LASIK is a popular procedure designed to provide permanent correction for common vision errors like nearsightedness, farsightedness, and astigmatism. It works by reshaping the cornea, the transparent front surface of the eye, so light focuses correctly onto the retina. The success of this surgery relies on having an accurate and unchanging vision prescription, which is why a history of prescription changes often disqualifies a person from getting LASIK.
Why Vision Stability Is Mandatory for LASIK
LASIK uses a laser to permanently alter the curvature of the cornea, basing the correction on the refractive error measured at the time of surgery. If the eye’s natural focusing power continues to change after the procedure, the vision correction will become inaccurate over time. This leads to a return of blurry vision and dissatisfaction with the result.
The industry standard for a stable prescription requires no significant change for 12 to 24 months before the procedure. A significant change is defined as a shift of more than 0.5 diopters in the spherical or cylindrical measurement. Ensuring stability minimizes the risk of needing an enhancement surgery, which involves a second procedure to fine-tune the result.
Factors That Cause Prescription Fluctuations
Instability in a vision prescription can be attributed to several biological and systemic factors, often requiring a patient to wait until the underlying cause resolves or stabilizes. Eye growth during youth is a common factor, as prescriptions for nearsightedness often worsen until the eye has completed its development, typically in the mid-twenties. Performing LASIK too early means the correction would be quickly negated by this natural growth.
Hormonal changes also affect the eye’s shape and refractive error, making conditions like pregnancy and breastfeeding temporary contraindications for the surgery. Fluctuating hormone levels can cause the cornea to swell slightly, altering its curvature and leading to temporary vision shifts. Certain medications, including some steroids or those affecting fluid balance, can also temporarily impact vision.
Underlying health issues, most notably uncontrolled diabetes, are another source of prescription instability. High blood sugar levels can cause fluid to shift into and out of the eye’s lens, leading to significant and unpredictable changes in vision. Similarly, certain autoimmune conditions can affect the eye’s surface or internal structures, introducing instability that must be managed before any elective eye surgery is considered.
How Eligibility Is Clinically Determined
The process of determining LASIK eligibility goes beyond simply asking a patient about their prescription history. The surgeon’s team meticulously reviews refraction history, often requiring records from the previous two to three years to confirm the absence of a progressive change. This documented history is essential to verify that the patient meets the standard of stability.
Sophisticated imaging techniques like corneal topography are used to create a detailed map of the corneal surface and its curvature. This map is crucial for planning the precise laser treatment and detecting progressive corneal diseases like keratoconus. Keratoconus causes the cornea to thin and bulge, leading to rapid prescription changes. Pachymetry, a test that measures corneal thickness, is also performed to ensure there is enough tissue for safe correction.
Other factors unrelated to the prescription, such as the size of the pupil in dim light and the health of the tear film, are also assessed. A severe case of dry eye can compromise the healing process and is often a temporary or permanent reason for disqualification. These clinical measurements are used to build a complete profile of the eye’s health and stability before surgery can be approved.
Alternative Paths for Unstable Vision
For individuals disqualified from LASIK due to an unstable prescription, the most common path is monitoring and waiting. If the instability is related to age, such as being in the early twenties, or a temporary factor like a hormonal change, the prescription will likely stabilize with time. The patient is advised to return for re-evaluation once their prescription has remained consistent for the required time frame.
If the instability is deemed permanent or the patient is otherwise not a candidate, other surgical options exist. Photorefractive Keratectomy (PRK) is a procedure similar to LASIK that involves reshaping the cornea’s surface without creating a flap. PRK is sometimes preferred for patients with thinner corneas, though stability is still necessary for a successful outcome.
Implantable Collamer Lenses (ICLs) offer a different approach, involving implanting a small lens inside the eye without altering the corneal tissue. ICLs are often recommended for patients with very high prescriptions or corneas that are too thin for LASIK. For those with underlying systemic conditions, such as diabetes, the primary action is to work with their physician to achieve strict control over their health before any elective eye surgery.