Laser eye surgery is one of the methods of refractive surgery. Refractive eye surgery refers to surgery performed by an ophthalmologist to correct the blurred vision caused by various refractive errors of the eye (such as myopia, hyperopia and presbyopia). The goal of these surgeries is to eliminate the need for glasses or at least to reduce it. The most widely used surgical method today is laser eye surgery, in which the shape of the cornea (the transparent front surface of the eye) is altered using a laser. Refractive errors are also corrected with various lens surgeries. In 2018, an estimated 12,000 laser surgeries and 5,500 presbyopia-correcting lens surgeries were performed in Finland.

Laser eye surgery and refractive surgery

Laser surgeries are usually used to correct refractive errors, myopia and astigmatism in young people, for example in those who have problems with contact lenses. Laser technology reshapes the cornea so that the patient’s refractive error can be corrected. Modern lasers are also precise in correcting hyperopia, but hyperopia is associated with somewhat more limitations. With the latest laser techniques, in addition to refractive errors, presbyopia can also be corrected safely. This is because, after about the age of 40, the most common laser surgery methods do not correct near vision, unless monovision is used (one eye sees far and the other near) or a method specifically designed for correcting presbyopia is used. In addition to ordinary refractive errors, lasers can also be used to correct problems caused, for example, by various corneal diseases, injuries and surgeries, such as anisometropia and astigmatism. You can find more information about the different refractive errors in the separate article on refractive errors of the eye.

Due to the growth of the eye, the final refractive power may still change during adolescence. Most typically, the progression of refractive errors slows down significantly after the age of 25. For this reason, surgeries are preferably performed on those over 20 years of age, and under no circumstances on those under 18. Certain long-term or eye diseases may also be a contraindication for refractive surgery. Laser surgeries are precise roughly between +5 and -10 diopters. With lenses placed inside the eye and artificial lenses, even larger refractive errors can be corrected. Sometimes, in extreme cases, it may be necessary to resort, for example, to a combination of lens surgery and laser surgery in order to correct large refractive errors, even those exceeding -20D.

Because refractive errors can also be corrected with glasses and contact lenses, refractive surgery is not covered by public health care. In the private sector, on the other hand, laser eye surgery is one of the most common eye operations.

Laser eye surgery and refractive surgery – how it is performed

During eye surgery, the patient lies on their back under a surgical microscope. At the beginning of the surgery, the eye is anaesthetised pain-free with eye drops. The eyelids are held open with lid retractors. During the eye surgery, the patient usually looks at a blinking target point. The laser phase of the laser surgery usually lasts only a few seconds, and the whole procedure is over in about 15 minutes. In laser surgery, only the surface of the eye is treated, whereas in lens surgery the surgeon goes behind the cornea, into the anterior chamber of the eye. Patients’ experiences of lens and laser surgeries are very similar.

The most traditional and oldest laser surgery method is PRK (photoreactive keratectomy). In this surgery, the surface cells of the cornea are first removed and then the refractive error of the cornea is corrected with an excimer laser directly on the surface of the cornea. Nowadays this method is most often used only in corrective surgeries for other methods. However, the method is associated with a greater tendency for regression, i.e. the return of the refractive error, than other current methods. In addition, the eyes must be protected from UV light for about a year because of the risk of haze (a scar formation that clouds the cornea), which some find burdensome. Haze can be prevented with mitomycin treatment (a cytostatic drug). After the surgery, vision stabilises more slowly than with other methods, and because of the removal of the surface cells, the operated eye is usually somewhat tender during the first days following the surgery.

In femto-LASIK (laser in situ keratomileusis), a flap is cut into the cornea with a femtolaser; the flap is lifted and the refractive error is corrected under the flap with an excimer laser. The method is painless and vision recovers quickly. Thanks to the eye-movement tracking system, the correction of even large astigmatism is safe. Because a flap is made in the eye in this method, it is not suitable, for example, for those who engage in contact sports such as boxing, but the surgery is suitable for a large part of the population, because it can correct even large refractive errors and the method is suitable for both myopic and hyperopic patients.

Supracor is a surgery performed with the femto-LASIK technique, with which, in addition to ordinary refractive errors, presbyopia can also be corrected. The surgery is also suitable for eyes in which a cataract has already been operated on. In the surgery, the cornea is reshaped so that, in addition to correcting the refractive error, an area for near vision is formed in the centre of the cornea. Compared with monovision, the distance vision of the reading eye does not deteriorate as much, but the method still achieves good reading vision in addition to good distance vision in a large proportion of cases.

The most popular laser surgery technique in Finland at the moment is ReLEx Smile (small incision lenticule extraction). In Smile surgery, no flap is made; instead, a lenticule drawn with a femtolaser, i.e. the desired area, is removed through a small incision. Recovery from Smile surgery is fast, and the surgery is also suitable for those who engage in contact sports. Eye dryness after Smile surgery is less than with other laser procedures. With the Smile technique, however, hyperopia cannot yet currently be corrected. The speed of the method, the rapid recovery and its suitability for all kinds of hobbies have made the procedure an excellent option for a large proportion of patients.

