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Refractive Surgery | Apr 2010

Surface Ablation With PresBvis

Multifocal ablation with a solid-state laser offers a potential improvement upon monovision.

The Pulzar Z1 (CustomVis, Balcatta, Australia) is the first solid-state refractive laser with an available presbyopia software package, PresBvis. My interest in using this laser for presbyopia treatments was piqued when I participated in an independent assessment of clinical results with PresBvis. Patient outcomes were impressive, with 96% of participants either very happy or happy with their result. Near UCVA improved from an average of 20/73 preoperatively to 20/23 postoperatively.

PresBvis is a unique approach to presbyopia correction. The treatment is an improved version of monovision because it provides excellent reading vision without sacrificing distance vision to the extent seen with standard monovision. The dominant eye is corrected for distance, and the nondominant eye receives the PresBvis multifocal treatment in which three zones are created to enhance the patient's depth of field. The central zone is for far vision; the intermediate zone is a 2.00 D add for near; and the outer zone is again for far vision. The near vision add dominates the power of this multifocal treatment. The inner two zones have fixed zone sizes, but the outer zone can be adjusted at the surgeon's discretion (eg, a larger zone for large mesopic pupils). The transition from zone to zone is smooth to further enhance the depth of field.

ADVANTAGES OF THE SOLID-STATE LASER
PresBvis was performed during LASIK in other clinical trials; however, I prefer to use it with surface ablation. In much less dependence on the hydration state of the cornea. Eliminating the effect of corneal hydration on the ablation rate enhances accuracy and provides good results after corneal presbyopia correction. The small spot size and highly precise eye tracking of the Pulzar Z1 are also important; they sculpt the intricate shape of the multizonal, multifocal PresBvis ablation pattern.

INDEPENDENT ASSESSMENT
I have now performed three PresBvis treatments by surface ablation. All patients are extremely happy, reporting excellent reading vision (N5 or better) and excellent intermediate/computer vision. Distance UCVA in the PresBvis-treated eye was slightly worse following surgery; however, there was no loss in distance BCVA, and all patients reported being very happy with bilateral distance vision. Patients indicated good stereopsis and reported no problems with daily activities including playing sports or driving. Overall, patient-reported subjective quality of vision was substantially higher compared with a contact lens monovision trial.

Laser ablation is more predictable and the results more stable than conductive keratoplasty and the new femtosecond concentric circle hexagonal radial keratectomy-type procedure. It can also have the benefit of producing an additional refractive correction. Furthermore, procedures that have the near vision zone in the center—whether created by laser or corneal inlay—can introduce unacceptable levels of coma with slight decentration. PresBvis does not suffer from this potential problem.

CONCLUSION
As a surgeon, I am more comfortable creating a multifocal cornea in only one eye, particularly when there is no loss of BCVA, as I have seen thus far with PresBvis. The high patient satisfaction seen in my patients matched the level seen in an earlier trial, suggesting that PresBvis is an outstanding option for treating presbyopia.

Ian Anderson, FRACO, practices with the Subiaco Eye Clinic, Perth, Australia. Dr. Anderson states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: ian@ianseyesite.net.

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