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Laser Eye Surgery for Astigmatism and High Prescriptions: How Much Can Be Corrected?

Excimer laser suite for laser eye surgery

Laser eye surgery for astigmatism is done in the same treatment as short or long sight. The Royal College of Ophthalmologists gives the usual laser range as up to −10.00 D of short sight, +4.00 D of long sight and ±6.00 D of astigmatism, with some higher prescriptions treatable. Corneal thickness and shape matter as much as the number. Prof. Dr. Ahmet Satıcı or Op. Dr. Aysan Bayram decides after scanning your corneas.

What counts as a high prescription or high astigmatism?

A "high" prescription is a strong number on your glasses prescription, and the threshold depends on the type of error. The International Myopia Institute (IMI) uses −6.00 dioptres (D) or stronger as the threshold for high short sight (myopia). EyeWiki, the American Academy of Ophthalmology's (AAO) clinical encyclopaedia, calls long sight (hyperopia) high at +5.25 D or more. For astigmatism, a 2023 systematic review in Optometry and Vision Science grades it as mild below 1.50 D, moderate from 1.50 to 2.50 D and significant above 2.50 D.

ErrorWhere to find it on your prescriptionCommonly called "high"
Short sight (myopia)SPH, a minus number−6.00 D or stronger (IMI)
Long sight (hyperopia)SPH, a plus number+5.25 D or more (EyeWiki)
AstigmatismCYL (the strength) and AXIS (a number from 0 to 180)Above 2.50 D (2023 review)

Astigmatism is common: the same review puts its pooled prevalence at about 40% of adults worldwide. It also affects how you see at night. Among people with uncorrected astigmatism, the review reports glare in 53–77%, halos in 28–80% and night-driving difficulty in about 66%. That is why many people with astigmatism look into laser eye surgery.

Laser eye surgery guides

Can laser eye surgery fix astigmatism?

Yes. Laser eye surgery reshapes the cornea so that its steeper and flatter curves focus light at the same point. It is not a separate operation: the NHS lists astigmatism, short sight and long sight together as the conditions laser surgery can correct, and your astigmatism is treated in the same session as the rest of your prescription.

Three laser methods can treat astigmatism, and your surgeon chooses between them:

  • Femto-LASIK: a thin flap is made with a femtosecond laser, and a second laser reshapes the cornea underneath. It treats short sight, long sight and mixed astigmatism.
  • SMILE Pro and ReLEx SMILE: a keyhole method with no flap, approved for short sight with or without astigmatism.
  • PRK and no-touch Trans-PRK: surface treatments with no flap, often chosen when the cornea is thinner.

Alignment is what makes astigmatism different. Astigmatism has a direction, so the laser must line up with the exact rotation of your eye. EyeWiki notes that the eye can rotate by about 2–4 degrees when you lie down for surgery, and that a misalignment of about 4 degrees can leave around 14% of the cylinder uncorrected. Modern lasers use eye tracking and iris registration to follow the eye, and the VisuMax 800 platform used for SMILE Pro has a feature for cyclotorsion correction.

How accurate is the astigmatism correction? In the US regulatory study of SMILE, 304 eyes received a treatment that included astigmatism of up to −3.00 D. Six months later, 71.7% were within ±0.25 D of the target cylinder, 87.7% within ±0.50 D and 97.3% within ±1.00 D (FDA summary, 2018).

Laser eye surgery astigmatism limits: how much can be corrected?

The usual guide is up to ±6.00 D of astigmatism, and the limits differ by method and by country. The Royal College of Ophthalmologists (RCOphth), in its current patient information, says you are most likely to be suitable if your prescription is within −10.00 D, +4.00 D and ±6.00 D, and that "laser vision correction can be effective for higher prescriptions in some patients". The limits regulators have approved for specific devices are narrower or wider depending on the laser:

TreatmentShort sightLong sightAstigmatismSource
Laser vision correction, usual UK guideup to −10.00 Dup to +4.00 Dup to ±6.00 DRCOphth
SMILE (VisuMax), US approval−1.00 to −10.00 Dnot covered−0.75 to −3.00 DFDA, 2018
LASIK, US approvals (varies by laser)up to −12.00 D on one platform; up to −7.00 D on anothernot given in this sourceup to −6.00 D (one platform); up to −3.00 D (another)EyeWiki
Toric ICL (implantable lens), US approval−3.0 to −15.0 Dnot covered1.0 to 4.0 DEyeWiki, from FDA labelling

Approved ranges describe what a device was tested for. They are not a promise that every eye inside them is suitable, and your surgeon may treat outside them in selected eyes.

