REFRACTIVE SURGERY FEATURE STORY High-Resolution Wavefront Aberrometry This technology is most beneficial for the measurement and correction of astigmatism. BY STEVEN C. SCHALLHORN, MD he popularity of wavefront-guided laser vision correction is growing. Now, with the use of more precise aberrometry, surgeons can provide their patients with maximal refractive outcomes. OneT of the latest technologies, the iDesign (Abbott Medical Optics Inc.), uses high-resolution aberrometry to enhance surgical precision. Results from a recent study demonstrated that, even without nomogram adjustments, the iDesign per- forms better than an earlier technology, the WaveScan Wavefront System (Abbott Medical Optics Inc.). Like its predecessor, the iDesign aberrometer uses a Fourier recon- struction algorithm and Hartmann-Shack technology, but it has a greater dynamic range, captures five times as many lenslet data points (up to 1,200 depending on pupil size), and incorporates a corneal topographer, Figure 1. In a study of LASIK in low to moderate myopes, among other new features. predictability of correction at 1 month was slightly higher with the iDesign than with the WaveScan. ANALYSIS We evaluated results from 1,201 eyes of 641 patients with Express centers in the United Kingdom. All eyes had at least low to moderate myopia (manifest spherical equivalent 1-month follow-up, and all flaps were created with the iFS [MSE], -0.25 to -6.00 D) undergoing primary LASIK at Optical femtosecond laser (Abbott Medical Optics Inc.). Results A B Figure 2. Double-angle plots show that the accuracy of cylinder correction was higher and there were fewer outliers with the iDesign aberrometer (A) compared with the WaveScan (B). 24 CATARACT & REFRACTIVE SURGERY TODAY EUROPE FEBRUARY 2014 REFRACTIVE SURGERY FEATURE STORY Figure 3. As a result of the improved predictability and Figure 4. Patients reported greater satisfaction and less cylinder correction, 1-month postoperative UCVA was higher difficulty with halos and other postoperative symptoms with in the iDesign group than in the WaveScan group. high-definition aberrometry. were compared with a large matched cohort of more than than expected. They also reported less difficulty with 27,000 eyes (14,589 patients) treated with WaveScan aber- postoperative starbursts, glare, and halos (Figure 4). rometry in 2012 and 2013. Complaints of severe difficulty with visual symptoms At 1 month, 95.3% of eyes in the iDesign group had an were low in both groups. MSE within ±0.50 D of intended correction, and 99.5% were within ±1.00 D. Not only was this more predictable CLOSER TO PERFECTION than the comparison group (Figure 1), but also the correla- With modern technology, most patients—especially tion coefficient of attempted-versus-achieved MSE (0.96) those with low to moderate myopia—have the poten- indicated a tight spread of the results. Compared with tial to achieve better than 20/20 vision postoperatively, the standard aberrometry (WaveScan) group, the iDesign and many can come close to the limits of human vision group also had fewer outliers, as depicted by double-angle at 20/12.5 or 20/10 vision. However, achieving maximal plots (Figure 2). Additionally, in a subgroup of patients who results routinely requires good technology, good pro- underwent astigmatism correction, the axis shift did not cesses for screening candidates, and the ability to mea- exceed ±5° in 64% of those patients in the iDesign group sure beyond 20/20 in the first place. versus 59% in the WaveScan group. At the high end of the visual acuity spectrum, gains are As a result of the improvements in predictability and small and incremental, but still worth celebrating. Getting the ability to accurately correct cylinder, monocular closer to 100% of patients achieving 20/20 visual acu- UCVA at 1 month was 20/20 or better in 96% of the ity and more patients achieving 20/16 or better is what iDesign eyes and 20/16 or better in 84%, compared will continue to drive patient satisfaction, referrals, and with 94% and 80%, respectively, in the WaveScan group a stronger laser vision correction market. We must also (Figure 3). The results achieved with iDesign represent reduce the variability and increase the predictability of the best cylinder correction I have ever seen following our results, so that every patient achieves the high-quality laser vision correction. optics and vision that we want him or her to have. One remaining cause of variability is the healing PATIENT-REPORTED OUTCOMES response. Improvements in ablation profiles have We also reviewed patient-reported outcomes (PROs), helped to modulate the healing response. Consistent, an important metric in the upper ranges of what this tech- uniform healing reduces variability and maximizes the nology is capable of. PROs help us understand whether chance of achieving visual outcome goals. Personalized patients experience a difference in quality of vision and nomograms that take into account differences in heal- whether the procedure has met their expectations. ing response based on age, for example, also help to Patients reported greater satisfaction with iDesign- improve predictability. driven treatments compared with WaveScan-driven Many surgeons have well-developed nomograms, so it treatments (97.3% vs 95.2%). About half of the patients is encouraging to see good early results in our study, even in the iDesign group said their vision was much better (Continued on page 32) FEBRUARY 2014 CATARACT & REFRACTIVE SURGERY TODAY EUROPE 25 REFRACTIVE SURGERY FEATURE STORY (Continued from page 25) TakE-HOME MESSAGE • Achieving maximal results routinely requires good technology, good processes for screening candidates, and the ability to measure beyond 20/20. • Getting closer to 100% of patients achieving 20/20 visual acuity and more patients to 20/16 or better is what will continue to drive patient satisfaction, referrals, and a stronger laser vision correction market. • The iDesign incorporates multiple measures, including wavefront aberrometry, full-gradient topography, autorefraction, pupillometry, and keratometry. without nomogram adjustments. We can expect to see further improvement and tightening of the standard devia- tion as surgeons begin to modify their nomograms with the iDesign aberrometer. A better capture of the true ocular wavefront from more data points also reduces variability in the correction, as we see in the cylinder correction data. ADDITIONAL BENEFITS Easier capture with the iDesign improves the flow of patients through the preoperative work-up. We have treated hundreds of complex eyes with the iDesign, although these were not included in our analysis. In these cases, image capture is much easier than with previous generations of aberrometers. The iDesign also has a great- er dynamic range, making it possible to design treatments for more highly aberrated eyes and perform diagnostic captures of eyes with keratoconus and other conditions that are not suitable for laser vision correction. The interface of the aberrometer has been refined, and the device incorporates multiple measures, including wavefront aberrometry, full-gradient topography, autore- fraction, pupillometry, and keratometry (K). The ability to measure corneal curvature and automatically incorporate K into the treatment design eliminates the step of manu- ally entering K readings. While the iDesign has not yet replaced topography in our clinics, it will be interesting to see how this capability may be utilized in the future. CONCLUSION As we move into a new era of high-definition wave- front, I am excited to see how our results continue to improve. n Steven C. Schallhorn, MD, is the Global Medical Director of Optical Express. Dr. Schallhorn states that he is a paid consultant to Abbott Medical Optics Inc. He may be reached at tel: +1 619 920 9031; e-mail: [email protected]. 32 CATARACT & REFRACTIVE SURGERY TODAY EUROPE FEBRUARY 2014.