Farsightedness (hyperopia) is a common refractive error where vision is clear at a distance but often blurry up close. This occurs because the eyeball is slightly too short, or the cornea is too flat, causing incoming light to focus behind the retina instead of directly on its surface. LASIK (Laser-Assisted In Situ Keratomileusis) is a procedure that reshapes the cornea with a laser to correct vision errors. This article examines the viability of LASIK for correcting hyperopia and the factors that influence the procedure’s success.
The Suitability of LASIK for Hyperopia
LASIK is technically capable of correcting farsightedness, but the procedure is generally more complex and has narrower treatment parameters compared to nearsightedness (myopia) correction. Modern excimer laser technology has improved the predictability of hyperopic LASIK outcomes, but the range of hyperopia that can be safely and effectively treated remains limited.
The procedure is most successful for patients with low-to-moderate hyperopia. Surgeons typically find the best results for prescriptions up to approximately +4.50 diopters (D), though the FDA has approved some lasers for corrections up to +6.00 D. Correcting prescriptions beyond this range often leads to a higher risk of regression, where the eye’s natural healing process reverts the cornea toward its original shape. This potential for the vision problem to return requires stringent patient selection.
The Mechanism of Hyperopia Correction
The goal of hyperopic LASIK is to increase the refractive power of the cornea so that light focuses correctly onto the retina. To achieve this, the excimer laser must reshape the cornea to make its central curvature steeper, which is the reverse of myopic LASIK.
The laser accomplishes this steepening by removing tissue in a precise ring-shaped pattern around the peripheral edges of the cornea, leaving the central tissue relatively untouched. This annular ablation causes the central cornea to steepen into the resulting space, increasing its focusing power. This reshaping must create an appropriately sized optical zone—the central area responsible for vision—to ensure clear sight.
The excimer laser uses a computer-controlled beam of ultraviolet light to vaporize targeted corneal tissue without causing thermal damage. The depth and width of the ablated ring are calculated based on the patient’s prescription to deliver the required increase in central curvature. A typical optical zone for hyperopic correction is around 6.5 millimeters, often combined with a transition zone extending the total treatment area to 9.0 millimeters.
Factors Limiting Successful Correction
Physiological and prescription constraints make candidate selection for hyperopic LASIK restrictive. The most significant limitation is the magnitude of the hyperopia, as high prescriptions demand pronounced steepening of the central cornea. This excessive reshaping requires more peripheral tissue removal, which can lead to biomechanical instability and increase the likelihood of regression.
The eye’s healing response is also a concern. Healing often involves epithelial remodeling, where the outermost layer of the cornea fills in the ablated peripheral zone. This remodeling can neutralize the achieved correction, leading to a high rate of enhancement (touch-up) procedures. Furthermore, the large amount of peripheral tissue removal can result in a smaller effective optical zone, which may induce higher-order aberrations. Patients with large pupils may experience glare, halos, or reduced contrast sensitivity at night because their pupils dilate beyond the treated zone.
The patient’s age and the presence of presbyopia also complicate correction. Presbyopia is the natural age-related loss of near focusing ability, which hyperopia correction can exacerbate. Correcting distance vision in an older individual can eliminate their remaining ability to focus up close. Surgeons must carefully manage this distance and near vision trade-off, often by intentionally under-correcting the non-dominant eye for monovision.
Alternative Refractive Procedures
Individuals unsuitable for LASIK—usually due to high prescription, thin corneas, or advanced age—have several other effective vision correction options. Photorefractive Keratectomy (PRK) is a laser-based alternative that uses the same ablation profile as LASIK to steepen the cornea. PRK avoids creating a corneal flap, making it viable for those with thinner corneas, though recovery is typically longer.
A lens-based approach is often recommended for those with high hyperopia or presbyopia. Refractive Lens Exchange (RLE) involves surgically removing the eye’s natural lens and replacing it with an artificial intraocular lens (IOL). This procedure provides a stable and comprehensive correction, especially for patients over 40. Another option for younger patients with high prescriptions is the implantation of a Phakic Intraocular Lens (ICL), placed inside the eye in front of the natural lens. ICLs are an alternative because they do not require corneal tissue removal and are reversible.