Why the number is not the whole answer. The more correction you need, the more corneal tissue the laser removes. The FDA safety summary for SMILE rules out surgery if the corneal tissue left behind (the residual stromal bed) would be less than 250 microns thick, and EyeWiki gives 250 microns as the minimum recommended for LASIK too. Two people with the same prescription can therefore get different advice if their corneas have different thickness. Your surgeon also checks corneal shape on scans, because the AAO lists keratoconus, corneal disease and insufficient corneal thickness among the reasons a person is not a good candidate for LASIK.

Why this matters for safety. The main long-term risk linked to thin or heavily treated corneas is ectasia, a weakening and bulging of the cornea. A 2024 review in Community Eye Health puts it at 0.04–0.5% of patients, most commonly in people who are young and have high short sight. EyeWiki gives about 1 in 5,000 with modern screening and lists high myopia, a thin residual stromal bed, thin corneas before surgery and abnormal scans as risk factors.

How good are the results with a high prescription?

Results are good in most eyes, but they are less predictable as the prescription rises, and it is honest to say so. The US FDA warns that results are generally not as good in people with very large refractive errors of any type. EyeWiki summarises the published LASIK studies like this:

LASIK for short sight (published studies)Uncorrected vision 20/40 or betterWithin ±0.50 D of targetWithin ±1.00 D of target
Low to moderate (studies' median)94–100% (median 98%)not reported here75–100% (median 92%)
High, −8.00 to −14.25 D, after the first treatment76–97% (median 89%)55%83%
High, after a retreatmentnot reported here69%95%

Averages from published studies as summarised by EyeWiki; they describe groups of eyes, not what will happen to yours.

Three things follow from these numbers.

  1. Retreatment is more common with high prescriptions. The table shows how a second laser treatment moves more eyes close to the target. The RCOphth says up to 1 in 10 patients overall need some form of additional surgery to get the best result. In a large 18-year audit of 53,731 eyes reported by EyeWiki, the retreatment rate was 2.55%.
  2. The correction can slowly drift back. EyeWiki reports about 10% myopic regression over time at 12 years for moderate-to-high short sight, at roughly −0.12 D a year for up to −10 D and −0.25 D a year above −10 D. Short sight and astigmatism normally stabilise in the late teens or early 20s, but the RCOphth notes that natural prescription changes can occur at any age, so laser sometimes needs repeating.
  3. Night vision is the main trade-off. The RCOphth says most patients have some glare, halos or starbursts early on, "particularly those who have treatment for higher spectacle prescriptions", and that with modern lasers these are usually mild and improve within a few months. EyeWiki lists a pupil that opens wider in the dark than the treated zone, and high myopic corrections, as risk factors. In the US PROWL studies, 43–46% of people without symptoms before LASIK reported a new visual symptom at 3 months, while only 1–4% were dissatisfied with their vision. Lasting problems are unusual but possible: the FDA notes that some people develop glare, halos or double vision that seriously affects night vision.
Dry eyes and halos after laser surgery: causes and fixes

Which treatment suits which prescription?

The treatment follows your eyes, not the other way round. Compare the main options for a strong prescription or astigmatism:

OptionOften considered whenWhat to know
Femto-LASIKHealthy, adequately thick corneas; astigmatism within the laser range, including mixed astigmatismFastest visual recovery; many people are back at work the next day (RCOphth)
SMILE Pro / ReLEx SMILEShort sight with astigmatism; active lifestyles; preference for no flapVisual recovery may be slightly slower than LASIK (RCOphth); EyeWiki notes a tendency to slightly under-correct low to moderate astigmatism up to 2.00 D, which your surgeon plans for
PRK / no-touch Trans-PRKThinner corneasLeaves more of the cornea untouched (EyeWiki); a 2026 meta-analysis of 946 thin-cornea eyes reported no cases of ectasia; recovery is slower and the eye is sore for longer
Toric ICL (implantable lens in front of your own lens)Prescription beyond the laser range, thin corneas, higher short sight with astigmatismNo corneal tissue is removed; the lens can be removed; FDA labelling covers ages 21–45
Toric lens replacement (RLE or cataract surgery)From around the mid-40s, early cataract, high long sightThe RCOphth says RLE is often preferred to laser in the retirement age group

Why an implantable lens can be the better choice for a very high prescription. The RCOphth states that phakic intraocular lenses (PIOLs, lenses placed in front of the natural lens) are often a good alternative in younger patients whose prescription falls outside the normal laser range. EyeWiki says the ICL has been found superior for higher degrees of short sight and produces fewer higher-order aberrations and better contrast sensitivity than wavefront-guided LASIK. A 2026 non-randomised study of 146 eyes with −2.0 to −18.0 D found both methods predictable (90.4% within ±1.0 D), with a higher share of eyes gaining best-corrected vision after ICL (54.8% vs 32.9% at 3 months).

