If we have to pick favourite diseases, mine is retinal detachment in cats. One day your cat goes suddenly blind, and the next they can see again. All thanks to a simple and low cost treatment.
However, for this to happen, you need to know what to look for, and act quickly.
How To Tell If Your Cat Has Poor Vision
Here are the common signs of vision loss or blindness in cats:
- Bumping into things they should be able to see
- Dilated pupils (large black eyes)
- Sudden anxiety about moving around or going outside
- Crying or aimless wandering
- Blood in the eye or a cloudy eye
The cat pictured above has a dilated pupil, but even that is not as wide as we typically see in a blind eye. Often you can barely see any of the usual yellow or green iris colour.
The actual cause of blindness does not always come on as suddenly as it seems. Cats can cope very well with poor vision and it’s often only when the lights go out completely that you will notice.
The Causes Of Sudden Blindness In Cats
There is a long list of possible causes of blindness in adult cats, of which only two are common.
- Anterior uveitis
- Damage to the eye or its nerve supply
- Tumours anywhere along the vision pathways
- Progressive retinal atrophy or PRA
Of these, eye damage can be from head trauma secondary to car injury or lacerations from cat fights. PRA is a genetic disease causing retinal degeneration, and only likely in young purebreeds (I saw my first ever case just last week in a Toyger). Tumours are rare (often iris melanoma) and cataracts and glaucoma even rarer (these diseases are explained here).
Of the two common causes, anterior uveitis is seen as a red, painful or cloudy eye that’s no longer clear inside. The cause is usually an immune response to infections like FIV, FIP or toxoplasmosis. It needs to be treated quickly to avoid blindness but is usually quite obvious.
The one I want to focus on in depth is feline hypertension. This is the most likely reason for sudden blindness in older cats and its effects are often reversible.
How Hypertension Causes Blindness
Hypertension, or raised blood pressure, is common in old cats. It’s often secondary to kidney disease or hyperthyroidism, but also occurs on its own. If untreated, it can cause two things to happen the eye:
- The retina (the light sensitive layer) separates from the rest of the back of the eye. This is retinal detachment.
- Blood vessels burst leading to bleeding inside the eye or on the retina. The blood then blocks vision.
The picture shows a severe case of retinal detachment. You can see a widely dilated yellow pupil, and the greenish bulging retina in the middle.
Treatment Of Hypertension
My experience is this: if retinal detachment is detected while the retina is only partly peeled away, it will reattach once the blood pressure is controlled. In other words, cats who are brought in as soon as the problem is noted have a very good chance of their vision being restored.
When we see a disease known to be linked with hypertension, we will measure blood pressure. I saw such a cat a few weeks ago with blood in the eye. Within a few hours we had tested her and started her on antihypertensive medication. Her blood pressure is now normal, and she’s made a full recovery.
Medication for high blood pressure in cats is only once daily, cheap and generally very effective. Of course, we always check the response after a few weeks just to be sure.
So the take home message is not to overlook even the slightest hint of eyesight problems. While cats can live happily even after losing their sight, for many of them, it never needs to happen.
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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These help topics are from a series regularly posted on email and Twitter. Subscribe via email here to never miss a story! The information provided here is not intended to be used as a substitute for going to the vet. If your pet is unwell, please seek veterinary attention.