Custom PRK?

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Custom PRK?

Postby carioca » Wed Aug 15, 2007 5:07 am

Could you please give me some advice? Sorry for the long post...

My left eye is -4.5, -1.33 ast, and my right eye dropped from -1.0 to -1.5, -2.25 ast in the last few years. Because of the big difference between my eyes (anisometropia), I've had a lot of trouble fitting glasses or contacts, I would get dizzy if i looked to the side or move my head. I did not get a driver's licence for many years just because of that. Finally, my doctor found the optimal solution: a -3.5 soft contact only in my left eye, to bring them up to the same level, and glasses on top of that to correct the rest in both eyes.

Even though this is the best solution so far, I ended up mostly wearing one contact, and only wear glasses when i really need to see far. However, driving in my glasses is still uncomfortable, and I have gotten by on wearing the contact only, even though I shouldn't since i don't get a good enough vision with just that. I could manage occasional driving in the small town I live, but i will be moving soon, and I might not get by with not wearing my glasses then. I'm also troubled that my "good" eye dropped from -1.0 to -1.5 in the last 3 years, maybe it's because it does all the work, and because I've been using my computer 8-12 hours every day. Therefore, I've been considering "fixing-up" my left eye with laser surgery.

I had a LASIK consultation today. The doctor recommended Custom PRK because the surface of my cornea was uneven.

My measured pupil size, as of today, was 7mm. I had another Lasik consultation a couple of years ago (in a different country), and I think my measured pupil size was larger than 7mm, but I don't have the records. They dilated my pupils today and they seem huge, I even asked my friend to literally hold a measuring tape and then a ruler basically touching my eye, and he measured over 8mm. (Don't laugh at my self-diagnosis here :-) ) Maybe I'm just imagining after I read all the pupil-size-related horror stories. He doctor said they would do a 6mm zone on my eye, and "smooth out" another 1/2mm so that I won't have the sharp edge betw. treated and untreated areas.

I asked why they wouldn't do a larger zone and he said that this would mean removing more tissue, which is not good. My cornea was measured at 560-570 microns, which is supposedly not too thin. Here's one question: how are PRK healing, cornea thickness, and treatment zone size all related?

One curious fact, http://www.allaboutvision.com/visionsur ... aser_2.htm lists different laser models and their specifications. Now, the Visx Star S4 IR laser that this doctor uses has the optical zone of 6mm, so that's the size they are limited by!

He also said he would put me on $100/month Restasis eye drops for dry eye. I don't normally have dry eyes, only late at night after working at the computer all day (I'm a programmer).


By the way, this is with [a national chain]. Anyone had any good / bad experience with [a national chain]? Is $1,500 per eye + $200 "lifetime treatment" a reasonable price for Custom PRK?

Thanks!!!!!!!!

P.S: I asked whether a flap after Lasik grows back to its normal strength (even though I'm doing PRK, so it doesn't matter), and he said "yes, even stronger, because the scar tissue is thicker" - ????? ......hm........

Note: Edited to remove name of Lasik clinic.
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Re: Custom PRK?

Postby LasikExpert » Tue Aug 21, 2007 4:39 am

You have significant astigmatism and astigmatism that is greater than half your sphere (myopia, nearsighted, shortsighted). High astigmatism is much more challenging for Lasik or PRK to correct.

carioca wrote:The doctor recommended Custom PRK because the surface of my cornea was uneven.


Depending upon what the doctor meant by "uneven", PRK may not have any advantage over Lasik beyond the normal advantages of PRK over Lasik (primarily, no Lasik flap). If the doctor is referring to astigmatism, then my opinion (I'm not a doctor) is that a surface ablation like PRK would be the more appropriate option.

carioca wrote:My measured pupil size...


The size that is important is the size of your naturally dilated pupils in a low-light environment. Pharmacologically dilated pupils are not a valid measurement. Also, measurements with infrared light in total darkness (Colvard) are usually around 1.0mm larger than in low, but visible, light. You will want to confirm this information.

carioca wrote:He doctor said they would do a 6mm zone on my eye, and "smooth out" another 1/2mm so that I won't have the sharp edge betw. treated and untreated areas.


This will make the change more gradual than without the transition zone, but 0.5mm is not much of a transition and if this undercorrected area is within the size of your naturally dilated pupils, you may have an elevated risk of night vision problems. You should read our Lasik and night vision article.

carioca wrote:I asked why they wouldn't do a larger zone and he said that this would mean removing more tissue, which is not good.


It is correct that the larger the ablation zone, the greater the amount of tissue that needs to be removed to correct the same refractive error.

carioca wrote:My cornea was measured at 560-570 microns...


About five decades of surgery has shown that a healthy cornea will remain stable if at least 250 microns of tissue remains untouched (more is always better). Based upon laser ablation correction calculations, you have significantly more cornea than necessary for PRK, and enough for Lasik even with a larger ablation zone.

carioca wrote:...how are PRK healing, cornea thickness, and treatment zone size all related?


Thickness and treatment zone is discussed in detail in the article referenced and linked above. PRK healing generally would not be a relevant issue.

carioca wrote:[The] laser that this doctor uses has the optical zone of 6mm, so that's the size they are limited by!


The zone is actually significantly smaller in your situation. To correct your high astigmatism, the ablation pattern is elliptical rather than round. The narrow sides of the ellipsis may be as small as 5.0mm

carioca wrote:He also said he would put me on $100/month Restasis eye drops for dry eye.


If you have dry eye, treatment and medication would normally be covered under your major medical health insurance. You should check this first.

carioca wrote:I don't normally have dry eyes, only late at night after working at the computer all day (I'm a programmer).


Expect a delayed recovery. Heavy computer users don't blink as often and tend to have slowed healing due to dry eye issues. You will need to be diligent about closing your eyes for 20-30 seconds on a regular basis, and using preservative-free artificial tears. Write a program to remind you!

carioca wrote:By the way, this is with [a national chain].


Sorry about the edit, but we refrain from naming doctors or clinics.

carioca wrote:P.S: I asked whether a flap after Lasik grows back to its normal strength...


The information is simply wrong. The Lasik flap does heal, but not like a scratch on your arm. It is always different and provides less than 3% of the structural strength of the cornea compared to preop. That is why corneal thickness is such an important measurement.

You need to have a long talk with your surgeon.
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