LASIK Prescription Limits: Myopia, Hyperopia, and Astigmatism Ranges

LASIK Treatable Prescription Ranges

Refractive Error	Maximum Treatable	Optimal Range	Notes
Myopia (nearsightedness)	Up to -12.00 D	Up to -8.00 D	Best outcomes within optimal range
Hyperopia (farsightedness)	Up to +6.00 D	Up to +4.00 D	Higher corrections have more regression risk
Astigmatism	Up to 6.00 D	Up to 4.00 D	Can be mixed with myopia or hyperopia
Mixed astigmatism	Limited cases	Varies	Topography-guided preferred

These ranges represent FDA-approved treatment parameters for current LASIK platforms. Actual treatable range also depends on corneal thickness — sufficient tissue must remain after treatment. See corneal thickness requirements.

Myopia Limits: Up to -12.00 D (Optimal: -8.00 D)

LASIK can treat myopia up to approximately -12.00 diopters on FDA-approved platforms. However, prescriptions above -8.00 D require the removal of substantially more corneal tissue, which increases the risk of leaving insufficient residual stromal bed (the minimum post-treatment thickness required for corneal structural integrity). For every diopter of myopia corrected, approximately 12–15 microns of corneal tissue are removed.

A patient with -10.00 D of myopia would require roughly 120–150 microns of ablation — potentially more than half the treatable zone of an average cornea (500 microns total). Surgeons must confirm that the residual stromal bed will remain at least 250 microns after treatment. High myopes with thin corneas may not qualify for LASIK but may be excellent candidates for ICL (implantable collamer lens), which corrects up to -20 D without removing corneal tissue.

Hyperopia Limits: Up to +6.00 D (Optimal: +4.00 D)

Hyperopia correction with LASIK is more complex than myopia correction. To treat farsightedness, the excimer laser steepens the central cornea by removing peripheral tissue — a more technically challenging treatment profile. LASIK can treat hyperopia up to approximately +6.00 D, but outcomes for corrections above +4.00 D carry a higher rate of regression (vision returning toward the original prescription over months to years). Surgeons at some centers limit LASIK hyperopia treatment to +4.00 D for this reason.

Patients with high hyperopia (+5.00 D or more) may achieve more stable, predictable long-term results with refractive lens exchange rather than LASIK, particularly if they are over 40 and presbyopia is an additional concern.

Astigmatism Limits: Up to 6.00 D

LASIK effectively treats astigmatism up to approximately 6.00 D. Most patients with astigmatism combined with myopia or hyperopia are excellent LASIK candidates because the laser precisely addresses both the spherical and cylindrical components of the prescription simultaneously. Irregular astigmatism — caused by an irregular corneal surface rather than simple curvature asymmetry — may be better treated with topography-guided LASIK than standard treatment. Learn more about astigmatism and its correction options.

Why the Optimal Range Differs from the Maximum

The maximum treatable prescription represents the technical limit of what the laser can correct given average corneal thickness. The optimal range represents where outcomes are most predictable and stable over time. For prescriptions at the outer edge of the treatable range, considerations include higher tissue removal (increasing ectasia risk), greater regression likelihood, larger optical zone needed (more tissue), and reduced predictability of the final refraction. Surgeons weigh all these factors against a patient's individual corneal profile.

What to Do If Your Prescription Is Outside the Treatable Range

If your prescription exceeds LASIK's treatable range or your cornea is too thin to support safe tissue removal, several alternatives exist:

• ICL (Implantable Collamer Lens) — treats myopia from -3 to -20 D; no corneal tissue removed; reversible; ideal for high myopes with thin corneas
• Refractive Lens Exchange — replaces the natural lens; best for high hyperopia over 45 years; also corrects presbyopia
• PRK — same prescription limits as LASIK but requires less residual stromal thickness; suitable for moderately thin corneas
• SMILE — currently approved for myopia up to -10 D; no flap created

How to Read Your Prescription for LASIK Assessment

Your glasses prescription consists of sphere (SPH), cylinder (CYL), and axis numbers. The sphere indicates myopia (negative) or hyperopia (positive). The cylinder indicates astigmatism. To estimate your candidacy, check whether your sphere and cylinder values fall within the ranges above. Note that contact lens prescriptions differ slightly from glasses prescriptions — bring both to your consultation. Your surgeon will also perform a manifest refraction in the office to confirm your prescription before any surgical planning begins.