Journal of Refractive Surgery

The articles prior to January 2013 are part of the back file collection and are not available with a current paid subscription. To access the article, you may purchase it or purchase the complete back file collection here

Wavefront Analysis Comparison of LASIK Outcomes With the Femtosecond Laser and Mechanical Microkeratomes

Fabricio W Medeiros, MD; William M Stapleton, MD; Jeffery Hammel, MS; Ronald R Krueger, MD; Marcelo V Netto, MD; Steven E Wilson, MD

Abstract

ABSTRACT

PURPOSE: To evaluate differences related to ocular aberrations after customized LASIK for myopia using three different microkeratomes.

METHODS: Charts of 410 patients who underwent customized LASIK with the Alcon LADARVision4000 excimer laser were reviewed. Patients were stratified according to the device used to create the flap: Moria M 2 mierokeratome, Bausch & Lomb Hansatome microkeratome, or Intra Lase laser. The difference between the wavefront pre- and postoperative value received a positive or a negative sign if the change occurred toward or away from zero, respectively, and it was compared to preoperative minus postoperative manifest refraction spherical equivalent (MRSE).

RESULTS: Patients showed increase in the aberration level after LASIK with the three devices used in this study. Intra Lase spherical aberration change tended to be better than mechanical microkeratomes for higher MRSE values (Intra Lase compared to Hansatome, P^. 023 for MRSE values ^4.00 diopters [D]; IntraLase compared to Moria, P^. 015 for MRSE values ^2.00 D). For total aberrations, the improvement values for IntraLase tended to be higher than those for Moria (Intra Lase com pa red to Mo ria, P^. 021 for M RS E va lues 2=3.00 D). For total higher order aberrations, IntraLase values tended to be better than Moria and Hansatome microkeratomes (IntraLase compared to Hansatome, P^.047 for MRSE values between 3.00 and 8.00 D; IntraLase compared with Moria, P^. 002 for MRSE values 2=2.00 D). Change in coma root-mean-square was similar for the three groups.

CONCLUSIONS: The findings suggest the femtosecond laser provides a better platform for LASIK than the commonly used microkeratomes analyzed in this study. [J Refract Surg. 2007;23:880-887.]

Abstract

ABSTRACT

PURPOSE: To evaluate differences related to ocular aberrations after customized LASIK for myopia using three different microkeratomes.

METHODS: Charts of 410 patients who underwent customized LASIK with the Alcon LADARVision4000 excimer laser were reviewed. Patients were stratified according to the device used to create the flap: Moria M 2 mierokeratome, Bausch & Lomb Hansatome microkeratome, or Intra Lase laser. The difference between the wavefront pre- and postoperative value received a positive or a negative sign if the change occurred toward or away from zero, respectively, and it was compared to preoperative minus postoperative manifest refraction spherical equivalent (MRSE).

RESULTS: Patients showed increase in the aberration level after LASIK with the three devices used in this study. Intra Lase spherical aberration change tended to be better than mechanical microkeratomes for higher MRSE values (Intra Lase compared to Hansatome, P^. 023 for MRSE values ^4.00 diopters [D]; IntraLase compared to Moria, P^. 015 for MRSE values ^2.00 D). For total aberrations, the improvement values for IntraLase tended to be higher than those for Moria (Intra Lase com pa red to Mo ria, P^. 021 for M RS E va lues 2=3.00 D). For total higher order aberrations, IntraLase values tended to be better than Moria and Hansatome microkeratomes (IntraLase compared to Hansatome, P^.047 for MRSE values between 3.00 and 8.00 D; IntraLase compared with Moria, P^. 002 for MRSE values 2=2.00 D). Change in coma root-mean-square was similar for the three groups.

CONCLUSIONS: The findings suggest the femtosecond laser provides a better platform for LASIK than the commonly used microkeratomes analyzed in this study. [J Refract Surg. 2007;23:880-887.]

