Every refractive procedure does the same thing: it changes the shape of the cornea so that light lands on the retina without glasses. The differences are in how the cornea is reached, how it recovers, and which eyes it is safe for. Those differences are real, and they are the whole decision.
The three procedures, one at a time
LASIK, and Femto LASIK
A thin flap of the front cornea is created, lifted like a page, and an excimer laser reshapes the tissue beneath it. The flap is laid back and seals itself. Vision is usable within hours and most people are at work in a day or two, with a few hours of watering and light sensitivity on the day itself. The flap heals but never fully re-bonds, so a hard blow to the eye can, rarely, displace it even years later. Because corneal nerves are cut when the flap is made, dry eye is more common in the first months. It treats short sight, long sight and astigmatism. In Femto LASIK the flap is made by a femtosecond laser instead of a blade: thinner, more even, more predictable, and more expensive.
SMILE
A femtosecond laser cuts a thin disc of tissue, called a lenticule, inside the cornea, and I remove it through an opening of two to four millimetres. There is no flap. The front surface stays largely intact, fewer nerves are cut, dry eye is less frequent on average, and there is nothing to displace, which matters for anyone in contact sports, the uniformed services, or who cannot stop rubbing their eyes. Vision is good the next day but takes a few days longer than LASIK to become fully crisp. It treats short sight and astigmatism; long sight is not routinely treated on most platforms. If a touch-up is ever needed, it is more involved than after LASIK.
PRK and TransPRK
No flap and no lenticule. The thin surface layer, the epithelium, is removed, by alcohol, a brush or the laser itself, and the excimer laser reshapes the surface directly. The epithelium grows back in three to five days under a bandage contact lens. Those days are uncomfortable, and fully sharp vision takes three to six weeks. In exchange the cornea keeps all of its structural strength. It is my choice for thin corneas, for people whose epithelium is loosely attached, for those in jobs with a real risk of eye injury, and for some mild surface irregularities. It is also the least expensive of the three.
Side by side
| LASIK | Femto LASIK | SMILE | PRK | |
|---|---|---|---|---|
| Flap | Yes, blade | Yes, laser | No | No |
| Corrects | Myopia, hyperopia, astigmatism | Same | Myopia and astigmatism | All three |
| Vision usable | Next day | Next day | 1 to 3 days | 5 to 7 days |
| Fully sharp | 1 to 2 weeks | 1 to 2 weeks | 2 to 4 weeks | 3 to 6 weeks |
| Discomfort | Hours | Hours | Hours | 3 to 5 days |
| Early dry eye | More | More | Less | Moderate |
| Risk from a blow to the eye | Flap | Flap | None specific | None specific |
| Thin cornea | No | Borderline | Borderline | Best option |
| Touch-up later | Straightforward | Straightforward | More involved | Possible |
| Cost band | Low to mid | Mid to high | High | Low |
What the tests tell me
- Corneal topography and tomography. The shape of the cornea, front and back. This is where early keratoconus hides, and an eye with even a hint of it should not have a laser near it. Non-negotiable.
- Pachymetry. Corneal thickness. Every dioptre corrected removes a little tissue, and a safe margin has to remain afterwards. A high number on a thin cornea is the commonest reason I move someone from LASIK to PRK or to an ICL.
- Stability of your number. No meaningful change over the last twelve months. Operating on a prescription that is still moving is a way to be back in glasses in two years.
- Tear film. Tear volume, break-up time and surface staining. A dry eye is treated first, not operated on.
- Pupil size in dim light. Large pupils with a high correction mean more glare at night, and change how wide the treatment zone needs to be.
- The dilated retina. Higher myopes often have thin patches at the edge of the retina. If there is one, it is sealed with a small laser before any refractive surgery.
- Age and general health. Eighteen is the legal floor; I prefer twenty-one for stability. Pregnancy and breastfeeding mean waiting. Uncontrolled diabetes and active autoimmune disease need discussion. Over forty, we talk about reading glasses before anything else.
Who I say no to, and what I offer instead
- Keratoconus, or a topography that looks suspicious. No laser at all. If the cornea is stable, an ICL may be possible. If it is progressing, cross-linking comes first.
- A cornea too thin for the number. PRK if it is borderline, an ICL if it is not.
- Very high myopia, roughly beyond minus 8 to minus 10. Removing that much tissue costs quality of vision. An ICL usually gives a better result.
- An unstable prescription. Come back in a year.
- Dry eye that does not settle with treatment. Wait, or consider an ICL, which does not cut corneal nerves.
- Under eighteen, pregnant or breastfeeding. Wait.
- Expectations that no procedure can meet. Someone of forty-eight who wants perfect near and distance vision with no glasses ever again needs a conversation before a laser.
Being turned down is not a verdict on your eyes. It is the screening doing its job.
Before the screening: the contact lens holiday
Contact lenses mould the cornea, and a map taken too soon will mislead both of us. Leave soft lenses out for at least one week, two if they are toric or extended-wear. Rigid gas-permeable lenses need three to four weeks, sometimes longer. Bring your old spectacle prescriptions if you have them; they show me how stable your number has been.
