Laser Eye Surgery Safety: Is It Harmful?
Here is how today’s lasers differ from the old radial keratotomy, and what really matters for laser eye surgery safety.
Laser eye surgery is a safe method for suitable patients. It should not be confused with radial keratotomy, which is no longer used. In the 1980s, surgeons made radial cuts in the cornea with a knife. With SMILE Pro, Femto-LASIK and No Touch, however, a laser reshapes the cornea according to planned measurements. So what decides safety is a correct measurement of whether your cornea and your prescription suit the laser.
What was the old method, radial keratotomy?
The old method was radial keratotomy (RK). Prof. Svyatoslav Fyodorov developed this operation in Moscow in the late 1970s, and it spread worldwide in the 1980s. To reduce myopia, the surgeon cut the clear front layer (the cornea) with a diamond knife. The cuts ran outward like the spokes of a bicycle wheel. They flattened the centre of the cornea and so reduced myopia.
For its time, the method was an important step. However, it had clear limits. In the 10-year PERK study in the USA, 70% of patients could see in the distance without glasses. Even so, 43% of the eyes drifted toward hyperopia by 1 diopter or more over the years. The cuts also left permanent scars on the cornea. In some patients they caused vision that fluctuated during the day and light scatter at night.
“Radial keratotomy is actually a very old method. It carried risks and was even harmful for some eyes. That method belongs to the past, but people often still confuse it with today’s lasers.”
— Prof. Dr. Fırat Helvacıoğlu, from the video
Is laser eye surgery harmful?
In 1 minute, Prof. Dr. Fırat Helvacıoğlu explains how the old radial keratotomy differs from today’s laser methods.
Why today’s lasers improve laser eye surgery safety
Today’s treatments use no knife to make incisions. Instead, a computer-calculated laser program corrects the eye, based on your prescription and your corneal map. The laser works with micron-level precision, and tracking systems follow your eye movements. As a result, the outcome no longer depends on the speed of the surgeon’s hand. It depends on the accuracy of the measurements and the planning.
This difference shows in the results. A broad review combined high-quality studies from 1995 to 2003. In it, average patient satisfaction after LASIK was 95.4%, and the authors regarded LASIK as one of the most successful elective surgical procedures. Since then, technology has advanced further. Femtosecond lasers, personalised topography planning and flapless methods such as SMILE have all contributed.
From radial keratotomy to today’s lasers
In radial keratotomy, the old method, surgeons cut the corneal surface radially with a knife in the 1980s. In laser eye surgery today, laser energy calculated from your measurements reshapes the cornea.
- Radial keratotomy (old)The cornea was cut radially with a knife. Results depended on the surgeon’s hand and on healing, and the prescription could drift over the years.
- LASIK / SMILE Pro (today)A femtosecond laser works inside the cornea. The correction follows a laser program planned from topography.
- No Touch (today)The excimer laser treats the surface without touching the eye. No incision and no flap are created.
Current methods in brief
| Method | How it is performed | Key feature |
|---|---|---|
| No Touch laser | The excimer laser treats the corneal surface without any instrument touching the eye. | No incision and no flap; a safe option for thin corneas. You may feel a stinging for the first 3–4 days. |
| Femto-LASIK (iLASIK) / Q-LASIK | A femtosecond laser creates a thin flap, and the correction is made underneath. | Vision improves very quickly; you return to daily life the next day. |
| SMILE Pro | The correction is prepared inside the cornea as a small lenticule, which is removed through a 2–4 mm incision. | No flap; healing is fast, which is an advantage for people who play contact sports. |
I explain in detail how we choose the right method for you in the article “Which laser method is best?”
Laser eye surgery safety depends on suitability
With current lasers, the most important safety issue is not the method itself but choosing the right patient. The most serious (but rare) complication is ectasia, in which the cornea weakens and bulges forward. One of its strongest indicators is the “percent tissue altered” (PTA), which shows how much of the cornea is changed. Among eyes with normal topography that developed ectasia after LASIK, 97% had a PTA of 40% or more. For this reason, we calculate corneal thickness, topography and PTA together in every plan. Then we choose a safer method instead of a risky plan, or we do not recommend a laser at all.
