Ocular functional optical zone following hyperopic LASIKPRK Analysis

Ocular functional optical zone following hyperopic LASIK/PRK: Analysis based on polychromatic retinal image quality Mitchell P. Weikert, MD Li Wang, MD, Ph. D Douglas D. Koch, MD Cullen Eye Institute Baylor College of Medicine Houston, TX Financial disclosure: none.

Background n n n Traditionally, the functional optical zone (FOZ) is analyzed based on corneal topography* Wavefront-guided treatments correct ocular aberrations on anterior cornea Optical quality of the anterior corneal surface may not represent retinal image quality of the whole eye q Due to the effect of the internal optics * Holladay & Janes. JCRS 2002; Boxer Wachler et al. JCRS 2002; Racine, Wang & Koch. AJO 2006; Tabernero et al. IOVS 2007

Purpose n To investigate the size of the ocular FOZ before and after wavefront-guided hyperopic LASIK/PRK q Based on optical image quality of the whole eye

Patients and Methods n n Consecutive cases who underwent AMOCustom. Vue LASIK or PRK (CVLASIK/PRK) for Hyperopia by one surgeon between 1/1/05 to 6/1/09 Inclusion criteria: q q Available follow-up at 6 months post-op Custom. Vue wavefront measurements ≥ 6 mm at both pre-op and 6 months post-op

Patients n 30 eyes of 21 subjects included q q Age: 51 ± 8. 4 years (31 to 66 years) Pre-op CV SE: +1. 70 ± 0. 82 D (+0. 20 to +3. 53 D) Post-op CV SE: +0. 86 ± 0. 63 D (-0. 53 to +2. 10 D) Refractive correction: -0. 84 ± 0. 57 D (0. -1. 755 to +0. 35 D)

Methods n n Based on Custom. Vue wavefront measurements, ocular wavefront aberrations were calculated for simulated pupils from 2– 6 mm in 0. 1 mm intervals Assuming full correction of 2 nd order aberrations, optical image quality of higher -order aberrations (HOAs, 3 rd-6 th order) was evaluated

Methods n n Using Zernike. Tool program (AMO), polychromatic modulation transfer function (MTF) at 9 cyc/deg with Stiles-Crawford effect calculated for 2 -6 mm pupils FOZ defined as the size over which the MTF at 9 cyc/deg was ≥ 0. 18 q MTF ≥ 0. 18 maintains visual acuity of ≥ 20/20 Tabernero J, Klyce SD, Sarver EJ, Artal P. IOVS 2007

Results: FOZ range: pre-op: 5. 2 - 6. 0 mm post-op: 4. 1 - 6. 0 mm 77 100 100 87 73 Preop Postop % of eyes 100 90 80 70 60 50 40 30 20 100 ≥ 6 ≥ 5 ≥ 4 FOZ (mm) ≥ 3

FOZ Change Following Myopic CV-PRK Δ in FOZ (mm) % of eyes 0. 6 – 1. 0 13 0. 1 – 0. 5 3 0 58 0. 1 – 0. 5 0. 6 – 1. 0 1. 1 – 1. 5 1. 6 – 2. 0 0 13 10 3

FOZ vs. 4 th-Order Spherical Aberration (SA) Hyperopic CV-LASIK/PRK 7 6 FOZ (mm) 5 4 R 2 = 0, 3263 3 R 2 = 0, 2918 2 Pre-op 1 Post-op 0 -0, 6 -0, 4 -0, 2 0 0, 2 4 th order SA coefficient (microns) 0, 4 Post-op FOZ with spherical aberration (r 2 = 0. 33, P<0. 001 ) 0, 6

FOZ vs. Higher Order Aberrations (HOAs) Hyperopic CV-LASIK/PRK 7 6 FOZ (mm) 5 R 2 = 0, 3069 4 R 2 = 0, 2988 3 2 Pre-op 1 Post-op 0 0 0, 2 0, 4 0, 6 HOAs (microns) Post-op FOZ with HOAs (r 2 = 0. 31, P<0. 001 ) 0, 8 1

Change in FOZ vs. Change in SA Hyperopic CV-LASIK/PRK 1, 5 Change in FOZ (mm) R 2 = 0, 3097 1 0, 5 0 -1 -0, 8 -0, 6 -0, 4 -0, 2 0 -0, 5 -1 -1, 5 -2 Change in SA (microns) FOZ with SA (r 2 = -0. 31, P<0. 001 ) 0, 2

Change in FOZ vs. Change in HOAs Hyperopic CV-LASIK/PRK 1, 5 R 2 = 0, 3645 Change in FOZ (mm) 1 0, 5 0 -0, 4 -0, 2 0 0, 2 -0, 5 -1 -1, 5 -2 Change in HOAs (microns) FOZ with HOAs (r 2 = 0. 36, P<0. 001 ) 0, 4 0, 6

Change in FOZ vs. refractive correction Hyperopic CV-LASIK/PRK 1, 5 R 2 = 0, 0057 Change in FOZ (mm) 1 0, 5 0 -2 -1, 5 -1 -0, 5 0 -0, 5 -1 -1, 5 -2 Change in SE (D) FOZ stable with refractive correction (r 2 = 0. 01, P<0. 001 ) 0, 5

Summary n n 26% of eyes had post-op FOZ < 6 mm 74% of eyes had post-op FOZ ≥ 6 mm Post-op FOZ positively correlated with SA and negatively correlated with HOAs Hyperopic FOZ: q q q with SA with HOAs No change with amount of refractive correction

Limitations n n Results are not correlated with measures of visual function Analysis only done up to 6 -mm zone

Conclusion n FOZ following wavefront-guided hyperopic LASIK/PRK: q q n n Increased to area > 6 mm in 17% of eyes Decreased to area < 6 mm in 20% of eyes These results may lead to further refinement of treatment parameters Study investigating optical FOZ following myopic LASIK/PRK presented as additional poster.