If you are over 40
Laser surgery corrects distance vision. It does not stop presbyopia, the stiffening of the natural lens that brings reading glasses to everyone in their mid-forties. There are honest ways to handle this: full distance correction in both eyes and a pair of readers; monovision, where one eye is left slightly short-sighted for near work, which I only recommend after a trial in contact lenses; or, if there is already early cataract, a lens-based procedure instead of a corneal one. What I will not do is promise a forty-five-year-old that they will never need reading glasses.
The risks, stated plainly
- Dry eye. Common in the first months, usually settles by three to six months, persistent in a small minority.
- Glare and halos at night. Common early, usually fades. More likely with large pupils and higher corrections.
- Under-correction, over-correction or regression. An enhancement is usually possible.
- Flap problems, LASIK only. Rare, and mostly avoidable with a femtosecond flap and sensible precautions in the first weeks.
- Infection. Rare. Drops and hygiene matter.
- Ectasia. Rare, and almost always a screening failure. This is the reason topography is not optional.
- Loss of best-corrected vision. Very rare.
I list these not to alarm you. In my experience the well-informed patients are the calm ones.
What the day looks like
Numbing drops, a clip to keep the lids open, ten to fifteen minutes per eye in the room. You will feel pressure and see the light go dim for a moment. Then home in dark glasses, with someone else driving. Sleep for a few hours. The next morning we check the eyes, and most people are surprised by how much they can already see.
What I would choose
If my cornea were normal and thick and my number moderate, I would be content with Femto LASIK or SMILE, and let dry eye and lifestyle break the tie. If I played contact sport, SMILE or PRK. If my cornea were thin, PRK. If my number were beyond minus 9, an ICL. The procedure with the loudest advertising does not enter into it.
What each of these costs, and what a fair quote has to include, is in the companion guide on LASIK surgery cost in Mumbai.
Questions patients ask me about choosing a procedure
Is SMILE better than LASIK?
Not for everyone. SMILE avoids a flap, so it tends to cause less dry eye and has no flap to displace, which suits contact-sport players and people who rub their eyes. LASIK gives faster crisp vision, treats long sight as well, and is easier to touch up. For a normal, thick cornea with a moderate number, both give excellent results. The screening and your lifestyle decide.
Which is the safest: LASIK, SMILE or PRK?
All three are safe in properly screened eyes. PRK keeps the most corneal strength and has no flap-related risks, at the cost of a slower, more uncomfortable recovery. SMILE avoids a flap with a fast recovery. LASIK has the quickest visual recovery but carries the small, lifelong flap consideration. The biggest safety factor is not the procedure but whether your cornea was screened properly.
Is LASIK safe?
Yes, in a correctly screened eye. LASIK is one of the most studied elective procedures in the world. The serious complication, corneal ectasia, is rare and almost always traceable to a cornea that should have been turned down on topography. That is why a screening that includes corneal mapping and thickness is not optional.
Who is not eligible for LASIK?
Anyone with keratoconus or a suspicious corneal map, a cornea too thin for their number, a prescription that is still changing, uncontrolled dry eye, active eye disease, or who is under eighteen, pregnant or breastfeeding. Very high myopia is usually better served by an ICL. Being turned down is the screening working as it should.
What is the difference between LASIK and Femto LASIK?
In both, a flap is made and an excimer laser reshapes the cornea underneath. Standard LASIK makes the flap with a mechanical blade; Femto LASIK makes it with a femtosecond laser, which gives a thinner, more even and more predictable flap. The reshaping step is the same. Femto costs more.
Can LASIK be done twice?
An enhancement is possible if enough corneal thickness remains and the eye is otherwise healthy, which is why a safe tissue margin is planned from the start. Most people never need one. After SMILE, a touch-up is more involved and is usually done as a surface treatment.
Does LASIK last a lifetime?
The correction is permanent. The eye, however, keeps ageing: reading glasses arrive in the mid-forties regardless, and a cataract may develop decades later, as it does in everyone. Neither is undone by LASIK, and both can be treated normally afterwards.
Which is better for high myopia, LASIK or ICL?
Beyond roughly minus 8 to minus 10 dioptres, an ICL usually gives better quality vision because no corneal tissue is removed. It is also the option for thin corneas and for some dry eyes. It costs more and involves a lens inside the eye, so it needs its own careful screening.
About the author
Dr. Shirish Patel is a Consultant Eye Surgeon at Advanced Eyecare Centre, Goregaon West, Mumbai. He trained at Seth G.S. Medical College and KEM Hospital (MBBS) and at PBMA's H.V. Desai Eye Hospital, Pune (DNB Ophthalmology), and holds the FICO (A+B). Over nine years of practice he has performed more than 8,000 cataract surgeries and 400+ refractive procedures. He also consults at Apex Hospitals, Kandivali and Envision Eye Hospital.
This guide is general information written to help you ask better questions. It is not a diagnosis and does not replace an examination. Where price ranges are mentioned, they reflect what is commonly quoted in Mumbai at the time of writing and will vary by hospital, technique and individual case. For sudden vision loss, severe eye pain or injury, contact the clinic or your nearest emergency department immediately.