Wavefront-Guided LASIK Using the VISX CustomVue™ Star S4 Laser System With and Without Iris Registration™: A Retrospective Comparative Study Sonal B. Dave, MD Ladan Espandar, MD Majid Moshirfar, MD John A. Moran Eye Center Salt Lake City, Utah

Purpose To compare visual outcomes after laser in situ keratomileusis (LASIK) using the VISX Star S4 CustomVue™, with and without Iris Registration™ (IR) technology. Is there a difference between Iris Registration™ and non-Iris Registration™ LASIK?

Methods Retrospective study 239 myopic eyes of 142 patients with or without astigmatism underwent LASIK Primary LASIK treatment with the VISX Star S4 CustomVue™ laser (VISX Incorporated, Santa Clara, CA) with or without Iris RegistrationTM technology 121 eyes with IR 118 without IR Primary outcome measures: uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and manifest refraction Secondary outcome measures: higher-order aberrations (HOA) and vector analysis of residual astigmatism

UCVA 6 months post LASIK

6 months post LASIK

Postoperative month 3 (±0.5 D lines)

Change in BSCVA (Snellen lines) 6 months postoperatively

Results At 6 months, the mean values for logMAR UCVA: 0.00 ± 0.09 in the IR group -0.01 ± 0.11 in the non-IR group (p=0.587) UCVA of 20/20 or better: 79% of eyes in the IR group 73% in the non-IR group (p=0.518) Within ±0.5 D of emmetropia: 92% of the eyes in the IR group 90% in the non-IR group (p=0.999) Mean postoperative absolute changes in total root mean square (RMS) higher order aberrations HOA (μm): IR group 0.22 non-IR group 0.19 (p=0.6) At 3 months, the mean magnitude of error of surgically induced astigmatism: -0.09 in the IR group -0.04 in the non-IR group (p=0.24)

Why did IR not have better outcomes? Eyes were marked at the limbus and patients were adjusted accordingly IR was performed prior to lifting of flaps resulting in possible patient movement after iris verification Stromal remodeling and epithelial hyperplasia may mask benefits of IR Other thoughts???

Conclusions Wavefront-guided LASIK with the VISX Star S4 CustomVue™ laser system, independent of Iris Registration™ status, is effective, safe, and predictable. This study did not find any statistical significance supporting the better achievement of visual acuity, astigmatism correction, or the lesser induction of HOA using Iris Registration™ in comparison to a non-Iris Registration™ system.

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