Binocular Vision and Space Perception

1. Binocular Vision and Space Perception Eric Borsting, OD, MS Professor

2. Dr. B • Graduate from SUNY in 1987 • Residency in Peds/VT • Staff in VT • Teaching at SCCO for over 20 years • Teaching this course for 3 years • Live in Brea with my wife and 2 kids

3. Overview • Ground rules • Lecture and lab schedule • No labs week of January 3 • Outside of class work • Quizzes, presentations, self-study material

4. Ground Rules • Office Hours C126 • Attendance • Grading • Textbook

5. Testing • Mainly multiple choice • Study guide questions • No surprises • Problem Sets • Quizzes

6. Moodle • Assignments • Quizzes • Calendar • Grades

7. Lab • Bring trial lens set to all labs • Demonstrate principles taught in lecture • Presentation • C113

8. Why is this important? • The visual system helps us orient and move through space. • The visual system provides the most precise information about our position and the position of objects in the environment.

9. Two systems used for perceiving space • Monocular • Several cues • Occlusion • Binocular • Stereopsis

10. Why is this important? The visual system is highly adaptable. This course will look at the ability to adapt to lenses and prism that alter space perception. • The visual system will adapt to developmental or acquired anomalies that affect binocular vision or space perception.

11. Clinical applications • Strabismus • Amblyopia • Aniseikonia • Unilateral visual neglect

12. Clinical applications • Monovision • Correcting anisometropia • Correcting astigmatism • Occlusion therapy • Bifocal correction

13. One Eyed Optometry • This is what we do most of the time

14. Two-Eyed Optometry • Binocularity makes us look at one eyes condition relative to the other eye.

15. Problems

16. Why do we need two eyes? • Advantages of two eyes • Stereopsis • Insurance policy • Wider visual field for binocular viewing • Spatial vision

18. Why do we need two eyes? • Disadvantages of two eyes • Prevalence of binocular problems quite high

19. Why do we need two eyes? • Linkage of the two eyes • Very precise compared to other systems • Hands versus eyes

20. Evolutionary Aspects

22. Why do we need two eyes? • Correspondence • Examples

23. Defining Visual Space • Objective visual space • Infinite boundaries • Objects move without being deformed • Can measure very precisely

24. Defining Visual Space • Image Space • The image of space at the retina

25. Defining Visual Space • Subjective visual space (perceived, phenomenal, or experiential spaces) • The space of perceived things • Finite boundaries • Objects can be distorted

27. Defining Visual Space • Subjective visual space • Body (personal) space • Reaching (peripersonal) space • Far (extrapersonal) space

28. Monocular or Oculocentric Visual Direction • Local sign: Each neuron encodes a unique visual direction • Principle visual direction: The direction signaled by the fovea • Secondary visual direction: All directions other than the principle direction

30. Clinical application • Eccentric Fixation • Occurs when the principle visual direction is different from the fovea. This can occur in strabismic amblyopia. • Objective visual direction • Visuoscopy • Subjective visual direction

31. Clinical application • Eccentric viewing: Patient uses a point other than the fovea when looking straight ahead secondary to vision loss at the fovea. Commonly seen in macular degeneration.

32. Demonstration • Use ophthalmoscopes to find the fovea • Look at the center of the target • Now look off to the side

33. Subjective Visual Direction • The perception of looking straight ahead • Eccentric viewing • Eccentric fixation • The principle visual direction has shifted away from the fovea.

34. How do we combine two different views of the world? • Two separate principle visual directions • Correspondence problem

35. Law of identical visual direction • Objects lying in the same visual direction in each eye will be seen as lying in a single visual direction under binocular viewing conditions. The foveas indicate the same principle visual direction

36. How do put the two eyes together? • Hering window experiment • Hole in your hand • Sausage

38. Egocentric localization • Objects from striking each fovea are perceived to fall on a single point midway between the two eyes. This has been called the cyclopean eye.

39. Dominant Eye • Common methods used to determine • Effect on egocentric localization • Most individuals egocentric point is shifted towards the dominant eye.

40. Corresponding retinal points • These are pairs of points one in each that when stimulated simultaneously give rise to a common visual direction.

41. Vieth Muller Circle • This is a geometric representation of the corresponding points in each eye. It is formed by drawing a circle through the fixation point and the entrance pupil of each eye.

43. Binocular disparity • What happens to objects not lying on the Vieth-Muller circle? • The difference in visual direction between the two eyes. This occurs when non-corresponding points are stimulated.

45. Binocular Disparity • Horizontal disparity gives rise to stereopsis or the perception of depth. • Vertical disparity does not give rise to depth perception.

46. Binocular Disparity • Crossed disparity • Uncrossed disparity

48. Panum’s Area • Allows for small disparities to give rise to depth perception within and single vision within a certain range.

50. Diplopia • Physiological diplopia occurs when images are outside of Panum’s areas and are on non-corresponding points. • Crossed and uncrossed diplopia • Examples