Another Large Pupil

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Another Large Pupil

Postby lbell » Thu Oct 19, 2006 7:43 pm

I am scheduled for LASIK in a week. My concern is my large pupil size at 7.6mm and 7.9mm. My doctor is certfied on 3 different systems and recommended Ladarvision 4000 due to the larger treatment zone. I was told I was a good candidate but there is always the chance of having night vision problems with such a large pupil.

Does anyone have any idea what the success rate is with Custom Wavefront and large pupils?

My corneal thickness was 536 and 539 and I am also wondering if I will have enough tissue left for enahancements with such a large ablation zone and blend zone.

2 Doctors said that would do Lasik and the 3rd said they don't do anyone over 7mm (I think due to the limitation of their Visx).

I am considering Dr. MC out of Birmingham (He used to be in Atlanta).

Thanks!
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Postby LasikExpert » Thu Oct 19, 2006 8:55 pm

A part of the pupil size issue is the amount of refractive error being corrected. If your current prescription is low (under about 4.00 diopers) then the probability of problems is considered less than if your prescription is high (over about 8.00 diopters).

Be sure to read our article about Lasik Pupil Size issues.

Be sure to use our 50 Tough Questions For Your Lasik Doctorto evaluate your potential surgeon.
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prescription

Postby lbell » Thu Oct 19, 2006 9:21 pm

Thanks Glenn.

My current contact prescription is:

Right Eye -2.00 -1.75 x 10
Left Eye -2.00 -1.25 x 180
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Postby LasikExpert » Fri Oct 20, 2006 10:16 pm

This is both good news and not great news. Your myopia (nearsighted, shortsighted) vision is quite low, but your astigmatism is high and high in comparison to your myopia. The myopia would probably have a high probability of good correction, but don't be surprised if the astigmatisim requires enhancement surgery. Residual astigmatisim would likely cause slight ghosting until corrected - especially in low light environments.
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Thanks

Postby lbell » Sat Oct 21, 2006 2:45 am

Thanks again Glenn.
This is what my Lasik Surgeon said as well. He said there is a good 5-10%chance that I would need an enhancement.
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Postby pljenkins » Sat Oct 21, 2006 6:11 am

Ibell,

My pupil size was measured at 7.75 both eyes, and I have no significant night vision problems. The only problems I have are when my eyes are tired (12 hours at work staring at a screen in dry environment kind of tired) and it's VERY dark, I'll get a slight starbursting, which I find to be not very distracting. It also resolves as soon as I get a shot of headlights from oncoming traffic. :)

My pre-surgury numbers were a little lower then yours across the board, but not by much. My surgeon used the VisX laser with Wavefront. I'm 10 months post-op and my acuity is 20/15.

Paul
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Large pupils (7.5mm), moderate myopia (-4): good for Lasik?

Postby murvaja » Sun Nov 19, 2006 10:54 pm

I have read that anyone with pupils larger than 6.5 mm might be inappropriate candidates for LASIK. I was told by two doctors that I was a good candidate, even though my dilated pupils go all the way to 7.7mm.

My detailed eye measurements are:

OD:
Dilated pupil size: 7.7 mm x 7.4 mm @ 107
Corneal thickness at center: 525 microns
Myopia: -3.75
Astigmatism: -0.75

OS:
Dilated pupil size: 7.3 mm x 7.2 mm @ 55
Corneal thickness at center: 540 microns
Myopia: - 3.75
Astigmatism: -0.50

Given my pupil sizes are around 7.4 mm, it appears that a 8mm ablation zone would be appropriate to avoid nightime halos. As I understand it, an 8mm ablation zone requres removal of 84 microns (21 per diopter) from the cornea. That, added to the 180 microns required for the flap would means that for the OD eye, means I would only have

525
- 180 (flap)
- 85 (ablation)
-----
260 microns of untouched cornea left. Is this safe for a long-term stable cornea? Or would LASEK/Epi-Lasik be more appropriate for me since they don't require a flap?

Also, I understand some lasers allow for larger treatment zones: which ones currently have the widest range (I assume those would be ideally suited for my eyes)?
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Postby LasikExpert » Mon Nov 20, 2006 3:03 am

A flat statement that a particular pupil size becomes a contraindication for Lasik is too simplistic and inaccurate. You should read Lasik Pupil Size for a detailed explanation.

