Lasik: 3 Doctors to choose from. Need help ...

If you are thinking about having Lasik, IntraLasik, PRK, LASEK, Epi-Lasik, RLE, or P-IOL eye surgery, this is the forum to research your concerns or ask your questions.

Lasik: 3 Doctors to choose from. Need help ...

Postby aalrutte » Sun Jun 25, 2006 1:56 pm

Dear Glenn,

My prescription is as follows:

Left Eye: 596 micron cornea thickness, -7.50 myopic, -1.25 astigmatism, 45 degree
Right Eye: 594 micron cornea thickness, -9.50 myopic, -1.00 astigmatism, 116 degree
Pupil Size: I got quite different results from the surgeons respectively from their optometrists/consultants which worries me a little. All of them said that the size of my pupills would be no issue. Please see also below.

1st Doctor:
The optometrist recommends PRK using Bausch and Lomb 217Z. This provider claims to have also Visx S4 and Nidek EC5000. Size of the pupils 4 to 5 mm in bright light and 5 to 6 mm in dimmed light. The optometrist mentioned that they usually use 6.5 mm for the optical zone and 1 mm for the transition zone. When I asked the optometrist why PRK he said: "maybe the surgeon will make on the day of the surgery a different decision".

2nd Doctor:
Surgeon recommends Lasik (mechanical microkeratome) using Ladar Vision 4000. Size of pupils 2 mm in bright light and 3 mm in dimmed light (I was very surprised to here these small values). The surgeon said he would do a 5.7 mm optical zone + 1 mm transition zone.

3rd Doctor:
Optometrist recommends Lasik (laser microkeratome, Intralase) using Bausch and Lomb 217Z. This provider claims to have Visx S4, Allegretto and Nidek EC5000. Size of pupils around 4 mm in bright light and around 5.5 mm in dimmed light.

My Questions:
(1) If all doctors are equally good which one would you choose based on the equipment in my case (I know you don't recommend to choose based on equipment)?

(2) Why would the 2nd doctor use a 5.7 mm optical zone although he told me the size of my pupils are 2 mm (bright) / 3mm (dimmed)?

(3) Do you see any chance with my prescription to get wavefront optimized ablation from the 3rd doctor if he would use the Allegretto Laser?

(4) The 3rd provider stopped the eye examination before the eye were dilated by drops. The consultant said without scheduling the surgery they would not conduct all tests needed. What are the results the doctor can get from the tests with artifically dilated eyes? Has that anything to do with the size of the pupils in dimmed light?

(5) Any comment from you on the size of the pupils since I have received all kinds of answers? What is typical for bright light and for dimmed light? Does the result for the size of the pupils from the 2nd doctor sound reasonable to you? I got this answer from both the optometrist as well as from the surgeon of the 2nd provider.

(6) How does the doctor determine the size of the optical zone and the transition zone? Is this mainly determined by what the laser is able to do or by how much cornea is available respectively by the size of the pupils/prescription?

(7) Do you think that Intralase would give any noticeable advantage in my case (3rd Doctor)?

(8) I am a little bit concerned about the beam diameter from the B&L laser of 2 mm compared to 0.95 mm (Allegretto) or 0.8 mm (Ladar Vision). Is this an important detail?

(9) The frequency range of the eye tracking feature starts at 120 Hz (B&L) and goes up to 4000 Hz (Ladar Vision). Is 120 Hz sufficient?

(10) Is there any combination of equipment currently available which might deliver even better results e.g. in Germany or somewhere in USA?

(11) Is it possible in my case to get a wavefront guided ablation after the 1st surgery as an enhancement or is there maybe not enough cornea left?

(12) Why is pre-dilation required when using the Ladar vision laser? I found this on your webpage where all lasers currently available are compared.

(13) Any surgeon you would recommend in my area (Farmington Hills, 48335, MI)?

(14) You recommend to take Vitamin C before and after having PRK. Is there any medicine you would recommend for Lasik?

I apologize for so many question and I would like to thank you in advance for all your answers.

Best regards,
Posts: 1
Joined: Thu Jun 15, 2006 10:43 pm

Postby LasikExpert » Sun Jun 25, 2006 6:28 pm

Great questions Ralph. You have obviously been doing your homework.

Let’s discuss some general issues and then I’ll dive into your questions.

My first concern is corneal thickness. At least 250 microns of tissue must be untouched for a healthy eye to remain stable after surgery. A conventional laser ablation will remove approximately 12 microns of tissue for every 1 diopter of refractive change. Your eye with the greatest amount of refractive error would require approximately 10 diopters of change. This translates to 120 microns of tissue removal with conventional ablation. Wavefront guided ablation commonly requires more tissue removal than conventional, however your surgeon should be able to determine exactly how much tissue will be removed and where it will be removed prior to surgery. For our purpose let's just use conventional data.

You're right eye has 594 microns of tissue and requires 10 diopters of refractive change. If you have Lasik or IntraLasik a flap of corneal tissue will be required. This flap could be as thin as 110 microns with IntraLasik, or more commonly 140 microns with a mechanical microkeratome. The laser microkeratome use with IntraLasik is significantly more accurate in flap thickness and provides a greater safety margin.

So we start with 594 microns of tissue subtract from that 140 microns of tissue for a flap and subtract from that 120 microns of tissue for ablation, leaving 334 microns of untouched tissue. This is enough residual corneal tissue that even with a thicker flap or more ablation because of wavefront guided treatment you have a significant margin for error and safety. This means that Lasik or IntraLasik would appear to be appropriate options.

