Short-sightedness (myopia)

Short-sightedness means seeing well up close and blurred in the distance: faces are hard to recognise, signs smear together, at the cinema you find yourself screwing up your eyes. In children it usually starts during the school years and grows along with the eye; in adults it tends to sit still. Glasses or contact lenses restore sharpness straight away, but two further things are worth knowing and are rarely mentioned: in children the progression can be slowed down, and strong short-sightedness leaves behind, for life, one warning that must not be missed.

What is happening inside the eye

The eye works like a camera: the cornea and the lens bend light so that the image lands exactly on the retina. In short-sightedness it comes together slightly too early, in front of the retina, and reaches it already blurred. The reason is almost always that the eyeball is too long from front to back; less often, that the cornea is too steeply curved.

That explains why short-sightedness is a childhood story. The eye grows with the child, and if it grows too much in length the prescription creeps up year after year. Most often this begins somewhere between the ages of six and thirteen; by the end of the teenage years the eye has stopped growing and the numbers usually settle. It can appear in an adult too, but then it rarely advances as fast.

Heredity shows: if both parents are short-sighted the child's chances are highest, and if one is, they are somewhere in between. But heredity is neither a sentence nor the only thing that decides the outcome.

The strength of a prescription is not simply a matter of how thick the lenses are. The longer the eye, the more its inner layers are stretched, and the higher the lifelong risk of complications. That is why with children the aim is not only to correct the vision but to hold back the increase.

How it shows up in a child

Children almost never complain of poor sight. They do not know it can be any different and take a blurred distance for normal, so it is behaviour you have to watch:

• screwing up the eyes when looking into the distance, or tilting the head slightly to one side;
• sitting right up against the television, holding a tablet or phone close to the face;
• not being able to read the board from the back of the class but managing from the front; a teacher mentioning that the child keeps asking or copies from a neighbour;
• complaining of tired eyes and headaches after lessons;
• rubbing the eyes often, blinking more than usual;
• no longer recognising people in the street from a distance, becoming more cautious in the playground or in unfamiliar places;
• schoolwork slipping with no obvious reason — sometimes this is the first visible sign.

It is also worth covering one of the child's eyes and then the other. If one eye sees worse, the other compensates and everything looks fine from outside; that one-sided short-sightedness is only picked up at a test.

Routine eye tests are needed even without complaints: before school and regularly afterwards, and all the more so if short-sightedness runs in the family. An adult with no complaints does well to be checked every one to two years.

What actually affects how fast it grows

There is plenty of folklore here and rather little that has been tested. Taking it in turn:

Time outdoors in daylight. This is the most solid thing known. Children who spend around two hours a day outdoors become short-sighted less often, and in those who already are, the prescription climbs more slowly. What matters is the brightness of natural light, not the exercise: under an open sky there is tens of times more light than in the brightest room, and that influences how the eye grows. A walk on an overcast day still counts. Lamplight is no substitute.

Long stretches of close work. Hours of reading and screen time without breaks are associated with faster progression, particularly when the book or phone is held too close. The practical conclusion is simple: keep the text no nearer than the distance from elbow to knuckles, look up every twenty to thirty minutes and spend a few seconds looking out of the window, and do not switch the room light off.

What does not work. Carrots and bilberries do not restore vision. Eye exercises do not reduce the prescription: the eye has become longer, and no amount of exercise shortens it. Glasses do not "ruin your eyes" or make them "lazy"; on the contrary, deliberately weak, under-corrected glasses do not slow short-sightedness down and by some evidence speed it up. Wear the glasses that were prescribed, and wear them as the specialist advised.

What can slow short-sightedness down in a child

Hardly anyone knows about this, and it is the most useful part of the subject. Ordinary glasses and ordinary contact lenses do one thing: restore sharpness. They do not hold back the increase. But there are separate methods whose whole purpose is to slow progression:

• myopia control spectacle lenses — from the outside these are ordinary glasses, but alongside the main zone they carry a specially designed periphery which alters the growth signal to the eye;
• specially designed soft contact lenses, dual-focus or multifocal, working on the same principle;
• orthokeratology — rigid lenses worn overnight; they temporarily reshape the cornea, and during the day the child sees without glasses;
• low-concentration atropine eye drops, put in at bedtime; at that dose they do not widen the pupil enough to be a nuisance, but they slow the lengthening of the eye.

In studies these methods slow progression by roughly a third to a half, varying from child to child. They are not a cure and they do not give sight back: the prescription will still rise, but more slowly, and the final figure in adulthood will be lower. And the lower that figure, the smaller the lifelong risk of complications — which is the whole point of the exercise.

