Laser-Assisted In Situ Keratomileusis (LASIK) is widely known for correcting distance vision issues like nearsightedness and farsightedness. Presbyopia, an age-related condition involving the progressive loss of near focusing ability, presents a different challenge. Standard LASIK was not initially engineered to address this natural aging process. Modern technology has adapted the procedure to offer solutions for those seeking reduced dependence on reading glasses.
The Mechanics of Presbyopia and Standard LASIK
Standard LASIK cannot correct presbyopia because the procedures affect distinct biological parts of the eye. LASIK operates by reshaping the cornea, the clear, dome-shaped outer layer of the eye, using an excimer laser. This alteration changes how light is refracted onto the retina, correcting fixed refractive errors such as myopia, hyperopia, and astigmatism.
Presbyopia is not a corneal issue; it is caused by changes to the eye’s internal crystalline lens. As a person ages, typically starting in their early to mid-40s, the lens loses elasticity and the surrounding muscle weakens. This loss of flexibility, known as accommodation, prevents the eye from changing shape sufficiently to focus light from close objects onto the retina. Since standard LASIK only modifies the cornea, it cannot restore the function of the hardened internal lens.
Adapted LASIK Techniques for Near Vision
Since the lens cannot be restored by a corneal procedure, adapted LASIK techniques modify the cornea to mimic the function of a flexible lens. The most common laser-based approach is Monovision LASIK, which intentionally creates a difference in refractive power between the two eyes. The dominant eye is fully corrected for distance vision, while the non-dominant eye is left slightly nearsighted to achieve functional near vision.
This technique relies on the brain’s ability to seamlessly blend the images from both eyes, using the distance-corrected eye for far tasks and the near-corrected eye for reading. The difference in focus is subtle but sufficient to provide a functional range of vision for many daily activities. Monovision success can often be simulated beforehand using contact lenses to ensure patient adaptation.
Another advanced technique is PresbyLASIK, also called multifocal ablation, which reshapes the cornea into multiple zones of different powers. The laser applies a complex pattern to the corneal surface, creating concentric rings that provide near, intermediate, and distance focus simultaneously. Different designs exist, such as central PresbyLASIK, where the center of the cornea is corrected for near vision and the surrounding area for distance. This multifocal approach allows light rays from different distances to be focused on the retina.
The Patient Experience: Compromises and Expectations
While adapted LASIK techniques reduce the need for spectacles, they introduce specific visual trade-offs. Monovision, despite its high success rate in achieving spectacle independence, requires a period of neuro-adaptation. The visual compromise can include a reduction in depth perception, especially at intermediate distances, because the brain receives two differently focused images. Most carefully selected patients report favorable outcomes after the initial adaptation challenges.
Multifocal corneal treatments like PresbyLASIK carry compromises related to the simultaneous focus of light. Patients may experience reduced contrast sensitivity, meaning they have difficulty distinguishing an object from its background, particularly in low-light conditions. Glare and halos around lights at night are also common visual symptoms due to the concentric rings created on the cornea.
Patients must maintain realistic expectations, as these procedures aim to reduce, not eliminate, the reliance on reading glasses. While most patients can read a newspaper or check a phone without glasses, very fine print or prolonged reading may still require low-power reading glasses. The goal is functional vision across multiple distances, not the perfect vision of youth.
Non-Corneal Surgical Alternatives
When corneal reshaping is not the optimal solution for presbyopia, lens-based surgical alternatives offer a pathway to near vision correction. Refractive Lens Exchange (RLE), sometimes called Clear Lens Extraction, is similar to cataract surgery but performed on a clear, non-cataractous lens. The eye’s natural lens is removed and replaced with an artificial Intraocular Lens (IOL).
This method bypasses the problem of the hardening natural lens by replacing it with a static, non-aging implant. A variety of advanced IOLs are available to restore a range of vision. These include multifocal IOLs, which provide multiple points of focus, and Extended Depth of Focus (EDOF) IOLs, which stretch a single focal point to provide a continuous range of clear vision.
RLE is often recommended for patients with high refractive errors or those in the early stages of developing cataracts, as it treats both issues at once. Unlike LASIK, which modifies the front surface of the eye, RLE is an internal procedure that permanently addresses the source of presbyopia.