Underresponse and enhancement questions

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Underresponse and enhancement questions

Postby jz5168 » Thu Aug 23, 2007 3:15 pm

Hi,

I had custom lasik (wavefront guided) on 7/17 and since the start, my left eye has been blur. I paid 4 visits so far and left eye has been unchanged, this past Tuesday's (8/21) visit showed left eye was at 20/50. Right eye has been up and down, noticebly in the past week it has down, and 8/21 visit showed it was at 20/40. The doc said left was -1.0 and right was -0.5 with a bit astigmatism left. My before op was -6.0 left, -5.25 right + 0.75 astigmatism.

My doc is supposed to be good and was referenced by one of my good friends and he's one of the 100 top US optomolygist in the country, he has good reputation. So the result was something I was not very well prepared. Now the doc (it's the same doc for all my pre and post ops, but this doc is a different one than the one who did my surgery), the doc now said we should plan on enhancement.

I'd like to hear your expert opinion on these questions I have:

1) the doc said I was underresponsive. How do I interpret this? Does this mean I heal too fast? But my left has been this way since after the op, no change I noticed. Right eye drifted from 20/25 at 2 weeks after op to 20/40 4 weeks after op.

2) For enhancement, do you suggest I do one eye at a time?

3) The doc did say I should be able to see 20/20 after enhancement. Do you agree?

4) Do they use suction right for enhancement? I know they'll lift the flap.

5) Which is preferred for enhancement with my situation, conventional or wavefront lasik? LasikExpert you said in another thread that wavefront for such minor correction tends to overcorrect.

Thank you very much, this is a great site and now I only wish I knew it before the surgery. What I mean is I'll most likely pick Epi-Lasik over Lasik.
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Re: Underresponse and enhancement questions

Postby LasikExpert » Thu Aug 23, 2007 4:23 pm

jz5168 wrote:1) the doc said I was underresponsive. How do I interpret this?


Each pulse of the excimer laser removes corneal tissue. The actual amount of tissue that is removed is usually consistent from patient to patient, but some patients will have more (overcorrection) or less (undercorrection) tissue removed with the same amount of pulses.

One of the reasons this occurrs is corneal hydration. If the cornea is overly hydrated, the laser is not as effective at removing tissue and an undercorrection is likely. If the cornea is underhydrated, such as someone with untreated dry eyes, the laser is more effective when applied to the cornea. It is difficult to preoperatively diagnose overly hydrated corneas.

The healing response can be very different from one patient to another. Aggressive or uneven healing can induce myopia (nearsighted, shortsighted) vision or irregularities like astigmatism.

Corneal edema is a common part of the healing process. At about five weeks postop you could still have some edema, which could cause or contribute to your myopia and astigmatism.

Lasik induced dry eyes can cause or exacerbate corneal edema.

It is possible that everything was planned and performed correctly, but did not turn out as desired. That is one of the real-world problems with any surgery.

jz5168 wrote:2) For enhancement, do you suggest I do one eye at a time?


One eye at a time is a reasonable option.

jz5168 wrote:3) The doc did say I should be able to see 20/20 after enhancement. Do you agree?


Certainly it is possible, but the probability needs to be predicted by the surgeon who knows all the information. One advantage is that the doctor now knows how the cornea reacts.

jz5168 wrote:4) Do they use suction right for enhancement?


Suction is not required during normal Lasik enhancement.

jz5168 wrote:I know they'll lift the flap.


Not necessarily. Because the amount of required change is so small, the doctor may recommend PRK on the Lasik flap. This will be something to discuss with the doctor.

jz5168 wrote:5) Which is preferred for enhancement with my situation, conventional or wavefront lasik?


Like the first time, which is better will depend upon the data that the wavefront systems are able to gather.


jz5168 wrote:LasikExpert you said in another thread that wavefront for such minor correction tends to overcorrect.


