Vision correction surgery, such as Laser-Assisted In Situ Keratomileusis (LASIK), is a common way to reduce or eliminate the need for glasses and contact lenses. LASIK works by creating a thin, hinged flap on the cornea, which is lifted so a laser can reshape the underlying tissue before the flap is returned. While highly effective, this technique is not suitable for everyone, particularly individuals with corneas that are too thin or those with certain dry eye concerns. For those who are not candidates for standard LASIK, several established alternatives exist, ranging from different laser-based methods that avoid creating a corneal flap to procedures that involve implanting a corrective lens inside the eye.
Corneal Surface Procedures (PRK and LASEK)
Photorefractive Keratectomy (PRK) and its variation, Laser Epithelial Keratomileusis (LASEK), are the oldest forms of laser vision correction and are considered when LASIK is unsuitable. These surface ablations reshape the cornea without creating a permanent flap. This approach is recommended for patients with corneas too thin for LASIK, or for those in high-impact professions, such as military personnel or athletes, where a corneal flap could be at risk of dislodgement.
The methodology involves removing the cornea’s outermost protective layer, the epithelium, before an excimer laser precisely sculpts the deeper corneal tissue. In PRK, the entire epithelial layer is removed and allowed to regenerate naturally over several days. LASEK is a modification where the epithelial layer is softened using an alcohol solution, gently pushed aside, and then repositioned after treatment, though the healing process remains similar to PRK.
The main trade-off for these surface procedures is a significantly longer and more uncomfortable initial recovery period compared to LASIK. Since the epithelium must heal and regrow, patients typically experience moderate discomfort, light sensitivity, and blurry vision for three to five days post-surgery. A protective bandage contact lens is worn during this initial period, and stable visual clarity may take several weeks to fully achieve. Despite the slower recovery, the final visual outcomes of PRK and LASEK are comparable to those of LASIK.
Small Incision Lenticule Extraction (SMILE)
Small Incision Lenticule Extraction (SMILE) is a third-generation laser vision correction, offering a minimally invasive, flapless approach distinct from LASIK and PRK. This procedure uses a single femtosecond laser to perform the entire correction within the corneal tissue. The laser creates a small, lens-shaped piece of tissue, known as a lenticule, inside the cornea, corresponding to the patient’s prescription.
The surgeon removes this lenticule through a tiny incision, typically less than four millimeters wide, eliminating the need for the larger flap created in LASIK. Because the small incision leaves most of the corneal surface intact, the structural integrity of the cornea is better preserved. This technique also minimizes the disruption of corneal nerves, which may lead to a reduced risk of post-operative dry eye symptoms compared to traditional LASIK.
The visual recovery time with SMILE is generally rapid, falling between the quick recovery of LASIK and the longer healing time of PRK. This procedure is currently approved for correcting nearsightedness (myopia) and astigmatism, and its small incision size makes it appealing for patients with active lifestyles.
Implantable Collamer Lenses (ICLs)
When laser-based corneal reshaping is not suitable due to an extremely high prescription or insufficient corneal tissue thickness, an intraocular surgical approach is necessary. Implantable Collamer Lenses (ICLs) are a type of phakic intraocular lens, meaning the natural lens of the eye remains in place. This procedure involves surgically placing a custom-made, biocompatible lens, made of a collagen-polymer material called Collamer, inside the eye.
The ICL is positioned between the iris and the natural crystalline lens, acting as an internal contact lens to correct vision. ICLs are beneficial for patients with high degrees of nearsightedness, sometimes correcting up to -20 diopters, which is beyond the range of most laser procedures. Since the procedure does not require the removal of corneal tissue, it is an excellent option for those with thin corneas or chronic dry eyes who are ineligible for laser surgery.
A significant advantage of ICLs is their reversibility; the lens can be removed or replaced if a patient’s vision changes or if issues arise. This flexibility, combined with the high-quality, sharp vision and improved contrast sensitivity reported by patients, makes ICLs a compelling alternative. Candidates are typically adults between the ages of 21 and 45 with a stable prescription.
Refractive Lens Exchange (RLE)
Refractive Lens Exchange (RLE), sometimes called clear lens extraction, is an intraocular procedure that focuses on the eye’s natural lens. Unlike the ICL procedure, RLE involves removing the natural lens entirely and replacing it with an artificial Intraocular Lens (IOL). This procedure is identical to cataract surgery but is performed to correct refractive errors before a cataract has developed.
RLE is typically recommended for older patients, generally those over 40 to 45 years of age, who are experiencing presbyopia (age-related loss of near focusing ability). By replacing the natural lens, RLE can address a wide range of refractive errors, including nearsightedness, farsightedness, and astigmatism, while simultaneously correcting presbyopia with a multifocal or accommodating IOL. The procedure offers the long-term benefit of preventing future cataract development, as the natural lens has been removed.
Candidates for RLE include those with high refractive errors or thin corneas who are unsuitable for laser vision correction, but the primary demographic remains those in middle age and older. The replacement IOL is permanent, providing a stable, long-lasting solution to vision correction.