Laser in situ keratomileusis (LASIK) is the most commonly performed refractive surgical procedure despite recent trends toward increased use of surface ablation. Although laser ablation is considered the principal source of surgically induced higher order aberrations such as coma, trefoil, and spherical aberration, flap creation also has been associated with increased aberrations, which can influence the outcome of customized corneal ablation and may be associated with postoperative complications such as glare, halos, starbursts, and double vision.12

The femtosecond laser and mechanical microkeratome are alternative methods used to form the flap in LASIK. Studies have demonstrated the femtosecond laser, when applied to LASIK as a microkeratome, produces a more planar flap than mechanical microkeratomes.3 Some studies have reported excellent results with the femtosecond laser4,5 and even superior results in some parameters compared to the microkeratome.6 However, fewer studies have systematically compared the changes in optical aberrations between the femtosecond laser and microkeratomes.

This study examined the differences in outcomes related to ocular aberrations after customized LASIK for myopia performed with the IntraLase (IntraLase Corp, Irvine, Calif) femtosecond laser compared to the Moria M2 (Moria, Antony, France) and Hansatome (Bausch & Lomb, Rochester, NY) microkeratomes.

Figure 1. Graph shows the distribution of preoperative coma values among the groups. The blue bars show the mean (circle in the center of the bar) and 95% confidence intervals for each group. Mean values were 0.26?0.16, 0.29?0.18, and 0.25?0.15 ??) for the Hansatome (H-Lasik), IntraLase (IL), and Moria (M) groups, respectively.

Figure 1. Graph shows the distribution of preoperative coma values among the groups. The blue bars show the mean (circle in the center of the bar) and 95% confidence intervals for each group. Mean values were 0.26?0.16, 0.29?0.18, and 0.25?0.15 ??) for the Hansatome (H-Lasik), IntraLase (IL), and Moria (M) groups, respectively.

PATIENTS AND METHODS

Four hundred ten eyes of 410 myopic patients who underwent wavefront-guided customized LASIK between 2002 and 2006 performed by two surgeons (S.E.W., R.R.K.) were evaluated retrospectively. Both surgeons performed LASIK with the femtosecond laser; only one of the authors performed LASIK with either the Hans atome microkeratome (S.E.W.) or the Moria microkeratomes (R.R.K.). One eye was excluded at random (a coin was tossed to make the exclusion) from patients who had bilateral LASIK with the intention of full correction. In patients who had mono vision as a surgical plan, the reading eye was excluded and the distance eye was included in data analysis. All postoperative data were collected 3 months after the primary LASIK procedure, prior to any enhancements or other surgical manipulations. In all procedures, the tenets of the Declaration of Helsinki were followed, and the study was approved by the Institutional Review Board of the Cleveland Clinic Foundation.

Preoperatively, all patients underwent a complete ophthalmologic examination that included manifest refraction spherical equivalent (MRSE), cycloplegic refraction, slit-lamp microscopy, intraocular pressure, pachymetry, computerized corneal topography (ATLAS, MasterVue software; Zeiss-Humphrey, Dublin, Calif), and fundus examination. The wavefront maps were acquired by a trained technician after pupil dilation using a Hartmann- Shack device, the LADARWave (Alcon Laboratories Ine, Ft Worth, Tex). A pupil size of 6 mm was used to analyze all wavefront maps.

Laser in situ keratomileusis surgery was performed in all three groups using identical laser methodology with the LADARVision 4000 excimer laser (Alcon Laboratories Ine). The laser ablation setting was 6.5 mm for the optical zone and 1.25 mm for the transitional zone. Many of the eyes that had flaps formed with a mechanical microkeratome had surgery prior to acquisition of the femtosecond laser at the Cleveland Clinic. All patients who had femtosecond laser flaps underwent surgery with either the 15-KHz or 30-KHz IntraLase femtosecond laser using standard methodologies recommended by the manufacturer, including side-cut and lamellar-cut energies. Patients were divided into three groups according to the device used to create the LASIK flap: Moria microkeratomes (205 eyes of 205 patients), Hansatome microkeratome (51 eyes of 51 patients), and IntraLase femtosecond laser (154 eyes of 154 patients).

