What Is a Refractive Error?
Refractive error means that the shape of your eye does not bend light correctly, resulting in a blurred image. The main types of refractive errors are myopia (nearsightedness), hyperopia (farsightedness), presbyopia (loss of near vision with age), and astigmatism.
The causes of the main types of refractive error are described below:
Astigmatism Astigmatism usually occurs when the front surface of the eye, the cornea, has an asymmetric curvature. Normally the cornea is smooth and equally curved in all directions, and light entering the cornea is focused equally on all planes, or in all directions. In astigmatism, the front surface of the cornea is curved more in one direction than in another. This abnormality may result in vision that is much like looking into a distorted, wavy mirror. Usually, astigmatism causes blurred vision at all distances.
Laser refractive surgery comprises a group of advanced ophthalmic procedures designed to correct refractive errors through precise laser reshaping of the cornea — the transparent anterior surface of the eye responsible for focusing light onto the retina. By modifying the curvature and optical power of the cornea, these procedures reduce or eliminate refractive errors such as myopia, hyperopia, and astigmatism, with the goal of improving visual acuity and minimizing or eliminating the need for glasses or contact lenses.
Modern laser vision correction techniques are classified according to the corneal layer at which the procedure is performed. The primary categories include stromal (mid-corneal) procedures, surface ablation procedures, and minimally invasive intrastromal techniques.
SMILE is a next-generation refractive surgical procedure designed for the correction of myopia and astigmatism. The technique is performed exclusively with a femtosecond laser and represents a minimally invasive alternative to traditional LASIK procedures. Unlike LASIK, SMILE does not require the creation of a corneal flap. Instead, a precise intrastromal lenticule is created within the cornea and removed through a small incision of approximately 2–4 mm.
This flapless approach preserves the biomechanical stability of the cornea, reduces disruption of corneal nerves, and significantly lowers the incidence of postoperative dry eye symptoms. The procedure is performed under topical anesthesia (eye drops), is virtually painless, and typically takes only a few minutes per eye.
Visual recovery is rapid, with most patients experiencing significant improvement within the first few days. Refractive stability is achieved in a short postoperative period. SMILE is particularly recommended for patients with moderate to high myopia and for individuals with active lifestyles, as the absence of a flap reduces the risk of trauma-related complications.
Femto LASIK is an advanced laser refractive procedure that combines femtosecond laser technology for corneal flap creation with excimer laser technology for precise corneal reshaping. The use of a femtosecond laser eliminates the need for a mechanical microkeratome, enhancing precision, safety, and uniformity of the corneal flap.
The procedure is indicated for the correction of myopia, hyperopia, and astigmatism, providing predictable and stable visual outcomes. It is performed under topical anesthesia and typically takes only a few minutes per eye. Most patients notice a significant improvement in vision within 24 hours after surgery.
Femto LASIK allows for highly customized treatment based on individual corneal measurements, optimizing visual quality and minimizing the risk of complications. The combination of advanced imaging diagnostics and laser precision ensures excellent long-term refractive results.
LASIK is one of the most widely performed and established refractive surgical procedures for the correction of myopia, hyperopia, and astigmatism. The technique involves the creation of a thin corneal flap, traditionally made using a mechanical microkeratome. The flap is gently lifted to allow an excimer laser to precisely reshape the underlying corneal stroma. After laser application, the flap is repositioned, where it naturally adheres without the need for sutures.
By reshaping the cornea, LASIK modifies its refractive power, enabling light to focus accurately on the retina and thereby improving visual acuity. The procedure is performed under topical anesthesia (eye drops), is generally painless, and typically takes only a few minutes per eye.
Visual recovery after LASIK is usually rapid, with many patients experiencing significant improvement within 24–48 hours. Long-term outcomes are stable and predictable when appropriate patient selection and thorough preoperative evaluation are conducted.
Phakic lenses implantation
People with extremely high diopter values (over -10.0 or +6.00) or corneas (transparent front part of the eye) that are too thin or irregular (diagnosed during examination) and because of it laser vision correction would expose them to the risk of complications, have an option of phakic lens implantation (Implantable Collamer Lens-ICL, or iris claw-Artisan, Artiflex) into the eyes.
Phakic lenses are implanted into the anterior eye segment (in front of or behind the pupil), without removing the natural lens and they function as a contact lens in the eye, but the patient does not feel them and does not have to take care of them.
Multifocal Intraocular Lenses
Advances in technology have incited the development of multifocal intraocular lenses that have 2 or 3 focuses and enable the patient to have good vision at different distances without glasses. Most multifocal lenses are bifocals. These lenses provide good distance vision and good near vision, but somewhat weaker vision at medium range distances (80-100 cm).
The latest generation of multifocal lenses are trifocal lenses, which with good distance vision and close vision also provide a good vision on the middle distance, which is especially important for patients that work at the computer. In Universal Eye Hospital, for many years, we use the latest and more advanced multifocal lenses available in the market.