Situations in which we may recommend another solution instead of a laser
- A thin cornea, or a corneal map that raises suspicion of keratoconus
- A prescription that changed noticeably in the last year (especially under 18)
- Very high prescriptions, where an implantable lens (ICL) may be more suitable
- Pregnancy and breastfeeding, uncontrolled diabetes, and marked dry eye
“If your cornea and your prescription are suitable, you can have treatment with confidence after getting detailed information from your doctor.”
— Prof. Dr. Fırat Helvacıoğlu, from the video
Laser eye surgery safety: possible side effects
Like any surgical procedure, laser treatment can have side effects. Knowing them in advance helps you set the right expectations:
- Dry eye: It is common in the first months. Drops usually control it, and it fades over time.
- Night light scatter (halos, glare): It can occur especially in the first weeks and is usually temporary.
- A small remaining or returning prescription: Some eyes may need a touch-up (a second correction), which is possible if the cornea is suitable.
- Haze after surface lasers: It can occur with high prescriptions, but a suitable medication protocol reduces the risk.
Haze after surface lasers and trans-PRK results are among the topics our clinic has shared at international congresses.
What is measured before laser surgery?
The laser suitability examination takes about 1–1.5 hours and includes the following measurements:
- Confirming your prescription with drops (which relax the eye’s focusing)
- Corneal topography/tomography (the corneal map) and thickness measurement
- Dry eye tests and tear quality
- Pupil size in the dark and intraocular pressure
- Examination of the back of the eye (retina)
If you wear contact lenses, you need to stop wearing them before the examination so that the measurements are accurate. You can learn the exact period when you book your appointment.
Frequently asked questions
No, medically they are not the same. Radial keratotomy is an old method that surgeons performed with a knife in the 1980s and no longer use. Today’s procedures use computer-controlled lasers.
In properly selected patients, serious vision loss is extremely rare. To keep risks as low as possible, all measurements, such as the corneal map and thickness, must be completed before surgery. In addition, no laser should be performed on unsuitable eyes.
It is usually done after the age of 18, provided your prescription has not changed noticeably for at least a year. After the age of 40, the need for near vision is also considered in the planning.
In most patients the result is permanent. However, in some eyes a small prescription may remain or return over time. If the cornea is suitable, a second correction (touch-up) can be done.
In eyes that have had radial keratotomy, the prescription may change over the years. If laser or cataract surgery is planned for these eyes, special measurements and lens calculation formulas are needed. After a detailed examination, we determine the option that suits you.
Related pages
References
- Fyodorov SN, Durnev VV. Operation of dosaged dissection of corneal circular ligament in cases of myopia of mild degree. Ann Ophthalmol. 1979;11(12):1885-1890. PMID: 556142.
- Waring GO 3rd, Lynn MJ, McDonnell PJ. Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study 10 years after surgery. Arch Ophthalmol. 1994;112(10):1298-1308. doi:10.1001/archopht.1994.01090220048022
- Solomon KD, Fernández de Castro LE, Sandoval HP, et al. LASIK world literature review: quality of life and patient satisfaction. Ophthalmology. 2009;116(4):691-701. doi:10.1016/j.ophtha.2008.12.037
- Santhiago MR, Smadja D, Gomes BF, et al. Association between the percent tissue altered and post-LASIK ectasia in eyes with normal preoperative topography. Am J Ophthalmol. 2014;158(1):87-95. doi:10.1016/j.ajo.2014.04.002
- Shortt AJ, Allan BDS, Evans JR. Laser-assisted in-situ keratomileusis (LASIK) versus photorefractive keratectomy (PRK) for myopia. Cochrane Database Syst Rev. 2013;(1):CD005135. doi:10.1002/14651858.CD005135.pub3
- Kaya Ünsal S, Helvacıoğlu F, Sunay E. Visual, refractive, topographic and wavefront outcomes of trans-photorefractive keratectomy in virgin eyes. 37th ESCRS Congress, Paris, September 2019 (paper).
- Helvacıoğlu F. Haze after excimer laser. Schwind User Meeting, Istanbul, March 2016 (presentation).
This article is for patient information only and does not replace an examination or medical assessment. The treatment that suits you is decided after an eye examination and measurements. Publication date: 25 September 2026.
Contact Prof. Dr. Fırat Helvacıoğlu with your questions
Prof. Dr. Fırat Helvacıoğlu · Veni Vidi Eye Clinic, Bağdat Cad. No: 257, Caddebostan – Kadıköy / Istanbul