The wavefront parameters included in this study were root-mean-square (RMS) coma, total aberrations, total higher order aberrations, and spherical aberration. The difference between pre- and postoperative values received a positive or a negative sign if the change occurred toward or away from zero (ideal correction), respectively (intended direction analysis). Therefore, if one patient had a positive preoperative aberration value and after LASIK this value was even higher, the difference between them was considered negative (increase in the aberration level). If the postoperative value was lower, the difference was considered positive even if this patient presented a negative value postoperatively because there was a trend toward zero with the LASIK surgery in this case. Conversely, if the one patient presented with a negative preoperative aberration value, we have the same two options; if this patient showed a less negative value or a positive value postoperately, the difference was considered positive because the change occurred toward the zero (improvement in the aberration level). However, if the postoperative value was even more negative, the difference was considered negative because there was a trend away from zero (worsening in the aberration level). Thus, if an eye had a preoperative RMS coma value of 0.25 pm and the postoperative RMS coma value was 0.15 pm, there was a difference of + 0.10 ??? (ie, an improvement of coma RMS after the procedure). On the other hand, if the same eye had a postoperative RMS coma value of 0.35 pm, there would have been a worsening in this aberration, and the difference value would have been recorded as ?0.10 µm.

Figure 2. Graph shows the distribution of preoperative spherical aberration values among the groups. The blue bars show the mean (circle in the center of the bar) and 95% confidence intervals for each group. Mean values were 0.19+0.23, 0.23?0.22, and 0.20?0.19 µm for the Hansatome (H-Lasik), IntraLase (IL), and Moria (M) groups, respectively.Figure 3. Graph shows the distribution of preoperative total aberrations values among the groups. The blue bars show the mean (circle in the center of the bar) and 95% confidence intervals for each group. Mean values were 6.24±2.62, 6.75±2.55, and 6.47?2.73 µm for the Hansatome (H-Lasik), IntraLase (IL), and Mona (M) groups, respectively.

Figure 2. Graph shows the distribution of preoperative spherical aberration values among the groups. The blue bars show the mean (circle in the center of the bar) and 95% confidence intervals for each group. Mean values were 0.19+0.23, 0.23?0.22, and 0.20?0.19 µm for the Hansatome (H-Lasik), IntraLase (IL), and Moria (M) groups, respectively.

Figure 3. Graph shows the distribution of preoperative total aberrations values among the groups. The blue bars show the mean (circle in the center of the bar) and 95% confidence intervals for each group. Mean values were 6.24±2.62, 6.75±2.55, and 6.47?2.73 µm for the Hansatome (H-Lasik), IntraLase (IL), and Mona (M) groups, respectively.

Statistical analyses were performed by a biostatistician (J.H.). Group comparisons of categorical variables were performed using the chi-square test. Quantitative and ordinal variables were compared using the Kruskal-Wallis test for all three groups and the Wilcoxon rank sum test for pair- wise comparisons. A P value <.05 was considered significant.

RESULTS

Mean patient age was 40. 6? 10.4 years for all patients. In the Hansatome, IntraLase, and Moria groups, mean patient age was 41.3?11.5, 42.7?10.6, and 38.8?9.7 years, respectively. There was a statistically significant difference in mean age for the Moria group compared with the IntraLase group (P<.001). Two hundred six (50.2%) patients were women, and 204 (49.8%) patients were men.

Mean overall MRSE was -4.30?1.90 diopters (D); mean MRSE in the Hansatome, IntraLase, and Moria groups was -4.10±1.80, -4.40±1.80, and -4.20±1.90D, respectively. Mean overall sphere was -4. 60±1.90 D; mean sphere in the Hansatome, IntraLase, and Moria groups was -4.30±1.80, -4.80±1.80, and - 4.50±2.00 D; there was no statistical difference among the three groups. The IntraLase group had a higher level of astigmatism preoperatively than the Moria group (0.70?0.70 and 0.50?0.50 D, respectively, P=. 007). Although there were no statistically significant differences among preoperative values for spherical aberration and total aberrations, the Moria group had less preoperative total higher order aberrations compared to the IntraLase group (P=. 001). The IntraLase group had more coma preoperatively than the Moria group (P=. 022). The distribution of preoperative coma, spherical aberration, total aberrations, and total higher order aberrations values is shown in Figures 1 through 4.

