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

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Presentation on theme: "Aberrometry and the Tear Film Understanding new methods Thomas O. Salmon, OD, PhD Northeastern State University, Oklahoma, USA."— Presentation transcript:

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 A.Dry eye introduction B.Aberrometry basics C.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 dont agree Objective signs subjective symptoms Need for better tests New technologies – Corneal topography – Tear osmolarity – Aberrometry OSDI TearLab

7 B. Aberrometry basics 1.What are aberrations? 2.What do aberrometers measure? 3.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 … not …but rather … chromatic aberrationsmonochromatic aberrations Seidel aberrations coma spherical aberration oblique astigmatism field curvature Petzval Zernike aberrations coma trefoil spherical aberration Z(4,-4), Z(4,-2) … Others

10 Summary 1 B.Aberrometry basics 1.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 Autorefraction keratometry Wavefront Whole eye optics HD autorefraction Corneal topography Corneal surface shape HD 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 aberrationsHigher 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 EmmetropiaMyopia + astigmatism

20 Summary 2 B. Aberrometry basics 1.What are aberrations? 2.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. sphereastigmatismtrefoil

22 Zernike analysis

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

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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 Downloadable data Keyword search: Zernike norms

29 Summary 3 B.Aberrometry basics 1.What are aberrations? 2.What do aberrometers measure? 3.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 1994LiangAberrometry of the human eye JOSAA 1999Thibos, HongTear film break up OVS 2006Koh, MaedaNormal tears film over time IOVS 2008Koh, MaedaDry eye changes over time IOVS Cornea 2008Koh, MaedaContact lens wetting ECL 2009Burger, HeadArtificial tears CEO

33 Pioneers in dry-eye aberromery Dr. Junzhong LiangDr. Larry ThibosDr. Shizuka Koh

34 Blink (sec) Etafilcon A with PVP Etafilcon A Koh S. Effect of Internal Lubricating Agents of Disposable Soft Contact Lenses... Contact Lenses. Eye Cont Lens 2008;34: Contact lens wetting (Koh, et al.)

35 Serial aberrometry (Koh's method) A.Every 1 sec, for 60 sec, blink every 10 sec B.For each eye, ~60 measurements in 1 minute 1.~60 HO RMS values 2.Plot HO RMS as a function of time 3.Fluctuation index (FI) & Stability index (SI) RMS 60 measurements HO RMS over time SI FI

36

37 > blink ->

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

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