An ICL is still an operation inside the eye. In a review of 35 studies and 2,904 eyes with the V4c lens, cataract opacities occurred in 0.17% of eyes, a lens rotated by more than 30° in 0.27%, and glare or halos were reported in 2.4–27% depending on the study. Endothelial cell loss (loss of the cells lining the inner cornea) was 0.43–2.88% at 3–5 years. Your surgeon measures the space inside your eye before recommending an ICL; EyeWiki lists an anterior chamber depth of at least 3.00 mm in the FDA indication.

The retina matters if you are very short-sighted. The NHS lists glaucoma, detached retina, cataracts and macular degeneration as possible complications of severe short sight, and the US National Eye Institute (NEI) also says high myopia raises the risk of retinal detachment. Laser reshapes the cornea; it does not change the rest of the eye. That is why a retina check is part of the assessment before any surgery.

Why not laser after 45? Laser vs lens surgery by age
Close-up of a blue eye

What does the assessment check before surgery?

The aim is to decide whether laser is safe for you, and which method fits, before any date is set. For a high prescription or astigmatism, your examination in Istanbul includes:

  1. Full refraction with and without dilating drops, including your CYL and AXIS values.
  2. Corneal topography and tomography: maps of the front and back of the cornea that show whether the astigmatism is regular (like a rugby ball) or irregular, and whether the cornea shows early signs of keratoconus.
  3. Corneal thickness (pachymetry): to work out how much tissue can safely be treated.
  4. Pupil size in dim light, to plan a treated zone that suits your night vision.
  5. Dry-eye assessment, because dry eye affects both the result and the comfort of recovery.
  6. Retina check, especially if you are strongly short-sighted.

Stop wearing contact lenses before the examination. Lenses change the shape of the cornea, and the measurements must show your natural eye. The US FDA advises stopping soft lenses 2 weeks before the first evaluation, toric soft or rigid gas-permeable lenses at least 3 weeks before, and hard lenses at least 4 weeks before. Your coordinator confirms the timing for your lenses.

Irregular astigmatism is a different question. If your scans show keratoconus or an uneven cornea, standard laser is usually not suitable. Doç. Dr. Muhammet Derda Özer, our cornea specialist, reviews these cases ("Doç." is the Turkish title for Associate Professor). He speaks Turkish and English.

Your surgeons for astigmatism and high prescriptions

  • Prof. Dr. Ahmet Satıcı performs laser eye surgery (LASIK, SMILE Pro, PRK) and ICL surgery, as well as cataract and premium lens surgery, so he can compare laser, ICL and lens replacement for your prescription.
  • Op. Dr. Aysan Bayram performs laser eye surgery and cataract surgery and treats retinal disease. She is a female surgeon and speaks English.
  • Doç. Dr. Muhammet Derda Özer treats corneal conditions, including keratoconus and cross-linking, and retinal disease. He reviews irregular astigmatism.

Surgery takes place in a fully equipped, Ministry of Health–licensed operating theatre in Istanbul. Most patients stay 3–5 days for laser surgery, and most can fly 1–3 days after laser, once their surgeon has checked their eyes. Your surgeon checks you again before you fly home, and your coordinator and surgeon follow your recovery remotely.

Frequently asked questions

Yes. Laser eye surgery corrects astigmatism by reshaping the cornea, in the same treatment as short or long sight. It works for regular astigmatism in a healthy, stable cornea of adequate thickness. Irregular astigmatism, for example from keratoconus, usually needs a different approach.

The Royal College of Ophthalmologists gives up to ±6.00 D as the usual range. Individual lasers have approved limits, such as −0.75 to −3.00 D for SMILE in the US. Above the limit for your chosen method, or with thin corneas, a toric implantable lens is often more predictable.

As a usual guide, up to −10.00 D of short sight and +4.00 D of long sight, according to the RCOphth. Some higher prescriptions can be treated if the corneas are thick enough. Your total correction and your corneal thickness decide, not the number alone.

It can be, if the cornea is thick enough and healthy, but risks rise with the size of the correction. High myopia is a listed risk factor for ectasia and night-vision symptoms, and moderate-to-high myopia can regress over the years. A very high prescription may be safer to treat with an ICL.

Many people notice some glare or halos for the first weeks or months, more often after treatment of higher prescriptions. They usually improve within a few months, and lasting problems are unusual. Before surgery, uncorrected astigmatism itself often causes halos and glare at night.

Neither is better for everyone. Femto-LASIK recovers fastest, while SMILE Pro is flap-free and EyeWiki notes a tendency to slightly under-correct low to moderate astigmatism. For higher astigmatism your surgeon may prefer LASIK, PRK or a toric lens.

There are alternatives. PRK or no-touch Trans-PRK leaves more corneal tissue and is often used for thinner corneas. A toric ICL suits very high short sight with astigmatism, and lens replacement suits older patients. Your surgeon explains why laser is not right and what is.

