The Aberration Structure of the Keratoconic Eye

Transcription

1 The Aberration Structure of the Keratoconic Eye Geunyoung Yoon, Ph.D. Department of Ophthalmology Center for Visual Science Institute of Optics Department of Biomedical Engineering University of Rochester Wavefront Congress 7

2 Optical quality of the keratoconic eye compared with normal Keratoconus Normal µm 15 Total aberration -1 Corneal topography

3 Theoretical visual benefit when corrected the higher order aberration. 1 1 Advanced KC Visual benefit in keratoconic eyes Visual Benefit FE SC SM SM KB JP JP MB SL SG SG JF Avg. Normals Subject

4 Statistical significance (p<.1) of each Zernike mode from zero for normal and keratoconic population Pantanelli S et al., Ophthalmology, in press (7) Zernike coefficient (microns) Defocus * * Lower order Vertical coma * Spherical aberration Higher order Normal myopia Keratoconus * * Vertical nd astigmatism

5 Why negative vertical coma? Corneal curvature causes relative phase advances and phase delays. superior Keratoconic cornea Phase advance Aberration free cornea Resultant wavefront Phase delay inferior MB

6 Coma, Z 3-1 and Z 31, is the most significant higher order aberration in keratoconic eyes Except for defocus, all the Zernike rms values are significantly different from normal eyes. Zernike rms (microns) Normal myopia Keratoconus Lower order Higher order

7 Abnormal eyes have a significantly greater proportion of higher order aberration compared to normal eyes. HO Variance Total Variance = Normal: 1 ± 1 % KC: 1 ± % Proportion of HOA to HO variance in keratoconic eyes Coma (Z -1 3 & Z 31 ) HO Variance Trefoil (Z -3 3 & Z 33 ) HO Variance Spherical Aberration (Z ) HO Variance = ± 3 % = 1 ± 7 % = ± 13 %

8 Early detection of keratoconus suspect using corneal first surface higher order aberration B_hren J et al., Am. J. Ophthal., in press (7) Moderate KC KC suspect (fellow eye of the KC eye) Normal eye 11 Zernike modes, total HOA RMS, coma RMS and third-order RMS Zernike modes, Z 3-1 and Z 5-1

9 Optical and surgical options to improve vision of keratoconic eyes - Spectacles - Contact lenses Hard and rigid gas permeable lenses Soft lenses Hybrid lenses (hard in the center + soft skirt) Piggyback lens (rigid gas permeable over soft) Other specialized lenses (Rose K, multi curve aspheric, scleral) - Cornea transplants - Intrastromal corneal ring segments - Corneal cross linking with Riboflavin - Adaptive optics - Customized soft contact lenses Front surface customized Back surface customized Both surface customized

10 Large stroke adaptive optics makes it possible to correct large amounts of the higher order aberration of keratoconic eyes Without AO With AO Wavefront height (microns) Total rms = 1.7 µm Higher order rms = 1.3 µm Total rms =.1 µm Higher order rms =. µm

11 Front surface customized soft contact lenses With conventional contact lens Blurred image With customized contact lens Sharp image

12 Correcting the higher order aberration with customized soft contact lenses Sabesan R et al., Optics Letters, in press (7) Keratoconic eyes mm pupil 1 1 With conventional lens HO rms = 3.7 µm With customized lens µm µm Wavefront height (µm) 1 1 HO rms = 1.5 µm µm µm -

13 Improving visual acuity with customized contact lenses in keratoconus High High contrast letter (1%) mm pupil Visual acuity (logmar) Visual acuity (logmar) lines improved RGP 1 3 SC MX MB Subject Subjects Conventional lens Customized Series1 Series lens

14 Back surface customized soft contact lens Irregular cornea Laser beam Better fitting Better optics Ablating back surface of the lens Residual aberration Laser beam Best quality vision

15 Surface ablation of conventional soft contact lens with an ArF excimer laser Wavefront sensor Excimer laser Two axis steering mirror Soft contact lens Beam delivery optics

16 Laser ablation of the back surface of soft contact lens with an Excimer laser Excimer laser beam Two axis steering mirror Back surface of soft contact lens Soft contact lens Lens mount

17 An arbitrary back surface profile of soft contact lenses can be generated precisely with excimer laser ablation. Zernike coefficients (microns) Zernike mode Design Measurement

18 Scatter effects caused by surface roughness after ablation SH sensor spot patterns with intensity saturated Before ablation Optical zone (5 mm in diameter) After ablation

19 Conclusion 1. Wavefront data from both wavefront sensor and cornea topography can be used as an objective tool to discriminate keratoconus from normal eyes.. Back surface customized soft contact lenses have the potential to correct higher order aberrations of keratoconic eyes and to provide better lens fitting.