Long-sightedness, medically known as hyperopia, is a common vision condition where light focuses behind the retina instead of directly on it. This occurs because the eyeball is slightly too short or the cornea, the clear front surface of the eye, is too flat. People with mild hyperopia often see distant objects clearly, but they frequently struggle with close-up tasks, which can lead to eye strain and headaches. Laser eye surgery is an effective treatment option to correct long-sightedness, though its success depends heavily on the degree of correction required.
How Laser Surgery Reshapes the Cornea
Laser vision correction works by precisely altering the curvature of the cornea to change how light enters the eye. The goal is to ensure light rays focus exactly on the retina. For long-sightedness, the cornea needs a steeper curve to increase its focusing power, effectively pulling the focal point forward onto the retina.
This process involves using an excimer laser, which uses a cool beam of ultraviolet light to remove microscopic amounts of tissue. To steepen the central cornea for hyperopia correction, the laser removes tissue from the peripheral areas of the cornea. This contrasts with the treatment for short-sightedness (myopia), where the laser removes tissue from the center of the cornea to flatten it.
The precise removal of corneal tissue reshapes the eye’s outer lens, increasing the central curvature and allowing the eye to bend light more strongly. This change in shape is calculated using advanced imaging technology to match the patient’s prescription. Because the laser removes tissue from the periphery, the central optical zone is left steeper, achieving the necessary increased power to correct hyperopia.
Specific Techniques for Hyperopia
Two primary laser-based techniques are used to correct long-sightedness: Laser-Assisted In Situ Keratomileusis (LASIK) and Photorefractive Keratectomy (PRK). Both procedures employ the excimer laser to reshape the cornea, but they differ in the initial steps and the subsequent recovery process.
Hyperopic LASIK is the most common procedure and begins with the creation of a thin, hinged flap on the cornea’s surface, often using a femtosecond laser. The surgeon lifts this flap to access the underlying corneal tissue (the stroma), where the excimer laser performs the precise reshaping to steepen the center. Once the laser treatment is complete, the flap is repositioned, adhering naturally without the need for stitches. LASIK typically offers a rapid visual recovery, with many patients experiencing clear vision within 24 to 48 hours.
The second technique, Hyperopic PRK, is a surface ablation procedure that does not involve creating a flap. Instead, the surgeon removes the cornea’s outermost layer, the epithelium, before applying the excimer laser directly to the underlying stroma. A protective contact lens is then placed over the eye while the epithelium regenerates over several days. While PRK avoids potential flap-related risks, the healing process is slower, and vision may take several weeks to stabilize. Both procedures can achieve comparable long-term visual outcomes.
Factors Determining Patient Eligibility
Determining eligibility for hyperopia correction is complex, as the procedure is often less predictable than for short-sightedness, especially at higher prescriptions. A primary consideration is the stability of the long-sighted prescription, which must have remained unchanged for at least 12 months prior to surgery. If the prescription is still fluctuating, the visual correction achieved by the laser may regress, necessitating further treatment.
The maximum treatable prescription strength is a limiting factor for long-sightedness, more so than for short-sightedness. While some advanced lasers are approved for corrections up to +6.00 diopters, many clinics prefer to treat mild to moderate hyperopia, often limiting the range to about +4.00 diopters for reliable long-term results. Higher levels of correction require more peripheral tissue removal, which can lead to greater unpredictability, increased risk of regression, and reduced stability.
Corneal thickness also plays a role, as the procedure requires enough tissue to safely steepen the cornea without compromising its structural integrity. The primary concern is the residual stromal bed, the tissue left untouched beneath the area of correction. For a flap-based procedure like LASIK, the remaining layer must be at least 250 microns thick to prevent complications like corneal ectasia, where the cornea weakens and bulges forward.
Age is another factor, as long-sightedness correction can be complicated by the onset of presbyopia, or age-related difficulty focusing up close, which often begins after age 40. Since laser surgery addresses the shape of the cornea, it does not correct the age-related stiffening of the eye’s natural lens that causes presbyopia. Patients nearing or past this age often require a more comprehensive plan, which may include alternatives like Refractive Lens Exchange (RLE) to address both distance and near vision.