What is Nuclear Sclerosis?
Imagine this scene: You sit down at the end of a long day and pick up a good book. Your senior dog is at your feet, ready to curl up with you. But, you also notice something oddly adorable - he's got reading glasses on. While this scene is highly improbable as dogs don't need reading glasses as they age, many do acquire an age-related condition called nuclear sclerosis.
Also known as lenticular sclerosis, nuclear sclerosis in dogs causes discoloration to the center of the eye. For middle-aged to senior dogs with this condition, a blue or gray transparent "haze" develops in the lens of the eye. This is sometimes easier to see when looking at the affected eye from the side.
In some cases, this condition may make it somewhat more difficult for a dog to see objects that are close to them, but it does not significantly impact vision.
Fortunately, since dogs don't need to use their close-up vision for reading like we do, they don't require reading glasses. In fact, many dogs don't seem to be troubled by the condition and their vision may not be significantly affected.
However, you may wonder how well your dog can see, if eye discoloration is normal, if they are in pain, or whether you're seeing cataracts or something else. You may also have other questions or concerns a veterinary ophthalmologist can address.
Dog Eye Anatomy
It might be useful to understand a few things about dogs' eye anatomy to gain some understanding about the changes caused by nuclear sclerosis.
When light first enters the eye, it passes through the cornea (the clear part of the front of the eye) before traveling through the fluid-filled anterior chamber. It then passes through the pupil (the colored portion of the eye). The pupil can constrict or dilate to control how much light gets through.
The light then passes through the back chamber of the eye to the lens (a disc-like structure that focuses the light beam). To do this, the lens must be able to stretch or condense slightly as required - a process called accommodation. Normally, the lens is clear and made up of renewable fibers.
The final part of the light's journey happens when it travels through the gelatinous vitreous humor before reaching the retina. The retina's photoreceptors then transform the light into a nerve signal. The signal then makes its way down the optic nerve to the brain, where it's recognized as an image. If any part of this process is disrupted, the eye's appearance can change or its appearance may be threatened.
Causes of Nuclear Sclerosis in Dogs
Nuclear sclerosis generally occurs in middle-aged or older dogs - typically those over the age of 7. Any breed can be affected, and increased exposure to UV radiation (typically sunlight) may make the condition happen more rapidly.
While the exact cause of lenticular sclerosis is poorly understood, it appears that the lens gradually hardens with age.
Lens fibers are produced throughout your dog's lifetime, but the lens does not become bigger. It's believed that new fibers deposited on the outer "rings" of the lens compress the central lens, leading to hardening and opacification of the lens.
Nuclear Sclerosis vs. Cataracts
Senile cataracts develop in many older pets, and occur when the fibers in the aging lens degenerate. These white opacities of the lens may form at the center of the lens (the same place as nuclear sclerosis) and significantly affect a dog's vision. .
Cataracts are not a normal consequence of aging, but may be caused by genetics, eye trauma, toxins, nutritional deficiencies, or endocrine disease.
However, though a cataract may eventually encompass the entire lens, nuclear sclerosis usually remains confined to the center. Because light isn't able to penetrate through the opaque lens to the retina, some dogs with cataracts will go blind. And online nuclear sclerosis, cataracts can also cause other eye health problems such as glaucoma.
Though many dogs develop cataracts after having nuclear sclerosis, there does not appear to be a causal relationship between the two, meaning that not all pets with nuclear sclerosis will develop cataracts.
Remember that senile cataracts develop in many senior pets, so there is a high likelihood of your pet developing lenticular sclerosis and/or a cataract.
Nuclear Sclerosis in Dogs: Signs & Symptoms
When it comes to lenticular (nuclear) sclerosis in dogs, symptoms can vary. Though you'll likely be able to see a change in the lens of your dog's eye if they have nuclear sclerosis, the condition does not significantly impact vision.
You may notice symptoms of far-sightedness, almost as if your dog requires reading glasses. Dogs with the condition may also have depth perception issues, which may make it more challenging for them to navigate stairs or walks, or to catch a ball during playtime.
Diagnosis of Nuclear Sclerosis in Dogs
Our veterinary ophthalmologist at Northwest Animal Eye Specialists will examine your dog's eyes using a light to visualize the lens. If the lens has a milky or gray color in the center and is clear around the edges with no true areas of opacity, this points to nuclear sclerosis.
The light bouncing off the tapetum (a reflective structure in the back of a dog's eye) may also cause a yellow-green glow. the tapetum is responsible for the green glow we see in an animal's eyes when light hits them in the dark.
If the veterinary ophthalmologist sees a tapetal reflection, that means that light is getting through the lens and reaching the back of the eye. It can then be detected by the retina and converted into an image by the brain.
Treatment & Support for Nuclear Sclerosis in Dogs
While many eye conditions should be surgically treated, for nuclear (lenticular) sclerosis in dogs, treatment is unnecessary. No specific medications will reverse these changes, which are a normal part of the aging process.
However, there are some ways you can support your canine friend if they are diagnosed with this condition.
If you think there may be something wrong with your dog's eyes, schedule an appointment with your veterinarian or veterinary ophthalmologist who can make a definitive diagnosis.
Pets diagnosed with nuclear sclerosis should be examined regularly in case a cataract develops. If this does occur, the cataract should be detected and treated early for the best outcome.
As for at-home management of visual impairment, you can create a safe, secure environment by using anti-slip rugs and other items to offer your dog a bit of added traction and boost in confidence if you find your dog's vision is affected by nuclear sclerosis or visual impairments.
Note: The advice provided in this post is intended for informational purposes and does not constitute medical or behavioral advice regarding pets. Please make an appointment with your vet for an accurate diagnosis of your pet's condition.