Surgery Figure 2: Uncorrected Vision on Post-operative Day 1
100 80 60 40 20 0
20/12.5 or better
20/16 or better 20/20 or better
Uncorrected visual acuity at day one Visx
WaveLight Figure 3: Uncorrected Visual Acuity at Six Months
100 80 60 40 20 0
20/12.5 or better
20/16 or better 20/20 or better 20/25 or better
Uncorrected visual acuity at six months Visx
WaveLight
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<0.05), but not clinically significant. The VISX-treated eyes had a mean spherical equivalent refraction of about -0.10 D while the WaveLight eyes had a mean spherical equivalent refraction around +0.10 D.
Figure 2 shows the percentage of eyes achieving a given level of uncorrected visual acuity one day after surgery. Two out of three eyes in both the VISX and Wavelight groups had 20/16 or better visual acuity on the day after surgery. There was no statistically significant difference between treatment groups at this time point. Figure 3 shows the percentage of eyes achieving a given level of uncorrected visual acuity at the six-month visit. Again, there was no statistically significant difference between treatments. More than two-thirds of subjects in each treatment group achieved an uncorrected visual acuity 20/16 or better. At six months, 15 of 17 subjects in each group had an uncorrected visual acuity better than, or equal to, their pre-operative best corrected acuity.
Subjects were questioned about their preference for one eye or the other at all post-operative visits. At one day post-operative, 57 % of subjects indicated no preference, with 21 % preferring the Wavelight eye
16 <20/25 20/25 or better
and 22 % preferring the VISX-treated eye. This was not significant (p>0.9). At three months, 56 % of patients indicated no preference, with the remaining 44 % indicating a preference for the WaveLight-treated eye, a statistically significant difference (chi square test, p<0.05).
The patient reported outcomes showed a similar incidence of post-operative glare and halos reported between the two treatments. The incidence and severity of glare and halos were reported to be higher than pre-operative levels in the early post-operative period but similar to, or lower than, pre-operative levels at the three-month and later visits, though differences were not statistically significant. The clarity of each eye at night was also reported as better at three months, but again the difference was not statistically significant.
Discussion
The results here demonstrate that a decision tree to select between a wavefront-guided or wavefront-optimized treatment algorithm for laser refractive surgery produces results that are equivalent to those achieved on an all wavefront-guided platform. On the first day post-operative, the ‘wow’ factor was achieved in both cases, with two of three eyes in either treatment groups achieving an uncorrected visual acuity of 20/16 or better.
The equivalence of clinical results allows surgeons to take advantage of the benefits of wavefront-optimized surgery. Of greatest benefit, perhaps, is that a high percentage of patients will be treated without the need for a wavefront measurement, based on their responses to the answers in the first box of the decision tree. Of the remainder who eceive a wavefront measurement a significant percentage will have pre-operative HOAs ≤0.3 µ—they will receive a wavefront-optimized treatment. Previous study results suggest that more than 80 % of patients will be suitable for wavefront-optimized treatment. The wavefront-optimized treatment removes any requirements for wavefront measurement and alignment of the measurement at the time of treatment, introducing significant time savings without any apparent compromise in clinical results.
As noted earlier, the WaveLight study submitted to obtain FDA approval for wavefront-optimized surgery showed that when pre-operative HOAs are high (e.g., >0.35), wavefront-guided surgery provides a slightly better result. In some sense, this is a measure of the ability to correct pre-operative HOAs with wavefront-guided surgery. When HOAs are lower than 0.3 µ RMS the noise in the wavefront-guided treatment, perhaps from centration or rotational alignment errors and measurement repeatability, is of a magnitude that makes a reduction in overall HOAs unlikely. When HOAs are higher than 0.3 µ RMS, the noise is a smaller relative factor, and real reductions in pre-operative HOAs can be achieved. Conversely, because the wavefront-optimized treatment is designed to prevent the induction of HOAs, high levels of pre-operative aberrations will remain after surgery—no attempt is made to treat them.
There have been a number of other studies comparing refractive surgery results between wavefront-guided and wavefront-optimized procedures. Perez-Straziota et al. reported no significant differences in visual performance or HOAs between a wavefront-guided and a wavefront-optimized treatment group.7
An interesting observation by
those authors was that 14 eyes scheduled for wavefront-guided treatment were treated with a wavefront-optimized procedure due
US OPHTHALMIC REVIEW
Percentage of eyes
Percentage of eyes
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