dreamy wrote:Hey guys, I developed severe myopia since I was 10 and my prescription is almost -10 on both eyes with some astigmatism.
To be precise, your right eye (OD) is -8.75 -1.00 @ 85 with a
Spherical Equivalent (SE) of -9.25 and your left eye (OS) is -9.75 -0.50 @ 57 SE -10.00. This is indeed high
myopia (nearsighted, shortsighed) and is
pushing the outer reaches for laser vision correction.
dreamy wrote:Now I am 26 and my eyesight is still dropping (although my eyes stopped growing five years ago), albeit slowly (-0.25 to -0.75 per year).
This is too much change. You need two consecutive years with less than -.25 diopters of change.
dreamy wrote:I spoke to a surgeon and he suggested me - provided I'm OK with the correction operation - to either implant PIOLs or perform a cornea surface ablation correction (I don't like an idea to have a corneal flap in the stroma). Of these, the clinics in the country I live (Ukraine) offer PRK, LASEK and Epi-LASIK operations; having read the Internet thoroughly I am leaning towards Epi-LASIK.
My wife is from Ukraine. I've been to Kiev, Odessa, Liviv, and Khmelnitsky may times, most recently just before Euro2012. The country has changed a lot in the last ten years.
You should be very careful of using surface ablation like
PRK,
LASEK, or
Epi-Lasik. I generally agree that no
Lasik flap means no possibility of a Lasik flap problem; however the probability of
corneal haze is elevated with more than about 6.00 diopters of refractive change. The doctor could use mitomycin C, but MMC is strong medicine that may be appropriate when necessary, but should be avoided if possible. The Lasik flap moderates the wound response and the probability of haze is nearly eliminated. This would indicate Lasik may be the better choice if you will be using corneal
ablation.
dreamy wrote:I wonder if I am eligible for the latter, given I also have the retinal peripheral dystrophy (see links below); and if I do, does my cornea thickness and pupil size allow good correction with low complication risks?
Your corneas are OD 581 microns minimum thickness and OS 597 minimum. With a 100 micron Lasik flap and an expected 60-72 microns of tissue removed by the laser (
Munnerlyn formula), you would still have about 400+ microns of untouched corneal tissue. For a healthy eye, 250 microns of untouched corneal tissue is considered enough to maintain stability (more is always better).
You mentioned
large pupil size. Although European
excimer lasers commonly have a large optical ablation zone, it is common practice for surgeons to reduce the size of the ablation zone to reduce the amount of tissue removal required. It will be absolutely important for your
optical ablation zone to be equal to or larger than the size of your naturally dilated pupils in a low light environment.
Your corneal curvature (K readings) indicate that you would have a very flat cornea after any sort of corneal refractive surgery. Surgery will flatten it down
the central cornea. Some docs use 37K as a cutoff. Ask your doctor to calculate the projected Ks after surgery. Flat corneas are considered a contributing factor to reduced contrast sensitivity and halos around light sources at night.
The peripheral retinal
dystrophy, although likely to limit your visual field, is not likely to be a major issue for corneal refractive surgery. That said, the microkeratome used for Lasik and Epi-Lasik will briefly raise the
intraocular pressure (IOP). Than can be problematic for a distressed retina.
A
phakic intraocular lens (P-IOL) may ultimately be the best option for a few years. It has the advantage of maintaining the shape of your cornea and keeping
accommodation. P-IOLs are a
temporary solution. All must be removed at some time due to the onset of cataracts (an age you need not worry about yet) or about 10 years, whichever comes first. They cause serious
endothelial cell loss and must be removed before the cornea becomes unhealthy.
Another concern is corneal disease. Although the Tomey scans indicate a somewhat regular astigmatism, it is slightly inferior. This may indicate forme fruste
keratoconus. Does anyone in your biological family have a history of corneal transplants?
The bottom line is that you are not an ideal candidate for any type of refractive surgery. Corneal based refractive surgery is likely to cause quality of vision problems. Lens based refractive surgery is temporary and may put your corneas at risk. Furthermore, you do not have a stable refractive error and may have (slight chance) a corneal disease.
Before proceeding, get the opinion of a retinal specialist. You may need to travel for this evaluation. Also, if you decide on P-IOLs, you may want to select a surgeon who does a lot of cataracts as the surgical skills or P-IOL are closer related to cataract lens surgery than Lasik or PRK. We have a list of
50 Tough Questions For Your Lasik Doctor that will help guide you in surgeon selection.
I’ll be very interested in your decision and the results of your surgery, if you decide to proceed.