Introduction
Refractive surgery is a type of eye surgery performed to improve the refractive error (unable to focus light appropriately) of the eyes. It is indicated in myopia (nearsightedness), hyperopia (farsightedness), astigmatism (blurred vision), and presbyopia (inability to focus on nearby objects due to reduced flexibility) cases. Refractive surgery was first developed by Jose Barraquer in 1963. However, over the past decade, refractive surgery has evolved with various advanced techniques and is an appropriate vision corrective option for patients. The goal of this surgery is not only to reshape the cornea (clear dome-shaped portion of the eye) but also to reduce the requirement for glasses or contact lenses.
How Is Refractive Surgery Performed?
Refractive surgery, also known as vision correction surgery, is performed to improve the focus of the light by reshaping the cornea, thus providing better visibility to the patient. It is done to reduce the dependency on contact lenses or glasses. Recently, refractive procedures have been classified as corneal procedures and lens-based surgery. A complete medical history and a detailed eye examination are conducted and are mandatory for all patients undergoing refractive surgery. Patients must be above 18 years of age with a stable refractive error. Before the procedure, the eye is made numb by applying eye drops but kept open by an eye speculum. The specialist's surgical technique depends on the refractive error and its severity. After the surgery, the eyes may itch or pain. Therefore, pain relief medicines are prescribed to reduce discomfort to the patient, and follow-up is recommended after one or two days. Refractive surgery is considered to be reliable and associated with very minimal complications.
What Are the Innovations in Refractive Surgery?
Swift advances in surgical methodologies have enhanced the safety and efficacy of refractive surgery and promised optimum results. Some of the recent innovations in refractive surgery include:
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Laser In Situ Keratomileusis (LASIK): It is the most commonly performed eye surgery where a special type of laser is used to change the shape of the cornea. Approved by the Food and Drug Administration (FDA), LASIK is a second-generation laser surgery that effectively corrects visual defects. During this surgery, a flap of corneal tissue is created using a mechanical microkeratome (small blade) or a femtosecond laser. The flap is then turned back, and the underlying tissues are photo-ablated (vaporizing tissues) with an excimer laser. The surface epithelium is not disrupted, and the flap is replaced without suturing. It is employed in patients with myopia, hyperopia, and astigmatism but may be associated with complications such as flap problems, over-corrections, under-corrections, double vision, and dry eyes.
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Small Incision Lenticule Extraction (SMILE): In this technique, a small peripheral corneal incision (cut) is made, and a thin layer of intrastromal lenticule of tissue is removed using a femtosecond laser. It is recommended for myopia and myopic astigmatism. The safety and efficacy of SMILE are similar to that of LASIK but have the additional benefit of reduced corneal denervation and accelerated corneal nerve regeneration. However, the drawback of this procedure is the requirement for additional surgeries to correct the residual refractive errors.
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Photorefractive Keratectomy (PRK): In this type of surgery, unlike LASIK, a corneal flap is not created, but the corneal epithelium is removed, and the anterior curvature of the corneal bed is sculpted using an excimer laser. A protective lens is placed in the area until the epithelium regrows. The first-generation laser procedure is beneficial for patients with astigmatism, myopia, and hyperopia. It is also preferred in patients with thin corneas or in epithelial membrane dystrophy (weakness) cases. The procedure is associated with an increased potential for corneal haze formation, and the patient is instructed to use corticosteroid drops for several months following the surgery. The intraocular pressure also needs to be monitored regularly in the postoperative period due to the risk of corticosteroid-induced glaucoma. It is associated with postoperative discomfort for two to three days, and visual recovery usually takes longer than other procedures.
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Phakic Intraocular Lenses (IOLs): These are intraocular implants (artificial lenses) used as an alternative to laser correction in treating patients with moderate to high myopia with or without astigmatism. The phakic intraocular lens is inserted anterior or posterior to the iris (the colored part of the eye) through a small incision, but the natural lens is not removed. The advantages are that there is no need to alter the corneal curvature, unlike laser surgery, and it provides superior visual quality without the risk of corneal ectasia. However, it may be associated with infection, inflammation (swelling), cataracts (clouding of the lens), and glaucoma (damage to the optic nerve).
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Refractive Lens Exchange (RLE): It is similar to a cataract surgery wherein the specialist makes a small incision at the edge of the cornea, removes the natural lens, and replaces it with an implant. It is recommended in severe cases of myopia, hyperopia, or other corneal abnormalities. This method can also be combined with LASIK to correct astigmatism. In patients with presbyopia, a multifocal lens replaces the natural lens, which helps see both near and far objects. This technique is called presbyopic lens exchange (PRELEX).
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Corneal Inlays: These implants are made of polyvinylidene fluoride and carbon, with a small aperture, and are inserted into the corneal stroma by creating a flap. It is indicated in presbyopia (non-dominant eye) and is known to improve near vision by increasing the focus depth. However, it includes certain complications such as dryness of the eyes, epithelial tissue ingrowth, and the requirement of long-term use of topical corticosteroids.
What Are the Benefits of Refractive Surgery?
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Refractive surgeries are proven to be safe and effective, with well-documented results in a majority of people.
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It provides clear vision, reducing the reliability of glasses or contact lenses.
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These surgeries are associated with minimal postoperative infections or discomfort.
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The advantages of LASIK surgery include minimal postoperative pain and a shorter rehabilitation period.
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The stability and biomechanical strength of the cornea are preserved, and dryness of the eyes is significantly lower in the SMILE surgery.
Conclusion
Refractive errors are common ophthalmic abnormalities reported in clinical practice and may be associated with significant morbidity. Refractive surgery is an evolving field, and recent advances in operative techniques have resulted in accurate vision correction and patient satisfaction. Recovery time depends on the surgical technique and can vary from weeks to months. However, careful patient selection, expertise in planning, execution of appropriate surgical techniques, and regular follow-ups can result in better treatment outcomes and prevent complications.