Figure 4. Graph shows the distribution of preoperative total higher order aberrations values among the groups. The blue bars show the mean (circle in the center of the bar) and 95% confidence intervals for each group. Mean values were 0.52?0.26, 0.52?0.19, and 0.46?0.16 ??) for the Hansatome (H-Lasik), IntraLase (IL), and Moria (M) groups, respectively.Figure 5. Scatte rp lot of manifest refraction (MR) spherical equivalent versus spherical aberration change in intended direction. The P value for common lines was <.001 (Hansatome vs IntraLase, P=. 015; Hansatome vs Moria, P=. 052; IntraLase vs Moria, P<.001). H-LASIK = Hansatome, IL = IntraLase, and M = Moria

Figure 4. Graph shows the distribution of preoperative total higher order aberrations values among the groups. The blue bars show the mean (circle in the center of the bar) and 95% confidence intervals for each group. Mean values were 0.52?0.26, 0.52?0.19, and 0.46?0.16 ??) for the Hansatome (H-Lasik), IntraLase (IL), and Moria (M) groups, respectively.

Figure 5. Scatte rp lot of manifest refraction (MR) spherical equivalent versus spherical aberration change in intended direction. The P value for common lines was <.001 (Hansatome vs IntraLase, P=. 015; Hansatome vs Moria, P=. 052; IntraLase vs Moria, P<.001). H-LASIK = Hansatome, IL = IntraLase, and M = Moria

Figure 5 shows the spherical aberration change in intended direction compared to the difference between pre- and postoperative MRSE. In most cases, there was no improvement because most of the values were negative. The data for the Hansatome and Moria groups approached but did not reach statistical significance (P=. 052). The spherical aberration change for the IntraLase group was statistically different from the Moria and Hansatome groups (P<.001 and P=. 015, respectively). IntraLase spherical aberration change tended to be better than mechanical microkeratomes for higher MRSE values (IntraLase compared to Hansatome, P^. 023 for MRSE values ^4.00 D; IntraLase compared to Moria, P^.015 for MRSE values ^2.00 D). Therefore, IntraLase patients tended to have a better clinical result with respect to spherical aberration when comparing pre- and postoperative values. Table 1 shows spherical aberration change per amount of correction attempted according to the device used for flap creation.

Table

TABLE 1Spherical Aberration Change in Intended Direction per Amount of Correction Attempted According to Device Used for Flap CreationTABLE 2Total Aberrations Change in Intended Direction per Amount of Correction Attempted According to Device Used for Flap CreationFigure 6. Scatte rp lot of manifest refraction (MR) spherical equivalent versus total aberration change in intended direction. The P value for common lines was .004 (Hansatome vs IntraLase, P=. 08; Hansatome vs Moria, P =.69; IntraLase vs Mona, P=. 001). The IntraLase group had greater improvement compared to the Moria group, especially in certain ranges of correction. H-LASIK = Hansatome, IL = IntraLase, and M = Mona

TABLE 1

Spherical Aberration Change in Intended Direction per Amount of Correction Attempted According to Device Used for Flap Creation

TABLE 2

Total Aberrations Change in Intended Direction per Amount of Correction Attempted According to Device Used for Flap Creation

Figure 6. Scatte rp lot of manifest refraction (MR) spherical equivalent versus total aberration change in intended direction. The P value for common lines was .004 (Hansatome vs IntraLase, P=. 08; Hansatome vs Moria, P =.69; IntraLase vs Mona, P=. 001). The IntraLase group had greater improvement compared to the Moria group, especially in certain ranges of correction. H-LASIK = Hansatome, IL = IntraLase, and M = Mona

The correlation between total aberrations change in intended direction and the attempted correction is shown in Figure 6. The regression lines for the Hansatome and IntraLase groups were similar (P=. 08), and the Moria and Hansatome groups were not significantly different (P=. 69). However, the IntraLase group had statistically better outcomes compared to the Moria group (P=. 001). Improvement values for the IntraLase group tended to be higher than those for the Moria group for higher preoperative values (IntraLase compared to Moria, P^.021 for MRSE values ^3.00 D). Table 2 shows total aberrations change per amount of correction attempted according to the device used for flap creation.

