Nearsightedness, medically known as myopia, is a common refractive error where vision is clear up close but blurry at a distance. This condition occurs because the eyeball grows slightly too long from front to back, or the cornea is excessively curved. In a myopic eye, incoming light rays converge to a focal point in front of the retina instead of directly on its light-sensitive surface. This misalignment causes distant objects to appear indistinct. Intervention is needed to restore clear distance vision.
External Corrective Lenses
The most widely used and non-invasive approach to correcting nearsightedness involves placing a concave lens in front of the eye. These external lenses—in the form of prescription eyeglasses or contact lenses—work by diverging, or spreading out, the light rays just before they enter the eye. This strategic divergence moves the light’s focal point backward, ensuring it lands precisely on the retina. The power of these corrective lenses is measured in diopters, always indicated with a minus sign on a prescription to denote their concave shape and light-diverging function.
The material composition of eyeglass lenses influences their thickness and weight, especially for higher prescriptions. Standard lenses are often made from CR-39 plastic, which results in thicker edges for myopic correction. Lighter, more impact-resistant options include polycarbonate and Trivex. For very high prescriptions, high-index plastic lenses are preferred because they bend light more efficiently, allowing the lens to be manufactured thinner and lighter.
Contact lenses operate on the same optical principle but sit directly on the cornea, offering a wider field of view. They are categorized into soft and rigid gas permeable (RGP) types. Soft lenses, made from hydrogel or silicone hydrogel materials, are the most common choice due to their comfort and flexibility. Silicone hydrogel allows a greater amount of oxygen to reach the cornea, supporting eye health.
RGP lenses are smaller, more durable, and provide sharper vision than soft lenses because they maintain a consistent shape. They are custom-made from oxygen-permeable materials. Their rigidity makes them effective for correcting moderate to severe astigmatism that often accompanies myopia. Both soft and RGP lenses are available in daily disposable or planned replacement schedules, but they must be worn consistently to maintain clear vision.
Laser Refractive Surgery
Surgical procedures that reshape the cornea using precise laser technology offer a permanent solution for nearsightedness. This approach reduces the cornea’s excessive curvature, diminishing the eye’s focusing power and moving the light’s focal point onto the retina. The three primary methods are Laser-Assisted In Situ Keratomileusis (LASIK), Photorefractive Keratectomy (PRK), and Small Incision Lenticule Extraction (SMILE). Candidates must have a stable prescription, be over a certain age, and possess adequate corneal thickness.
LASIK is the most widely known procedure, characterized by rapid visual recovery. A femtosecond laser creates a thin, hinged flap in the outer layer of the cornea. This flap is lifted to expose the underlying stromal tissue. An excimer laser then precisely ablates microscopic amounts of stromal tissue to flatten the cornea and correct the refractive error. The flap is repositioned, adhering naturally without stitches, allowing for minimal discomfort and often clear vision within 24 hours.
PRK is a flap-free procedure where the outer epithelial layer of the cornea is removed before the excimer laser treatment begins. Applying the laser directly to the corneal surface makes PRK a safer option for patients with thin corneas, as it preserves more stromal tissue than LASIK. The trade-off is a longer healing period, as the epithelium must fully regenerate, a process taking several days to a week. Patients may experience more initial discomfort, though the long-term visual outcomes are comparable to LASIK.
SMILE is a minimally invasive, flap-free alternative. A femtosecond laser creates a small, lens-shaped piece of tissue, known as a lenticule, entirely within the intact cornea. This lenticule is then removed through a small, keyhole-sized incision, typically less than four millimeters long. Because the procedure avoids a large flap and preserves more corneal nerves, SMILE may be associated with a lower risk of post-operative dry eye compared to LASIK.
Specialized and Implantable Correction
For individuals who are not ideal candidates for external lenses or laser surgery—such as those with high prescriptions or specific corneal conditions—specialized and implantable options provide alternatives. These methods include Orthokeratology and the surgical placement of Phakic Intraocular Lenses. Both techniques offer vision correction without permanently altering the corneal tissue or requiring daytime corrective eyewear.
Orthokeratology (Ortho-K) is a non-surgical method involving wearing specially designed rigid gas permeable contact lenses only while sleeping. These custom-fitted lenses apply gentle forces to the tear film, temporarily reshaping the cornea’s outermost layer, the epithelium. Upon waking, the lenses are removed, and the cornea retains its corrected shape, allowing for clear vision throughout the day. Since the effect is temporary, the lenses must be worn nightly to maintain correction.
Phakic Intraocular Lenses (ICLs) represent a permanent surgical option that does not involve removing or reshaping corneal tissue. These lenses are made from a biocompatible material and are surgically implanted inside the eye, typically positioned between the iris and the natural lens. ICLs function as an internal contact lens, adding focusing power to the eye’s natural optical system. This procedure is recommended for patients with high levels of nearsightedness outside the range for laser surgery, or for those with thin corneas.