LASIK vs PRK: Which is better for thin corneas?

LASIK and PRK are forms of laser eye surgery, both of which involve reshaping the cornea to correct vision. The cornea is the curved, see-through surface on the front of your eye. Its job is to help focus light so you can see clearly.

In short, PRK is often a better option for thin corneas because it doesn’t require the creation of a corneal flap.

Our team of Re:Vision eye surgeons, who've performed over tens of thousands of laser eye surgeries, put this guide together. It goes through how LASIK and PRK affect the cornea, which procedure often works best for thin corneas, and what they assess to help patients decide which option to go with.

LASIK and how it works on the cornea

LASIK is a type of laser eye surgery that corrects short-sightedness, long-sightedness, and astigmatism via corneal shape. During LASIK, the eye surgeon:

• Uses a femtosecond laser to create a thin, hinged flap in the cornea
• Uses an excimer laser to change the shape of the corneal tissue underneath the flap
• Puts the flap back in its original position, where it heals on its own, without stitches

Corneal suitability

Corneal thickness is a major factor in LASIK suitability because there needs to be enough tissue to:

• Create the flap
• Reshape the cornea
• Leave a layer underneath that's strong enough

This is especially important for people with stronger prescriptions. Generally, the greater the correction, the more reshaping (and more corneal tissue removal) is required. Thinner corneas can limit how safely LASIK can be performed. However, that's not to say that thin corneas automatically exclude this procedure.

Pre-surgery assessment

Corneal measurements are only part of the picture. The surgeon will also conduct a thorough assessment of the patient's:

• Overall eye health
• Prescription strength and stability
• Tear production and existing dry eye
• Pupil size and the risk of glare, halos, or night-vision problems
• Medical conditions or medications that could affect healing
• Work, sport, and the likelihood of direct eye trauma

Aside from corneal thickness, the patient’s lifestyle can also influence their LASIK suitability. PRK can be a safer choice for people who play contact sports or do other activities where a significant eye impact could dislodge a LASIK flap.

PRK and how it works on the cornea

Like LASIK, PRK is a type of laser eye surgery that corrects short-sightedness, long-sightedness, and astigmatism. It also achieves this by changing the shape of the cornea. During PRK, the eye surgeon:

• Removes the thin layer of cells (epithelium) covering the surface of the cornea
• Uses an excimer laser to change the shape of the corneal tissue underneath
• Puts a protective contact lens over the eye while the epithelium grows back

The main difference between LASIK and PRK surgery is that during PRK, the surgeon doesn't create a corneal flap.

Corneal suitability

Because the eye surgeon doesn't create a flap during PRK, less of the cornea's deeper structural tissue is touched than with LASIK. This is what makes PRK a good option for some people who don't have sufficient corneal tissue for LASIK.

It's important to realise that PRK still uses an excimer laser to remove corneal tissue and correct the prescription. And, like with LASIK, the greater the correction required, the more tissue generally needs to be removed. So, while PRK is often an option for people with thinner corneas, some corneas may still be too thin.

In these cases, the surgeon might recommend another form of vision correction, such as an implantable contact lens (ICL). This method corrects vision without reshaping the cornea.

Pre-surgery assessment

Once the surgeon has assessed the cornea’s thickness, shape, and overall health, they’ll also consider the patient's:

• Overall eye health
• Prescription strength and stability
• The health of the eye’s surface and epithelium
• Tear production and existing dry eye
• Medical conditions or medications that could affect healing
• Work, lifestyle, and the ability to manage a longer recovery

Together, these factors help the surgeon decide if your eyes are a good match for PRK and whether its recovery process works with your general circumstances.

Which is better for thin corneas?

PRK is usually preferred for thinner corneas because it doesn’t require a flap, allowing for more corneal tissue to be preserved. This doesn't mean it's the safest option for everyone with thinner corneas, though. 

Depending on the corneal measurements and the patient’s broader suitability:

• Mildly thin cornea: LASIK could still be suitable
• Too thin for LASIK: PRK might be the safer option
• Too thin for either procedure: Implantable contact lenses may be the way to go

Laser Eye Surgery Auckland

PRK can be a fantastic laser eye surgery option for thin corneas, but it isn’t the only one! At our Auckland eye clinic, we offer a full-suite of vision correction options, including LASIK, PRK, implantable contact lenses, refractive lens exchange, and cataract surgery.

Every treatment recommendation starts with a thorough eye assessment. We use a combination of precise measurements using advanced technology with an understanding of your prescription, eye health, lifestyle, and long-term vision goals to find the safest and most suitable option for you.

To have our experienced team guide you through your options, book a vision correction assessment today!