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The technical term for it is GIGO (garbage in, garbage out).
First clue is "self-reported dry eye". Second clue is "a questionnaire" - as opposed to specifying the name of a scientifically validated questionnaire. Now if they really did use a decent questionnaire I'll have a new case of foot in mouth disease but in my experience if they're going to use a validated questionnaire, they say so in the abstract.
The result? Naturally, nobody has dry eye after LASIK or PRK in this study after 12 months. - Interesting in the context of the gobs of other studies in which anywhere from 2% to 36% had dry eye at 6 to 12 months postop.
Why on earth would anybody bother to document this, other than for marketing purposes?
I mean I'm sorry but if you're going to talk about dry eye at all, do what people do in real dry eye studies: pick 4 to 6 items off the well known standard clinical measures and symptom questionnaires, making sure you have both signs and symptoms covered.
I expect things like this from back in the dark ages (i.e. 1990s) of LASIK... but in this day & age, we should be measuring things that are meaningful and putting them in context.
Prospective, Randomized Comparison of Self-reported Postoperative Dry Eye and Visual Fluctuation in LASIK and Photorefractive Keratectomy.
PURPOSE:
We sought to prospectively compare postoperative symptoms of dry eye, visual fluctuations, and foreign body sensation in patients undergoing LASIK and photorefractive keratectomy (PRK).
DESIGN:
Randomized clinical trial.
PARTICIPANTS:
Sixty-eight eyes of 34 patients were treated with wavefront-guided LASIK and PRK.
METHODS:
One eye was treated with LASIK and the fellow eye was treated with PRK. Eyes were randomized by ocular dominance. Patients completed a questionnaire preoperatively and at each postoperative visit evaluating symptoms of dry eye, dry eye severity, vision fluctuations, and foreign body sensation.
MAIN OUTCOME MEASURES:
Change in self-reported dry eye with secondary outcome measure of visual fluctuations and foreign body sensation scores after LASIK and PRK.
RESULTS:
Both groups of eyes experienced significant increases in symptoms of dry eye, vision fluctuation, and foreign body sensation after LASIK and PRK at postoperative months 1, 3, and 6. However, by the 12-month postoperative visit, there was no increase in dry eye symptoms over the preoperative baseline levels in either group. Patients undergoing PRK experienced significantly higher levels of vision fluctuation at postoperative month 1 than those undergoing LASIK.
CONCLUSIONS:
Both LASIK and PRK caused an increase in dry eye symptoms and severity, vision fluctuations, and foreign body sensation over baseline in the early postoperative period. At postoperative month 1, PRK caused greater vision fluctuations than LASIK. By 1 year postoperatively, all symptoms of dry eye, vision fluctuations, and foreign body sensation returned to their baseline, preoperative levels.
We sought to prospectively compare postoperative symptoms of dry eye, visual fluctuations, and foreign body sensation in patients undergoing LASIK and photorefractive keratectomy (PRK).
DESIGN:
Randomized clinical trial.
PARTICIPANTS:
Sixty-eight eyes of 34 patients were treated with wavefront-guided LASIK and PRK.
METHODS:
One eye was treated with LASIK and the fellow eye was treated with PRK. Eyes were randomized by ocular dominance. Patients completed a questionnaire preoperatively and at each postoperative visit evaluating symptoms of dry eye, dry eye severity, vision fluctuations, and foreign body sensation.
MAIN OUTCOME MEASURES:
Change in self-reported dry eye with secondary outcome measure of visual fluctuations and foreign body sensation scores after LASIK and PRK.
RESULTS:
Both groups of eyes experienced significant increases in symptoms of dry eye, vision fluctuation, and foreign body sensation after LASIK and PRK at postoperative months 1, 3, and 6. However, by the 12-month postoperative visit, there was no increase in dry eye symptoms over the preoperative baseline levels in either group. Patients undergoing PRK experienced significantly higher levels of vision fluctuation at postoperative month 1 than those undergoing LASIK.
CONCLUSIONS:
Both LASIK and PRK caused an increase in dry eye symptoms and severity, vision fluctuations, and foreign body sensation over baseline in the early postoperative period. At postoperative month 1, PRK caused greater vision fluctuations than LASIK. By 1 year postoperatively, all symptoms of dry eye, vision fluctuations, and foreign body sensation returned to their baseline, preoperative levels.
Byers Eye Institute, Department of Ophthalmology, Stanford University School of Medicine, Stanford, California.
Ophthalmology. 2012 Aug 11. [Epub ahead of print]
You know, this kind of thing really pisses me off. I have been working my way up through a month or two of studies & newsclips I hadn't gone through, so it was not until AFTER I posted on the blog about the study that I saw all the publicity they got for it ("Gee, look, you're really no more likely to get dry eye with LASIK than PRK after all! Guess we were wrong all those years!") They're always just so flagrant with this stuff.
When you've cherry-picked your participants, you can get to the point where the results are NOT generalizable to the population.
My impression is that the authors report their inclusion/exclusion criteria because these are the "normal/standard" criteria for anyone getting Lasik/PRK in the real world. That's the only way these results can be applied to the real world... if the Lasik/PRK places use the same stringent criteria when choosing who to operate on. Do they???
The question is if they are pickier than all the other Lasik/PRK places.