Refractive Surgery Outcomes Comparison


treatment showed that the visual acuity, contrast sensitivity and preoperative to post-operative aberration changes were similar between a wavefront-guided ablation profile and a wavefront-optimized ablation profile.6


Figure 1: Decision Tree to Select Wavefront-optimized or Wavefront-guided Treatment


The exception to this was in the case where measured pre-operative HOAs exceeded 0.3 µ root mean square (RMS). At that point, the wavefront-guided procedure appeared to provide a better surgical outcome. It is worth noting that only 17 % of the eyes in the study had pre-operative HOA magnitudes ≥0.3 µ RMS.


The following study was designed to determine if a decision tree based on the criterion above would provide clinical results similar to those achieved by treating all patients with a wavefront-guided procedure.


Methods


This study was designed to compare results obtained using an excimer laser with wavefront-guided capability to a laser with both wavefront-optimized and wavefront-guided capability. The wavefront-guided system was a VISX Star S4 (Abbott Medical Optics Inc., Santa Ana, CA) with a Wavescan aberrometer (based on Shack-Hartmann principles). The wavefront-optimized/wavefront-guided system was a WaveLight Allegretto Wave Eye-Q laser (Alcon Laboratories, Inc., Fort Worth, TX) with a WaveLight Analyzer aberrometer (based on Tscherning principles). All subjects were prophylactically treated with a corticosteroid and a fluoroquinolone antibiotic four times daily for three days prior to surgery.


For the WaveLight system, a decision tree was developed to minimize the number of patients on whom a wavefront measurement would be required, and limit the number of patients with measured wavefronts who would undergo a wavefront-guided procedure. The primary driver for choosing wavefront-guided versus wavefront-optimized treatment was good pre-operative visual acuity, good night vision and good self-reported visual quality. All of these three were unlikely to be true if high pre-operative aberrations were present. If any of these conditions were not met a wavefront measurement was made, if possible. If total HOA RMS was >0.3 µ then a wavefront-guided procedure was performed. Otherwise a wavefront-optimized procedure was performed, or a topography-guided treatment if topography was atypical and a wavefront could not be measured. This decision tree is shown in Figure 1.


Institutional review board approval was applied for and obtained. A total of 20 subjects were planned for this study, all with normal eyes except for refractive error. Subjects served as their own controls so age and gender were the same between groups while refractive error was expected to be similar between groups. Eyes were randomly assigned to treatment for each subject with one eye receiving CustomVue wavefront-guided surgery and the contralateral eye receiving WaveLight surgery, either wavefront-guided or wavefront-optimized, as the decision tree indicated. A maximum of 12 eyes were enrolled in the wavefront-optimized group, so that a sufficient ‘n’ for analysis was obtained in the WaveLight wavefront-guided group.


Measures of interest were refractive error and uncorrected visual acuity. Subjects were also asked which eye they preferred, and were given a subjective questionnaire to fill out related to glare, halos, and other visual disturbances. Comparisons between groups were made


US OPHTHALMIC REVIEW Yes


Wavefront- guided


treatment


Good visual acuity >20/20


Good night vision Good visual quality


Yes


Wavefront- optimized treatment


Yes No


Wavefront measurement possible?


No RMSh>0.3 No


Wavefront- optimized treatment


Yes


Wavefront- optimized treatment


Regular topography? No


Topography- guided


treatment


Table 1: Summary of Refractive Data over Time Pre-operative One month Three months Six months


Visx Range -4.44 D


Wavelight -4.44 D (Range)


Visx Range -0.42 D


Wavelight -0.44 D (Range)


-0.13 D -0.12 D 0.15 D -0.17 D


(-6.75 to -1.00) (-0.75 to 0.25) (-0.50 to 0.50) (-0.75 to 0.25) 0.09 D


0.12 D (-6.75 to -1.00) (-1.00 to 0.63) (-0.50 to 0.75) (-0.25 to 0.50) -0.03 D -0.01 D 0.00 D 0.00 D


(-2.50 to 0.00) (-0.25 to 0.00) (-0.25 to 0.00) (0.00 to 0.00) -0.02 D


0.0 D (-2.50 to 0.00) (-0.25 to 0.00) (0.00 to 0.00) (0.00 to 0.00)


using paired t-tests for parametric variables or analysis of variance if the three conditions were tested independently (wavefront-guided VISX, wavefront-guided WaveLight, wavefront-optimized WaveLight). In the case of non-parametric data a Wilcoxon matched pairs test was used. All tests were considered significant at p<0.05.


Results


Twenty subjects were recruited and treated in a four-month period. Surgery was performed using a superior hinge and an optical zone between 6.0 and 6.7 mm with flap creation using a femtosecond laser (IntraLase FS Laser, Abbott Medical Optics Inc., Santa Ana, CA). All surgeries were performed by one surgeon (KGS) and were uneventful. One subject was lost to follow-up at one week, leaving 19 subjects for analysis. Two additional subjects did not complete their six-month visit. Of those subjects with data, 12 received wavefront-optimized treatment while seven subjects received a wavefront-guided treatment with the WaveLight laser. All WaveLight wavefront-guided eyes had HOAs >0.3 µ RMS.


Average pre-operative sphere and cylinder were not significantly different between the VISX and WaveLight eyes (p >0.9). The maximum sphere treated was -6.75 D with a maximum cylinder of -2.50 D. Table 1 shows the average refractive error (sphere, cylinder and the MRSE,


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