The wide range of pupil sizes is unusual but reflects the different methods in different environments. The only measurement that is important is your naturally dilated pupil in a low light environment. The largest measurement which apparently was in dim light was 5.5 mm, and this is about the average.

Pupil size alone is a very poor predictor of who may develop night vision problems after surgery, however the parameter with the greatest margin for safety would be to have the full optical ablation zone equal to or greater than the size of your naturally dilated pupil in low light environment. All lasers which you are considering have the ability to provide a 5.5 mm or greater optical ablation zone. Although pupil size alone is a poor predictor of night vision problems there is a general tendency for night vision problems to develop when a significant amount of refractive error is corrected. Read all the details Pupil Size And Lasik.

I am personally a strong advocate of the surface ablation techniques PRK, LASEK, and Epi-Lasik, however these techniques do have a higher probability of developing corneal haze with significant correction. Both of your eyes require significant correction. The probability of developing corneal haze with Lasik or IntraLasik is almost nil. I recommend you seriously consider Lasik or IntraLasik only.

1) Based on equipment only I would recommend a third doctor most highly of the three. This is primarily because doctor and number three is offering a laser microkeratome.In

2) I don't believe doctor number two’s laser could go down to 3 mm optical ablation zone. I also doubt that the doctor actually believes your dim light pupils are 3 mm. This would be a highly irregular circumstance.

3) All ablations are wavefront optimized when the Allegretto laser is used. Be sure you understand the difference between custom wavefront guided and wavefront optimized by reading Wavefront Lasik.

4) The dilation process provides many important facts regarding the health of your eye, its refractive state, and whether or not you are appropirate for refractive surgery. He does not provide a measurement for your naturally dilated pupil. It is common for surgeons to do many preliminary tests to determine candidacy, but make a final decision about whether or not you should actually have surgery on the day of surgery when all required tests are completed. It is rare that a case must be canceled because something is discovered that was not found in the preliminary evaluation, but it can happen.

5) The typical size of naturally dilated pupils in the general population is 6.0 mm to 6.5 mm. The 5.5 mm measurement seems reasonable.

6) If you asked ten doctors the appropriate optical ablation zone and transition zone for the same patient parameters you will get 9 1/2 different answers. The measurement of the most significant importance is the optical ablation so. The transition zone tends to very based upon amount of refractive change with a wider transition zone the greater the amount of refractive change. This provides a more gradual change from full correction to know correction intends to be more compatible with a mechanic changes cause in the cornea by refractive surgery. Of course all doctors are limited by the physical limitations of their lasers, however all lasers you're considering with the exception of the Nidek EC-5000 have the ability to accommodate your needs. I recommend you do not consider the Nidek.

7) Yes. The Intralase femtosecond laser microkeratome is able to provide a thinner flap, a flap with a uniform thickness through out, a flap with a greater reliability of thickness, and a flap with the more predictability of size. I recommend you consider most seriously IntraLasik.

8) There is actually a small advantage to a larger laser beam for a patient with a significant amount of refractive error. The greater the amount of time during the laser procedure the greater the probability of overcorrection. This is because of hydration issues. Although it is possible for the algorithm and the doctor's nomogram to adjust for this variable, the less time the laser is ablating tissue better. Because of its ability to go to a larger size the Bausch & Lomb has a small advantage in this regard. Whether or not the nuance of the ablation would be affected by the difference of .8 mm to 2.0 mm will depend upon the unique higher order aberrations of your eyes. You need to discuss this with your doctor.

9) When you're considering the features of eye tracking frequency you need to consider the closed loop. A closed loop is the process of measurement, determine change, make adjustment of the laser, measure for verification. When you look at closed loop data all currently available eye tracking systems are very close to the same and all have been shown to be able to provide adequate tracking for normal eyes. This is probably not an issue of importance in your case.

10) Other than the limitations on custom wavefront guided ablation, equipment in the United States is going to be adequate for your needs and compared to equipment outside the United States.

11) Yes. Wavefront guided ablation enhancement surgery would undoubtedly be appropriate in your case. You should expect to need enhancement surgery due to your significant refractive error and a high probability of regression. Discuss with your doctor his or her philosophy on deliberate overcorrection to accommodate probable regression. You may ultimately be better to initially corrected to plano, wait 3-6 for regression, and then have wavefront guided enhancement surgery to resolve any refractive error. Ten diopters is a large amount of correction and almost guarantees some regression.

12) The LADARVision laser utilizes a dilated pupil margin as a part of its tracking system, therefore dilation for surgery is necessary. Other systems use other methods for tracking.

13) Unfortunately there are no surgeons certified by our organization in Michigan. The closest is in Toledo. There are several well respected refractive surgeons in the Detroit area. I highly recommend you use our 50 Tough Questions For Your Lasik Surgeon to evaluate a potential doctor.

14) Taking 500 mg of vitamin C twice a day for one week before surgery and for at least two weeks after surgery, plus wearing 100% UVA and UVB sunglasses if you even think of going outside has been shown to significantly reduce the probability of corneal haze. If you elect to have Lasik or IntraLasik the probability of corneal haze is already very low, however unless you have an allergy to vitamin C you will do no harm with this extra precaution.
Glenn Hagele
Volunteer Executive Director

Lasik Info &
Lasik Doctor Certification

I am not a doctor.
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