The higher the level of attempted correction of myopia, the more prominent was the induction of total higher order aberrations at 3-month follow-up, although this was less pronounced in the IntraLase group (Fig 7). The regression lines for the mechanical microkeratome groups were similar (P=. 2 6). However, values in the IntraLase group tended to be better than those for the mechanical microkeratome groups, especially for higher MRSE corrections (IntraLase compared to Hansatome, P^.047 for MRSE values between 3.00 and 8.00 D; IntraLase compared with Moria, P^. 002 for MRSE values ^2.00 D). Table 3 shows total higher order aberrations change per amount of correction attempted according the device used for flap creation.

Figure 7. Scatte rp lot of manifest refraction (MR) spherical equivalent versus total higher order aberration change In intended direction. The P value for common lines was <.001 (Hansatome vs IntraLase, P=. 012; Hansatome vs Mona, P=. 26; IntraLase vs Moria, P<.001). The IntraLase group was significantly better than the Hansatome and Mona groups. H-LASIK = Hansatome, IL = IntraLase, and M = MoriaFigure 8. Scatterplot of manifest refraction (MR) spherical equivalent versus coma rootmean-square (RMS) change in intended direction. The P value for common lines was .24 (Hansatome vs IntraLase, P=. 20; Hansatome vs Moria, P=. 90; IntraLase vs Moria, P=. 12). The difference among the groups was not statistically significant. HLASIK = Hansatome, IL = IntraLase, and M = Moria

Figure 7. Scatte rp lot of manifest refraction (MR) spherical equivalent versus total higher order aberration change In intended direction. The P value for common lines was <.001 (Hansatome vs IntraLase, P=. 012; Hansatome vs Mona, P=. 26; IntraLase vs Moria, P<.001). The IntraLase group was significantly better than the Hansatome and Mona groups. H-LASIK = Hansatome, IL = IntraLase, and M = Moria

Figure 8. Scatterplot of manifest refraction (MR) spherical equivalent versus coma rootmean-square (RMS) change in intended direction. The P value for common lines was .24 (Hansatome vs IntraLase, P=. 20; Hansatome vs Moria, P=. 90; IntraLase vs Moria, P=. 12). The difference among the groups was not statistically significant. HLASIK = Hansatome, IL = IntraLase, and M = Moria

Coma RMS change related to the attempted correction of myopia was similar for the three groups (Fig 8). With all three instruments, coma RMS values tended to increase at 3 months after surgery, especially for higher attempted corrections of myopia.

DISCUSSION

The major goal of wavefront-guided laser refractive surgery is to correct all aberrations of the eye or to at least reduce aberrations. The LASIK procedure has been shown to induce higher order aberrations.7"12 Although the laser ablation itself is the principal cause of induced aberrations after LASIK, other components of the procedure also are important contributors.7"12 One of these factors is the changes in aberrations that occur with production of the epithelial-stromal LASIK flap. Ablations in LASIK are based on wavefront analyses performed prior to surgery, which likely offer a reasonable approximation in many eyes. Depending on flap morphology, however, new aberrations that are not incorporated into the ablation are likely present in a significant proportion of eyes.

Figure 9. Sections from human cadaver eyes that had LASIK flaps formed with the A) Hansatome microkeratome and B) 15-KHz femtosecond laser. Note the more uniform planar shape of the flap cut with the femtosecond laser compared to the flap cut with the microkeratome, which is thinner in the center (original magnification × 40).

Figure 9. Sections from human cadaver eyes that had LASIK flaps formed with the A) Hansatome microkeratome and B) 15-KHz femtosecond laser. Note the more uniform planar shape of the flap cut with the femtosecond laser compared to the flap cut with the microkeratome, which is thinner in the center (original magnification × 40).

