Cataract: when the lens turns cloudy

Behind the pupil sits a clear lens. It focuses light onto the retina and changes shape as we look up from a book to the window. Over the years the proteins it is built from lose their tidy arrangement, and the lens clouds and yellows. That is a cataract. Nothing shows from the outside: no film forms over the eye, the eye is neither red nor sore, only the picture changes — and it changes so slowly, over years, that people get used to it and put it down to tiredness or age. One thing is worth settling at the start: a cataract takes sight away gradually, so if vision drops within a day or a few hours, the cause is something else and it needs sorting out urgently.

How vision changes

Complaints differ because a lens can cloud at the edge, in the centre, or just under the back capsule. What people notice most often is this:

• the picture looks slightly hazy, contrast fades and faces are harder to recognise at a distance;
• haloes appear around street lamps and headlights, oncoming light dazzles more than it used to, and driving after dark becomes uncomfortable;
• reading takes more and more light; under ordinary lighting the letters run together;
• colours look washed out and shift towards yellow, with blues and violets the hardest to tell apart;
• an object looks double or triple with one eye alone — covering the other eye does not remove it;
• glasses need changing more often than usual, and each new prescription lasts a short time;
• sometimes the opposite happens: a person suddenly reads without glasses and is delighted. That is not an improvement but a sign that the hardening core has shifted the focus towards short sight.

The two eyes cloud unevenly, and the better one covers for the weaker for a long time. Check your sight one eye at a time, with the other covered by your hand: many people first spot the problem exactly that way.

Why the lens loses its clarity

The main factor is simply years lived: past seventy some degree of clouding is found in almost everyone, and the only question is whether it gets in the way. But the pace depends on other things too.

• ultraviolet light: years in the sun without glasses, work on water or in the mountains, welding without protection;
• smoking;
• diabetes, especially when poorly controlled: the cataract arrives years earlier and grows faster;
• long-term corticosteroids in tablets, in eye drops or inhaled at high doses; this type settles under the back capsule, right on the optical axis, and gets in the way early;
• any eye injury, including a blunt blow many years ago, and previous surgery inside the eye;
• chronic inflammation inside the eye and severe short sight;
• radiotherapy to the head;
• cataract in close relatives at a relatively young age.

No diet, eye exercise or supplement restores clarity. The only things you can influence are the ones above: not smoking, keeping diabetes controlled, and wearing glasses with an ultraviolet filter.

When an appointment cannot wait

Cataracts produce nothing sudden. Anything that happens abruptly calls for emergency care rather than a booked appointment.

• Vision drops within hours or a day, a dark curtain moves in from below or from the side, flashes and a shower of floaters appear: that is how a detaching retina behaves, and there the clock counts in hours.
• Severe pain in the eye and half the head, redness, rainbow rings around lights, nausea and vomiting, an eyeball that feels hard: this is an acute attack of angle-closure glaucoma. A neglected, swollen cataract can set it off by itself, which is one reason not to postpone surgery indefinitely.
• A missing patch in the field of vision, straight lines that look wavy, a grey spot in the centre: the trouble is in the retina, not the lens.
• Pain, sensitivity to light and redness without any injury: inflammation inside the eye.
• In a child, a pupil that comes out white or yellowish in flash photographs instead of the usual red, a newly turned eye, a baby who does not follow faces. The child should be examined within days: behind such a reflection lies either a congenital cataract, which is operated on early, or retinoblastoma, a tumour of the retina where speed decides more than sight alone.

What happens at the eye examination

The doctor checks visual acuity with and without glasses, measures the pressure inside the eye and examines it with a slit lamp: under it the lens is seen as if in cross-section, so it is clear where the clouding sits and how dense it has become. Drops are then put in to widen the pupil so the retina can be examined; light dazzles for a few hours afterwards, so no driving that day.

The back of the eye is examined not for the cataract but for everything else: age-related macular changes, glaucoma, diabetic damage to the retina. That is the crux of the matter, because replacing the lens removes the cloudy glass but repairs neither the retina nor the optic nerve. If more than one thing is reducing vision, an honest forecast is needed before surgery, not after. When a cataract is so dense that the back of the eye cannot be seen, an ultrasound scan is done. Before surgery, biometry is added: the eye is measured so the power of the artificial lens can be calculated.

Surgery is the only thing that removes a cataract

There are no drops or tablets that dissolve the clouding; products promising it only cost you time. A cloudy lens can only be replaced.

It is done under local anaesthetic: the person is awake and feels no pain. Through an incision a couple of millimetres wide the lens is broken up with ultrasound and washed out, and a soft artificial lens is unfolded into the capsule that has been kept in place. It usually takes under half an hour, stitches are rarely needed, and you go home the same day. The second eye is done separately. The implanted lens does not wear out and never needs replacing.

The lens is chosen in advance. A standard monofocal gives sharp vision at one distance, and glasses are needed for the rest, usually for reading. Lenses with more complex optics reduce dependence on glasses, but the price is haloes around lights and lost contrast in dim conditions. Tell the surgeon plainly whether you drive a lot at night and whether you work at a screen: the choice follows from that, not from the price tag.

The timing of surgery is decided not by the cataract's "ripeness", an outdated rule, but by whether your sight is getting in the way of living: driving, reading, working, recognising people. Nor is it wise to put it off for years: the denser the core, the harder the operation and the higher the risk.

Afterwards you use drops for a few weeks as prescribed, do not rub the eye, avoid lifting heavy things and stay out of open water until the doctor allows it. Sight improves within the first days, and glasses are prescribed after about a month. Complications are rare, but two warnings are worth knowing by heart. Increasing pain with redness and falling vision, all the more with discharge, in the first days or weeks means infection inside the eye; flashes and a curtain mean a detaching retina. Neither waits for the next appointment. A separate and harmless matter is clouding of the back capsule months or years later: vision blurs again, but this is not a cataract coming back, and it is cleared with a laser in a few minutes and without any incision.

While surgery is still a long way off

An early cataract may barely interfere for years, and all that time simple things help.

• update your glasses — often that is enough for a good while;
• add light: put the lamp behind you and to one side, lighting the page rather than your eyes;
• large type and high contrast on screens, matt surfaces instead of glossy ones;
• glasses with an ultraviolet filter and a peaked cap outdoors, against dazzling glare;
• clear away cables and slippery rugs and light the stairs and hallway: a fall with a fracture costs far more than the cataract itself;
• be honest about driving: night trips are the first to go, because night-time glare gives a cataract away earliest. Fitness to drive is judged by a doctor on acuity and field of vision, and the rules are local ones.

Online consultation

A remote appointment is a good way to get your bearings before seeing a surgeon. The doctor will ask exactly how your vision has changed and judge whether the complaints fit a cataract; explain what the eye report says — the type of clouding, the acuity, the state of the retina; and help you work out whether it is time to operate or you can wait calmly, and what to ask about the choice of implant. Your regular medicines will be reviewed at the same time, corticosteroids above all, along with what to do if something worries you after surgery. A slit lamp and a look at the back of the eye cannot be replaced remotely, and the warning signs listed above need immediate in-person care.

This material is for information only and does not replace medical advice.