LASIK has measurable upper limits, set by FDA-approved diopter ranges and by how much corneal tissue a laser can safely remove. Knowing where those limits fall, and what corrects vision beyond them, matters before assuming LASIK is or isn’t an option for a strong prescription.
What’s the worst eyesight LASIK can fix?
LASIK can correct up to roughly −12.00 diopters of nearsightedness, +6.00 diopters of farsightedness, and 6.00 diopters of astigmatism under FDA-approved ranges. Those numbers mark the technical ceiling and are not a guarantee for every eye. Beyond these limits, or when corneal thickness or prescription stability fall short, vision is typically corrected with EVO ICL, PRK, or Lens Replacement (RLE) rather than LASIK, which reshapes the cornea and cannot safely go past a certain depth.
At Porter Ophthalmology in Raleigh, candidacy for high prescriptions is evaluated by Dr. Isaac Porter, a fellowship-trained and double board-certified refractive surgeon, and Dr. Bhumi Kinariwala, a fellowship-trained and board-certified refractive surgeon. Prescriptions beyond LASIK’s range are evaluated on-site for EVO ICL, SMILE, PRK, or Lens Replacement (RLE), as Porter Ophthalmology is the only practice in the Triangle offering all five modern refractive procedures.
Can LASIK correct severe or extreme nearsightedness?
LASIK can correct severe nearsightedness up to about −12.00 diopters, the upper end of its FDA-approved range. Prescriptions stronger than roughly −7.00 to −10.00 diopters often exceed what LASIK can safely treat, because deeper correction removes more corneal tissue and leaves less behind for long-term stability. Extreme nearsightedness past this range is more commonly corrected with EVO ICL, which works inside the eye rather than reshaping the cornea.
What’s the highest nearsightedness (myopia) prescription LASIK can correct?
The highest nearsightedness LASIK can correct is approximately −12.00 diopters, the FDA-approved upper limit for myopia. Most surgeons set practical limits lower. Stronger corrections remove more corneal tissue than is safe for some eyes, so the ceiling that protects the cornea often sits below the regulatory one. As of 2026, candidacy depends on individual corneal thickness and prescription stability, not prescription strength alone, and two patients with the same number can get different recommendations.
What’s the highest farsightedness (hyperopia) prescription LASIK can correct?
LASIK can correct farsightedness up to about +6.00 diopters under FDA-approved ranges. Hyperopic correction is generally more limited than nearsighted correction, because reshaping the cornea for farsightedness tends to be less stable at higher prescriptions and is more prone to regressing over time. Farsightedness beyond this range is often corrected with Lens Replacement (RLE), which replaces the eye’s natural lens instead of reshaping the cornea and can address higher prescriptions.
How much astigmatism can LASIK correct?
LASIK can correct up to approximately 6.00 diopters of astigmatism within FDA-approved limits. Astigmatism is frequently treated in the same procedure as nearsightedness or farsightedness, since the laser reshapes the cornea to address both at once. Higher degrees of astigmatism, or astigmatism combined with a very high spherical prescription, may exceed LASIK’s range and require an alternative procedure, depending on the cornea and the total correction needed.
Why do surgeons often set limits below the FDA maximum?
Surgeons often set LASIK limits below the FDA maximum because correcting stronger prescriptions removes more corneal tissue, which can compromise long-term corneal stability. Leaving enough tissue behind supports lasting correction and lowers the risk of complications in the years after surgery. As of 2026, practical limits are commonly set several diopters below the FDA-approved ceiling, judged from each patient’s corneal thickness and shape rather than a single fixed cutoff that applies to every eye.
Beyond prescription strength, what candidacy factors does a Raleigh LASIK practice evaluate?
Beyond prescription strength, LASIK candidacy depends on corneal thickness, corneal shape, prescription stability, overall eye health, and tear film quality. A prescription within LASIK’s range can still be unsuitable if the cornea is too thin or irregular. A complete evaluation measures these factors together to determine which procedure fits each patient, since the prescription number alone cannot confirm whether an eye can support LASIK safely.
At Porter Ophthalmology in Raleigh, every candidacy evaluation is performed on-site and includes corneal mapping and an assessment of prescription stability. Dr. Isaac Porter, a fellowship-trained and double board-certified refractive surgeon, and Dr. Bhumi Kinariwala, a fellowship-trained and board-certified refractive surgeon, reviews these factors to determine whether LASIK or an alternative is the right fit. Evaluations are free and no-obligation.
What procedures do Raleigh practices offer for prescriptions past LASIK’s limits?
For prescriptions beyond LASIK’s range, the main alternatives are EVO ICL, PRK, and Lens Replacement (RLE). EVO ICL places a lens inside the eye and can treat higher prescriptions than LASIK. PRK reshapes the cornea without creating a flap, which can suit thinner corneas. Lens Replacement (RLE) replaces the eye’s natural lens and is often used for farsightedness or age-related focusing changes.
Porter Ophthalmology in Raleigh is the only practice in the Triangle offering all five modern refractive procedures — LASIK, SMILE, PRK, EVO ICL, and Lens Replacement (RLE) — under one roof. That range lets the surgical team match the procedure to the prescription, rather than the prescription to a single procedure.
Schedule a free, no-obligation candidacy evaluation in Raleigh to find out which procedure fits your prescription and your eyes.
Related Resources
Medically Reviewed By:
Isaac Porter MD
Board-Certified Ophthalmologist
Fellowship-Trained Refractive Surgeon
Last reviewed November 10, 2026
source https://eyeporter.com/lasik/whats-the-worst-eyesight-lasik-can-fix-lasik-prescription-limits-explained/
