Cataracts explained: symptoms and surgery

What a cataract is

Inside the eye, just behind the coloured iris, sits a clear lens that focuses light onto the back of the eye so we see sharply. A cataract is when this lens becomes cloudy, rather like a clean window frosting over. Light can no longer pass through clearly, so vision becomes misty and dim. Cataracts usually develop slowly over years, and most are simply part of getting older, as the proteins in the lens gradually change. They often affect both eyes, though one may be worse than the other. A cataract is not a growth or a film over the eye, and it is not caused by using the eyes too much — it is a change within the lens itself.

Symptoms and causes

Cataracts tend to cause a gradual, painless decline in vision. People notice that things look blurred, cloudy or dim, colours seem faded or yellowish, and they may struggle in low light. Bright lights, such as car headlights or sunshine, can cause glare or haloes and feel dazzling. Reading and recognising faces can become harder, and glasses may seem to need changing more often. Ageing is by far the most common cause, but other factors can increase the risk or bring cataracts on earlier, including diabetes, smoking, heavy alcohol use, long-term use of certain medicines, previous eye injury or surgery, and a lot of sun exposure over the years. Cataracts can occasionally affect younger people and, rarely, babies.

Getting diagnosed

Cataracts are usually picked up during a routine eye test with an optometrist, which is why regular eye checks matter, particularly as we get older. The optometrist examines the eye and can see the clouding of the lens, and will check how much vision is affected. If a cataract is significant enough to affect daily life, they can refer the person to a hospital eye service to discuss surgery. Because cataracts develop slowly, some people do not realise how much their vision has changed until it is measured. An eye test also checks for other conditions, so it is worth attending even if you simply put blurring down to getting older.

When to treat

Having a cataract does not automatically mean needing surgery straight away. In the early stages, when the cataract is mild, stronger glasses, better lighting and reducing glare may be enough to manage. The decision to have surgery is based mainly on how much the cataract affects a person's daily life — their ability to read, work, drive, get around and enjoy hobbies — rather than on the cataract reaching a particular stage. There is no need to wait until vision is very poor before treating it. Equally, if a cataract is not troubling someone, it is reasonable to keep it under review. It is a personal decision, made together with the eye team.

Cataract surgery

Cataract surgery is a common, quick and highly successful operation, usually done as day surgery under local anaesthetic, so the person is awake but the eye is numbed and they feel no pain. The surgeon removes the cloudy lens and replaces it with a clear artificial one that stays in the eye permanently. The operation itself typically takes well under an hour, and most people go home the same day. Vision often improves within days as the eye settles, and eye drops are used for a few weeks to aid healing. As with any surgery there are small risks, which the eye team will explain, but serious complications are uncommon and the vast majority of people see much better afterwards.