How does laser surgery correct farsightedness?

The objects around us reflect light rays into our eyes. The rays are first refracted by the cornea and lens. Inside the eye, the rays of light rays then meet (converge) at one point. That focal point is normally right on the retina, which converts the light into nerve signals and passes them on to the brain through the optic nerve, producing a clear image.

Light refraction in an eye with normal vision (side view)

Farsighted eyes don’t refract the light enough. The focus point is then not on the retina, meaning the light rays don’t converge there. The reason for that is usually that the eyeball is too short, so the retina is closer to the cornea and lens. This means that the image is blurred.

The eye can compensate for that by itself with light rays coming from objects farther away, but not when the light rays are coming from closer objects where the light has to be refracted especially strongly.

Light refraction in a farsighted eye where the eyeball is too short

The operated cornea increases light refraction

During laser surgery, part of the cornea is removed so that it curves more, increasing its refractive power. Ideally, the cornea then refracts the light rays so that they converge directly on the retina again.

The standard laser surgery procedure for farsightedness is called LASIK (laser-assisted in situ keratomileusis). Other procedures like PRK (photorefractive keratectomy) and LASEK (laser-assisted epithelial keratomileusis) are only rarely used for farsightedness.

What conditions must be met for laser surgery?

Experts only recommend laser surgery under certain circumstances:

• The refractive error isn’t too severe – because otherwise that increases the risk of side effects and the refractive error is often not corrected enough. LASIK is recommended for up to +3 diopters. If you have been informed of the increased risks, you can also choose to have the procedure for up to +4 diopters. LASEK and PRK can be used up to +3 diopters, but special medical consultation is needed here, too.
• You don't have any other medical conditions that would rule out surgery, including things like cataracts with vision impairment, glaucoma with severely limited field of vision, and wet macular degeneration, but also wound healing disorders or cornea diseases.

It is also important that the farsightedness hasn’t changed significantly in the last twelve months. That is why laser surgery is usually only done in adults. It isn’t an option for children and teenagers because their vision is still changing.

The procedure isn’t suitable for pregnant or breastfeeding mothers. This is because things like water retention can temporarily affect the thickness and curvature of the cornea.

What happens during laser surgery?

The surgery is typically carried out as an outpatient procedure in a clinic or specialist eye surgery practice. Your eyes will be closely examined there a few days before. That includes checking the shape and thickness of your cornea. It’s important not to wear any soft contact lenses for at least one week before these examinations and not to wear any hard contact lenses for at least two weeks before, because they can temporarily change the shape of the cornea.

You will normally stay awake during the procedure. Your eyes will be numbed with drops, meaning you normally only feel a slight pressure. But if you prefer, you can be given a sedative. A special instrument called an eyelid speculum holds your eyelids apart during surgery.

In LASIK, the surgeon first separates part of the cornea surface with a small scalpel or laser and then opens it up like a flap. That gives them access to the cornea tissue below. That is then slightly ground down at the edges with a laser to increase the curvature of (steepen) the cornea. The cornea surface is then folded back down and grows back by itself within a few days.

PRK and LASEK work in a similar way. But in those procedures, only the cells of the uppermost cornea layer (epithelium) are scraped off or pushed to the side to laser the tissue below.

The laser is applied for only a few seconds, and the whole procedure takes just a couple of minutes. After a rest of usually about 30 to 45 minutes, you can be picked up and taken home.

How effective is laser surgery?

There has not been much good-quality research on the advantages and disadvantages of laser surgery in farsighted people. Studies have mainly focused on the various procedures in people with shortsightedness. They usually don't need to wear glasses or contact lenses anymore after the procedure, but there is no guarantee. A second procedure is sometimes needed, particularly in people with major refractive errors. Or they can wear glasses with less powerful lenses.

Even people who don’t need glasses or contacts after the procedure will develop presbyopia starting at the age of about 40 and need reading glasses.

What are the risks of laser surgery?

