Long-sightedness

Long-sightedness is a way the eye can be built: distance is clearer than close up. It also goes by the names hypermetropia and hyperopia. It is very common and in the vast majority of cases glasses sort it out completely. Two things about it are worth knowing in advance, though. First, it is constantly confused with age-related presbyopia, and the two are different conditions with different fates. Second, in children it knows how to hide while doing lasting damage to sight, so there timing is everything.

Why the eye cannot focus up close

The eye works like a camera lens: the cornea and the lens bend the light so the image lands exactly on the retina. In long-sightedness the focus falls behind the retina and the image on it comes out soft. The usual reason is simple — the eyeball is a little shorter than average. Less often the cornea is too flat, or the lens bends light more weakly than it should.

Now for the interesting part. The lens can change shape and add focusing power, an ability called accommodation. A young eye with mild long-sightedness simply pulls itself into focus out of that reserve: the person sees well both far and near and is convinced their sight is fine. The price is constant effort. Hence tiredness, heavy eyes and headaches in someone who reads the chart in the consulting room from top to bottom. This is called latent long-sightedness.

The reserve of accommodation shrinks with the years in everyone, and in a long-sighted person it runs down sooner, because part of it has been spent on compensation all along. At some point the hidden becomes obvious: first there is not enough for reading, later not enough for distance either. That is where the impression comes from that long-sightedness "starts after forty". In fact it was there from birth and has merely stopped hiding.

What it feels like

• Letters up close blur, you want to push the book or the phone further away, and at arm's length the text really does read better.
• Near vision is worse in the evening than in the morning: the day has used up the reserve.
• The eyes tire, sting and feel heavy after reading, sewing or screen work.
• The forehead and brows ache after close work, and the headache clears on holiday.
• During long close work things occasionally double, the lids redden and the eyes beg to be rubbed.

Children almost never complain: they have seen nothing else and assume their picture is normal. Watch the behaviour instead — the child avoids books and drawing, tires quickly in lessons, buries their nose in the exercise book or, conversely, pushes it away, has one eye drifting inwards by evening, and gets frequent headaches.

How long-sightedness differs from presbyopia

These two are confused more than anything else, and older reference books sometimes list presbyopia outright as a cause of long-sightedness. That is wrong.

• Long-sightedness is a property of a particular eye's optics, usually its shorter length. It is there from birth, set by anatomy, and will not go away by itself.
• Presbyopia is the age-related stiffening of the lens, which stops it changing shape. It arrives in everyone without exception: in the short-sighted, in the long-sighted and in people with perfect vision. It is not a disease but the normal ageing of a tissue.

The practical difference is this. Presbyopia needs only reading glasses, put on for the task. Long-sightedness often needs correction at other distances too, and in a child it cannot be left alone at all. And one more thing: a long-sighted person meets presbyopia earlier and finds it harder, because both reserves run out at once.

Long-sightedness in children

All babies are long-sighted — the eye is short and grows over the first years of life, gradually bringing the focus onto the retina. Moderate long-sightedness in a preschooler is a normal variant and needs no glasses. What is dangerous are the marked degrees, which a child compensates for with enormous effort. Two problems then follow.

• A convergent squint. To focus, the eye simultaneously and effortfully turns in towards the nose — that is how focusing and converging are wired together. Such a squint often disappears with correctly prescribed glasses alone, but only if it is caught in time.
• Amblyopia, the lazy eye. If one eye is more long-sighted than the other, the brain stops using its blurred picture and gradually suppresses it. The child complains of nothing at all: the other eye works for two and everything looks fine from outside. By school age the difference sets, and past a certain age no glasses and no surgery will bring that eye's sight back.

Hence the central rule of this topic: children are checked on schedule, not when they complain. Preventive eye checks in early childhood exist precisely to catch what a child will never report; look up the exact ages in your country's schedule of preventive checks. And one more detail that matters: a child's examination is done with drops that widen the pupil and switch off focusing for a while. Without them latent long-sightedness simply will not show, and it is the latent kind that does the damage.

What the eye examination involves

The examination is short and painless. It usually includes:

• a chart test for each eye separately, at distance and up close;
• trying lenses: different glasses are placed in front of the eye and you say which is sharper;
• an instrument measurement of the eye's focusing power — a quick objective figure, especially useful in small children;
• drops that relax focusing, an obligatory step in children and young adults;
• an examination of the back of the eye and a measurement of the pressure inside it;
• an assessment of the angle through which fluid drains out of the eye: in long-sighted people it is narrower on average, and this is worth knowing in advance.