Table

TABLE 3Total Higher Order Aberrations Change in Intended Direction per Amount Of Correction Attempted According to Device Used for Flap Creation

TABLE 3

Total Higher Order Aberrations Change in Intended Direction per Amount Of Correction Attempted According to Device Used for Flap Creation

Recent studies have demonstrated flaps formed with the femtosecond laser are more likely to remain astigmatically neutral, to have greater predictability with regard to flap thickness, and to have reduced incidence of flap-related complications.613"16 However, few detailed studies have compared the effects of microkeratomes and the femtosecond laser in eyes that have had concurrent LASIK surgery.

In our study, the femtosecond laser yielded significantly better outcomes with regard to LASIK-induced aberrations. There was a greater increase in total higher order aberrations in eyes that had LASIK with the Moria microkeratome compared to eyes that had LASIK with the femtosecond laser; there was no significant difference between the IntraLase and Hansatome groups. There was less increase in spherical aberration in eyes that had LASIK with the femtosecond laser than eyes that had LASIK with the mechanical microkeratomes. Outcomes with regard to change in RMS coma were not significantly different among the three groups. Although only the Moria group showed worse results with respect to total aberrations compared to the IntraLase group, the Hansatome group included a lower number of eyes, and therefore, the difference between the IntraLase and Hansatome groups could have reached significance if there were a larger number of patients included in the Hansatome group. It is important to note that in general, all of the measured aberrations tended to increase after LASIK surgery. The advantage of the femtosecond laser was that the increases in aberrations after LASIK tended to be less than for surgery performed with the microkeratomes included in this study.

Presumably, the reason the femtosecond laser results tended to be better was that on average, the laser produces a more uniform flap. Flaps that are cut in cadaver eyes with the femtosecond laser tend to be more uniform in thickness across the diameter of the flap, whereas flaps cut with a microkeratome tend to be thinner in the center relative to the periphery (Fig 9) (S.E.W., unpublished data, 2004). Compounding this is the greater variability in flap thickness with microkeratomes.3 Other characteristics of either femtosecond laser flaps or microkeratome flaps are also potential contributors to increases in either specific or overall optical aberrations in the eye. For example, even small levels of flap decentration can induce significant higher order aberrations.17,18

Clearly, other factors are also important in confounding attempts to eliminate all aberrations via refractive surgery. Biomechanical effects and wound healing effects, such as epithelial hyperplasia, remain important influences on the final outcomes of wavefront-guided custom LASIK.1920 Cyclorotation and resulting poor registration, along with tracking errors, are other variables that may confound the outcomes of wavefrontguided surgical procedures.

Thus, this retrospective study of the Moria and Hansatome mechanical microkeratomes and the IntraLase femtosecond microkeratome for LASIK using the Alcon LADARVision4000 laser demonstrated an increase in higher order aberrations for all three microkeratomes, with a less increase in spherical aberration and total higher order aberrations for the IntraLase, which suggests that the better flap uniformity obtained with the femtosecond laser provides an improved platform for excimer laser ablations.

REFERENCES

1. Chalita MR, Ch?vala S, Xu M, Krueger RR. Wavefront analysis in post-LASIK eyes and its correlation with visual symptoms, refraction, and topography. Ophthalmology. 2004;111:447-453.

2. Pallikaris IG, Kymionis GD, Panagopoulous SI, S?ganos CS, Theodorakis MA, Pallikaris AL Induced optical aberrations following formation of a laser in situ keratomileusis flap. / Cataract Refract Surg. 2002;28:1737-1741.

3. Binder PS. Flap dimensions created with the IntraLase FS laser. J Cataract Refract Surg. 2004;30:26-32.

4. Kurtz RM, Liu X, Einer VM, Squier JA, Du D, Mourou GA. Photodisruption in the human cornea as a function of laser pulse width. J Refract Surg. 1997;13:653-658.

5. Nor dan LT, S lade SG, Baker RN, Suarez C, Juhasz T, Kurtz R. Femtosecond laser flap creation for laser in situ keratomileusis: six month follow-up of initial US clinical series. / Refract Surg. 2003;19:8-14.

6. Kezirian GM, Stonecipher KG. Comparison of IntraLase femtosecond laser and mechanical keratomes for laser in situ keratomileusis. / Cataract Refract Surg. 2004;30:804-811.

