1. A New Definition of Refraction: Basics and Beyond Austin Roorda, Ph.D. Unversity of Houston College of Optometry

2. First use of Optics as Vision Aids 1000 AD reading stones from 1000 AD

3. 1268 Roger Bacon discussed possibilities of magnification with lenses Roger Bacon 1284 Salvino D'Armate built the first spectacles which were used as reading glasses 1451 Nicholas of Cusa uses negative lenses to cure myopia (nearsightedness) Kepler 1604 Kepler describes the optics of near and far sightedness

4. 1748: Benjamin Franklin invents the bifocal lens 1827: Sir George Biddel Airy invents spectacles for astigmatism

5. Retinoscopy

6. Phoropter

7. Autorefractor

8. Refraction Systems

9. Aberrometers VISX Wavescan Summit Autonomous Custom Cornea B&L Zywave Wavefront Sciences Complete Optical Analysis System TraceyTech Tracey 1

10. What is the Wavefront? converging beam = spherical wavefront parallel beam = plane wavefront

11. What is the Wavefront? ideal wavefront parallel beam = plane wavefront defocused wavefront

12. What is the Wavefront? parallel beam = plane wavefront aberrated beam = irregular wavefront ideal wavefront

13. What is the Wavefront? aberrated beam = irregular wavefront diverging beam = spherical wavefront ideal wavefront

14. What is the Wave Aberration? diverging beam = spherical wavefront wave aberration

15. -3-20123 -3 -2 0 1 2 3 Wavefront Aberration mm (right-left) mm (superior-inferior) Wave Aberration: Defocus

16. Wave Aberration: Astigmatism -3-20123 -3 -2 0 1 2 3 Wavefront Aberration mm (right-left) mm (superior-inferior)

17. Wave Aberration: Coma

18. Wave Aberration: All Terms

20. How Do We Interpret the Wave Aberrations?

21. Wave Aberration Surface Map

22. -2012 -2.5 -2 -1.5 -0.5 0 0.5 1 1.5 2 Wave Aberration Contour Map mm (right-left) mm (superior-inferior)

23. Breakdown of Zernike Terms -0.500.511.52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Zernike term Coefficient value (microns) astig. defocus astig. trefoil coma trefoil spherical aberration 2 nd order 3 rd order 4 th order 5 th order

24. Root Mean Square astigmatism term defocus term astigmatism term trefoil term ……

25. Point Spread Function

26. Point Spread Function vs. Pupil Size pupil images followed by psfs for changing pupil size 1 mm2 mm3 mm4 mm 5 mm6 mm7 mm

27. Simulated Images 20/40 letters 20/20 letters

28. Strehl Ratio diffraction-limited PSF H dl H eye actual PSF

29. Modulation Transfer Function 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 050100150 spatial frequency (c/deg) contrast Area under the MTF 20/2020/10

30. Applications for Aberrometry

31. Can we Build a Better Autorefractor? -0.500.511.52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Zernike term Coefficient value (microns) astig. defocus astig. trefoil coma trefoil spherical aberration 2 nd order 3 rd order 4 th order 5 th order choose the spectacle correction that minimizes the second order Zernike terms

32. Can we Build a Better Autorefractor? perfect PSF choose the spectacle correction that maximizes the strehl ratio defocus/astigmatism

33. Can we Build a Better Autorefractor? 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 -1.4-1.2 -0.8-0.6-0.4-0.2 0 0.20.40.60.8 1 Defocus (D) Area under MTF (0 - 50 c/d) choose the spectacle correction that maximizes the area under the MTF

34. Can we Build a Better Autorefractor? Challenge –RMS, Strehl, and MTF area are not correlated Solution –population data (Rochester, Indiana) –early results suggest maximizing metrics like the Strehl ratio works best

35. Aberrometric Refraction conventional autorefractors are accurate to ~ 0.5 D aberrometric autorefractor should achieve ~ 0.1 D accuracy ** ** ± 0.25 D is an acceptable correction error

36. Diagnosis of High-order Aberrations

37. Post - RK Post - LASIK

38. Keratoconus