The drops widen the pupil for several hours, sometimes a whole day: afterwards everything close up blurs and light is uncomfortable. Better not to drive that day, and take sunglasses out with you.

Glasses and contact lenses

Glasses remain the simplest and safest solution. Where long-sightedness meets presbyopia you need either two pairs or varifocals — the latter take a week or two to get used to, and that is normal.

Contact lenses do not suit everybody and they demand discipline. A few rules that are expensive to break: do not sleep in lenses that are not designed for it; never rinse them in or store them in tap water, which harbours an organism that causes a severe corneal infection taking months to treat and leaving a scar; change the case on time and do not stretch the wearing period. If the eye becomes painful or red or the vision clouds, the lens comes out and you see a doctor.

And a common worry worth putting to rest: glasses do not spoil sight or make an eye lazy. In children the opposite is true — the right glasses stop amblyopia and squint developing. Prescriptions change over time, so adults do well to be checked every year or two, and children as often as the doctor advises.

Laser correction and lens replacement

Both are done under anaesthetic drops, awake and without pain, but neither suits everyone.

Laser correction reshapes the cornea so the focus falls on the retina. For long-sightedness its reach is more modest than for short-sightedness: the range of correctable dioptres is smaller, the result is less predictable and some of it may drift back over the years. It is done only on a stable prescription — once the eye has finished growing and the numbers have held for at least a year. A thin or irregular cornea, inflammation, pregnancy and a number of general illnesses are reasons to say no.

Replacing the lens with an artificial one is discussed in high degrees of long-sightedness and in older people, particularly where a cataract is ripening at the same time: one operation then settles two problems. A multifocal implant can free you from reading glasses as well, but it brings its own quirks of vision — haloes around street lights, slightly lower contrast — and does not suit every temperament or occupation.

And here is what matters about either operation: it frees you from glasses but does not rebuild the anatomy of the eye. A short eye stays short, a narrow drainage angle stays narrow, and eye checks continue as before.

When a visit cannot wait

Long-sightedness itself changes over years. Anything that happens quickly has nothing to do with it, and none of the following should be endured:

• Sudden severe pain in and around the eye, redness, abruptly clouded vision, rainbow rings around lights, nausea and vomiting, an eyeball that feels hard to the touch. This is an acute attack of closed-angle glaucoma, and long-sighted people are noticeably more prone to it: the eye is shorter, there is less room inside, the drainage angle is narrower. The clock runs in hours, and lost time means lost sight. This needs emergency care — an eye unit or an ambulance, not an appointment later in the week.
• Sudden loss of sight in one eye, loss of part of the field of vision, a dark curtain coming across from one side.
• Flashes of light and a sudden shower of floating specks — this is how a detaching retina announces itself.
• Double vision, a squint appearing for the first time in an adult, a drooping lid, pupils of different sizes: the cause here is not in the optics but in the nervous system.
• A marked drop in vision over days or weeks, especially alongside thirst, frequent urination and weight loss. Diabetes sometimes announces itself this way: a high blood sugar changes how the lens bends light. The vision returns once the sugar is controlled, but the diagnosis has to be made.
• In a child — a white or yellowish glint from the pupil in flash photographs instead of the usual red. That sign is checked without delay.

Online consultation

Fitting glasses needs instruments and a hands-on examination, so the prescription itself comes from an in-person visit. A great deal around it, though, is settled remotely and quickly. In an online appointment the doctor will go through the complaints and say whether this looks like long-sightedness, presbyopia, a dry eye or something that needs seeing today. They will explain the prescription you have been given — what the plus dioptres mean, what the astigmatic part is, why the two eyes differ — and why new glasses feel odd for the first few days. With parents there is a separate conversation about why the child needs drops before the test, why the glasses are worn all day rather than "for lessons", and when to come back. Online is also a good place to weigh glasses against contact lenses, to go through lens hygiene, to think about whether surgery is worth it and what to ask the surgeon. And if any of the warning signs above have appeared, the doctor on the call will say so plainly and send you where you will be helped within the hour.

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