Aberrometry and the Tear Film — Understanding new methods —

1. Aberrometry and the Tear Film— Understanding new methods — Thomas O. Salmon, OD, PhD Northeastern State University, Oklahoma, USA

2. Northeastern State University

3. Today's lecture - overview • Dry eye introduction • Aberrometry basics • Aberrometry and dry eye research

4. A. Introduction - Dry eye (DE) • Prevalence ~15-30% • Quality of life (QOL) • More common among • Women • Elderly • Contact lenses wearers • Refractive surgery patients • Computer users • With some medications

5. Diagnosis of DE • Traditional clinical tests • Schirmer test • Tear break-up time • Corneal staining • Slit lamp evaluation • Subjective surveys • Patient complaints • Questionnaires

6. Diagnostic dilemma • DE test don’t agree • Objective signs ≠ subjective symptoms • Need for better tests • New technologies • Corneal topography • Tear osmolarity • Aberrometry OSDI TearLab

7. B. Aberrometry basics • What are aberrations? • What do aberrometers measure? • How do we interpret aberrometer data?

8. 1. What are aberrations? • Aberrations = refractive errors • Lower order aberrations • Sphere (myopia, hyperopia) • Astigmatism • Other refractive errors, they are the … • Higher order (HO) aberrations • Coma, trefoil, spherical aberration, …

9. These aberrations are …

10. Summary 1 • Aberrometry basics • What are aberrations? • Aberrations = refractive errors • Lower order = sphere & astigmatism • Higher order = other more complex abs • Monochromatic aberrations • Pupil size = critical parameter!

11. 2. What do aberrometers measure? • Refractive errors • Similar to autorefractors • Sphere, astigmatism, … & • Higher order aberrations COAS

12. Aberrometry ≠ corneal topography Wavefront Whole eye optics HD autorefraction Corneal topography Corneal surface shape HD keratometry Autorefraction ≠ keratometry

13. What do aberrometers measure? • Optical wavefronts exciting the eye • Single pass through all the eye's optics • Perfect wavefront = flat

14. In an aberrated eye … • refractive errors distort the wavefronts. • Analyze wavefront shape to learn which refractive errors caused the distortion. myopia

15. Video courtesy of Alcon

16. Color maps, surface plots

17. Total & higher order maps Total aberrations Higher order aberrations

18. A wealth of information • Metrics of optical quality • MTF • PSF • Strehl ratio … • Estimate visual performance • Simulate vision • Design optical corrections MTF Simulated vision

19. Simulated retinal images Emmetropia Myopia + astigmatism

20. Summary 2 • Aberrometry basics • What are aberrations? • What do aberrometers measure? • Wavefronts that have passed through the eye's optics. • Distortions caused by refractive errors • Lower and higher order aberrations • Much other information

21. 3. How to interpret the wavefront? Each refractive error (aberration) causes one particular wavefront shape. sphere astigmatism trefoil

22. Zernike analysis

24. Common higher order aberrations Z(3,-3) Z(3,-1) Z(3,1) Z(3,3) Horizontal coma Horizontal trefoil Oblique trefoil Vertical coma Z(4,0) - 0 + Spherical aberration

26. Sample COAS printout COAS

27. RMS wavefront error • A useful summary statistic • Magnitude of combined Zernike modes • Can be used for any combined aberrations • Examples • Vertical + horizontal coma = total coma RMS • Third order RMS • Higher order RMS • Total RMS

28. Reference norms Journal of Cataract and Refractive Surgery, December 2006. Downloadable data Keyword search: “Zernike norms”

29. Summary 3 • Aberrometry basics • What are aberrations? • What do aberrometers measure? • How do we interpret aberrometer data? • Zernike coefficient for each aberration • ± µm, … specify pupil size! • RMS wavefront error – combined aberrations • Diagnose by comparing data to norms

30. C. Aberrometry in DE research • Tear film - many functions • Nutrition, wetting, comfort • The eye's primary refracting surface • DE -> tear film ∆s -> optical effects • Example: DE -> blurred vision • Aberrometry – can be used to evaluate DE

31. Serial aberrometry • Tear film - constantly changing over time • Evaporation, blinking, gravity, eye movement, etc. • Important to measure changes as a function of time • Koh & Maeda's method: • Serial aberrometry

32. Tear film aberrometry research

33. Pioneers in dry-eye aberromery Dr. Junzhong Liang Dr. Larry Thibos Dr. ShizukaKoh

34. 1 2 3 4 5 6 7 8 9 Contact lens wetting (Koh, et al.) Blink Blink (sec) Etafilcon A Etafilcon A with PVP Koh S. Effect of Internal Lubricating Agents of Disposable Soft Contact Lenses ... Contact Lenses. Eye Cont Lens 2008;34:100-5.

35. Serial aberrometry (Koh's method) • Every 1 sec, for 60 sec, blink every 10 sec • For each eye, ~60 measurements in 1 minute • ~60 HO RMS values • Plot HO RMS as a function of time • Fluctuation index (FI) & Stability index (SI) HO RMS ∆ over time RMS FI SI 60 measurements

37. 1 2 3 4 5 6 7 8 9 -> blink blink blink -> 51 52 53 54 55 56 57 58 59

38. Change HO RMS with time

39. Fluctuation Index (FI), Stability index (SI)

40. Summary 4 • Need for better diagnostic tests for dry eye • Dry eye -> tear film -> changes in the eye's optics • Serial aberrometry - measures changes over time • Applications • Normal tear dynamics • Dry eye diagnosis • Contact lens wetting • Artificial tears • Others

41. ご清聴ありがとうございました