Ocular functional optical zone following hyperopic LASIK/PRK: Analysis based on polychromatic retinal image quality

Mitchell P. Weikert, MDLi Wang, MD, PhDDouglas D. Koch, MD

Cullen Eye Institute Baylor College of MedicineHouston, TX

Financial disclosure: none.

Background

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 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

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

eye

Patients and Methods

Consecutive cases who underwent AMO-CustomVue LASIK or PRK (CV-LASIK/PRK) for Hyperopia by one surgeon between 1/1/05 to 6/1/09

Inclusion criteria: Available follow-up at 6 months post-op CustomVue wavefront measurements ≥6 mm

at both pre-op and 6 months post-op

Patients

30 eyes of 21 subjects included Age: 51 ± 8.4 years (31to 66 years) Pre-op CV SE: +1.70 ± 0.82 D (+0.20 to +3.53D) Post-op CV SE: +0.86 ± 0.63 D (-0.53 to +2.10D) Refractive correction: -0.84 ± 0.57 D (0.-1.755 to

+0.35 D)

Methods

Based on CustomVue wavefront measurements, ocular wavefront aberrations were calculated for simulated pupils from 2–6 mm in 0.1 mm intervals

Assuming full correction of 2nd order aberrations, optical image quality of higher-order aberrations (HOAs, 3rd-6th order) was evaluated

Methods

Using ZernikeTool 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 MTF ≥ 0.18 maintains visual acuity of ≥ 20/20

Tabernero J, Klyce SD, Sarver EJ, Artal P. IOVS 2007

Results: FOZFOZ range: pre-op: 5.2 - 6.0 mm

post-op: 4.1 - 6.0 mm

77

100

100

100

73

87

100 100

010

20

30

40

50

60

70

80

90

100

≥ 6

≥ 5

≥ 4

≥ 3FOZ

(mm)

% o

f ey

es

PreopPostop

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 0.6 – 1.0 13 1.1 – 1.5 10 1.6 – 2.0 3

FOZ vs. 4th-Order Spherical Aberration (SA)

Post-op FOZ with spherical aberration (r2 = 0.33, P<0.001 )

FOZ vs. Higher Order Aberrations (HOAs)

Post-op FOZ with HOAs (r2 = 0.31, P<0.001 )

Change in FOZ vs. Change in SA

FOZ with SA (r2 = -0.31, P<0.001 )

Change in FOZ vs. Change in HOAs

FOZ with HOAs (r2 = 0.36, P<0.001 )

Change in FOZ vs. refractive correction

FOZ stable with refractive correction (r2 = 0.01, P<0.001 )

Summary

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:

with SA with HOAs No change with amount of refractive correction

Limitations

Results are not correlated with measures of visual function

Analysis only done up to 6-mm zone

Conclusion

FOZ following wavefront-guided hyperopic LASIK/PRK: 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.