Healio
Healio
ByEric D. Donnenfeld, MD
March 15, 2005
4 min read
Save

Improving Custom Ablation Outcomes

ByEric D. Donnenfeld, MD

Customized ablation technology is quickly becoming the standard for the best surgical outcomes in refractive procedures. Several different platforms are available to refractive surgeons in the United States. However, not all perform equally well for all patients. This is why I use the LADARVision System (Alcon Laboratories, Inc., Fort Worth, Texas) to ensure the best results and maximum patient satisfaction for all my patients.

Studies comparing platforms

Several studies compare the results with the different customized ablation platforms. James P. McCulley, MD, and colleagues performed a study comparing the ability to capture higher-order aberrations between the LADARWave (Alcon Laboratories, Inc.) and WaveScan (Visx, Santa Clara, Calif.) aberrometers. The results of the study showed that, as pupil size increases, LADARWave has the ability to detect and capture more higher-order aberrations than WaveScan.1

Eric D. Donnenfeld, MD [photo]Eric D. Donnenfeld, MD, is co-chairman of cornea and external diseases at the Manhattan Eye and Ear Hospital in New York. Dr. Donnenfeld is also a member of the Ocular Surgery News editorial board.

Stephen G. Slade, MD, performed a contralateral study of the Alcon and Visx custom platforms — CustomVue (Visx) and CustomCornea (Alcon Laboratories, Inc.) — in order to most accurately measure the results of one system vs. the other. With no adjustments made to either system, CustomCornea provided better results than CustomVue in uncorrected visual acuity (UCVA) at 3 months (Figure 1).2 More importantly, when asked about overall satisfaction with the eyes treated on each system, more patients were satisfied or extremely satisfied with the results from CustomCornea than with CustomVue. Knowledge of patient satisfaction is important because the information provides proof to the clinician that proper results are being achieved when using the superior laser system.

According to a study by Kerry D. Solomon, MD, evaluating the accuracy of treatment of CustomCornea vs. CustomVue and Zyoptix, 70% of patients with CustomCornea had an accuracy within ±0.25 D.3 Comparatively, CustomCornea provided better accuracy within ±0.25 D than CustomVue and Zyoptix (Bausch & Lomb, Rochester, New York). Regarding photopic contrast sensitivity without glare, more than 80% of CustomCornea patients experienced no change in sensitivity from preoperative states. Furthermore, the study found that, at 1 month, total higher-order aberrations had decreased in CustomCornea patients and increased in CustomVue and Zyoptix patients (Figure 2).

Figures 1-2

LADARVision CustomCornea technology also provides side-by-side viewing of the wavefront image and the live surgical tracked image, which facilitates more consistent limbal ring placement at the laser and better registration.

Daniel Durrie, MD, and colleagues, conducted a study comparing CustomCornea and Zyoptix platforms for LASIK treatment. In almost all instances, CustomCornea provided better results than Zyoptix in UCVA at 3 months. In evaluating mesopic contrast sensitivity change at 3 months, study data illustrated that more patients’ eyes improved or stayed the same with CustomCornea than with Zyoptix (Figure 3).4

Figure 3

Fixed-feature registration important

CustomCornea results in improved visual acuity and better quality of vision because it uses a quality wavefront image capture and matches or registers that capture to a patient's eye before applying treatment. To capture images and match appropriately, fixed-feature registration, such as limbus registration, is required. Several studies have concluded that limbus registration reduces the induction of higher-order aberrations, improves mesopic contrast sensitivity and results in highly satisfied patients.1-5

Wavefront measurements vary with pupil location and pupil size. Measured wavefronts must be registered to a fixed feature of the eye, such as the limbus, for accuracy. In contrast, the pupil, on which most systems center, is a moving target. For custom ablation, the limbus must be identifiable at the time of measurement and at the time of treatment. Pupils, on the other hand, are found to constrict physiologically and move nasally, causing decentered ablations. Therefore, because better patient outcomes are dependent upon accurate centration and registration, I provide CustomCornea with the LADARWave and LADARVision4000 to confirm the ablation is applied to the right area.

With the the LADARVision System’s unique registration system, a dilated wavefront is captured before surgery and is referenced to the limbus on the LADARWave aberrometer. During surgery, the wavefront is again referenced to the limbus on the LADARVision laser. Unlike referencing to the pupil, no wavefront shift occurs when referencing to the limbus.

However, if the wavefront is captured in dim light and referenced to the pupil center, as is done with other systems, the centration will only be accurate preoperatively. When the ablation is performed under bright light, the pupil will move superiornasally, creating decentration because the wavefront pattern is applied to the wrong area, thus inducing aberrations (Figures 4A and 4B).

Figures 4A-B

Iris tracking on the Visx platform may eventually be able to track the eye accurately and, in turn, may account for cyclotorsion. However, iris registration alone will not yield a stable reference from which to apply a wavefront because, unlike CustomCornea’s platform, centration is manually performed on the pupil, leaving room for error.

Furthermore, in our study, 22% of patients shifted 250 µm or more when illumination was changed from dim light at 0.65 fc to bright light at 130 fc.6 We found that the mean change of pupil position was 177 µm, and 10% of patients shifted 300 µm. The pupil shift caused significant higher- and lower-order aberrations and induced coma, cylinder and spherical changes affecting quality of vision.

Advances in wavefront technology

Figure 5 Recent advances in the LADARWave aberrometer features improve the capture process to save time, ensure consistency and increase accuracy by automatically registering the capture for one-click accuracy confirmation (Figure 5).

Future technology advances will support higher-speed ablation and 100 Hz capabilities. Pupil dilation and aberrometry will be performed prior to the day of surgery and a limbal tracker will work on a nondilated pupil, making patient flow as fast or faster than the flow of any other laser presently available.

Conclusion

LADARVision CustomCornea achieves better visual outcomes than all other platforms available today. In addition, this platform is improving surgeons’ efficiency and patient flow and has the technology to further improve visual acuity and quality of vision in the future.

References
  1. Awwad ST, El-Kateb M, Bowman RW, Cavanagh HD, McCulley JP. Wavefront-guided laser in situ keratomileusis with the Alcon CustomCornea and the VISX CustomVue: Three-month results. J Refract Surg. 2004;20(5):S606-S613.
  2. Slade S. Contralateral comparison of Alcon CustomCornea and VISX CustomVue wavefront-guided laser in situ keratomileusis: One-month results. J Refract Surg. 2004;20(5):S601-S605.
  3. Solomon KD, Fernandez de Castro LE, Sandoval HP, Vroman DT. Comparison of wavefront sensing devices. Ophthalmol Clin North Am. 2004;17(2):119-127.
  4. Durrie DS, Stahl J. Randomized comparison of custom laser in situ keratomileusis with the Alcon CustomCornea and the Bausch & Lomb Zyoptix systems: One-month results. J Refract Surg. 2004;20(5):S614-S618.
  5. Speaker MS, Tullo W, Chokshi A. Custom LASIK outcomes: CustomCornea vs. CustomVue. Presented at the American Society of Cataract and Refractive Surgery annual meeting; May 2004; San Diego, Calif.
  6. Donnenfeld ED. The pupil is a moving target: Centration, repeatability, and registration. J Refract Surg. 2004;20(5):S593-S596.