A compensation algorithm was designed to reduce the induction of spherical aberration, resulting in what is now termed a wavefront-optimized ablation profile. The wavefront-optimized profile is less sensitive to relative positioning errors—a wavefront-guided treatment must be precisely centered and rotationally aligned to match the measured wavefront to the intended treatment if any beneficial effect is to be realized.
At that point, the wavefront-guided procedure appeared to provide a better surgical outcome. 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. 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.
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. 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.
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 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 Twenty subjects were recruited and treated in a four-month period. Surgery was performed using a superior hinge and an optical zone between 6. 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.
The maximum sphere treated was Table 1 shows the average refractive error sphere, cylinder and the MRSE, the mean refraction spherical equivalent [MRSE] results over time pre-operative to six months post-operative.
Post-operative refractive error was statistically significantly different p Figure 2 shows the percentage of eyes achieving a given level of uncorrected visual acuity one day after surgery.
An invisible, infra-red laser is shined into your eye and then it bounces back off of the retina in the back of your eye. The returning wave of light generated by this laser is distorted and affected by all the focusing elements of the eye on its light flow journey back out through your eye. The distorted wave of light that comes out of your eye is a measurement of light flow thorugh your eye. Your optical fingerprint is downloaded into the laser and reproduced onto your eye with billionth of an inch tolerances.
There are today various generations of wavefront technology. I personally prefer to use the VISX S4 IR laser which employs Fourier algorithms, iris registration systems, and three dimensional eye tracking to give what I consider to be the state of the art in wavefront guided treatment.
Wavefront-optimized LASIK is in many ways simply conventional surgery, but with modifications based on wavefront modeling and wavefront theory to improve outcomes beyond standard conventional LASIK. With wavefront-optimized LASIK, a refraction is still performed on the patient to generate a precription to be entered into the laser, as is the case with standard conventional surgery.
In this way, wavefront-optimized surgery simply is an improved version of conventional surgery. A highly respected colleague of mine, Dr. Steve Schallhorn who was head of the laser vision correction program for the U. These are distortions beyond simple nearsightedness, farsightedness, and astigmatism.
Our own study published in Ophthalmology found that WF-guided treatments performed with the WaveLight Allegretto demonstrated slightly superior predictability, better mean UDVA and less trefoil compared with WF-optimized treatments performed with the same machine.
Based on this small, prospective, comparative series of 22 eyes, we conclude that WF-guided and WF-optimized LASIK performed on hyperopic patients with or without astigmatism can provide similar results with respect to the parameters of safety, contrast sensitivity and refractive error. It is possible that WF-guided treatments offer some advantages over WF-optimized treatments, but this series lacked sufficient power to detect such differences if they were present.
It will be of interest to see whether future studies with larger samples confirm our postulates, which should be interpreted with caution. Liang, D. Williams and D. Miller, J. Mrochen, M. Kaemmerer and T. Seiler, J. Randleman et al. Golas and E. Manche, J. Cataract Refract. Manche and W.
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