# Why Corneal Thickness Matters in Laser Surgery

Source page: https://www.kudretgozistanbul.com/en/blog/eye-diseases/why-corneal-thickness-matters-in-laser-surgery

**Author:** Kudret Eye İstanbul | **Medical Approval:** Op. Dr. Mehmet Ali Özdil | **Date:** 2026-09-06

> **Summary:** Laser eye surgery corrects myopia, hyperopia and astigmatism by reshaping the cornea, so the cornea must be thick enough for the operation to be safe. Corneal thickness is measured painlessly by pachymetry before surgery; people with a cornea below 500 micrometres may not be suited to iLASIK or ReLEx SMILE PRO but can consider PRK (No Touch) or ICL.

## Quick Facts
- **Measurement:** Pachymetry with a pachymeter, in micrometres; painless and quick
- **Threshold:** Below 500 micrometres, iLASIK and ReLEx SMILE PRO may not be chosen
- **Alternatives for thin corneas:** PRK (No Touch) or ICL
- **After surgery:** No shower for the first 24 hours; no pools or sea for about 20 days

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## Why Corneal Thickness Matters
- Corneal thickness is the distance between the front and back surfaces of the cornea; it varies with genetics, past conditions and age.
- The laser removes part of the cornea to achieve the correction, so enough tissue is needed.
- A very thin cornea can be damaged and raises the risk of complications, which may cause other vision problems and need further treatment. A very thick cornea can also cause problems, so all checks are done before surgery.

## Measuring Corneal Thickness
- The person looks into a pachymeter and the cornea is measured in micrometres (pachymetry).
- Always measured by the doctor before laser surgery, painlessly with special devices.

## Laser Options and Corneal Thickness
- Methods: iLASIK, ReLEx SMILE PRO, PRK, No Touch; each needs sufficient corneal thickness.
- Below 500 micrometres: iLASIK and ReLEx SMILE PRO may not be chosen.
- **PRK:** The outer layer (epithelium) is removed and the tissue beneath reshaped by laser; recommended for thinner corneas, though suitability is still assessed by the doctor.
- **ICL:** Implantation that does not affect the cornea; an effective option for thin corneas.

## Examination Before Surgery
- Pachymetry, eye pressure and other tests, plus a comprehensive eye health screening.
- Checks whether the prescription is stable and whether there are other problems.
- If suitable, the most appropriate method is planned with corneal thickness in mind.

## After Laser Eye Surgery
- Risks are explained beforehand; common side effects are normal.
- Stinging and burning for a few days, then lessening; dry eye or watering may occur.
- Follow the doctor's instructions; do not scratch or touch the eye.
- Protect from the sun or wear special filtered glasses for the period the doctor sets.
- No shower for the first 24 hours; for the first week keep water, soap and shampoo out of the eyes; avoid pools and the sea for about 20 days.
- Results: refractive errors improve greatly and some patients stop using glasses and lenses entirely; with very large errors a very small prescription may sometimes remain.

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## Frequently Asked Questions

**Q: Why does corneal thickness matter for laser surgery?**
A: The laser reshapes the cornea, so sufficient thickness is needed for a safe operation.

**Q: Can I not have laser if my cornea is thin?**
A: Some methods may not be suitable, but PRK or ICL are possible alternatives; your doctor will assess this.

**Q: How is corneal thickness measured?**
A: With pachymetry, at the micron level; painless and quick.

**Q: What can be experienced after laser surgery?**
A: Stinging, burning or dryness in the first days, generally lessening within a few days.

**Q: Will my vision be corrected completely?**
A: The FAQ says the aim is to reduce refractive errors to zero; the body adds that with very large errors a very small prescription can sometimes remain.

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## References
- Preoperative Evaluation for LASIK Surgery, EyeWiki (AAO)
- Photorefractive Keratectomy, EyeWiki (AAO)
- Phakic Intraocular Lenses, EyeWiki (AAO)