You state "Dilated pupil size". If this is dilated with eye drops then the measurement is of little value. What is important is the naturally dilated pupil size in a low light environment plus several other factors.

A 180 micron flap is rather thick. These days doctors seem to prefer a thinner flap and some early studies indicate that a thinner flap is less likely to contribute to dry eye problems. If the flap is made with a mechanical microkeratome, a 110-130 micron flap is more likely. If the flap is made with a laser microkeratome (femtosecond laser), then an 80 to 100 micron flap is possible.

It is generally agreed that the minimum untouched corneal thickness to maintain stability on a healthy eye is 250 microns, but more is always better.

Because your refractive error is relatively low and your corneas are relatively thin, you should investigate if PRK, LASEK, or Epi-Lasik may be appropriate alternatives.
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Postby murvaja » Mon Nov 20, 2006 4:22 am

Thanks for the info. I really appreciate the help in this forum, and usaeyes.org has been by far the most informative site on the subject!

The numbers I gave for my pupil size were indeed obtained after dilation with eye drops. The numbers under bright/dim light are as follows:

bright dim
OD: 3.9 mm 7.0 mm
OS: 4.3 mm 7.2 mm

The article you pointed mentions that the size of the ablation zone is important as well. Given the pupil size measurements above, what would be a reasonable optical/transition zone for my pupils, and how much tissue would I expect to have removed?

I understand that the presence of High Order Aberrations (HOAs) is the main other factor that may help predict problems. In my case, I have 0.09 microns for my OD and 0.12 microns for my OS. I was told that this means I have very few HOAs, so a Custom Wavefront treatment would not be necessary. In fact, because the Custom lasers tend to remove more tissue, I would be better off with a Flying Spot laser since it has the widest optical zone range, and my pupils are medium-large. Is that true? If so, what ranges can I expect from these Flying Spot lasers?

Finally, I have indeed been considering Epi-Lasik, and here is what I have heard about its long-term effects compared to LASIK:

Advantages
- Less likelihood of dry eye problems
- No flap complications
- Less likely need for enhancements
- Leaves more of the cornea intact

Disadvantages
- Relatively new procedure, not as well tested as LASIK
- Does not allow for Epi-Lasik enhancements (only LASEK or PRK enhancements, which are more uncomfortable and might cause corneal haze).
- Causes significant more discomfort/irritation than LASIK, and the patient cannot drive nor work for 1/2 days after the procedure.

Cost
- Same as LASIK

If any of this is misguided please let me know.
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Postby LasikExpert » Tue Nov 21, 2006 2:28 am

murvaja wrote:The article you pointed mentions that the size of the ablation zone is important as well. Given the pupil size measurements above, what would be a reasonable optical/transition zone for my pupils, and how much tissue would I expect to have removed?


The largest optical ablation zone in the US is 6.5mm, which requires about 18-20 microns per diopter of refractive change. This will be a bit higher for wavefront-guided, and lower for wavefront-optimized and conventional laser ablation. The doctor is able to determine how much tissue will be removed and where before surgery.

murvaja wrote:I understand that the presence of High Order Aberrations (HOAs) is the main other factor that may help predict problems. In my case, I have 0.09 microns for my OD and 0.12 microns for my OS.


Something is not quite right. The Root Mean Squared (RMS) of HOAs for most people is in the 0.25 to 0.30 micron range. Being 0.09 is amazingly low.

murvaja wrote:I was told that this means I have very few HOAs, so a Custom Wavefront treatment would not be necessary.


There are two schools of thought on that. One is that someone with a very low HOA RMS would find a significant increase in HOA quite noticeable. Another is that if the HOA RMS is not likely raised above about 0.30 HOA RMS, then conventional would be appropriate.

It appears from most of the studies and data that fewer HOAs are induced by wavefront-guided than conventional, however wavefront-optimized may be appropriate.

I recommend that you follow the advice of your doctor on this one. S/he knows the results from his/her surgeries.

murvaja wrote:Finally, I have indeed been considering Epi-Lasik, and here is what I have heard about its long-term effects compared to LASIK:

Advantages
- Less likelihood of dry eye problems
- No flap complications
- Less likely need for enhancements
- Leaves more of the cornea intact

Disadvantages
- Relatively new procedure, not as well tested as LASIK
- Does not allow for Epi-Lasik enhancements (only LASEK or PRK enhancements, which are more uncomfortable and might cause corneal haze).


