Childhood cataracts

The word cataract is filed away under old age, yet the lens can turn cloudy in a newborn. The difference lies not in the cloudiness but in the timing. An adult who has surgery gets back the sight they had. In a baby a clouded lens does more than blur the view: it stops sight from forming at all, because during the first months the brain learns to see from the picture the eye sends it, and without a picture the necessary connections are never laid down. That is why a childhood cataract is not watched for years. It is looked for on the maternity ward and operated on within weeks.

Why the clock runs in weeks

A newborn's vision is a rough draft. Telling details apart, judging distance, merging two pictures into one — the brain learns all of this over the first months and years, and only by practising. An eye that supplies no sharp image during that window is gradually tuned out by the brain, and what develops is a lazy eye. Even if a perfect lens is fitted later, that eye will see worse than the healthy one, because the time for learning has passed.

Hence a rule that strikes parents as unexpectedly harsh: a dense opacity covering the pupil is operated on in the first weeks or months of life, not once the child is bigger and stronger. That goes double when only one eye is affected, since the brain then has a healthy eye to lean on and drops the other one readily.

Not every opacity is dangerous, though. Fine dots and streaks at the edge of the lens do not get in the way of sight at all; they are simply kept under review. What decides matters is not the existence of clouding but whether it covers the centre and how well the child sees.

What can be seen from outside

A small child will not complain and has nothing to compare with. Parents should take note of:

• a white or greyish pupil instead of a black one in ordinary light;
• one pupil coming out red in a flash photograph while the other looks white or dull — this small thing in family pictures picks up more cases than people imagine;
• a child who does not follow a face or a toy with the eyes;
• frequent involuntary flicking of the eyes from side to side;
• one eye that drifts or turns;
• screwing up the eyes and turning away from bright light more than usual;
• in older children, holding a book against the face, squinting, complaining of fog and of haloes around street lights.

A white pupil is the one sign on that list that cannot wait for a convenient appointment. It is not produced by cataract alone: retinoblastoma, a malignant tumour of the retina in which delay costs sight and sometimes more, looks exactly the same. A child with a white pupil should be seen by an eye specialist within days.

The checks that find it

It is for findings like these that every newborn's eyes are examined, and examined again at around six to eight weeks. The test takes seconds: a light is shone into the eye and the red reflex is assessed — that glow from the back of the eye which produces red eyes in photographs. With a clear lens the reflex is bright and the same on both sides; a dull reflex or none at all means something stands in the path of the light.

The child then goes to an eye specialist. Drops are put in to widen the pupil: they may sting, they do no harm and the effect wears off in a few hours. Under magnification it becomes clear where the opacity sits, how dense it is and whether one eye or both are involved. Bilateral cataracts almost always prompt wider testing to look for a cause. Some cases appear after the infant checks are over, so any doubt about how a child is seeing justifies an appointment at any age.

Why the lens clouds over

In roughly half of cases no cause can be pinned down, and that is an honest answer rather than a brush-off. Among the causes that are known, the commoner ones are:

• heredity — in about one child in five someone else in the family had the same thing;
• chromosomal and genetic syndromes, of which Down's syndrome is the best known;
• infections caught by the mother during pregnancy: rubella, toxoplasmosis, cytomegalovirus, chickenpox, herpes simplex;
• metabolic disorders, above all galactosaemia, in which milk sugar is not broken down. Here the clouding sometimes clears on its own once lactose is removed from the diet in time, which is why that test comes early in a baby with cataracts;
• injury to the eye and eye surgery;
• long courses of glucocorticoid medicines, and radiation;
• diabetes in an older child.

An inherited cataract cannot be prevented, but some of the infectious ones can: check and if necessary update rubella vaccination before conceiving rather than during pregnancy, and take care with raw meat, unwashed vegetables and the cat's litter tray. If a child with cataracts has already been born into the family and another pregnancy is planned, it is worth asking about genetic counselling.

Surgery and what replaces the lens

Not every opacity is operated on, only the kind that gets in the way of seeing. The procedure is done in hospital under general anaesthetic and usually takes an hour to an hour and a half: through a tiny cut in the cornea the clouded lens is removed.

Then comes the part parents rarely see coming. An eye without a lens cannot focus, and restoring that focusing power matters just as much as clearing the cloudiness. In older children an artificial lens is placed inside the eye during the operation. In babies under a year this is done less often: the eye is still growing fast, a lens calculated today will be the wrong one in a year, and complications are commoner at that age. For them contact lenses are usually fitted instead, or glasses if both eyes were operated on; these go on a week or two after surgery and are changed as the child grows.

When both lenses are cloudy, the eyes are operated on one at a time so that a single complication cannot affect both; the second operation usually follows within days. Afterwards the eye is covered with a dressing or a clear shield, the child normally stays in hospital overnight, and parents go home with anti-inflammatory drops to be given to the clock for the first few weeks. How to put them in is demonstrated before discharge.

Patching and glasses: years of work

Surgery is the beginning, not the end. The brain has to be made to use an eye it grew used to ignoring, and everything here rests on the family's patience.

The main tool is patching: the stronger eye is covered for a few hours a day so that the weaker one is forced into service. How many hours and up to what age is decided by the specialist following the development of vision. Children dislike patching, and the commonest reason for a poor result is not the surgery but a course that was given up. Alongside it come glasses or contact lenses, re-prescribed as the eye grows, and check-ups several times a year.

Nobody can say in advance how well a child will see. The operated eye often keeps some reduction in vision, and it is better to know that from the outset. Even so, most of these children attend an ordinary school and lead an ordinary life; the limits mainly concern occupations that demand flawless depth perception.

What can go wrong

The operation is well established and usually goes smoothly, but complications happen, and some of them call for attention for life:

• clouding of the back of the lens capsule — the thin membrane holding the artificial lens thickens and vision blurs again. This is not the cataract coming back; a short laser procedure clears it;
• glaucoma, meaning raised pressure inside the eye. The risk lasts for decades, so anyone who had a cataract removed in infancy needs the pressure measured at least once a year for life. Otherwise the loss of sight is noticed when it is already irreversible;
• a squint and a lazy eye, both needing treatment of their own;
• a pupil of altered shape, which usually does not affect vision;
• swelling at the centre of the retina and, rarely, a detached retina;
• infection inside the eye — rare, and the most serious of the lot.

Go straight back to the hospital where the surgery was done if the child is clearly in pain, is unsettled and rubbing the eye, if the eye turns red, if there is heavy or pus-like discharge or bleeding, or if the child suddenly sees worse or shies away from light.

Online consultation

A remote appointment handles well what troubles parents before and after the eye clinic. The doctor will ask how the child follows faces and objects, how the pupils look in different light and in flash photographs, whether there is a squint or flicking of the eyes, what happened during the pregnancy and whether anyone in the family had the same, and will say how urgently an in-person examination is needed. After surgery it is a good place to go through the drop schedule, the patching routine, contact lens care and the follow-up timetable. A white pupil and the warning signs after surgery are not assessed remotely: they call for an eye specialist straight away.

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