The reshaping is permanent, but eyes keep changing with age. The RCOphth notes that natural prescription changes can occur at any stage of life, so a touch-up is sometimes needed. A touch-up is possible only if enough corneal thickness remains.

Plan 3–5 days for laser eye surgery, including your examination, surgery and follow-up checks. Most patients can fly 1–3 days after laser, once the surgeon has checked their eyes. Lens surgery and surface laser usually need a few more days.

Not sure if laser suits your astigmatism or prescription?

Send us your glasses prescription and any scans. Your surgeon at Laser Istanbul Clinic tells you whether laser, an ICL or lens replacement is the safer fit, and says plainly if laser is not right for your eyes. Laser surgery is led by Prof. Dr. Ahmet Satıcı and Op. Dr. Aysan Bayram.

Free online consultation: upload your prescription and scansWhatsApp: +49 157 8373 9465
Laser eye surgery in Turkey / Istanbul
Sources for the facts on this page
  1. The Royal College of Ophthalmologists. Laser vision correction: patient information (document PROF/2024/499). Suitability range (−10.00 D, +4.00 D, ±6.00 D), higher prescriptions, PIOLs and RLE, light-scatter side effects, up to 1 in 10 additional surgery. https://www.rcophth.ac.uk/wp-content/uploads/2026/08/Laser-vision-correction-patient-information.pdf (landing page: https://www.rcophth.ac.uk/guidance-resources/laser-vision-correction/)
  2. US FDA. Summary of Safety and Effectiveness Data, VisuMax Femtosecond Laser, P150040/S003 (approved 4 Oct 2018): SMILE ranges, 250-micron residual bed, astigmatism accuracy. https://www.accessdata.fda.gov/cdrh_docs/pdf15/P150040S003B.pdf
  3. EyeWiki (AAO). LASIK for Myopia and Astigmatism: Safety and Efficacy. https://eyewiki.org/LASIK_for_Myopia_and_Astigmatism:_Safety_and_Efficacy
  4. EyeWiki (AAO). LASIK Complications. https://eyewiki.org/LASIK_Complications
  5. EyeWiki (AAO). Implantable Collamer Lens. https://eyewiki.org/Implantable_Collamer_Lens
  6. EyeWiki (AAO). Keratorefractive Lenticule Extraction (KLEx) Surgeries. https://eyewiki.org/Keratorefractive_Lenticule_Extraction_(KLEx)_Surgeries
  7. EyeWiki (AAO). Physiology of Astigmatism. https://eyewiki.org/Physiology_of_Astigmatism
  8. EyeWiki (AAO). Hyperopia. https://eyewiki.org/Hyperopia
  9. EyeWiki (AAO). Photorefractive Keratectomy. https://eyewiki.org/Photorefractive_Keratectomy
  10. Flitcroft DI, et al. IMI: Defining and Classifying Myopia. Investigative Ophthalmology & Visual Science 2019. PMID 30817826. https://pubmed.ncbi.nlm.nih.gov/30817826/
  11. Zhang J, et al. Epidemiology and Burden of Astigmatism: A Systematic Literature Review. Optometry and Vision Science 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10045990/
  12. Ying J, Roy A, Garg P, Chen W. Complications in patients who have undergone laser refractive surgery. Community Eye Health 2024;37(123). https://pmc.ncbi.nlm.nih.gov/articles/PMC11921254/
  13. Montés-Micó R, et al. Posterior-chamber phakic implantable collamer lenses with a central port: a review. Acta Ophthalmologica 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8246543/
  14. Baasanjav T, et al. Visual outcomes of implantable Collamer lens and laser-assisted in situ keratomileusis for all levels of myopia. International Journal of Ophthalmology 2026. PMID 42211202. https://doi.org/10.18240/ijo.2026.06.13
  15. Semnani F, et al. Photorefractive keratectomy in patients with thin corneas: systematic review and meta-analysis. Journal of Cataract and Refractive Surgery 2026. PMID 40947529. https://doi.org/10.1097/j.jcrs.0000000000001790
  16. US FDA. LASIK: What are the risks and how can I find the right doctor for me? https://www.fda.gov/medical-devices/lasik/what-are-risks-and-how-can-i-find-right-doctor-me
  17. US FDA. What should I expect before, during, and after surgery? (contact-lens stop times). https://www.fda.gov/medical-devices/lasik/what-should-i-expect-during-and-after-surgery
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  19. NHS. Laser eye surgery and lens surgery. https://www.nhs.uk/tests-and-treatments/laser-eye-surgery-and-lens-surgery/
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  21. National Eye Institute (NIH). Nearsightedness (Myopia). https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/nearsightedness-myopia