7. Waheed S, Chalita MR, Xu M, Krueger R. Flap -indue ed and laser-induced ocular aberrations in a two-step LASIK procedure. J Refract Surg. 2005;21:346-352.

8. Porter J, MacRae S, Yoon G, Roberts C, Cox IG, Williams DR. Separate effects of the microkeratome incision and laser ablation on the eye's wave aberration. Am J Ophthalmol. 2003;136: 327-337.

9. Potgieter FJ, Roberts C, Cox IG, Mahmoud AM, Herderick EE, Roetz M, Steenkamp W. Prediction of flap response. / Cataract Refract Surg. 2005;31:106-114.

10. Oshika T, Klyce SD, Applegate RA, Howland HC, El Danasoury MA. Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis. Am J Ophthalmol. 1999;127:1-7.

11. Buhren J, Kohnen T. Factors affecting the change in lower-order and higher- order aberrations after wavefront-guided laser in situ keratomileusis for myopia with the Zyoptix 3.1 system. J Cataract Refract Surg. 2006;32:1166-1174.

12. Subbaram MV, MacRae S, Slade SG, Durrie DS. Customized LASIK treatment for myopia: relationship between preoperative higher order aberrations and refractive outcome. J Refract Surg. 2006;22:746-753.

13. Lim T, Yang S, Kim M, Tchah H. Comparison of the IntraLase femtosecond laser and mechanical microkeratome for laser in situ keratomileusis. Am J Ophthalmol. 2006;141:833-839.

14. Tran DB, Sarayba MA, Bor Z, Garuf?s C, Duh YJ, Softes CR, Juhasz T, Kurtz RM. Randomized prospective clinical study comparing induced aberrations with IntraLase and Hansatome flap creation in fellow eyes: potential impact on wavefront-guided laser in situ keratomileusis. / Cataract Refract Surg. 2 005 ;3 1:97105.

15. Stonecipher K, Ignacio TS, Stonecipher M. Advances in refractive surgery: microkeratome and femtosecond laser flap creation in relation to safety, efficacy, predictability and biomechanical stability. Curr Opin Ophthalmol. 2006;17:368-372.

16. Durrie DS, Kezirian GM. Femtosecond laser versus mechanical keratome flaps in wavefront-guided laser in situ keratomileusis: prospective contralateral eye study. / Cataract Refract Surg. 2006;31:120-126.

17. Bueeler M, Mrochen M, Seiler T. Maximum permissible lateral decentration in aberration-sensing and wavefront-guided corneal ablation. / Cataract Refract Surg. 2003;29:257-263.

18. Mrochen M, Kaemmerer M, Mierdel P, Seiler T. Increased higher-order optical aberrations after laser refractive surgery: a problem of subclinical decentration. / Cataract Refract Surg. 2001;27:362-369.

19. Wilson SE, Netto M, Ambrosio R Jr. Corneal cells: chatty in development, homeostasis, wound healing, and disease. Am J Ophthalmol. 2003;136:530-536.

20. Dupps WJ Jr, Wilson SE. Biomechanics and wound healing in the cornea. Exp Eye Res. 2006;83:709-720.

TABLE 1

Spherical Aberration Change in Intended Direction per Amount of Correction Attempted According to Device Used for Flap Creation

TABLE 2

Total Aberrations Change in Intended Direction per Amount of Correction Attempted According to Device Used for Flap Creation

Figure 6. Scatte rp lot of manifest refraction (MR) spherical equivalent versus total aberration change in intended direction. The P value for common lines was .004 (Hansatome vs IntraLase, P=. 08; Hansatome vs Moria, P =.69; IntraLase vs Mona, P=. 001). The IntraLase group had greater improvement compared to the Moria group, especially in certain ranges of correction. H-LASIK = Hansatome, IL = IntraLase, and M = Mona

TABLE 3

Total Higher Order Aberrations Change in Intended Direction per Amount Of Correction Attempted According to Device Used for Flap Creation

10.3928/1081-597X-20071101-03

Sign up to receive

Journal E-contents