Cataracts in diabetes


Normally light enters the eye from the front, passes through a clear lens, and reaches the back of the eye so you can see.

If the lens becomes cloudy like frosted glass, light cannot pass through, and you cannot see properly. 'Cataract' is the name of the 'cloudy' human lens.

Think of a camera, with a lens that bends the light so that the light 'focuses' onto the film at the back. If this lens becomes scratched or greasy, it cannot bend the light in the correct direction, and the light is scattered in all directions. You may notice blurred or mis ty sight, see double, or notice colours appear much duller than they did previously.


top: a clear lens, no cataract. Light enters the eye directly
bottom: a cloudy lens = a cataract. Light entering the eye is scattered

What you can do

A cataract will not damage your eye in any way.  It can be operated on safely at any time, thick or thin. A cataract may change the focusing in the eye, and you may need new spectacles now and again. If you think you do, ask your optician or the doctor in the hospital eye clinic. But glasses themselves do not help you see better if you have a cataract.

Some cataracts get worse quickly, others slowly: most do get worse over months or years. If your sight gets worse very slowly, the cataract is only slowly becoming thick.

The thicker or cloudier the cataract becomes, the worse the sight.  A doctor cannot predict with certainty.


Large print is naturally much easier to read, and a magnifying glass may help (see Coping with poor vision).

A good light may help, particularly an anglepoise light behind the shoulder.

Stronger glasses that mean you can bring books closer to your eye to make reading easier, and an optician (optometrist) can advise you.


You may notice great difficulty driving at night, when car headlights are shining into your eye. This may be so bad you have to stop driving at night, and at this stage, if you want to keep driving, you may need a cataract operation.


You may notice difficulty seeing in sunlight. Dark glasses may help, or a hat with a large peak. Eventually you usually need an operation.

Causes of cataracts

Cataracts occur as people get older. They are much commoner if you smoke, whether cigarettes, cigars, or a pipe. They occur more often in diabetes, and they can run in families. Steroid tablets may help to cause cataracts if given at a high dose or for a long time. There are many other causes, including other types of eye disease and eye injury.

Does a cataract damage the eye, or your other eye?

A cataract does not usually damage your eye in any way. A cataract in one eye cannot lead to any damage in the other eye, and you cannot use the good eye too much and damage it. Similarly, sit close to the television if this helps you see it better: this will not damage your eyes. A cataract often develops in the other eye, but many people only get one in one eye.

Will your sight get worse?

Many cataracts do get worse, especially if you are middle aged and have diabetes. Many people with diabetes do eventually need cataract surgery.

Does a diet help?

There is no specific diet or drug treatment for cataracts, but following UK Department of Health advice may help: a diet low in animal fat and salt, with five portions of vegetables or fruit a day, with 30 minutes exercise such as walking, and not smoking.

In diabetes, diet, control of the blood sugar and blood pressure are important to prevent other problems (see Diabetes UK ).

  • When do you need an operation and should you control your diabetes?

    An operation to remove the cataract is usually the only way to make improve your sight. But before you can decide, you need to know the pros and cons of an operation. A cataract operation is generally safe, and with a surgeon who is experienced in cataract keyhole surgery, the risk of a serious problem is about 1%.

    So in a way you are the best person to decide: certainly, if you cannot do what you want to do, such as read, watch TV,  or walk in the street, an operation is usually helpful (if your eye has no other conditions.) Remember, many patients who have surgery are in their 80's.

    The diabetes ideally should be controlled before surgery, as otherwise complications are more likely. See and here.

    The Operation

    Typically, you have the operation as a day case. You go to the hospital in the morning, and go home later that day. You have a local anaesthetic injection, wait for it to work, then have the operation which takes about 20-30 minutes. A key hole operation is often used: a small tube is inserted into the eye to suck the cataract out, and a plastic lens implant is put in its place. The plastic lens implant is placed in the 'capsule' of the cataract.

    Routinely, the only major discomfort can be the local anaesthetic injection. At home, you have drops to put in, and routinely have one or two visits to the hospital, before seeing your optician for glasses. Normally after an operation, you see well.

    However, if there are other problems in your eye, such as a damaged retina (the film at the back of the eye), your sight will not be so good. In diabetes the operation may make the retinopathy worse and laser may be needed. Often the ophthalmologist recommends laser before the operation to try and stabilise the retinopathy. (See page concerning your type of retinopathy.)

    You usually do need glasses after an operation, because the implant cannot change its focus like a camera. You may need reading or distance glasses, or both.

    See animation & updated version of this page.

    cataract surgery: phaco
    lens implant after cataract surgery
    A small hole is made in the side of the eye and a probe is placed in the eye to cut and suck the cataract out.
    A plastic lens is placed in the eye to replace the cataract. The lens focuses the light onto the retina, like the lens of a camera.

    Extra risks in diabetes

    Unfortunately a few people do develop problems. Without diabetes, there is 1 in 100 risk of severe complications such as needing a second operation, infection, etc. But in diabetes there is a slightly greater risk of such problems as

    Macular oedema

    This is fluid collecting at the back of the eye, in the central area of the retina as in the diagram immediately below. This blurs the central vision. See.

    Treatment includes

    • waiting
    • adding non-steroidal eye drops to steroid drops
    • steroid injections under the eye
    • steroid injections in the eye itself.
    • for patients with retinopathy, start topical non-steroidals a week before surgery, and treat with steroid drops for at least 6 weeks post-operatively
    • if macular oedema is present, try and control for 3 months before surgery (laser & Avastin)
    patchy central vision with macular disease

    macula oedema...fluid accumulating after cataract surgery, causing reduced central and detailed vision

    Proliferative retinopathy & cataract surgery

    • there is an 8% risk of macular oedema occurring if proliferative retinopathy is present at the time of cataract surgery, 8 times normal.
    • unlasered patients with thick cataracts should have intra-operative panretinal (PRP) laser if at all possible
    • intracameral cefuroxime helps to prevent infections...there is a higher risk of infection, and standard precautions are needed. Care draping and cleaning the lids with polvidone iondine, and treating pre-existing blepharitis.
    • there is a high risk of fibrinous uveitis
    • if possible panretinal (PRP) laser should be carried out before surgery.
    • non-steroidal drops should be started before cataract surgery in anyone with retinopathy, but especially proliferative retinopathy.
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