1. Dynamic Accommodation in Reading Scott C. Cooper, OD, MEd, FAAO James Kundart, OD, MEd, FAAO Hannu R.V. Laukkanen, OD, MEd, FAAO Vision and Computer Displays Conference June 4-5, 2009

2. Introduction Describe accommodation and its function and related visual perception Explain its role in vision, especially nearpoint Convey how it interacts with other visual functions and perceptions Provide an idea of the impact of poor accommodation Outline approaches to improve accommodation and/or related perception …in about 5 minutes

3. Accommodation: A simplified description Regulation of Focus o Functional goal: clarity of vision for the desired level of detail

4. Accommodation: A simplified description Regulation of Focus

5. Accommodation: A simplified description Regulation of Focus

6. Accommodation: A simplified description Regulation of Focus

7. Accommodation: A simplified description Regulation of Focus

8. DOF

9. Accommodation: A simplified description Regulation of Focus DOF

10. Accommodation: A simplified description Regulation of Focus o Amplitude o Facility o Accuracy / Stability Note “accuracy”

11. Accommodation: LESS simplified Dual innervation o Parasympathetic Increase accommodation Reduce pupil size (increase depth of focus)  Allows reduced accuracy / effort o Sympathetic Decrease accommodation (far viewing) Increase pupil size (smaller depth of focus)  Requires better accuracy, control and effort

12. Accommodation: LESS simplified Input Variables Optical o Target distance- o Lenses o Pupil size o Physical or physiological limitations to clarity Cataract Poor tear film Other ocular defects

13. Accommodation: LESS simplified Input Variables “Non-optical” o Target’s visual features Examples: size, contrast, motion, screen or print quality, other o Vergence requirement / feedback o Proprioception o Proximal awareness o Other Autonomic nervous system changes…possibly/probably/maybe

14. Accommodation: LESS simplified Output Variables Garbage in – out o See Input Variable list Physical limitation (presbyopia)- Predisposition to poor development / control Practice effect Vergence control Many others: fatigue, medications, head injuries, etc.

15. Accommodation: An EVEN LESS simplified description Synergistically intertwined with vergence (two- eyed control) Example: AC/A and CA/C

16. DOF

17. Accommodation: An EVEN LESS LESS simplified description Bioengineering models of accommodation and vergence

18. Accommodation: An EVEN LESS LESS simplified description 150 years of research Normal and abnormal variability Chromatic aberration as directional cue Changes with position of gaze Etc.

19. Accommodative Performance: A “learned habit” Result of processing many physical and sensory cues Moderate variability from person to person Responses to cue changes are predictable overall, but may also vary from person to person Over time, accommodative performance can change or deliberately be modified to some extent

20. Accommodative Performance: Links to other visual functions Accommodation and vergence interaction and “skill” varies from person to person o A complete analysis of accommodation and vergence shows each individual’s challenge to clear, single vision without perception of effort or strain o Vergence performance has the same themes of individualized visual “habits” that respond to visual cue changes, and will change over time

21. Accommodative Performance: Links to other visual functions Eye movements in reading: o For some, the effort, control and visual perception of accommodation (and vergence) are key for support of eye movement accuracy in reading

22. Accommodative Performance: Links to other visual functions Depth Perception o Stereopsis Clarity, balanced clarity for each eye, same time Vergence control o Perspective / converging parallel lines o Texture o Interposition o Shadow o Kinesthetic perception o Accommodative effort

23. Accommodative Dysfunctions Hypo-responsive o Amplitude o Accuracy o Facility Hyper-responsive o Accuracy o Residual “tonus” when looking at far Distance blur Diplopia Warning: all prevalence studies have bias o ~20 to >30% of prepresbyopic patients o General agreement: more symptoms from accommodation than vergence dysfunctions

24. Accommodative Dysfunctions Common Symptom Examples o Reduced reading comprehension o o “Eye strain” o Headaches Impact on productivity: o Incorrect intrepretation of detall o Increased time and effort to correctly resolve and process detail o Avoidance of tasks due to resulting symptoms “Floating” text

25. Treatment Approaches Treating the dysfunctions o General lens prescriptions o Prescriptions to optimize function and minimize symptoms o Vision training o As possible, address physiological problems that may degrade clarity and/or accommodative performance Examples: dry eye, cataract

26. Treatment Approaches “Treating” the visual circumstance o Ergonomic features of the room/workstation Viewing distance, position Lighting, glare Posture Many other variables o Visual cues of the task Contrast Color Size Etc

28. Internal Symptoms Due to Accommodation and Video Displays Including a Pilot Study of Live Accommodative Measurements Vision and Computer Displays Conference June 4-5, 2009 Scott C. Cooper, OD, MEd, FAAO James Kundart, OD, MEd, FAAO Hannu R.V. Laukkanen, OD, Med, FAAO

29. Introduction In the past, our lab has studied mostly external symptom factors, such as: o Squint o Dry eye o Blink rate Yet, the internal symptom factors, like blur, have remained largely unstudied Internal symptoms are at least in part due to accommodation (focusing) of the eye This was the first experiment designed to study real-time accommodation while reading continuous text

30. Why Live Accommodative Research is Needed Previously, there were no published studies of dynamic accommodation, such as during the reading task While established methods (such as dynamic retinoscopy) have been used to sample accommodation, continuous methods were not available It would be highly useful for both the researcher and clinician to have a means to measure accommodation continuously during reading Over a dozen studies have been done with the WAM series of autorefractors to date

31. The Pacific Pilot Study http://www.aitindustries.com/pages/products/ecp/ophthalmic/wam5500_binocular_autorefractor.html

32. Purpose of Our Pilot Study Note that NONE of previous studies investigated accommodation during text reading -- why? This was thought to be impossible to do accurately, because of off-axis effects To determine the feasibility of collecting accurate, continuous accommodative data during reading Questions we hope to answer: o How wide a window can we use? o How many readings/second? o How accurate is each reading (in diopters)?

