I would like to thank Drs' Tennen, Friedman, and Ofner for their responces to the original question. I would be grateful to know if they or any other Doctors on the pannel have reviewed the study referred to by Dr Bickford -given its apparent seriousness- and for their and any other Doctor's assessment of the study.

you started a new thread so I can't quickly refer back to my previous response (without searching for it). I have not reviewed nor seen the article you mentioned. If you tell me where and when it was published, I'd be happy to review it.

Dear Dr Ofner,

I apologise for not continuing with the same thread due to my lack of familiarity with the format. The following is the reference in question:

" Reports are surfacing of significant retinal nerve fiber layer loss following LASIK, due to use of suction ring (used for creation of flap) and resulting elevated intra ocular pressure. First study was small, but 100% of the cases had documented nerve damage. Might doom LASIK if a fix is not found. Possible fixes to prevent damage to future patients: anti-glaucoma drugs prior to surgery, lower suction ring pressure, shorter time with faster microkeratomes. (See why skill of surgeon matters?)
Fix for the million or so prior patients: careful monitoring of age-related and glaucoma-induced nerve fiber layer loss as population ages with rapid treatment when indicated."

Larry Bickford, OD ()
Family Practice Eye Health and Vision Care

I believe that the above was sourced from the sci.med.vision newsgroup on or around Feb 23, 2000.

I understand that the TLC centres in Ontario have already modified their procedures in light of the above issueby only applying suction when the microkeratome is actually cutting , i.e. stopping the suction after the cutter has done its forward cutting action. Therefore there is no suction during the return/retreat of the cutter. Consequently suction is now applied for less than 10 seconds in all.

I am unable to find the article you cited. Should you find it, please let me know. I keep up with all of the American Ophthalmology literature and I've never heard of this and am very skeptical about any of it's truth. The reason some people remove the suction after the "cutting" pass is not to relieve any pressure on the optic nerve but rather some reports have indicated a decreased incidence of scratchs or abrasions on the corneal surface if there is no suction on the "back pass". This is not in any way related to pressure on the optic nerve, etc. Until anyone can show me some solid science behind such statement, I continue to believe that it is false. good luck!!
Steven Ofner, M.D.
Eugene, Oregon
http://www.eugeneeyecare.com

Dr Ofner,

I have been able to track down the study which was published in the Jan, 2000, Review of Optometry

http://www.revoptom.com/ISSUE/ro0100news.htm#lasik

Does LASIK Damage the Nerve Fiber Layer?

A recent pilot study in Illinois suggests that the intraocular pressure spike associated with LASIK may cause nerve fiber loss. What makes the study especially interesting is that the use
of brimonidine (Alphagan) appeared to prevent such damage in fellow eyes. Alphagan-manufacturer Allergan Pharmaceuticals is now funding a three-center study involving more than 2,000
patients to obtain more-definitive results.

"We've noticed, using the GDx Nerve Fiber Analyzer, that there is a dropout of between 5-15% of the total nerve fiber layer following LASIK in patients who have had the suction on the eye for 30 seconds or more," says Edward Yavitz, M.D., of the University of Illinois College of Medicine. "I only ran a group of 20 patients. But we had 20 out of 20 whose one eye showed nerve fiber thinning at one month. The opposite eye, which was treated by Alphagan, showed no loss."

To create a uniform flap in LASIK, surgeons apply a suction ring that raises IOP to about 80-85mm Hg. The suction time—which varies from about 15-45 seconds depending on surgical skill and the type of microkeratome—may be a determinant of potential
NFL thinning. Dr. Yavitz has found no nerve fiber loss (without Alphagan) in patients for whom the suction time was 20 seconds or less. In a separate study of 60 patients who received no Alphagan and had LASIK with suction times less than 30 seconds, New York surgeon Sanjeev Nath, M.D., likewise
measured no significant nerve fiber loss on GDx.

Perhaps the tool matters as well. A microkeratome housing an integrated suction ring may allow for a quicker pass than a less-wieldy two-piece unit. Dr. Yavitz and the other investigators in the multi-center study plan to use various microkeratomes to gauge the effect of different suction times.

Skeptics initially questioned whether Dr. Yavitz's findings might simply be artifacts reflecting postoperative changes in the
cornea, a medium of the polarization measured by the GDx. (The system features a corneal compensator.) Dr. Yavitz refutes the skepticism by noting the absence of nerve damage in the
Alphagan-treated eyes. The larger study aims to reproduce his findings using the same protocol as the pilot series: Alphagan tid in one eye and placebo in the other for three days pre-op and
one week post-op, with GDx measurements preoperatively and one month after surgery. Dr. Yavitz hopes to complete the study within about a year.

In the meantime, should you warn patients about a possible risk of nerve fiber layer loss in LASIK? Dr. Yavitz thinks we should wait and see. After all, his was merely a small series of 20 patients. And remember, the GDx changes appeared only in
cases where the suction time was 30 seconds or more. Besides, says Dr. Yavitz, the 5-15% NFL dropout measured in his patients may be clinically insignificant. The GDx measurements showed that, despite the loss, their NFL thicknesses remained within normal limits. "Since this is a patient population of high myopia, which is more prone to developing glaucoma later in life, we don't like to see any nerve fiber layer loss at this early age," Dr. Yavitz says.

Studies suggest that patients can sacrifice 30-50% of their nerve fiber layer before the onset of visual field loss. Even with that leeway, TLC's J. James Thimons, O.D., considers the extent of NFL loss in the Illinois study cause for concern: "It means you've eaten up a third of the available nerve fiber layer before they show a field loss, according to some of the studies. That's a huge
change in the normal anatomy and physiology of the eye."

Thank you for bringing up this study - we have talked about this at length among our colleagues. The basic concensus is that the study had many faults. The suction ring does not stay on for more than 30 seconds (generally about 8-12 seconds). The study also found that alphagan medication prevented the loss of nerve fiber.
Another recently published study found that there was no change in nerve fiber layer (I do not have its citation)
In this study, again the doctor found that alphagan prevented the nerve fiber changes. If one is very concerned, then this glaucoma medication can be used for a few days prior to surgery. I currently dod not recommend this for my patients as my suction times are short and I am not satisfied with the way the study was set up

I will be happy to answer further

Bill Trattler, MD
Miami, FL