In eyes that are not suitable for laser surgery, the refractive error can be corrected by using various lenses. In young people, whose own eye still has its accommodation, i.e. focusing ability, intact, the refractive error can be corrected with an ICL lens (Implantable Collamer Lens) placed inside the eye, resembling a contact lens. The lens is placed on top of the eye’s own accommodating natural lens, behind the iris. With this technique, refractive errors can be corrected even between +10 D and -18 D. Almost all refractive errors, even large ones, can be corrected by combining ICL surgery with laser surgery.

When the accommodation of the eye’s own natural lens ends after about the age of 50 and presbyopia reaches its full effect, lens surgery can be performed using the cataract surgery technique. In this case, a lens usually made of acrylic plastic is placed in the lens capsule of the eye’s natural lens. In cataract surgery, myopia, hyperopia and presbyopia can all be corrected. With the help of multifocal lenses, even a person over 50 can therefore manage even completely without glasses.

Benefits and risks of laser surgery

Before surgery, the aim is to ensure that the person’s refractive error is stable, i.e. unchanging. Refractive surgery performed in a stable situation increases the likelihood that the surgery will be beneficial for years to come. The chosen surgical method also matters. Some methods, such as PRK, have a slightly greater tendency for regression compared with other procedures. It must be remembered that a patient who has, for example, a -9 diopter refractive error is completely dependent on glasses or contact lenses and finds it really difficult to function if, for example, the glasses break suddenly or a contact lens falls out of the eye, and cannot manage at all without glasses in places such as a swimming hall. If in such a case the good result of laser surgery settles at, for example, -1 diopter, the patient’s quality of life is still better than before, because with a -1 D refractive error one manages well in normal everyday life even without glasses. Sometimes the goal of surgery is not even complete freedom from glasses, but rather to make everyday life easier by reducing the strength of the glasses. When studying the durability and effectiveness of surgical results, about 6% of patients wish for corrective surgery over a 10-year follow-up period.

Laser surgeries are extremely precise and the desired result is achieved in the majority of cases. Based on studies, regardless of the surgical method, a result within +-1 diopter is achieved in over 98 percent of cases. The larger the correction, the greater the risk of needing corrective surgery and, correspondingly, the smaller the correction, the less likely corrective surgery is needed. In addition to visual acuity, important matters are the quality of vision and the absence of symptoms. All laser surgery methods can increase eye dryness, especially during the weeks following the surgery. According to studies, however, this decreases significantly during the year after the surgery. In the surgeries, only a certain part of the cornea is treated, and as a result of the surgeries phenomena affecting the quality of vision may appear, such as ghost images, halo light phenomena and fluctuation in visual acuity. In the newest laser devices, the drawbacks of light phenomena caused by the procedure have been significantly reduced compared with older lasers. Visual disturbances, however, usually ease significantly over time on their own through neuroadaptation, i.e. adjustment. Symptoms can also be relieved with various methods such as artificial tears and temporary glasses.

Although laser surgeries are among the safest types of eye surgery, they too are associated with possible adverse effects. Bacterial infections, i.e. inflammations, are guarded against with antibiotics and good sterility, i.e. cleanliness. The risk of a bacterial infection in laser surgery is of the order of 0.01-0.05%. Compared, for example, with the incidence of serious contact lens infections (over 500 per year in the HUS region), the risk of infection is extremely rare. In rare cases (in about 0.5% of surgeries), surface cells of the cornea may end up in the surgical wound, in which case cleaning of the area with an additional procedure may be needed. The most feared and nowadays fortunately extremely rare complication is ectasia, i.e. a bulging of the cornea, in which, as a result of the treatment of the cornea, the structure of the cornea weakens so that it begins to bulge outward, causing a change in refractive power and astigmatism. For this rare complication (incidence about 0.06%), there is nowadays also a targeted treatment, corneal cross-linking. Corneal cross-linking given in time halts the progression and strengthens the cornea.

After laser eye surgery or refractive surgery

Laser eye surgery is a day-surgery procedure, i.e. the patient is discharged home on the same day as the surgery. After the procedure, vision is often blurry and unclear for at least a few hours, and it is therefore advisable to go home from the surgery with an escort. The doctor who performed the surgery gives instructions for follow-up care at home. Usually eye drops are administered to the eyes for 1-4 weeks after the surgery.

As a rule, there are two or three follow-up check-ups with the ophthalmologist within six months of the surgery. Usually the final vision stabilises within a few months.

Reimbursements

Refractive and laser surgeries are performed mainly in the private health care sector. It is possible to receive a Kela reimbursement for the preliminary examination visit. A Kela reimbursement for the surgery is only granted if the person has a disease or injury that prevents the use of both framed glasses and contact lenses, as well as one of the following: myopia of at least -10.0 diopters, hyperopia of at least +6.0 diopters, anisometropia of at least 3.0 diopters or astigmatism of at least 3.0 diopters.