33. Subjects Nine subjects (5 female, 4 male) were asked to complete three conditions while accommodation is measured: o Gaze at eccentric targets every 5 minutes from +15º to -15º targets o At +7.5º, 0º, and -7.5º from primary gaze, and o Subjects read from an electronically presented text

34. Apparatus Two computers were used; one collected data from the WAM-5500 via a serial cable o This computer was enabled with data collection software WCS-1 The second computer was used as a testing stimulus with a 12-pt Tahoma font Additionally, a Pocket PC device (HP iPAQ) was used as a stimulus o The iPAQ screen measures 5.5 cm square

35. The 4.75 m (>0.25D) Accommodative Target Targets are 2.5 degrees apart

36. Typical Window Size for Desktop Display Note the small vertical dimension

37. Participants View from behind the auto- refractor

38. The Handheld Display Setup

39. Typical Window Size for Handheld Display

40. Raw and Smoothed Autorefractor Data Note that all the autorefractor thinks it’s measuring is refractive error (negative = myopia)

41. The Accommodative Response vs. Demand

42. Accommodative Lag and Working Distance Left and Right Gaze were each 7.5 degrees off primary gaze

43. Distance is Significant, Gaze Position is Not A two-way repeated ANOVA was used to analyze the effects of the viewing distance and gaze position on accommodative measure The results show significant main effect of viewing distance (F(3, 24)=174.288, p<0.0001) but no significant effect from gaze position (F(1.105, 8.838)= 1.067, p=0.367) and interaction (F(1.702, 1.157)=0.569, p=0.552) This finding indicates that the derived accommodative measures were responsive to the change of viewing distance and were consistent with the testing range

44. Conclusions The Grand Seiko WAM-5500 open field autorefractor can accurately measure the accommodative response under certain parameters: o Within 3-4 text lines of central gaze vertically o Within ± 15 degrees of central gaze horizontally, if accommodative responses are > 1 D apart, as on the desktop display o Within ± 5 degrees of central gaze horizontally if accommodative responses are ≤ 1 D apart, as on a handheld display

45. What have we learned about the visual response with visually comfortable and uncomfortable subjects recently? In recent studies, we learned how to measure dynamic accommodative response and pupil size when subjects were engaged in the actual reading process

46. Unexpected pupil results asthenopic vs. non-asthenopic Counterintuitive pupil response differences to (+) lens Equally surprising pupil response differences to base- out prism

47. Unexpected accom results asthenopic vs. non-asthenopic Unexpected accom differences to (+) lenses Unexpected accom differences to (-) lenses

48. What next should be investigated? o What about vergence? o Accommodation, vergence, and pupil responses are all linked via the near triad o Simultaneously monitoring all 3 legs of the near triad will likely further advance understanding of the near response o Having 3 aggregate measures could conceivably better predict comfort, asthenopia, and visual efficiency

49. Our vergence measure tools EyeLink II Fast: 500 Hz sampling Precise: 0.5º accuracy 0.01º RMS resolution Straightforward setup, calibration, validation Would need to dismantle in order to work with Grand Seiko

50. Our vergence measure tools Visagraph III Not as quick: 60 Hz sampling Not as precise: >0.5º accuracy Straightforward setup, calibration May be possible to get Visagraph and Grand Seiko results simultaneously

51. What is visual response in artificial 3D environment and why are some people asthenopic?

52. Acknowledgements This research was funded by The ClearType and Advanced Reading Technologies Group of Microsoft Corporation

53. References Benzoni Jaclyn, Rosenfield Mark, Collier Juanita, McHugh Kimberley, Portello Joan. Does The Dynamic Cross Cylinder Test Measure The Accommodative Response Accurately? AAO Denver, 2006. Berntsen David A, Mutti Donald O, Zadnik Karla. Validation Of Aberrometry-based Relative Peripheral Refraction Measurements. AAO Denver, 2006. Bozic James M, McDaniel John, Mutti Donald O, Bullimore Mark A. Measuring The Accommodative Convergence To Accommodation (AC/A) Ratio With The Grand Seiko WR- 5100K. AAO Philadelphia, 2001. Coffey Bradley, Kosir Kristen, Plavin Joanna. Effects Of Laptop Computer Gaming On Refractive Condition And Visual Acuity. AAO Tampa, 2004.

54. References Collier Juanita, Rosenfield Mark. Accommodation And Convergence During Sustained Computer Work. AAO Denver, 2006. Huffman Sara J, Mutti Donald O, Zadnik Karla. The Repeatability Of Autorefractors. AAO Philadelphia, 2001. Win-Hall Dorothy M, Ostrin Lisa, Kasthurirangan Sanjeev, Glasser Adrian. Open-field Autorefractor Measurements Of Accommodation In Human Subjects. AAO Tampa, 2004. Win-Hall Dorothy, Cole Jason, Glasser Adrian. Comparison Of Objective And Subjective Measures Of Accommodation In Standard Pseudophakic Subjects. AAO Denver, 2006.