Am I a Candidate for LASIK? The Exam Findings That Make Me Say No

"I've worn contacts since I was fifteen, I've already booked four days in Seoul in March, and I just need to know before I pay for the flight — will you actually be able to do it?"

A version of that message lands in my inbox most weeks. It's a fair question and a reasonable way to think about a trip. It's also the one question I refuse to answer casually.

"Am I a candidate for LASIK" is not a question your prescription can answer, and any clinic that answers it from a photo of your glasses receipt is selling you a booking, not an assessment. Your prescription tells me how much corneal tissue would need to be reshaped. It tells me nothing about how much tissue you have, what shape it's in, how your tear film behaves, or how wide your pupils open in the dark — and those are the findings that decide. Below is exactly what I measure, exactly which results make me say no, and the risks I go through with every patient before they sign anything.

The measurements that decide it, before I say a word

A good outcome begins in the exam room, not the laser room. When you come in for a full workup, I'm not confirming a decision you've already made — I'm looking for reasons not to operate. Here is what I actually read:

• Corneal thickness (pachymetry). I need to know what's left underneath after a flap is created and tissue is removed. That residual stromal bed is the structural floor of your eye.
• Corneal topography and tomography. The shape map. This is where keratoconus and subtle asymmetric steepening show up — sometimes in a patient with no symptoms at all and 20/20 corrected vision.
• Refraction stability. I want a prescription that hasn't moved meaningfully in about a year. If it's still drifting, surgery is chasing a moving target.
• Tear film and meibomian glands. Dry eye is the most common post-LASIK complaint worldwide, and I'd rather find it before than after.
• Pupil diameter in dim light. Large scotopic pupils correlate with glare and halos at night, and that changes how I design the optical zone — or whether I operate at all.
• Intraocular pressure, endothelial cell count, and a dilated retinal check. Undiagnosed glaucoma, an early cataract, or a retinal problem changes the entire plan.

Who LASIK genuinely suits

LASIK does its best work in a fairly specific person: over 18 and ideally in their twenties or older, with a stable myopic or astigmatic prescription, a cornea of adequate thickness and normal shape, a healthy tear film, and expectations grounded in reality rather than in someone else's Instagram post. Add one more thing — a life that rewards fast recovery. Clear LASIK takes about ten minutes for both eyes and most patients are back to daily life in one to two days, which is why it fits people flying in with a limited number of days off.

If your night vision matters more than average — you drive at night for work, or you're simply fussy about contrast — the aberration-mapped approach on our Personal Custom LASIK page is usually the more sensible design, because it accounts for the higher-order aberrations a standard prescription test never sees. The technical detail of the fourth-generation flap design is set out on our Clear LASIK treatment page, and our Korean head office covers the same procedure in more depth on the 클리어라식 page at healingeye.co.kr.

Age is its own conversation. In your late forties, correcting distance perfectly can make reading harder sooner than you expected, which is a trade-off you should choose deliberately — I've written about where the boundaries sit in my honest take on the LASIK age limit.

The findings that make me say no

This is the part of the article I care most about. Being able to say "not you" is the whole reason a surgical consultation exists.

Findings where I will not operate

Keratoconus or suspicious topography. Even a forme fruste pattern — subtle inferior steepening, asymmetric astigmatism — is a hard stop for flap-based LASIK. Cutting a flap in a biomechanically weak cornea risks progressive ectasia, meaning the cornea bulges and vision deteriorates over months or years. There is no undo for that.

Insufficient residual cornea. If the arithmetic between your thickness and your prescription doesn't leave a conservative margin, the answer is no, regardless of how much you want it.

Established dry eye disease or an autoimmune cause. Sjögren's, significant meibomian gland dropout, or severe evaporative dry eye that hasn't responded to treatment. LASIK temporarily reduces corneal nerve function and tear production; an eye with no reserve has nowhere to go.

Uncontrolled glaucoma, a visually significant cataract, or a history of herpetic keratitis. Each of these changes the risk calculation entirely, and the first two mean a different procedure is the correct treatment, not laser correction.

Expectations I can't meet. If a patient tells me they need a guaranteed result to keep a job or a visa, I decline. Nobody can guarantee a visual outcome, and a surgeon who implies otherwise is the risk.

Findings where the answer is "wait," not "never"

The risks I say out loud, every time

LASIK is a well-studied procedure with a strong safety record, and it is still surgery on a healthy organ. These are the realistic downsides:

Dry eye. The most common complaint after surgery. For most patients it's a matter of weeks to a few months of drops; for a minority it lingers longer and needs active management. If you already have symptoms, read my honest talk about LASIK and dry eye risk before you book anything.

Night glare, halos and starbursts. Usually most noticeable in the first weeks and typically settling, but not guaranteed to disappear entirely — and more likely with larger pupils and stronger corrections. I've written about what this genuinely looks like behind the wheel in our piece on LASIK and night driving glare.

Under- or overcorrection and regression. Some eyes drift back toward myopia over the years, particularly higher prescriptions. Enhancement is sometimes possible, sometimes not, depending on how much cornea remains — which is why I calculate the margin for a possible future re-treatment on day one. Our LASIK and LASEK revision page explains where the limits of re-correction sit.

Flap-related problems. Rare, but real: microstriae, epithelial ingrowth, or flap displacement after a blow to the eye. If you box, do judo, or play contact sport for a living, I'll steer you away from a flap procedure entirely.

Infection or inflammation. Uncommon, treatable when caught early, and the main reason I want to see you for a post-op check before you fly home rather than after.

When the cornea says no, there is usually another road

Being turned down for LASIK is not the end of the conversation. A borderline-thickness cornea may suit a surface procedure such as LASEK, where no flap is made; a cornea with adequate thickness but a preference for a smaller incision may suit our SMILE procedure. A very high prescription, or an eye where I don't want to thin the cornea at all, often points toward an implantable lens instead — the ceiling for laser correction is a real one, and I've mapped out where it sits in our guide to the high prescription LASIK limit. You can see the full range side by side on our treatments overview.

Making one trip count

Stop soft lenses one to two weeks before your exam — longer for toric or rigid lenses — and bring your glasses. Allow a few days in Seoul rather than a single afternoon: exam and discussion on one day, surgery, then a post-op check before you fly. We're one minute from Sinnonhyeon Station and roughly 70 minutes from Incheon, with Japanese, Traditional Chinese and English interpreters on site, so you'll go through your own scan data in your own language before you decide anything. One surgeon stays with you from exam through aftercare, and follow-up continues by video call once you're home.

I'd rather you flew home still wearing glasses than flew home with a cornea I shouldn't have touched. Send me your prescription by all means — but come for the exam with the possibility of a "no" already in your pocket. If the answer turns out to be yes, you'll trust it far more.

— Dr. Kim Sun-young, Medical Director, Healing Eye Clinic (Cornea · Glaucoma · Cataract)