How can age-related farsightedness be corrected?

Light entering the eye through the pupil first reaches the lens of the eye. The outer edge of the lens is attached to a circular muscle (ciliary muscle) by fine fibers. When this muscle tightens and relaxes, it changes the shape of the lens. This allows the eye to focus on nearby objects and on objects that are further away: When you look at nearby objects, the ciliary muscle tightens, making the lens curve and thicken. When you look at things in the distance, the muscle relaxes and the lens becomes flatter and thinner. By changing the shape of the lens in this way (accommodation), the light entering the eye is focused onto the retina to produce a sharp image.

The lens becomes harder and less flexible with age. This makes it more difficult for the lens to curve and get thicker – but that has to happen in order for you to see nearby objects clearly. The lenses of eyeglasses make up for this (correct it): They bend (refract) and focus light before it reaches the lens of the eye. This makes up for the poor refractive power of the natural lens. So wearing reading glasses helps you see nearby objects clearly again.

The focusing power of the lens, known as the refractive power, is measured in diopters (D). This unit is also used to describe the strength of eyeglasses or contact lenses needed to correct your vision: Zero diopters is considered to be normal vision (no corrective lenses needed). A minus sign in front of the diopter value means nearsighted (short-sighted), and a plus sign means farsighted. So the greater the plus value in people with presbyopia, the more their vision needs to be corrected.

Simple ready-made reading glasses are available in different strengths – for instance, in drugstores or from an optician’s. But these kinds of glasses are only suitable if you don’t have astigmatism and both of your eyes can see distant objects clearly without corrective lenses. The refractive power of each of your eyes is usually different, though.

Prescription reading glasses can be specially made by opticians, taking into account the individual prescription strength needed. In Germany, the costs of reading glasses generally aren’t covered by statutory health insurers.

Many reading glasses are narrow enough for you to easily look over the top of them and see more distant objects clearly too.

People who already needed glasses before they developed presbyopia need two different strengths of corrective lenses. Those who find switching between two pairs of glasses too much of a hassle can opt for bifocal glasses (bifocals) instead. Bifocals are a type of multifocal glasses. The lenses of bifocals are divided into two zones: the lower zone is for looking at nearby objects, and the upper zone is for looking at objects that are further away. In bifocal glasses, the distance zone and the near/reading zone are divided by a visible horizontal line, which some people don't like. Bifocal glasses also don't allow you to see things clearly at intermediate distances (for instance, when working on a computer screen or in the kitchen).

The most common type of multifocal glasses are known as varifocal glasses. In varifocals, the lenses have been polished so there are no visible lines dividing the zones but you can see clear images of objects close to you and further away. This also makes it possible to see things clearly at intermediate distances.

Another type of multifocal glasses, known as trifocals, are an option if you want to see objects clearly at intermediate distances too, but you don't want to wear varifocal glasses. Trifocal glasses are made up of three zones that are divided by visible horizontal lines. One zone is for distance vision, one is for intermediate vision, and one is for near vision. As with bifocal glasses, some people don't like the visible lines between the zones.

It can be difficult to get used to varifocal glasses at first, and they may cause headaches and dizziness. Because the different zones merge into one another, you have to get used to looking through the right zone and avoiding the blurred areas at the edges of the lenses. Turning your head too while looking around can help.

Contact lenses may be a good alternative option, particularly for people who already needed glasses or contact lenses before presbyopia started. They are placed on the cornea of the eye (the clear part at the front), and float on a thin layer of tear fluid. Like glasses, contact lenses "correct" the refractive power of the natural eye lens. The advantage of contact lenses is that they don't change your appearance and they don't get in the way when doing activities like sports. The disadvantage is that they need proper care and handling, can sometimes irritate the cornea, and are associated with a small risk of infections. They have to be put in every morning and taken out every evening – if you’re able to wear them the whole day. Some people wear contact lenses for only a few hours a day, and then wear glasses the rest of the time.

Contact lenses are either hard or soft. To prevent them from getting dirty or drying out, they are left in a disinfectant solution overnight. The costs of contact lenses and care products may vary from brand to brand. Some types of soft contact lenses are disposable and are thrown away immediately after wearing them.

To get the right prescription strength for your eyes, you will need to see an ophthalmologist or optician. Bifocal or multifocal contact lenses are also an option for people with presbyopia. Like with the glasses, these contact lenses have different zones for looking at nearby and more distant objects. A further kind of contact lenses, known as "monovision" contact lenses, are also available. Here you wear one contact lens to see distant objects in one eye (your dominant or “distance” eye), and another contact lens to see nearby objects in the other eye (your non-dominant or “near” eye). In many cases the brain adapts to monovision contact lenses after a while. But if people continue to find it unpleasant, they may stop wearing them. Monovision contact lenses affect your ability to judge how close or far away things are, so people who wear them have to wear glasses as well when doing things like driving. Glasses also help the “near” eye to see clearly when looking at things that are further away.

Laser treatment can be used to treat eye conditions such as glaucoma and nearsightedness. But this treatment approach isn’t yet suitable for people who only have presbyopia and no other problems affecting their vision. Although laser treatment is advertised in magazines and on the internet (and sometimes recommended by doctors too), some procedures are still being developed or haven't proven successful. What's more, the outcomes of laser surgery can't be reversed. There are various kinds of laser treatment, including:

• Laser-assisted in-situ keratomileusis (LASIK) and photorefractive keratectomy (PRK): These approaches are only considered as treatment options for people who are already nearsighted or farsighted, or who already have astigmatism. Both of them involve using a laser to remove certain parts of the cornea in order to change the refractive power of the eye. In the treatment of presbyopia, one eye is generally changed to see nearby objects better, and the other eye is changed to see things that are further away better. Like monovision contact lenses, these laser treatments make your spatial vision worse. The brain can't always adapt to this change. Other negative effects of surgery include pain and worse vision at dawn, at dusk and at night.
• INTRACOR: This procedure involves using a laser to cut rings in the cornea. The aim is to correct presbyopia by slightly reshaping the cornea. But there hasn't been much research on this approach either. Previous experience shows that the refractive power of the eye only changes a little bit. As a result, most people who have had this treatment still need to wear reading glasses anyway, and some people find it harder to see things in the distance afterwards. This treatment can also lead to scarring of the cornea, which can further affect your eyesight. It may cause your eyesight to generally get worse too.

Like with laser treatments, there’s a lack of good research on surgical procedures for presbyopia, and the cosmetic or practical advantages have to be weighed against various associated risks. The following kinds of surgery are currently possible:

• Synthetic lens implantation: This is mainly considered as a treatment option for people who have a cataract and are also nearsighted or farsighted, or also have astigmatism. The procedure is similar to cataract surgery. The eyeball is cut open at the edge of the cornea, the lens of the eye is removed and then replaced with a multifocal synthetic lens. This approach is associated with a number of possible disadvantages: People may have trouble seeing at dawn, at dusk or at night after the operation. Light sources can be particularly dazzling or hazy. The area behind the synthetic lens may become cloudy a few months or even years afterwards (aftercataract). This can be treated with pain-free laser treatment in an outpatient setting. The surgery itself is associated with a small risk of infection if germs get into the eye.
• Implanting corneal inlays: This operation involves inserting a plastic implant (KAMRA) into the cornea of the non-dominant eye to increase its depth of field. This eye is then used as the "near" eye for doing things like reading. But people usually still need to wear reading glasses after the operation. The possible associated risks and side effects include an infection, scarring of the cornea, eye dryness, and worse vision at dawn, at dusk and at night.