Lasek Vs. Lasik for High Myopia
- Asked by charmer in Manhattan, NY
- 2 years ago
if you are a good candidate for both procedures, which is preferred for patients with high myopes (greater the -7.00). i would like a definitive answer. i keep getting differing answers.
LASIK vs LASEK for high prescriptions
You're getting different answers because the doctors you speak to are not explaining things to you in the detail necessary for you to make your own informed decision. I do things differently, i.e. assume my patients are smart enough to make the correct logical conclusions--provided I provide them with sufficient information (which I do)!
I was the 1st LASIK surgeon in NYC to have LASIK myself, which means out of the 1,000 eye surgeons in NYC who say they do LASIK, and the 10 who do this full-time/exclusively, I was the only one at that time who was willing to take the same commitment (and accept the same risks) that I was asking my patients to. Other LASIK surgeons in NYC whom I knew were hiding in contacts instead, which I found disingenuous/unethical.
My Rx was similar to yours, actually worse as I was a -7.50 - 1.50 x 180, which means I had more myopia and more astigmatism than you have. At that time (1999) FDA did not yet approve the simultaneous treatment of myopia and astigmatism, so I needed to be "double-carded" which means having one treatment card inserted into the laser to take off enough corneal tissue to treat my myopia, and then another card inserted right afterwards to treat my astigmatism--thereby taking off twice as much tissue as necessary.
To make the "right" answer to your question (LASIK vs. LASEK for high myopia) you need to understand some numbers. The math is very easy, so don't be intimidated by this!:)
The average corneal thickness is 500-550 microns (500 microns is 0.5 mm, or half the thickness of the smallest division on a ruler, to give you an indication of how small the measurements are we use).
When I was cutting LASIK flaps, the average flap I cut with a metal blade was 150 microns thick. You can also use a laser to cut a flap, which is called IntraLase or I-LASIK, but the thinnest flap you can cut this way is still 100 microns, or you might wind up with a partial flap, which would make the 2nd laser step unsafe/impossible. MDs are switching to IntraLase to cut thinner flaps than is possible with a metal blade to save tissue, but it's better to not cut a flap at all if this is your goal, as the following calculation will show.
To treat -7D of Rx, I would have to remove about 75 microns of tissue for a standard treatment, and 100 microns for a hi-def CustomVue WaveFront treatment, which pretty much everyone should get these days. Custom treatments always take off more tissue per diopter of Rx fixed than standard (low-def) treatments.
Therefore, if you start with 500 microns of cornea (I always use the lower number to be safe), and if you take off 150 microns to cut a flap (again, it's smarter/safer to use the higher number to be safe, as there is variability on what you aim for and what you get, even with a laser-cut flap), then take off 100 microns of tissue to get rid of your Rx, your untreated corneal stromal bed for safety is: 500 - 150 - 100 = 250
250 is the MINIMUM SAFE NUMBER OF UNTOUCHED CORNEA AFTER LASIK TO PREVENT THE PRESSURE OF YOUR EYEBALL TO CAUSE THE WALL OF THE CORNEA TO BULGE OUT WHICH IS CALLED IATROGENIC KERATOCONUS WHICH MIGHT REQUIRE A CORNEAL TRANSPLANT.
Now let's do the calculation for LASEK, which again is the ADVANCED SURFACE ABLATION that many top surgeons in the US (including myself) have switched to from LASIK because of this safety reason.
For LASEK, because I'm no longer cutting into the cornea and making a flap, the calculation looks like this:
500 - 0 (flap) - 100 (ablation) = 400 microns which is NO WHERE CLOSE to the 250 limit.
Now, KNOWING the information you need to make your own INFORMED DECISION, are you now CLEAR that LASEK is MUCH SAFER THAN LASIK for patients like you with higher prescriptions or thinner corneas?!:
Dr Emil Chynn, NYC
Recovery from LASIK is much quicker
I generally prefer LASIK but with a laser created flap. Recovery from LASIK is much quicker. The intralase (or femtosecond) laser has made bladeless LASIK more precise and safer for higher myopes.
LASEK vs LASIK for High Myopia
It is very easy to get lost in the "alphabet soup" letters surrounding the various Laser Vision Correction(LVC) procedures that we do. LASEK is, essentially, PRK, which is the performance of LVC on the outer surface of the eye. This procedure is typically reserved for less severe prescriptions and your myopia is in the "higher than average" group. I would recommend LASIK for a -7.00 patient, if your corneal thickness is adequate(above 520 microns should be sufficient). PRK(or LASEK) has a slower recovery time, but is recommended in some patients with a certain corneal thickness or shape, but, typically, LASIK is the procedure of choice.
Web reference: http://www.kameen.com
Recent LASIK Reviews
These answers are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.