You almost have all of that correct. Epi-Lasik is essentiall PRK, which is the earliest form of laser assisted refractive surgery. Several recent studies are finding that Epi-Lasik and LASEK have about the same rate of discomfort and/or haze as PRK.

murvaja wrote: - Causes significant more discomfort/irritation than LASIK, and the patient cannot drive nor work for 1/2 days after the procedure.


None of the surface ablation techniques (PRK, LASEK, Epi-Lasik) have the "wow" effect of Lasik, but those advantages may make a surface ablation more appropriate.
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Postby murvaja » Fri Jan 19, 2007 11:20 am

Hi Glenn,

I have continued to read up a lot on this, and even consulted a third center (this time one certified by usaeyes.org). I am gradually closing down on my options, but I still have a few questions -- I hope you can clarify them for me.

1) You said in the previous post: "I recommend that you follow the advice of your doctor on [using wavefront]. S/he knows the results from his/her surgeries. "

Two of the doctors I consulted recommended wavefront (they do so on virtually all patients that qualify for the procedure), and the other recommended B&L flying spot w/o wavefront (because it had a wider treatment zone, which is more appropriate for my large pupil size -- plus, it is also cheaper). I've seen good reviews for all 3 places -- which should I pick?

On one hand I feel inclined to pay extra for wavefront because it is considered safer, on the other I wonder if some doctors always recommend wavefront because they make more money on it, even if my eyes don't really need it -- in which case I might as well settle for the cheapest procedure that is suitable for my eyes.

2) None of the places I visited seemed willing to do PRK/LASEK/Epi-Lasik since I am a good candidate for LASIK. It seems tough to find surgeons willing to do PRK, yet it is something you suggested I consider. Should I look further for a doctor that is willing to consider the option?

3) I am 26 and will most likely get presbyopia in about 15 years. I am hoping that by then there will be a treatment for it; given the direction of current research, can we expect all of today's procedures (LASIK, PRK etc) will be forward-compatible with presbyopic treatment?

4) All 3 places suggested my case is essentially riskless, given today's technologies. Is that true, or hype (i.e. there is no such thing as riskless surgery)?

Thanks again!
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Postby LasikExpert » Sat Jan 20, 2007 5:28 am

murvaja wrote:1) Two of the doctors I consulted recommended wavefront (they do so on virtually all patients that qualify for the procedure), and the other recommended B&L flying spot w/o wavefront (because it had a wider treatment zone, which is more appropriate for my large pupil size -- plus, it is also cheaper). I've seen good reviews for all 3 places -- which should I pick?


Both methods are considered medically appropriate. If you have read our article on Lasik pupil size issues then you understand that this may be very important if you also have high refractive error.

Wouldn't it be nice if all doctors agreed on what is best?!

murvaja wrote:2) None of the places I visited seemed willing to do PRK/LASEK/Epi-Lasik since I am a good candidate for LASIK. It seems tough to find surgeons willing to do PRK, yet it is something you suggested I consider. Should I look further for a doctor that is willing to consider the option?


About 85% of patients who have laser assisted refractive surgery have Lasik, so the probability of it being the preferred method is not surprising. My bias is toward surface ablation, but that is a bias and someone (especially a surgeon) who has a bias toward Lasik is just as valid and quite likely more so. You need to decide how important a surface ablation technique is to you and your individual circumstances.

I am quite certain that if faced with a choice of surface ablation or you go elsewhere, all of your doctors would provide you surface ablation (assuming it is medically appropriate).

murvaja wrote:3) I am 26 and will most likely get presbyopia in about 15 years. I am hoping that by then there will be a treatment for it; given the direction of current research, can we expect all of today's procedures (LASIK, PRK etc) will be forward-compatible with presbyopic treatment?


There is already surgery for presbyopia. See NearVision CK. It is difficult to predict what will be available in 15 years. Lasik has been around for only 10 and PRK only a few years before that.

murvaja wrote:4) All 3 places suggested my case is essentially riskless, given today's technologies. Is that true, or hype (i.e. there is no such thing as riskless surgery)?


