Customized LASIK Treatment for Myopia Based on Preoperative Manifest Refraction and Higher Order Aberrometry: The Rochester Nomogram

Abstract

PURPOSE: To develop and test the efficacy of myopic treatment, based on preoperative manifest refraction and higher order aberrations, in enhancing the postoperative refractive error following customized LASIK treatment and compare results with the manufacturer-recommended sphere offset Zyoptix treatment nomogram, which does not account for the preoperative higher order aberrations. METHODS: One hundred seventy-five myopic eyes (89 patients) were treated based on the Rochester nomogram, which specified the amount of myopia to be treated based on preoperative manifest refraction and higher order aberrations, including third order aberrations and spherical aberration. Postoperative refractive error was measured at 1 month and compared to that theoretically estimated with the Zyoptix nomogram. RESULTS: The mean preoperative sphere and cylinder were -4.52±2.05 diopters (D) and -0.81±0.70 D, respectively. The mean postoperative spheres were +0.04±0.33 D and +0.31±0.54 D, using the Rochester and Zyoptix nomograms, respectively. The mean postoperative spherical equivalent refractions were -0.11±0.34 D and +0.15±0.53 D using the Rochester and Zyoptix nomograms, respectively. The Rochester nomogram reduced the range of postoperative spherical equivalent to ±1.00 D, which was significantly better than that using the Zyoptix nomogram (t=5.46, P<.0001), which would have resulted in 8% of eyes with a postoperative spherical equivalent refraction >±1.00 D. Using the Rochester nomogram, 93.1% of eyes attained a postoperative UCVA ≥20/20. The percentage of postoperative hyperopic overcorrection decreased to 2.8% in the Rochester nomogram group from 22.3% using the Zyoptix nomogram, which only adjusts spherical values based on preoperative sphere and does not account for preoperative aberrations. CONCLUSIONS: The Rochester nomogram compensates for the effect of preoperative higher order aberrations on sphere and provided reduced range of postoperative spherical equivalent refraction. [J Refract Surg. 2007;23:435-441.]

Accuracy of refractive outcomes in myopic and hyperopic laser in situ keratomileusis: Manifest versus aberrometric refraction

“…It seems that the possibility of manually altering sphere and cylinder in wavefront systems could improve postoperative refractive accuracy. Our findings are in agreement with the conclusions in previous studies 6,7 in which the authors concluded that nomogram adjustments were needed to increase refractive accuracy in wavefront-guided ablations. In our study, the effect of including spherical aberration in the sphere calculation of the aberrometric refraction (Seidel method) was also evaluated.…”

Multiple regression analysis in nomogram development for myopic wavefront laser in situ keratomileusis: Improving astigmatic outcomes

“…These include optical zone size, 4,5 age, 4 and higher-order aberrations (HOAs). [6][7][8] We recently described a LASIK nomogram development method based on multiple regression analysis designed to take into account factors other than the attempted MRSE change. 3 Briefly, this approach derives a regression equation that can be used as for simple linear regression to steer percentage adjustments to overall treatment energy (%boost or deboost) based on the slope coefficient for the 4.0 mm pupil wavefront refraction spherical equivalent (WRSE); however, dioptric adjustments to the target sphere are calculated individually for each eye by subtracting the sum of the weighted additional factors plus the intercept constant from the multiple regression equation.…”

Multiple regression analysis in myopic wavefront laser in situ keratomileusis nomogram development

“…Based on good results from the Rochester nomogram, 16 we believed it would be important to consider the influence of higher-order Zernike terms. There is no simple way to include vector terms or polarity in a regression model.…”

“…Subbaram and MacRae 16,17 describe improved results for the Technolas PV (formerly Bausch & Lomb, Zyoptix) platform in myopic wavefront LASIK based on a proprietary nomogram developed using multiple regression analysis to provide a weighted adjustment to the treatment sphere that takes into account 3rd-order (coma) and 4th-order (spherical aberration) Zernike terms. Their published description is not full enough to allow other investigators to repeat their methods; however, their successful use of multiple regression analysis in wavefront LASIK nomogram development offers a way forward.…”

“…These include optical zone size, 4,18 age, 4,19 average keratometry, 19 spherical aberration, 20 and other HOAs. 16,17 The relationship between these factors and achieved MRSE outcomes is not completely understood. Multiple regression analysis is an exploratory statistical technique that can be used to build a weighted influence for a series of factors into LASIK nomograms without requiring detailed knowledge of the mechanism of interaction.…”