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What Is Nuclear Sclerosis In Dogs?

Updated: Jun 17, 2023


As with humans, dogs are prone to developing eye problems with age - and certain breeds are more prone than others. Evidence of deteriorating vision isn't always noticeable at first, that’s why it’s important to know the signs so that you can act quickly when problems first begin to arise.

A few months ago, a friend pointed out that Yoto’s pupils were cloudy, as though he was developing cataracts. When I took a look myself, I noticed that they were indeed cloudy, with a bluish-gray hue. I also noticed that his left iris wasn’t contracting as well as it should in response to light.

Being a pet owner that suffers with health anxiety (both for myself and the boys), I immediately went online, researching the symptoms, looking for ways to slow the progression of cataracts and seeking a cost estimate and prognosis for cataracts surgery.

On further reading, however, I learned of nuclear sclerosis - an eye condition that affects many dogs from the age of 6 or 7 onwards, which can initially be mistaken for cataracts due to it causing visible clouding of the lens but with a bluish, rather than white, hue.

What Is Nuclear Sclerosis?

According to Clinician’s Brief, a magazine aimed at veterinary practitioners and students, nuclear sclerosis is a common, age-related condition that affects roughly 50% of dogs over the age of 9.

It occurs when the continued formation of normal lens fibers compresses the central nucleus, leading to increased density. While it may lead to a visible clouding of the lens, it does not usually cause vision deficits.

Nuclear Sclerosis
Fig. 1. Nuclear Sclerosis
Incipient Cataracts
Fig 2. Incipient Cataracts

These images from Clinician’s Brief show the difference in appearance of an eye with nuclear sclerosis vs one with incipient cataracts, when viewed through an ophthalmoscope.

Signs that your dog may have nuclear sclerosis include:

  1. He was aged 6 or over when the changes appeared.

  2. His pupils have a visible cloudiness or bluish discoloration.

  3. Despite the discoloration of his eyes, there does not appear to be any impairment of vision.

How To Tell If Your Dog Has Impaired Vision

If your dog has the symptoms described above and you aren’t sure whether or not he has impaired vision, there is an easy way that this can be determined without a visit to the vet: the cotton ball test.

It’s pretty simple, and anyone can do this at home. The only thing that you need is a cotton ball - like the ones you might use to apply cleansing lotion to your face.

The Cotton Ball Vision Test

1. Sit in front of your dog and get his attention by holding the cotton ball in front of his face, as though you are holding a treat.

2. Drop the cotton ball to one side, and monitor his gaze to see if he responds by watching it as it drops.

3. Drop the cotton ball to the other side, paying close attention once again.

4. Repeat a couple of times on each side.

When To Check With Your Vet

If your dog has any of the above symptoms and his vision appears to be impaired, it is imperative that you have your vet perform an eye exam to determine whether or not he is developing cataracts.

In most cases, there's not a great deal that can be done to slow the progression of cataracts, but if the cataracts are being caused by an underlying health problem or nutritional deficiency then swift intervention is necessary if you wish to preserve your dog's eyesight. '

How Is Nuclear Sclerosis Diagnosed?

If your vet is trained in ophthalmology, he will be able to diagnose cataracts or nuclear sclerosis by performing a distant direct ophthalmoscopy, or via distant illumination.

The vets at Bärenwiese, where I take Yoto for his full checkups with blood tests, do not have the right specialisation to perform these tests, though our local vet, Dr Beck, does.

For the princely sum of just €25, Dr Beck performed both of the above tests on Yoto and reassured me that he does not have cataracts.

However, he did have slight concerns about the fact that Yoto's left pupil is not contracting in bright light quite as it should.

He was of the opinion that it's likely nothing to worry about but advised that I take him to see Professor Eule at the Freie Universität for further tests and a second opinion.

While money is tight for us right now, as it is seemingly for everyone, I do intend to err on the side of caution and take Yoto for a consultation as, at age 7, he is still a rather young dog, and I would like to ensure that he maintains his senses for as long as possible, to ensure his quality of life.

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