Psychophysical Assessment of Visual Function As an O.D. you will measure (assess) vision.

1. Psychophysical Assessment of Visual Function As an O.D. you will measure (assess) vision. How well does the person see? Results depend on how you make the measurement

2. You: Any problems with your vision? Pt: Don’t seem to see so well, Doc. What do you do (how do you learn how well the patient sees)?

3. You measure the patient’s vision. This course is about the science that stands behind why you measure vision certain ways in the clinic.

4. There are many different eye charts • Which chart to use? • How many letters per line? • How far apart are the letters and lines? • How much smaller are the letters on the next line? • Which letters to use? • How far down the chart must the patient try to read? • How score the result? The acuity you get will differ depending these factors

5. It is a matter of judgment that determines how the visual system is tested and what constitutes normal variation in sensory processes. • The clinician must understand the scientific basis on which these judgments are made and how they can be made in the future as new tests of visual function are developed. • That’s what this course is about and why it is clinically relevant

6. Dr. Tom Norton 606 Worrell Building 934-6742 tnorton@uab.edu Graduate Student Teaching Assistant: Jason Wilson

7. Class – Mon- 9-10:50 Tues, 9-10:50 Wed, 11:00–11:50 Lab on 4 Thursdays Check the schedule for your day and time (Schedule will be distributed tomorrow) This week: Group C 1-3; gp A 3-5

8. Exams #1 Wed. Jan. 19 (100 pts) Ch 1-3 #2 Tues. Feb. 8 (100 pts) Ch 4-5 Final during Final Exam Period (130 pts) (110 pts new, 20 pts cumulative) Labs (4 x 10 pts) Possible pop quizzes (up to 30 pts total) Total possible points, 370 (up to 400) Letter grade determined @ end of course

9. Labs Attend at the assigned day and time (unless you make other arrangements with Dr. Norton in advance) Lab Reports due at Monday class after your lab Accurately recording and graphing your data is an important part of your lab grade

10. Student-submitted exam questions A way to control your own future! Procedure: Due several days before exam (email or Word files preferred) Norton reviews, corrects, photocopies Distributed to class (can use as a study guide) Some of the questions will be used on the exam

11. Three main purposes of course • Learn how vision is measured (scientific basis) • Basic facts about monocular visual function • What is normal? • Neural basis of visual function • Why does the visual system respond as it does?

12. Textbook The Psychophysical Measurement of Visual Function Norton*, Corliss, Bailey Richmond Products, Inc (*TTN’s author royalties [$2420.41 so far] donated to the UABSO)

13. We will cover 9 Chapters • Principles of Psychophysical Measurement • Absolute Threshold of Vision • Intensity Discrimination • Adaptation to Light and Dark • Spatial Acuity • Spatial Vision • Temporal Factors in Vision • Skip Chapter 8 (color) • 8) Postnatal Human Vision Development • The Aging Visual System

14. Overview At the beginning of each chapter. Contains a summary of the content of the chapter.

15. Declarative section headings summarize the section they precede “In the Method of Constant Stimuli the examiner randomly presents a set of stimuli with fixed, predetermined values” “Correct for guessing by incorporating catch trials”

16. Study Guide Questions at the end of each chapter intended to help you clarify your knowledge – (not as useful as I had hoped) Lecture overlaps with the book a lot … but questions also come from the book on topics I don’t cover in class!

17. Glossary – intended to help you know what terms mean for exam Definitions given in the text – definite full credit if you know them verbatim Equations – must tell what the variables mean

18. Equations – must tell what the variables mean “What is the Stevens Power Function?” where Y (psi) is the sensory magnitude, k (kappa) is an arbitrary constant determining the scale unit, F (phi) is the stimulus magnitude, and a (alpha) is an exponent that is characteristic of the stimulus used.

19. Graphs – The hardest part of this class (because they tend to all look alike) … but important because they show the relationship between stimuli and responses

20. Graphs – how to dissect and learn them What is on the X-axis? (& approx. scale) Usual arrangement: Physical Stimulus on X-axis (Independent Variable)

21. Graphs – how to dissect and learn them What is on the X-axis? (& approx. scale) What is on the Y-axis? (& approx. scale) Usual arrangement: Response on Y-axis What you are measuring (Dependent Variable) Physical Stimulus on X-axis (Independent Variable)

22. Graphs – how to dissect and learn them What is on the X-axis? (& approx. scale) What is on the Y-axis? (& approx. scale) How plot a data point? Usual arrangement: Response on Y-axis What you are measuring (Dependent Variable) Physical Stimulus on X-axis (Independent Variable)

23. Graphs What is different in each graph in a “family” of curves?

24. Lots of details to learn. Philosophy: better to have learned and forgotten than to not have learned in the first place. example

25. “Joke break” Break the monotony … but remember that the course has a serious purpose, and the exams can be difficult.

26. Student Response System Test to see if it works Will use for feedback Will not look at who responds Set to room code (23)

27. Chapter 1 Principles of Psychophysical Measurement Objectives: Psychophysical Methods Threshold Constant Stimuli Limits Adjustment Signal detection theory Sensory Magnitude

28. We study visual psychophysics, but there also is auditory psychophysics, somatosensory psychophysics, etc.

29. Why are there so many graphs in this course? Because graphs show relationships Usual arrangement: Response on Y-axis What you are measuring (Dependent Variable) Physical Stimulus on X-axis (Independent Variable)

30. Two basic types • of psychophysical measures • Threshold measures (Do you see it”) • 2) Sensory Magnitude measures • (“What does it look like”)

31. Do you see the light? Physical stimulus – light intensity Perceptual response – Seeing the light

32. How far down an eye chart can you read? Physical stimulus – Letter size Perceptual response – Identifying letters

33. letter size is the stimulus • identifying letters is response • We use psychophysical tools to find the threshold – the letter size you can see 50% of the time

34. Which is better, 1 or 2? Physical stimulus – Lens power Perceptual response – Clarity of the image

35. Why study psychophysics? Psychophysical measurements are fundamental in clinical practice Need to know the scientific basis for measuring vision The results you get depend on the way you measure vision New clinical tools will be developed after you graduate – you need the knowledge base to understand how they work and evaluate whether they are useful in your practice. Psychophysics questions have been plentiful on the boards

37. Visual thresholds are the most common psychophysical measurement

41. Key in measuring thresholds: Try to keep all dimensions unchangedexcept the one being measured

45. There are many possible values of L, But only 1 value (theoretically) for thresholdL (demo)