LASIK (synonym: laser in situ keratomileusis) is currently the most popular procedure for the treatment of an existing refractive error in refractive surgery (laser eye surgery for the treatment of refractive anomalies – myopia and hyperopia, see below). A decisive part in the development of LASIK was played by the Colombian professor José Ignacio Barraquer (1916-1998), who has been constantly developing refractive surgery since the 1940s. In the treatment of myopia (nearsightedness), this method has been successfully practiced in the United States and Europe for more than 15 years.
Indications (areas of application)
- Myopia – nearsightedness; from 2-8 dpt.
- Hypermetropia – farsightedness; up to 4 dpt.
- Astigmatism – imaging error of the human eye, which leads to a reduction in visual acuity; up to 4 dpt.
Contraindications
- Too much need for correction or too much ablation of the cornea.
- Diseases of the cornea – keratitis (corneal inflammation).
- In advanced glaucoma – glaucoma; disease associated with an increase in intraocular pressure.
- Diabetic retinopathy – retinal disease caused by diabetes mellitus; deterioration of vision to blindness.
The surgical procedure
The modern LASIK procedure offers the possibility of being used in a wide range of refractive surgeries and is a direct evolution of PRK (photorefractive keratectomy – oldest technique in the treatment of refractive anomalies). Originally, the use of LASIK was intended to eliminate the risk of scarring, which was a feared complication of PRK in rare cases. LASIK is of important diagnostic significance especially in the treatment of myopia (nearsightedness – defective vision, which can be due both to an elongation of the bulb (eyeball) and to an increased refractive power of the anterior parts of the eye) up to – 10 dpt (diopters; measure for determining the refractive power of the eye) and is considered a scientifically recognized procedure. The same applies to hypermetropia (farsightedness – also a defective vision based on a change in the length of the bulb. In contrast to myopia, however, in this case the bulb is shortened, so that the relationship between refractive power and bulb length results in reduced vision) and astigmatism (astigmatism of the cornea) up to 3 dpt. The use of LASIK for myopia over – 10 dpt and hypermetropia over 5 dpt is in the clinical trial stage. Although the application of LASIK is very effective and gentle for the patient, since it can be performed on an outpatient basis under local anesthesia (local anesthesia) of the eye, and therefore the risks of anesthesia (damage to the teeth, nausea, vomiting, etc.) are drastically reduced, not every patient is suitable for the treatment. The procedure of the outpatient surgery is as follows:
- In order for an ophthalmologist to consider LASIK surgery as a treatment for refractive error, the above limiting factors must be excluded. To determine the corneal thickness, an ultrasound pachymeter (measurement by placing the ultrasound head on the cornea) is used to examine the patient.
- At the beginning of the procedure, the cornea is anesthetized with eye drops so that analgesia (prevention of pain sensation) is achieved.
- Under this drip anesthesia, a microkeratome (corneal plane) is usually used to make an incision between 8 to 10 mm round. The area cut out is called the flap and is still connected to the cornea on one side (hinge) so that the flap can be “folded over” in one direction.
- Subsequently, by using the excimer laser (excimer laser ablation is based on the principle of generating electromagnetic radiation for the surgical treatment of refractive anomalies), the now exposed corneal tissue is ablated and thus the cornea is modeled. This makes it possible to correct the refractive error. By flattening the cornea in the center, myopia is corrected and by the annular ablation of corneal tissue around the center, hypermetropia is corrected.
- After putting back the flap, the interface is cleaned with irrigation fluid.
- Due to the physiology of the eye, after a few minutes, the previously excised corneal lamella is aspirated and the wound healing process of the eye allows a rapid scarless fusion of the corneal parts.
Possible complications
- Microperforations – minor perforation of the cornea due to the deep incision.
- Delay of wound healing
- Pain during wound healing
- Fluctuations in corneal curvature – this leads to changes in visual acuity.
- Light sensitivity and slight glare
- “Dry eye” / eye dryness
- Double vision *
- “Glare” (excessive light propagation from reflective objects) *
- “Halos” (light rings around light sources) *
- “Starburst” (rays around point light source as in photos) *
* ≥ 1 of the symptoms was reported by 43% of patients in the PROWL-1 study and by 46% of patients in the PROWL-2 study.
Benefit
As a logical evolution of PRK, LASIK represents a rapid procedure in refractive surgery that can be performed on an outpatient basis. The benefits of this technique include:
- Computer-controlled high-precision laser treatment without damage to the underlying tissue.
- Good predictability in the above scope of myopia, hypermetropia and astigmatism.
- Fast and painless healing
- Immediate improvement in visual acuity (vision) and only a minimal risk of losing the effect of successful laser treatment
- Possibility of repeating the procedure if the results are not completely satisfactory.
- Even less common than the need for recorrection is the occurrence of complications associated with worsening visual acuity (0.1% of all surgeries).