Of course cats have very good eyesight don’t they? When they are hunting they can spend hours watching for the slightest movement in the undergrowth and then pounce on an unsuspecting mouse. Equally they can while away an afternoon watching the world go by looking out of a window. But just how much detail do cats see through their eyes, and how can we tell if things are going wrong?
A cat’s view of their world
Cats have evolved to become good night-time hunters. For this to be possible though cats have had to trade in some of the finer details of vision that we humans possess. For a cat seeking its prey in the dark the fine detail isn’t too important compared to the need for improved nocturnal vision. For cats this is approximately six times better than us due to a combination of an extra layer in the back of their eye along with the ability to dilate their pupils widely, maximising the amount of light which enters the eye in dim lighting.
How easy is it to tell if a cat is losing its sight?
The simple answer is – not that easy. For the most part, with the ageing process, sight loss is a gradual affair for cats and they can adapt to their disability over time, learning where furniture and other obstacles are in the home. A sudden loss of vision is easier to notice. Bumping into objects is an obvious indication of failed sight, but as this is a very gradual process for most cats it may only become evident when furniture is moved or a door normally left open is closed. A cat’s awareness of the layout of their home is very good – so when their sight fails they only get caught out when this changes.
Other signs which may help in determining failing sight could include a reluctance to jump down from a height. Often they climb down by gingerly feeling their way with their feet first. They may adopt a crouched walk with their body closer to the ground, stretching their necks out further so as to feel their way with their long whiskers.
As well as these subtle behavioural changes a cat’s eyes may change in appearance. A colour change in one or both of the eyes recently may indicate a medical problem. Cloudy eyes are often a feature of cats that have developed cataracts. However, such changes could also be present in cats suffering with glaucoma where there is a raised pressure within the eye. A reddening of the eye may be the result of an increased blood pressure, but may also be the result of an inflammation or a tumour. For any sudden colour changes to your cat’s eyes a full eye examination by your Vet is advised. As a cat ages, during senior health checks, an ocular examination becomes a very important part of the check-up. The back of the eye is an early warning indicator for a developing high blood pressure, something that many cats will develop as they age, and which can be treated very successfully.
What can I do to help care for my blind cat?
For us humans there is a heavy reliance on our sense of sight, almost to the exclusion of our other senses. For cats, whilst sight is important, hearing, smell and touch are very important as well. Many owners are shocked to learn that their older cat has become blind, especially as they often can go out in to the garden, apparently as normal. For most of these cats though, they are more likely to be staying nearer to home. The key for these cats is their familiarity with their environment. Sudden changes in the layout of their familiar surroundings really does spell trouble. For a cat, losing their confidence in moving around this area can make them withdraw in to themselves. It may seem odd to find a visually impaired cat seeking refuge in higher hiding places, but as we know, cats feel secure if they are able to hide in havens off the ground. Getting access to such a place may prove a problem though. Smaller stepping points are useful for cats with poor vision so they are not called upon to jump up large distances. Ultimately a visually impaired cat can function very well in familiar surroundings. And with just a few very minor considerations their home can stay the safe place it always has been.
© copywrite Dai Gittins MRCVS.