I see a lot of older dogs in my veterinary practice. One of the more common things that I hear from owners is that they think their dogs have developed cataracts. These concerns are usually based on noticing a new, grey coloration to their dog’s pupils. While cataracts are certainly a possibility, more often than not something called lenticular (or nuclear) sclerosis is to blame. Let’s take a look at this common condition and what it means for dogs.
The lens is the part of the eye that focuses light onto the retina. Because the lens is normally clear we can’t see it within the eye, but it is held in place just behind the pupil (i.e., the dark "hole" surrounded by the colored iris).
Lenses are clear because the tissue fibers that make them up are arranged very precisely. However, as a dog gets older more fibers are added to the outside of his lenses. Because the lens is contained within a capsule, there is little room for it to expand. The new fibers push the older, inner fibers together, altering their orientation, and this makes the lens less clear.
Lenticular sclerosis typically gives the pupil a cloudy, blue-grey-white appearance. Most dogs start to develop lenticular sclerosis around 6-8 years of age, although many owners don’t notice the change until a dog is older and it has progressed and become more evident.
The good news is that lenticular sclerosis is not painful, does not significantly affect a dog’s vision, and requires no treatment. I tell my clients that if their dogs had to read the fine print on a bank statement, they might be in trouble, but to live a dog’s life, they’re fine. I’m sure really old dogs with very advanced lenticular sclerosis have more vision impairment, but we’re usually concentrating on other health issues by that point.
Your veterinarian can quickly differentiate between lenticular sclerosis and more serious eye problems like cataracts with an ophthalmologic exam. He or she will first look at your dog’s corneas, the outer layer of the eye, often using a slit-lamp. If the cloudiness is on or just behind the cornea, you are NOT dealing with lenticular sclerosis.
Next, your veterinarian will use an ophthalmoscope to look deeper into the eye. This may require medicated eye drops to prevent the pupils from constricting. When a dog has lenticular sclerosis, a vet can still see all the way back to the retina thorough the ophthalmoscope, even if things are a little bit fuzzy. On the other hand, a cataract will block the view of the retina, either completely or in part, depending on how big it is. If your vet can’t see through the lens, neither can your dog.
So, if you have noticed that your middle aged to older dog’s eyes are becoming a little cloudy, but everything else seems normal, you probably have nothing to worry about. Next time you are at the clinic, just ask your vet to perform an eye exam to confirm the likely diagnosis of lenticular sclerosis.
Dr. Jennifer Coates