Farsightedness (hyperopia): causes, symptoms and treatment in adults and children

Farsightedness (hyperopia, or long-sightedness) is a common refractive error in which the eye is slightly shorter than normal or its cornea is too flat, so light comes to focus behind the retina instead of on it. Near vision is usually the first to feel tiring or blurry, and distance vision can blur too when the error is high. Many people, especially children and young adults, compensate with extra focusing effort without noticing, so the complaint shows up as headaches and tired eyes after reading rather than obvious blur. It is corrected with plus (+) lenses in glasses or contact lenses, and sometimes with refractive surgery in adults. This guide covers how to tell whether you have it, how it differs from the near-vision change after forty, and why children need a special kind of exam to detect it.

What happens inside a farsighted eye

To see clearly, the cornea and then the eye's natural lens bend incoming light by just the right amount for it to converge precisely on the retina at the back of the eye. In farsightedness the eye is relatively short, or its focusing power is weaker than it should be, so the point of focus falls behind the retina. But the eye is not a fixed camera: its natural lens can temporarily add power using the focusing muscles, the same mechanism we use to look at things up close. A farsighted eye spends this reserve all day, a little for distance and a lot for reading and the phone, which is why its owner may see far away well and still complain of fatigue. It is the exact opposite of nearsightedness, where near things are clear and distance blurs. The American Academy of Ophthalmology notes that most babies are born mildly farsighted and that this usually decreases as the eye grows in the early years, which is why many children with mild degrees never need glasses at all.

• A short eye: the most common cause, when the eye is shorter than usual from front to back.
• Corneal curve or lens power: a cornea that is too flat or a weaker lens produces the same result.
• Genetics: farsightedness runs in families, so a parent who has it is one more reason to have the children checked.
• A sudden change in adults: if your near or distance vision changes suddenly, have it checked promptly rather than just changing your glasses, because fluctuating blood sugar and some other conditions can temporarily shift the eye's focus. Sudden loss of vision, or a change that comes with eye pain, means going to the emergency department right away.

Symptoms of farsightedness: not always blur

Many farsighted people do not know they are, because the eye covers the shortfall with extra focusing for as long as it can. That is why symptoms usually arrive as fatigue rather than blurred vision, and they get worse at the end of the day and after long stretches of close work. Signs worth noticing include:

• Blurred text or lines running together when reading or on a phone screen, or needing to hold text a little further away.
• Eye strain, burning and heavy eyes after reading or computer work.
• Headaches around the forehead or the eyes that come on after close work and ease with rest.
• Narrowing the eyes to see things clearly.
• In children: avoiding reading and homework, rubbing the eyes, losing their place on the line, or one eye turning inward.

With age the focusing reserve gradually shrinks, so farsightedness that used to be hidden starts to show. That is why many people discover they are farsighted in their thirties, and need reading glasses earlier than their peers.

Farsightedness or presbyopia? The key difference

In Arabic both conditions are commonly called by the same name, a constant source of confusion, and in English they are easy to mix up too. The farsightedness discussed here comes from the shape of the eye: it is usually present from birth, though its symptoms can show up at any age. Presbyopia, by contrast, is a natural stiffening of the eye's lens that begins for almost everyone around age 40, including people who are nearsighted or who have always had perfect vision. Both make near vision harder and both are corrected with plus lenses, but the practical differences matter:

• Farsightedness may need correction for both distance and near, and full-day wear at higher degrees.
• Presbyopia affects near vision only, and is corrected with reading glasses, bifocals or progressive lenses.
• A farsighted person who reaches forty faces both at once, so their near correction is needed earlier and is stronger than other people's.

Why children need a special exam to detect farsightedness

A child's focusing reserve is very large, so it can hide a moderate degree of farsightedness, and the child may read the distance letter chart at a school screening without a single mistake. That is why an eye doctor uses drops that temporarily relax the focusing muscles before measuring, so the full, true degree shows up. After these drops, near vision is blurry and light sensitivity is higher for some hours, sometimes longer depending on the drop used, which is expected and wears off on its own. Early detection matters because high, uncorrected farsightedness can push one eye to turn inward, since focusing effort is linked to the eyes moving toward the nose. This is called accommodative esotropia, and the American Academy of Ophthalmology notes that it most often appears between the ages of 2 and 3. It can also lead to a lazy eye (amblyopia), especially when one eye is much more farsighted than the other, so the brain relies on the clearer eye and neglects the other. The good news is that glasses alone correct accommodative esotropia in many cases, and lazy-eye treatment works better the earlier it starts. Signs that call for a child's eye exam include:

• One eye turning inward, even occasionally, especially when looking at something close.
• Closing one eye or tilting the head to see.
• Avoiding reading, a short attention span for close tasks, or complaining of headaches after school.
• A family history of high farsightedness, a squint or a lazy eye.

Any one of these signs is reason enough to book an eye doctor exam soon, and an eye that turns, even occasionally, should not wait for the next school screening. A squint that appears suddenly at any age, double vision, or a sudden drop in vision needs to be seen the same day; go to an emergency department if you cannot be seen right away.

Correction options: glasses, contact lenses and surgery

Farsightedness is corrected with a convex lens that converges light before it enters the eye, moving the point of focus back onto the retina. On a prescription you will find it in the SPH box with a plus sign, such as +1.50, and powers usually step in increments of 0.25 dioptres. A plus lens is thicker in the middle and makes the eyes look slightly larger to others, so high-index lenses and smaller frames help with strong prescriptions. Not every farsighted person wears glasses all day; some need them only for reading and close work, and that is the doctor's call. A child, though, should wear them exactly as prescribed, because leaving the glasses off can bring back the strain and, in a child with a squint, the eye turn.

• Glasses: the simplest and safest option, and the main option for children.
• Contact lenses: suitable for many adults, provided they are fitted by a professional and hygiene rules are followed.
• Laser refractive surgery: reshapes the cornea to steepen its curve, and suits some adults with mild to moderate degrees and a stable prescription after a detailed assessment.
• Lens surgery: replacing the eye's natural lens or implanting an additional one, considered for higher degrees or older adults depending on the surgeon's assessment.

Farsightedness has one more side worth knowing: a farsighted eye is often smaller, with a narrower drainage angle, which raises the risk of a type of glaucoma called angle-closure glaucoma, as the American Academy of Ophthalmology notes. Your eye doctor can assess this angle during an eye exam, but know the emergency signs: sudden severe eye pain with redness, blurred vision, halos around lights, headache and nausea. If you have these symptoms, or even sudden severe eye pain with blurred vision on its own, go to the emergency department right away. On ordinary days, if your work involves long periods of close-up focus, use the 20-20-20 rule recommended by the American Academy of Ophthalmology: every 20 minutes, look at something at least 6 metres (20 feet) away for 20 seconds to relax your focusing muscles.