There have been several reports of overcorrection with small refractive error changes when using wavefront-guided ablation, however doctors are changing their nomograms and technicians are "tweaking" the laser systems to reduce this probability. You need to talk with your surgeon about his practical experience in this regard.

jz5168 wrote:Thank you very much, this is a great site and now I only wish I knew it before the surgery. What I mean is I'll most likely pick Epi-Lasik over Lasik.


The type of procedure may not have made any difference at all if the cause was agressive healing, edema, dry eye, or corneal hydration.
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Postby jz5168 » Thu Aug 23, 2007 5:14 pm

Glenn,

Thank you very much for you invaluable input and such quick response.

The doc said they create really thin flap (90 micron with only 1 micron error margin, so 89-91) because Interlase was used. Knowing this, is PRK still a good option for enhancement because it will know make the flap really thin I guess.

Thank you very muck.
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From another agressive healer

Postby Silentseagull » Thu Aug 23, 2007 10:16 pm

jz5168,

I could copy your post, change a few names and it would be the exact experience that I had.

After my initial procedure left me 20/60 with a little astigmatism in each eye, my Dr. classified me as an aggressive healer in need of enhancement.

This statement was made 30 days after my initial procedure so I had to wait an additional 3 months before we could do the enhancement. (fortunately he gave me some corrective lenses that helped during this period).

I just recently had the enhancement surgury (both eyes) and am extremely pleased with the results. Currently I'm 20/15.

When talking with my Dr. he said, being an agressive healer put me outside of their typical healing norms (causing the near near-sighted results) But for the enhancement, he knew how I would heal and therefore could adjust for that situation. The outcome was outstanding.


I hope your results are the same.
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Postby aspenice » Thu Aug 23, 2007 11:46 pm

What does aggressive healing mean as far as an outcome for the lasik that was done? I think I may fall into this category a bit.
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Postby LasikExpert » Fri Aug 24, 2007 12:53 am

The healing response varies at many levels, but primary concerns are final thickness of the cornea, degree of scar (if any), and regularity of the cornea. An agressive healer may have undercorrection or irregularity (including astigmatism) because responsive cells have inflammed the cornea.
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Postby jz5168 » Fri Aug 24, 2007 2:04 am

Hi Silentseagull,

It's comforting to see someone have very similar experience and glad it worked out for you at the end. May I ask you:

1) what's your refractive error before op?
2) what procedure did you have, Lasik, wavefront Lasik, PRK, etc?
3) what procedure did you have for enhancement?
4) did you have enhancement for both eyes the same time, or one at a time?

My doc didn't say I'm aggressive healer, just said I have underresponded to the treatment.

btw, right now my close-up vision is great, text is crisp and sharp, this leads me believe my only major problem at this point is undercorrection.

My doc also said we will plan enhancement for 2 months later, which will be 3 months from the original treatment. Until then I'll just be blur for mid and long range.

Thanks.
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Postby Silentseagull » Fri Aug 24, 2007 3:55 pm

jz5168,

I was -5.75 in each eye with some astigmatism (I don't know the exact number but it was more than slight, but not high).

The procedure was wavefront Lasik for both the initial and enhancement.

I had procedure done on both eyes for the initial and the enhancement.

On a side note, the first 30 day period was EXTREMELY frustrating. I knew I could't see well (other than close up) but my Dr. kept saying that it was normal and that after 30 days things should be better. At my one month check, when he saw that I had not improved at all from my 1 week appointment, he immediatly gave me some corrective lenses and started planning for the enhancement. Having the corrective lenses changed my attitude completely( I could see again), it also helped that the Dr. who was always professional, but a little cold, suddently became very empathetic.

Good Luck!
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Postby jz5168 » Fri Aug 24, 2007 4:28 pm

Silentseagull,

Thanks for you response. One more question for you, what's your pre-op corneal thickness, residual thickness after 1st and 2nd treatment and flap thickness?
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Postby Silentseagull » Fri Aug 24, 2007 9:10 pm

jz5168,

I'll let you know in a week (my next appointment). I know I started at 620 and they said the slope of my cornea was helpful as well. I don't know what I was left with, but I'll ask.

