“I have a very high prescription (around -9.00 with astigmatism) and I’m interested in laser vision correction.I’m not necessarily looking for perfect 20/20 vision. Instead, I would prefer a partial correction so I can reduce my prescription to something much lower (for example -3.00 to -5.00) and still wear thinner glasses.

I strongly prefer LASIK because of the faster recovery time compared to PRK.

Is LASIK safe at this prescription level?
And would intentional under-correction make it safer?

What are my realistic options?”

Dr. Chynn’s Answer

When your prescription approaches -9.00 or higher, the primary concern is corneal thickness and long-term stability.

In traditional LASIK, a flap is created and tissue is removed to reshape the cornea. At very high prescriptions, removing too much tissue can weaken the cornea and create safety risks.

Historically, many surgeons set an upper safety limit around -8.00 for LASIK.

Even if you intentionally under-correct (for example leaving you at -2.00 or -3.00), the structural issue still exists: your starting prescription determines how much tissue must be treated.

What About PRK?

PRK avoids creating a flap, but at very high prescriptions, recovery can be:

• More painful

• Slower (2–3 weeks of blurred vision)

• Higher risk of haze or scarring

That’s why PRK is not always ideal for extreme prescriptions either.

Why LASEK May Be a Better Option

LASEK was developed specifically to treat patients who are not ideal LASIK candidates due to:

• Thin corneas

• High prescriptions

• Structural safety concerns

Unlike LASIK, LASEK preserves more corneal strength while still allowing full correction.

Dr. Chynn has treated over 1,000 patients with prescriptions worse than -9.00 and achieved excellent outcomes, including full 20/20 vision in many cases.

Is Partial Correction Safer for High Prescriptions?

Intentional under-correction does not eliminate structural concerns because:

• The total ablation depth is still influenced by your original prescription
• Corneal biomechanics matter more than final visual target
• Residual stromal bed thickness determines long-term stability

This is why high prescriptions require careful screening beyond simply choosing a lower final correction.

Learn More About Your Options

If you’re evaluating high prescriptions and laser vision correction, these resources can help you compare safety, procedures, and candidacy:

👉 LASEK: Non-cutting laser vision correction (excellent option for high corrections and safety)

👉 Schedule a laser vision consultation (free remote or in-office evaluation)

👉 Park Avenue LASEK Home (learn about our philosophies & safety approach)