Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr Liesel van der Merwe

As our dogs age they develop cataracts which cause visual issues. The problem is that not all cloudiness in the eye or visual deterioration is due to ageing. Our pets have several hereditary diseases which can cause damage to the retina resulting in vision loss.

This normally occurs in purebred dogs and can be tested for genetically in some breeds to prevent breeding with carrier parents. Definitive testing for these conditions once the animal is blind will require an examination of the eye at your veterinarian and generally a more detailed examination by a veterinary ophthalmologist.

The eye is also a secondary / target organ for several systemic diseases. High blood pressure may cause retinal detachment. This is quite common in cats with kidney disease and will result in sudden blindness and even bleeding into the eye. This can be seen as a red discoloration of the eye fluid or a blood clot settling at the bottom of the eye.

The area of the eyeball in front of the pupil is called the anterior chamber. The area behind is the posterior chamber and cannot be examined without an ophthalmoscope, as the lens blocks visualisation.

Long-term infections and some cancers, such as lymphoma, can also cause inflammation in the eye. This presents as a reddened, swollen-looking iris as well as a more obvious cloudy anterior chamber. You may see bleeding and white floating specks as well as a settled clot of tissue (inflammatory cells) settling at the bottom of the eye.

This symptom will require a complete examination and testing of the patient to look for the inciting cause. The eye will generally recover fully with proper treatment, but at the time is quite painful and the patient will be sun sensitive.

The cornea is the outer exposed area of the eye and is a clear ‘window’. Damage to the cornea occurs quite frequently. In cat fights the cornea is often scratched, sometimes completely lacerated. Some patients develop ulcers in the cornea due to problems with poor tear film, trauma, chronic irritation from hairs as well as secondary to viral diseases, such as feline herpes virus.

Corneal ulceration is painful as there are a lot of nerve endings in the cornea to protect the eye and cause us to blink quickly. Pain from the corneal ulceration will also cause the pupil to constrict on that side – a pinpoint pupil. The cornea can also develop more benign changes such as patches of white, which can just be lipid deposits.

However, it is best to always have these checked as these patches can also indicate corneal swelling form inflammation or damage from the inside if the lens is dislocated and moves out of position and rubs on the cornea.

Cloudiness of the pupil itself is due to changes in the lens. As our pets age the lens has more fibres laid down into the gel component and develops sclerosis. This causes some cloudiness but the patient can still see, although not as well because the lens is no longer as flexible.

Nuclear sclerosis is thus a normal, age-related change encountered in dogs over the age of eight years and cats over the age of 12 years. If a cataract has formed, the whiteness is a lot more severe and has a more rapid onset. Cataracts develop a crackled glass looking appearance and affect vision. Cataracts need surgery to remove them. This is only performed by an ophthalmologist and is expensive due to the highly specialized equipment used. 

In layman’s terms: a needle is inserted into the cataract, which causes vibration and the cataract is liquefied and sucked out. If it is decided not to remove the cataract due to costs or other factors, it is advisable to monitor and manage the eye with eye drops when any inflammation becomes evident because the cataract can cause irritation.

So, keep an eye on your pets’ eyes and intervene quickly as it is a delicate structure which can quickly develop irreparable damage.