EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/115557
90 EW REFRACTIVE SURGERY March 2013 Is efficacy ratio the new 20/20? by David J. Tanzer, M.D. Source (all): David J. Tanzer, M.D. There are new expectations and new ways to measure success after laser vision correction S everal factors in combination have made 20/16 or even 20/12 uncorrected vision a possibility after laser vision correction. These include modern lasers and improved pre-op, intra-op, and postop procedures. A study conducted by Steve Schallhorn, M.D., evaluated the relationship between patients' mean satisfaction after surgery as a function of uncorrected visual acuity. He found a statistically significant correlation between uncorrected visual acuity and overall satisfaction. Patients with uncorrected visual acuity of 20/12 were more satisfied with their outcomes than those with 20/20 and 20/25 uncorrected visual acuity. Additionally, multiple studies in different settings have demonstrated that rates of 20/20 uncorrected vision are consistently at or near 100%. So, if 20/20 is no longer a differentiator, a new benchmark or metric may be needed. In the past, the key benchmark has been uncorrected and best-corrected visual acuity. Today, we are paying closer attention to other metrics, such as the efficacy ratio. The efficacy ratio allows surgeons to compare how well a patient sees corrected before surgery to how well he or she sees uncorrected after surgery. For example, if a patient sees 20/20 before surgery with glasses and is now 20/20 uncorrected, the ratio is 1. Very often, patients are seeing better after surgery uncorrected than they were before surgery best-corrected, so the efficacy ratio would actually be 1+ (see table). Pre-op BCVA Post-op UCVA Efficacy ratio 20/20 20/25 0.80 20/20 20/20 1.00 20/20 20/16 1.25 20/20 20/12.5 1.6 These outcomes are possible because of advances in the excimer laser coupled with the femtosecond laser. Many patients have concerns about the flaps, specifically whether they can be displaced with minor trauma. Today, the femtosecond laser allows surgeons to create reverse beveled flaps, which are much stronger and safer than previous flap configurations.1 Additionally, today's excimer lasers are faster and smoother, have larger optical zones and better blend zones, and have less induction/actual reduction of aberrations. Surgeons also provide better patient care through more effective patient screening methods and post-op management. Naval Aviator Study results An example of the results that can be achieved with laser vision correction can be seen in the Naval Avia- tor Study, which included 548 myopic eyes, 60 eyes with mixed astigmatism, and 24 eyes with hyperopia treated with iLASIK (Abbott Medical Optics, AMO, Santa Ana, Calif.).2 At one day after surgery, 87% of myopic patients were seeing 20/16 or better, and more than half were seeing 20/12 or better. These results continued to improve at each follow-up visit. Regarding best-corrected visual acuity in the myopic patients, 6% were seeing 20/10, 65% were seeing 20/12, 99% were seeing 20/16, and 100% were seeing 20/20 pre-op. At 13 weeks post-op, 33% were seeing 20/10, 89% were seeing 20/12, 99% were seeing 20/16, and 100% were seeing 20/20. These results demonstrate a five-fold improvement in best-corrected vision at the 20/10 level, a remarkable achievement. From pre-op to one month postop, approximately half of the eyes in each category (50% of myopic eyes, 50% of mixed astigmats, and 52% of hyperopes) had no change in mesopic low-contrast acuity, and 43% of myopes, 40% of mixed astigmats, and 33% of hyperopic eyes gained one line of mesopic low-contrast acuity. Additionally, the results from the LASIK in U.S. Naval Aviation Study showed average efficacy ratios of one or higher in 90% of all eyes by three months following surgery. Putting the efficacy ratio into practice At the 2012 American Academy of Ophthalmology meeting, a survey was taken after a panel discussion on this topic, and 65% of the audi- ence said they would like to implement this testing in their practices. In a pre-registration survey, only 37% of attendees were testing laser vision correction patients beyond 20/20 and believed that it is important to do so, and only 6.5% used the efficacy ratio as a measure of success for laser vision correction in their practice. In the pre-test, before the discussion, 58% said their laser vision correction patients achieved an efficacy ratio of 1 or more at least 90% of the time. In the post-test survey, after the panel discussion, 40% said they would be comfortable/very comfortable talking about this ratio with patients. It is important to note that the efficacy ratio is a valid point of comparison to share with patients because they are thrilled to know that their uncorrected vision is better after surgery than it was before surgery with glasses. To implement these new measures in your practice, technicians and ODs must be trained to consistently push beyond the 20/20 line. Patient satisfaction can be increased by sharing the efficacy ratio and better than 20/20 results. In summary, the efficacy ratio is quick, easy, practical, and understandable, and it requires us to test our patients to the limit. EW References 1. Knorz MC, Vossmerbaeumer U. Comparison of flap adhesion strength using the Amadeus microkeratome and the IntraLase iFS femtosecond laser in rabbits. J Refract Surg. 2008 Nov;24(9):875-8. 2. Tanzer DJ, Brunstetter T, Zeber R, et al. A prospective evaluation of laser in situ keratomileusis in US Naval aviators. J Cataract Refract Surg. 2013, in press. Editors' note: Dr. Tanzer is in private practice in San Diego. He has financial interests with AMO. Contact information Tanzer: DJTanzerMD@yahoo.com