Change Text Size     A   A   A

Home > News & Events > The PROWL LASIK Study


PROWL stands for Patient Reported Outcome with LASIK. It is a FDA clinical trial started in 2009 to better understand the risk and potential problems that can result from LASIK. One clinical trial was conducted in the military and one was non-military.

PROWL-1 was completed in 2014 and had 262 participants. it involved participants completing a questionnaire that evaluated patient visual symptoms, and how those symptoms impacted the patient's quality of life post-LASIK.

PROWL-2 was completed in 2014 with 312 patients, also completed a similar questionnaire.

These clinical trials are the first studies to evaluate multiple aspects of a patient’s LASIK experience (expectations, satisfaction, visual symptoms and the impact of LASIK on daily life).

The Results: (from ASCRS at

Common findings in PROWL-1 and PROWL-2 trials

› Only 1 of 990 eyes lost 3 or more lines of visual acuity, and that eye saw 20/25 or better.

› The prevalence of all visual symptoms and bothersome symptoms studied (ghosting, halos, glare, and starbursts) was less at 6 months after surgery without correction than it was preoperatively with best correction (PROWL-1).

› Patients reporting difficulty or the inability to perform usual activities due to visual symptoms improved or were completely eliminated following LASIK in both studies.

› Visual symptoms throughout these trials must be understood in the context that there was no correction of residual refractive error. While the results are excellent, they would be even better if patients had been given the option to have additional LASIK or to wear glasses.

PROWL-1 summary (6 months)

› 99% of patients had a binocular uncorrected vision of 20/20 or better at 3 months.

› When asked how satisfied patients were with the results of their LASIK surgery, 98% reported being satisfied at 6 months and 2% were dissatisfied.

› When asked “How satisfied are you with present vision?” 97% were satisfied at 6 months and 3% were dissatisfied. This is a significant improvement, since 73% were dissatisfied preop.

› For each symptom index, up to 30% of patients reported new visual symptoms, while 91% of patients reported the resolution of symptoms they had prior to LASIK. Thus, 3 times more patients reported the resolution of preop visual symptoms than reported new visual symptoms.

› Very few patients reported that visual symptoms negatively impacted their daily activities.

› 21% (23 subjects) with a normal preop Ocular Surface Disease Index (OSDI) noted mild, moderate, or severe dry eye at 6 months. 65% of patients with preop mild, moderate, or severe dry eye symptoms had normal OSDI scores at 3 months. Thus, 3 times more patients experienced an improvement in OSDI after LASIK than noticed new OSDI symptoms. Subjects were not followed long enough to observe the resolution of the dry eye symptoms, which was reported to occur in the literature.

PROWL-2 summary (3 months)

› 96% of patients had binocular uncorrected vision of 20/20 or better at 3 months.

› 97% were satisfied with their LASIK surgery at 3 months.

› 96.2% were satisfied with their vision at 3 months, while 3.9% were dissatisfied. This is an improvement since 55.9% were dissatisfied preoperatively.

› Up to 1% of subjects, without glasses or contact lenses, experienced a lot of difficulty with or were unable to do usual activities due to visual symptoms at 3 months. The ability of glasses or contact lenses to correct visual symptoms was not presented.

› The prevalence of halos decreased from 51% (preoperatively) to 46% (at 3 months) in all patients following LASIK. 35% of subjects who had no halos prior to surgery developed new halos at 3 months. This was a subset of 31 patients out of the 260 patients examined at 3 months. The instances where preoperative symptoms (such as halos) disappeared following surgery were not presented.

› 28% of subjects who had a normal preop OSDI noted mild, moderate, or severe dry eye at 3 months. The percent of patients who had mild, moderate, or severe dry eye preoperatively, who had a normal OSDI postoperatively was not presented.

› The majority of the dissatisfied patients reported visual symptoms, such as glare, halos, ghosting or starbursts. The number of patients for whom refractive correction would have eliminated these symptoms was not presented.
Subjects were not followed long enough to evaluate the resolution of dry eye symptoms that typically occur after LASIK. Nor were they followed long enough to evaluate the long-term effects of LASIK.

Posted by



Leave a Reply

(Your email will not be publicly displayed.)

Captcha Code

Click the image to see another captcha.