All surgery carries risk. Your individual risk may be relatively low and for a procedure with a relatively high success rate, but all surgery carries risk. If it didn’t have risks, they would insist you sign those informed consent forms.

:)
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Postby murvaja » Sat Jan 20, 2007 10:06 am

"Wouldn't it be nice if all doctors agreed on what is best?!"

Indeed it would!

"My bias is toward surface ablation".

I understand it is largely personal choice, but would you mind sharing why you prefer PRK?

"There is already surgery for presbyopia. See NearVision CK."

People who've had Lasik or PRK do not qualify for the procedure, correct?

Just a couple more questions:

1) I read one doctor's Informed Consent on the web and it states that the patient is not entitled to any refund, even if the surgery does not improve (or even deteriorates) vision. Is this what typically happens to patients who don't improve, or would most doctors generally refund the fee in these cases out of niceness?

2) Is it polite to negotiate the price, or am I expected to take the price as is, i.e. the surgeon charges what he/she is worth?

3) In all places I visited, I felt that doctors/staff felt uncomfortable after I started asking too many questions (for instance, detailed questions about
the amount of tissue that would be removed). Is this normal? Or should I strive to find a place that is happy to answer all my questions?

Thanks again!
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Postby murvaja » Fri Jan 26, 2007 9:32 am

Hi Glenn, any tips on my last set of questions? Or am I reaching the limit of what can be answered in a forum? :)

Cheers,
-Murali
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Postby LasikExpert » Fri Jan 26, 2007 8:18 pm

murvaja wrote:I understand it is largely personal choice, but would you mind sharing why you prefer PRK?


The primary reason is that the elimination of the Lasik flap eliminates any possibility of a Lasik flap related complication at surgery or during the patient's lifetime. Even though the probability of a Lasik flap related complication is relatively low, no possibility is almost always better than low probability.

murvaja wrote:People who've had Lasik or PRK do not qualify for [CK], correct?


People who have had PRK may have NearVision CK. People who have had Lasik may not be able due to the Lasik flap interface. This will depend upon the surgeon's evaluation of the individual situation.

murvaja wrote:1) I read one doctor's Informed Consent on the web and it states that the patient is not entitled to any refund, even if the surgery does not improve (or even deteriorates) vision. Is this what typically happens to patients who don't improve, or would most doctors generally refund the fee in these cases out of niceness?


It is not so much a matter of nice as it is a matter of legality. Some doctors consider a refund as an admission of liability or wrongdoing. Others do not. This is the business side of Lasik and each clinic can set their own policy. Of course, even with such a clause there is nothing stopping a patient with an undesired outcome from asking for a refund. The worst that will happen is the doctor will decline.

murvaja wrote:2) Is it polite to negotiate the price, or am I expected to take the price as is, i.e. the surgeon charges what he/she is worth?


I personally think it is totally reasonable to state that a different doctor that you perceive to be of equal ability is willing to provide an equal procedure for a lower price and provide the opportunity for the lower price to be met. In the form of a question; "Why is doctor B less expensive than you?", some interesting information may be revealed. Again, this is business policy and the worst that can happen is the surgeon will decline.

murvaja wrote:3) In all places I visited, I felt that doctors/staff felt uncomfortable after I started asking too many questions (for instance, detailed questions about the amount of tissue that would be removed). Is this normal? Or should I strive to find a place that is happy to answer all my questions?


Some doctors feel that "ignorance is bliss" refers to patients. To a degree I do not agree. I think a patient who is well informed and seeks reassurance to legitimate concerns is the best patient. Some doctors don't like our 50 Tough Questions For Your Lasik Doctor because they think they are too intrusive, but in defense I don't see any of the 50 Tough Questions for which you would not want to know the answer.

Of course patients can go a bit overboard and seek every detail to the point of obsession. You must rely on the expertise of the surgeon; that is what you are paying for and why s/he received all that education.

You need to be confident and comfortable with your choice of surgeon. Someone who you perceive as dismissive is probably not someone you would want to rely on if things go wrong. You don't need to reinvent the wheel when someone else will be driving, but it is good to know your destination and be comfortable with the driver.
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