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Iris registration of little to no benefit in LASIK, study says
J Refract Surg. 2009;25(6):493-502.
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LASIK with iris registration adds little to no benefit in visual acuity outcomes or manifest refraction, according to a study.
Six months after surgery, uncorrected visual acuity was –0.01 logMAR in 118 eyes after LASIK using a Visx STAR S4 CustomVue platform (Abbott Medical Optics) and 0.00 logMAR in 121 eyes using the same platform with iris registration. Both groups had a similar percentage that achieved 20/20 or better vision: 78% without iris registration vs. 79% with iris registration.
"Our study suggests that wavefront-guided LASIK with the Visx CustomVue platform, independent of iris registration status, is effective, safe and predictable," the study authors said.
Predictability of outcomes was also similar; 90% of eyes without iris registration were within ±0.5 D of emmetropia compared with 92% with iris registration. There was no difference at any time point in mean postoperative absolute change in total root mean square higher-order aberrations: 0.19 µm without iris registration vs. 0.22 µm with iris registration.
This study suggests that the addition of iris registration does not improve LASIK outcomes in the typical myopic/myopic astigmatism patient over custom wavefront-driven LASIK when utilizing the Visx STAR S4 excimer laser. These outcomes are in conflict with two earlier reported series. Why the difference in outcomes? Most likely the patient cohorts studied were different. The Visx iris registration software, which also corrects for pupil centroid shift, would be expected to provide the greatest benefit in patients with high astigmatism, high coma, and in the hyperopic patient. In addition, those patients with significant shifts in treatment centration with pupil size change should benefit. Iris registration is also a safety feature, as it reduces the chance of operating on the wrong eye to near zero. I continue to do all I can to achieve iris registration, especially in the myopic patient with high astigmatism and high coma, and in the hyperopic patient. However, these results reassure the surgeon that in the patient where iris registration cannot be successfully achieved, an excellent outcome can still be anticipated with Visx STAR S4 Custom Vue treatment in the myopic/myopic astigmatism patient.
– Richard L. Lindstrom, MD
OSN Chief
Medical Editor