Summarize this article in one sentence.
If you suspect your cat has cataracts, take her to the vet as soon as you can. Getting an early diagnosis usually means you'll have more treatment options available, like getting surgical therapy. Also, recognizing that your cat has impaired vision can help you take safety precautions. For example, a cat with cataracts should live indoors so she's not bothered by other cats or at risk of getting injured in a road traffic accident. The vet will do a thorough examination before looking at your cat's eyes. Your vet may start by standing back and looking at your cat's eyes in order to get an overall impression. The vet will check to see if the eyes are the same size and whether there's increased eye pressure (a sign of glaucoma). The vet will also take a history of any changes with your cat (like changes in thirst, weight, and behavior). This helps rule out other conditions that can affect vision, like diabetes. The veterinarian will use an ophthalmoscope which is a lens with a light on it to examine your cat's eyes. The vet will stand back and shine the bright light in each eye to look for 'red eye.' 'Red eye' is similar to the reflection you get when you take a flash photograph and the flash reflects off the retina. If your cat has 'red eye', this means that the light has passed through the lens and isn't blocked by cataracts. Your cat may be affected by another condition. The veterinarian will also use an ophthalmoscope to look for a shadow on the retina. If your cat has a cataract, it will stop light from passing through the lens. This casts the shadow. The test is used to differentiate between a cataract and a cloudy lens caused by old age. A cloudy lens from old age still lets some light through, unlike cataracts which can blind the cat. If your cat is young or the cataract is very mild, your vet may recommend leaving it alone to see if it improves on its own. If the cataract begins to affect your cat's vision, you may want a specialist vet ophthalmologist to surgically remove the cataract, although this can be expensive. Or, the specialist can use a ultrasonic waves to remove the cataract (phacoemulsion). If your cat is affected by a condition other than cataracts, the vet will treat any underlying eye inflammation before starting treatment for the other health issue (like diabetes). If your cat has cataracts, she may have some discomfort. Ask the veterinarian about giving her anti-inflammatory eye drops. Your vet might also want to give her nutritional supplements if she's developing cataracts because of nutritional deficiencies. If left untreated, the cataracts may cause blindness and pain, at which point the eye might need to be removed.

Summary:
Take your cat to the veterinarian. Get your cat's eyes examined. Look for red eye in your cat. Look for a shadow on the retina. Follow the vet's treatment recommendations. Consider treating your cat's pain.