRA was suspected in 8 additional shibas. For the purposes of statistics CERF separates the categories “generalized” and “suspicious.” At this time there is no successful treatment for PRA; however, a number of scientists are studying treatments for this disease. If you are noticing vision changes in your aging dog please see your veterinarian to determine if the cause of the vision changes can be treated.
Shiba Sightline is an online chat group that was started to bring together owners of Shiba Inu with eye problems, especially Glaucoma, so they may exchange ideas and knowledge about this "Silent Thief"!