My Dr. made it sound like I had plenty of room for enhancements if needed.
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Postby jz5168 » Sat Aug 25, 2007 2:55 am

Glenn,

I'm really interested in the PRK overy flap option for my enhancement. Can you shed some light on this?

To be more specific, my doc only creates 90 micron flap, lets say if my correction needs to be -1.0, according to the doc, each 1.0 requires about 20 micron (or a little less) tissue to be removed. Also based on my research, the epithillium layer is about 50 micron, if that's case, then if PRK were performed, the doc would scrape away the 50 micron epithillium, then burn away 20 micron Boman's layer or Stromal layer, that would leave a 20 micron super thin flap? At least for the initial a couple of weeks before the the epithillium cells regenerate.

So my question is, is my case suitable for PRK over flap for enhancement?

My second question is, with so minor correction (lets say -1.0 ~ -2.0), haze shouldn't be an issue with PRK, right?

My third question, I have not checked w/ my doc yet, but it seems he only performs Lasik, so would PRK even be an option for him?

Again, thank you very much for your input.
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Postby LasikExpert » Sat Aug 25, 2007 3:21 am

The reason PRK on the Lasik flap is possible is the use of Mitomycin C. This changes the wound response and effectively eliminates corneal hazing.

A traditional 6.0mm laser ablation would remove 12 microns of tissue. Wavefront-guided is likely a bit more. The larger the size of the ablation area, the greater the amount of tissue removed to effect the same refractive change.

The 90 micron flap is not including the epithelium, but you would have a rather thin flap after PRK enhancement. This is not likely a problem unless there was some reason to lift the flap, which also is not likely.
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Postby jz5168 » Sat Aug 25, 2007 4:14 am

Glenn,

Thanks for the quick response. Just want to clarify what you said.

When you said: "A traditional 6.0mm laser ablation would remove 12 microns of tissue.", you mean 12 microns of tissue removed for every -1.0 correction, right?

You said: "The 90 micron flap is not including the epithelium", what do you mean by that?

You siad: "This is not likely a problem unless there was some reason to lift the flap". If the flap is too thin, what problem would it cause if being lifted?
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Postby jz5168 » Sat Aug 25, 2007 4:15 am

Glenn,

Thanks for the quick response. Just want to clarify what you said.

When you said: "A traditional 6.0mm laser ablation would remove 12 microns of tissue.", you mean 12 microns of tissue removed for every -1.0 correction, right?

You said: "The 90 micron flap is not including the epithelium", what do you mean by that?

You siad: "This is not likely a problem unless there was some reason to lift the flap". If the flap is too thin, what problem would it cause if being lifted?
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8th week checkup

Postby jz5168 » Tue Sep 11, 2007 9:56 pm

Just come back from my 8th week checkup. My vision change after op is:

First week: Left 20/50, right 20/25
Second week: Left 20/50, right 20/25
5th week: Left 20/60, right 20/40
6th week: Left 20/200, right 20/60
8th week (today): Left 20/50, right 20/80, with astigmatism 1.00 right and 0.5 left.

it's surprising to see my left eye has finally caught up, I noticed this just within last a couple of days. However, my concern is now the right eye is going downhill.

Another concern is the astigmatism. My old prescription has no astigmatism correct on my left eye at all (-6.0) and right eye had -.75 astigmatism. The doc told me today my left eye was corrected for .25 astigmatism, but now it has 0.5, and right eye now has 1.0, worse than before op.

Glenn, could this still due to the healing process? The doc never said I'm aggressive healer, but do I look like one based on my profile?

I know my eyes still fluctuate a lot, so I'll still keep patient.

My doc also told me today to stop Flarex drops.

My next visit is 16 days from now, my doc said next visit will take at least 1 hour and the doc will perform both computerized and manual wavefront measurement with pupils dilated.

The doc also said lens accomodation also can do trick for far distance vision not just close-up vision and think I still might have the problem.

I'll report back my findings after next visit.
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