Depending on the type of procedure, many people have symptoms like pain, the feeling of a foreign object in their eye, or stinging and watering eyes at first. But these problems are not cause for concern and usually go away again after a few days.

Other side effects include:

• Dry eyes
• Sensitivity to light
• Seeing bright rings (halos) around illuminated objects
• Low-contrast, hazy vision

This impairs vision at dusk and at night, which can cause difficulties when driving in the dark. But those symptoms usually go away within a few months.

LASIK can also cause complications on the corneal flap that can restrict vision. If the corneal flap slips or creases slightly after surgery, it can cause double vision or distorted eyesight for both nearby and distant objects (astigmatism). It is also possible that the epithelium (cells that cover the front of the cronea) might grow under the flap and cause blurred vision. More surgery might then be needed.

Complications that permanently impair vision are rare, but can include infections, severe scarring, or incision errors in the cornea.

Farsightedness can sometimes get worse in the weeks or months following surgery, or it might not be corrected enough, or is over-corrected. Follow-up laser surgery can then be an option.

There are no good-quality studies on how common these various complications are.

When is lens surgery an option?

Lens surgery can be an alternative if laser surgery is not possible, for instance because of severe farsightedness or cataracts. An artificial lens called an intraocular lens (IOL) is implanted in your eye that works like a contact lens: It has the right strength and makes sure that the light is refracted properly.

There are two different methods:

• Implantable Collamer lens (ICL): In younger people, an artificial lens is usually implanted in addition to the eye's natural lens.
• Refractive lens exchange (RLE): The eye's natural lens is replaced by an artificial lens. But the eye can't adjust that lens for looking at very close objects, either, because it is rigid (similar to age-related farsightedness), so you will still need reading glasses after the procedure. To avoid that, a multifocal lens can be implanted that corrects presbyopia at the same time. Lens exchange is more commonly performed in older people who already also have presbyopia.

The procedures are usually only an option when the refractive power is stable, which is why it’s not an option for children because their eyes are still growing. Lens surgery is not recommended for pregnant or breastfeeding women, either, because the shape of their cornea may change temporarily.

Lens implantation (ICL) is not possible if you have certain existing medical conditions, such as glaucoma with a severely restricted field of vision. Damage to the cornea, e.g. caused by illnesses or injuries, also means that ICL might not be possible. But lens exchange (RLE) is often still possible.

What does lens surgery involve?

The surgery is typically done as an outpatient procedure in a clinic or specialist eye surgery practice. Your eyes will be thoroughly examined there in the days leading up to the surgery.

Your eyes will be numbed with drops first so that you are not in any pain during the operation. A local anesthesia injection is sometimes also given below the eye. You can also ask to be given a sedative – or general anesthesia. Your eyelids are held open during the operation by what is known as an eyelid speculum.

What happens afterwards depends on the specific procedure being carried out, with both involving the implantation of an artificial intraocular lens (IOL):

• Implantable Collamer lens (ICL): A small incision (cut) has to be made in the cornea. An artificial lens is inserted through this cut and then implanted behind or in front of the iris.
• Refractive lens exchange (RLE): Ultrasound is used to first break down your eye’s natural lens. A laser is can also be used, but this is less common. The lens is then suctioned out through a small incision in the edge of the cornea. An artificial lens is put in its place.

Both procedures only take a few minutes, and you can go home again after a few hours. The incision in the cornea is usually so small that it doesn’t need to be sewn up and heals by itself within a few weeks.

Experts recommend not having surgery on both eyes on the same day, but instead waiting a couple of days in between, just in case there are any complications.

What are the possible complications?

If you have severe farsightedness, side effects are less common in lens surgery than in laser surgery. But bleeding and wound healing disorders can still occur, or the artificial lens can become dislodged. If the cornea is damaged it may cause redness, pain, or warping of the cornea. Vision at twilight can also be impaired, because the eyes are very sensitive to light or you see bright rings (halos) appear around sources of light. Complications like that normally don’t have any lasting effects. But they can make eyesight temporarily worse and make further treatment necessary.

