Laser-Assisted In Situ Keratomileusis (LASIK) is a precise surgical procedure that uses a laser to reshape the cornea, the clear front surface of the eye. This reshaping corrects refractive errors like nearsightedness, farsightedness, and astigmatism, allowing light to focus correctly on the retina. LASIK has provided millions of people freedom from glasses or contact lenses for distance vision.
Presbyopia is the gradual, age-related loss of the eye’s ability to focus on near objects. It typically becomes noticeable around age 40, requiring people to hold reading material farther away to see clearly. This article explores how laser eye surgery can be adapted to manage this specific age-related condition.
Why Standard LASIK Does Not Correct Age-Related Vision Loss
Standard LASIK surgery permanently alters the curvature of the cornea, which is responsible for about two-thirds of the eye’s total focusing power. It treats fixed refractive errors by sculpting the corneal tissue with an excimer laser. However, the procedure focuses only on this outermost layer of the eye and does not interact with the internal structures.
Presbyopia is caused by changes to the eye’s natural lens, which sits just behind the iris, not a misshapen cornea. As a person ages, the crystalline lens begins to harden and lose its elasticity. Concurrently, the ciliary muscles, which change the lens’ shape for focusing, lose some of their strength.
This combination means the eye loses its ability to “accommodate,” or change focus between far and near objects. Since traditional LASIK only corrects the cornea, it cannot restore the flexibility required for clear near vision. Therefore, a person who receives standard LASIK will still experience the onset and progression of presbyopia.
Corneal Laser Procedures Addressing Presbyopia
While standard LASIK does not address the cause of presbyopia, the procedure can be modified to improve near vision by altering how the cornea focuses light. These specialized techniques do not restore the natural focusing mechanism but create a functional range of vision using optical principles. The goal is achieving “spectacle independence” for most daily activities, rather than perfect vision at all distances.
Monovision LASIK
One common approach is Monovision LASIK, also known as blended vision. This technique corrects the dominant eye for clear distance vision, while the non-dominant eye is intentionally corrected for near vision. The difference in focus allows the brain to subconsciously select the clearer image for the task at hand. The brain adapts to this arrangement, blending the two images to provide functional vision across a wider range of distances.
Multifocal LASIK
Multifocal LASIK, often called PresbyLASIK, is a separate corneal laser technique. This procedure uses the excimer laser to create multiple power zones on the corneal surface, similar to a multifocal contact lens. The resulting corneal shape allows light rays from both far and near objects to be simultaneously focused onto the retina.
Determining Eligibility and Realistic Expectations
Candidacy for presbyopia-correcting laser procedures goes beyond the typical requirements for standard LASIK, such as having a stable prescription, healthy eyes, and sufficient corneal thickness. For Monovision LASIK, a necessary step is a pre-operative trial using monovision contact lenses to simulate the post-operative visual experience. This trial determines whether the patient’s brain can successfully adapt to having a distance eye and a near eye.
Patients must have realistic expectations about the outcome, which generally involves a compromise in visual quality. While the goal is to achieve independence from reading glasses for most tasks, these procedures rarely deliver sharp vision at every distance. Monovision can sometimes lead to a reduction in depth perception and may cause visual disturbances in low-light conditions.
Multifocal LASIK may also introduce visual trade-offs, such as increased glare or halos around lights at night, due to the complex nature of the corneal shape. Since presbyopia progresses over time, an enhancement or the eventual use of reading glasses for very fine print may still be necessary years later. Thorough pre-operative testing is essential for selecting the most appropriate laser profile and ensuring the best possible result.
Alternative Surgical Approaches Beyond the Cornea
When corneal laser procedures are not suitable, surgical options targeting the internal structures of the eye are available. Refractive Lens Exchange (RLE) is a procedure similar to cataract surgery, where the eye’s natural, stiffened lens is removed. This lens is then replaced with an artificial intraocular lens (IOL).
The implanted IOL can be a multifocal or extended depth of focus (EDOF) lens, designed to provide clear vision at multiple distances. RLE is often recommended for older patients, as it addresses the root cause of presbyopia by replacing the non-flexible lens and eliminates the need for future cataract surgery.