The choice of method belongs to the eye specialist, who weighs up the child's age, how much the prescription moved over the past year, the length of the eye and whether the child is ready for lenses. It makes sense to start while short-sightedness is still growing — that is, in childhood, not once everything has settled. If the prescription has jumped noticeably between two tests, that is the moment to ask about these options.

The eye test, glasses and surgery

At the appointment sight is measured with a letter chart, and then lenses are tried until the letters come into focus. Children are usually given drops that temporarily relax the focusing muscle: without them a child adjusts the eye involuntarily and the result comes out inaccurate. After the drops the pupil stays wide for several hours, close vision is worse and light feels harsh; this wears off on its own, but no driving that day. The specialist also examines the back of the eye and, in short-sightedness, looks especially carefully at the outer edges of the retina.

Glasses or contact lenses are then prescribed according to the result. Glasses suit any age; contact lenses suit older children and adults, provided the person will follow the hygiene rules, because otherwise a corneal infection is easy to acquire. If the prescription is rising, it is worth raising from the outset not simply correction but one of the control methods from the previous section.

Adults whose short-sightedness has stopped changing can be offered surgery: laser correction reshapes the cornea, and in high prescriptions an additional lens is implanted inside the eye or the natural lens is replaced. Not everyone is a candidate — the thickness and condition of the cornea, the stability of the prescription and other eye conditions all count. And there is an important caveat: surgery removes the need for glasses, but it does not shorten the eye again. A stretched retina stays stretched, so all the risks of high short-sightedness, and the eye checks that go with them, remain in place after a successful operation.

Signs that need an eye specialist immediately

This is what makes the page worth reading to the end. See an eye specialist urgently, the same day, if any of the following appears suddenly:

• flashes of light — brief lightning or sparks off to one side, most noticeable in the dark;
• new floaters — specks, threads or what looks like soot that were not there before, especially a shower of them arriving at once;
• a dark curtain or shadow creeping in from the edge of your vision;
• a sudden drop in vision or the loss of part of the visual field;
• straight lines appearing bent, or a patch in the middle of the picture.

That is how a detached retina announces itself. The retina lifts away from its support and stops being fed; tissue left without a blood supply dies within hours and days, and it cannot be brought back. A detachment operated on in time usually ends with sight preserved; a late one does not. In short-sightedness this risk is higher than in people without it, and it rises with the prescription, because a lengthened eye stretches and thins the retina.

So with short-sightedness there is no waiting for an appointment in a fortnight, and no reassuring yourself that it is probably just tiredness. Floaters that have been there for years and do not change are usually harmless; what is worrying is a sudden arrival or a sharp increase in their number, especially together with flashes.

What else high short-sightedness brings

In most people with a small prescription it all stops at glasses and there is nothing to worry about. But in high short-sightedness a stretched eye eventually brings other problems, which are better known about in advance — not to be frightened by them, but to be checked in time:

• glaucoma — raised pressure inside the eye that damages the optic nerve silently over years; it is picked up only at an examination;
• cataract — clouding of the lens, which in short-sighted people often arrives at a younger age;
• changes in the central part of the retina in very high prescriptions, which spoil precisely the central vision used for reading.

With small children there is a separate story: if short-sightedness goes uncorrected for a long time, the eye never receives a sharp image and its sight does not develop properly. That is amblyopia, a "lazy eye", and sometimes a squint follows. Putting this right later is far harder than in the early years, which is why missed childhood eye tests cost so much.

Hence the practical conclusion: both glaucoma and retinal tears are silent in their early stages, so in high short-sightedness a regular examination of the back of the eye with the pupil dilated is worth more than it seems.

Online consultation

An online appointment does not replace measuring visual acuity or examining the back of the eye — those need equipment. But a good deal of what people book an eye appointment for is settled by talking, and here it saves time.

Online is a convenient way to go through the results of a test already done and work out what the figures on a prescription mean; to judge how fast a child's prescription is climbing; to discuss the myopia control methods and which of them fits your child; and to work out whether surgery is worth considering and when.

Have to hand every spectacle prescription and test report you have kept: what matters is not the last figure but how it has changed. Note how much time the child spends outdoors and how much in front of a screen, and whether either parent is short-sighted.

That said, if there are flashes, floaters that have appeared out of nowhere, a shadow in the field of vision or a sudden loss of sight, do not spend time on an online appointment: this needs an eye specialist with equipment, and it needs one today.

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