Sometimes, farsightedness is not corrected enough, or it is over-corrected. The remaining refractive error can then usually be corrected with follow-up laser surgery. In particular, that can be necessary if you have severe farsightedness.

Other possible complications of lens surgery include:

• Clouding of the eye’s natural lens (cataract) or behind the artificial lens (secondary cataract, also known posterior capsule opacifcation). That causes gradual loss of sight.
• Damage to the iris, causing the pupil to be constantly dilated. Vision in the affected eye is blurred and more sensitive to light.
• Eye infection, causing pain or redness in the eye, swelling, or much worse eyesight.
• Detached retina – this causes various vision problems such as flashes of light, bright streaks, dark patches, or shadows in your field of vision. It can also lead to loss of sight in one eye.
• Sudden increase in the pressure inside your eye (intraocular pressure). That is a rare type of glaucoma called acute closed-angle glaucoma. The signs include sudden, severe pain and red eyes, headaches, nausea and vomiting, and sometimes also impaired vision.

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Seek help from an eye doctor immediately if you notice signs of infection, detached retina or acute closed-angle glaucoma. Blindness may result without swift medical attention.

It is not possible to say with any certainty exactly how often these various complications occur following lens surgery.

What do you need to be aware of after laser surgery and after lens surgery?

Your vision will be worse for a few days after the procedure because your eye will still be irritated. Your vision may still vary in the first few weeks until your eye has become acclimatized.

After lens surgery you will have to wear an eye bandage or protective contact lens, and after LASIK you will need an eye patch for sleeping. In the first few days after surgery it’s important not to rub your eyes so that they can heal well. You should make sure that no water, shampoo or soap gets in your eyes when showering or washing your hair. You should avoid physical exertion for about one week.

Depending on the procedure, you will have to use eye drops for about 1 to 4 weeks to prevent infection. If needed, tear substitutes can help to keep your eyes moist.

You will have several check-ups in the days and weeks following the procedure to check that your eyes are healing well. It is advisable to have a check-up once a year after lens surgery.

Depending on your job, you might not be able to work for about one week after the procedure. People who sit a lot at work can normally go back sooner; it can take a bit longer for people who do physically demanding work or who have to read a lot. But because the procedure is not medically essential, you have to take vacation and can't take sick leave. Driving is usually possible after a few days, but that depends on how well everything heals. It is best to talk to your eye doctor about that.

Are the costs for surgery covered by health insurance?

The costs for laser surgery or lens surgery are not covered by statutory health insurance in Germany because it is not classified as being medically essential. The costs vary widely. Depending on the method used, the hospital or clinic you go to, and your individual circumstances, the cost per eye can range from several hundred to several thousand euros.

You also have to pay for consultations and check-ups before and after surgery yourself.

But health insurers usually cover the costs of any complications requiring treatment.

Sources

• Kommission Refraktive Chirurgie (KRC), Berufsverband der Augenärzte Deutschlands (BVA), Deutsche Ophthalmologische Gesellschaft (DOG). Bewertung und Qualitätssicherung refraktiv-chirurgischer Eingriffe durch die DOG und den BVA – KRC-Empfehlungen. 2024.
• Lang GK. Augenheilkunde. Stuttgart: Thieme; 2014.
• Pschyrembel Online. Intraokularlinse (IOL). 2020.
• Settas G, Settas C, Minos E, Yeung IY. Photorefractive keratectomy (PRK) versus laser assisted in situ keratomileusis (LASIK) for hyperopia correction. Cochrane Database Syst Rev 2012; (6): CD007112. [PMC free article: PMC7388917] [PubMed: 22696365]
• Shortt AJ, Allan BDS, Evans JR. Laser-assisted in-situ keratomileusis (LASIK) versus photorefractive keratectomy (PRK) for myopia (Review). Cochrane Database Syst Rev 2013; (1): CD005135. [PMC free article: PMC11848121] [PubMed: 23440799]

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