Binocular Single Vision Ophthalmology .pptx

Binocular Single Vision

1. Binocular Single Vision Presenter : Dr Vishnu Prasad Rao Supervisor : Prof Dr. Shatriah Ismail

2. 01 Definition 02 Grading 03 Fusion vs Stereopsis 04 Development of BSV 05 Retinal Correspondence 06 Horopter/ Pannums Fusional Area 07 Anomalies of BSV 08 Investigations 09 MCQ Table Of Contents

3. Definition State of simultaneous vision which is achieved by coordinated use of both eyes so that separate and slight dissimilar images arising in each eye appreciated as single image by process of vision

4. Grading SIMULTANEOUS PERCEPTION FUSION STEREOPSIS

5. Simultaneous Perception Simultaneous perception exists when signals transmitted from the two eyes to the visual cortex are perceived at the same time. It consists of the ability to see two dissimilar objects simultaneously.

6. Fusion Fusion is the cortical unification of 2 images of an object, 1 from each eye, into a single percept. For retinal images to be fused, they must be similar in size and shape. For fusion of macular images (central fusion) to occur, there can be very little dissimilarity between t he images in each eye More image dissimilarity is tolerated in the periphery (peripheral fusion), where the receptive fields are larger.

7. Sensory Fusion based on the innate, orderly topographic relationship between the retinas and the visual cortex images falling on corresponding (or nearly corresponding) retinal points in the 2 eyes are combined to form a single visual percept. Motor Fusion Motor fusion is a vergence movement that allows similar retinal images to be maintained on corresponding retinal areas

8. Stereopsis Stereopsis is a binocular sensation of relative depth caused by horizontal disparity of retinal images. It is the highest form of binocular cooperation. The ability to fuse images that stimulates horizontally disparate retinal elements within Panum’s fusional area resulting in binocular appreciation of visual object in depth i.e. in the third dimension Able to perceive width, depth, and height ,when look at an object.

9. How it occurs? 3/30/2024 PRESENTATION TITLE 10 Retinal disparity (fixation disparity) is the basis of 3D perception Stereopsis occurs when retinal disparity is too great to permit simple superimposition of the two retinal images, but not great enough to elicit diplopia

10. Stereopsis and depth perception Stereopsis and depth perception are not synonymous. Monocular cues— which include object overlap, relative object size, highlights and shadows, motion parallax, and perspective also contribute to depth perception. Monocular patients can have excellent depth perception using these cues.

11. Monocular cues for depth perception

12. Fusion vs Stereopsis 3/30/2024 PRESENTATION TITLE 14

13. Advantanges of BSV Results in stereopsis Optical defects in one eye is compensated by the normal eye Enhanced visual acuity, contrast sensitivity Defective vision in any part of one visual field is masked, e.g. blind spot Wider visual field than monocular Normal monocular visual field 60̊ superior & nasal 75̊ inferiorly 95 temporally With BSV : 160-200̊ 3/30/2024 PRESENTATION TITLE 15

14. Development of BSV 3/30/2024 PRESENTATION TITLE 16 Basic visual functions are innate and therefore present at birth Their coordination, maturation, & refinement take place during early postnatal period

15. BSV milestones AGE2 MILESTONES Birth no bifoveal fixation. Monocular fixation is present at birth, but poor 2-3 weeks infant begins to make movements, turning his eyes to fixate an object 4-5 weeks can sustain monocular fixation of large near objects 6 weeks fixation alternates rapidly between two eyes & child begins to fixate binocularly with conjugate pursuit movements which are saccadic initially but become smooth and gliding by 3- 5mts of age. 3-6 months conjugate movements and disconjugate vergence movements 1 year fusional movements are firmly established. 2-3 years adult level of visual acuity is reached. 3/30/2024 PRESENTATION TITLE 17

16. Maturation of binocular function At birth, eyes act as 2 independent sense organs Foveas are not formed until the 3 rd month By trial and error the child learns that, when the image of an object is brought on to the 2 foveas simultaneously, the image is most detailed Hence visual axes are oriented in such a way that each fovea is directed at the object of regard 3/30/2024 PRESENTATION TITLE 18

17. Mechanism and terminologies in BSV 3/30/2024 PRESENTATION TITLE 19

18. Visual Axis A visual axis is defined as a line that connects an object point with its image on the retina Types; Principal - Fovea – area of highest VA, carries principal visual axis Secondary - Other retinal elements, secondary visual axis 3/30/2024 PRESENTATION TITLE 20

19. Retinal Correspondence Retinal correspondence is the term used when a viewed target stimulates paired retinal areas in an individual’s 2 eyes. These retinal locations are said to be corresponding. When the image of an object in space falls on corresponding points, it is perceived as a single object located in the same subjective or egocentric direction.

20. Egocentric localisation Perception of the location of an object in space with respect to either the eye 3/30/2024 PRESENTATION TITLE 22

21. Horopter T he horopter is defined as the locus of all points in space that stimulate corresponding retinal points D ouble vision would be expected when the target does not lie on the horopter Horizon of vision

22. Pannums Fusional Area T he visual system can combine slightly disparate points within a limited area surrounding the horopter, called Panum’s area of single binocular vision Objects within Panum’s area do not result in diplopia. Objects outside Panum’s area stimulate widely disparate retinal points, resulting in physiologic diplopia

23. Anomalies of BSV When a manifest deviation of the eyes occurs, the corresponding retinal elements of the eyes are no longer directed at the same object. This places the patient at risk for 2 distinct visual phenomena: visual confusion and diplopia.

24. Sensory Adaptations in Strabismus To avoid visual confusion and diplopia, the visual system uses the mechanisms of suppression and anomalous retinal correspondence. Pathologic suppression and anomalous retinal correspondence develop only in the immature visual system under binocular conditions.

25. Suppression Suppression is the alteration of visual sensation that occurs when an eye’s retinal image is prevented from reaching consciousness during binocular visual activity Can be classified as such - Central vs peripheral - Non alternating vs alternating - Facultative vs constant

26. Anomalous Retinal Correspondence Anomalous retinal correspondence (ARC) is a cortical adaptation that restores some degree of binocular cooperation despite a (usually small) manifest strabismus. In ARC, an object projects to the fovea of the fixating eye and to a pseudofovea in the deviating eye without diplopia. Anomalous binocular vision is a functional state that is superior to total suppression. The period during which ARC may develop probably extends through the first decade of life.

27. Classification of ARC Angle of Anomaly = Objective Angle - Subjective Angle Harmonious ARC This indicates that the ARC fully corresponds to the strabismus. provides a compensation for the angle of squint Eliminate the awareness of diplopia and confusion

28. Unharmonious ARC - angle of anomaly < objective angle of deviation - subjective angle # 0 Paradoxical - when the angle of anomaly > objective angle of deviation. - It occurs mainly after overcorrection of the squint surgery

29. Investigations Test for fusion - Bagollini striated glass test - Worth 4 dots test Test for stereopsis - TNO test - Frisby test - Lang’s stereo test - Synaptophore

30. WORTH FOUR-DOT TEST This is a dissociation test which can be used with both distance and near fixation, and differentiates between BSV, or ARC and suppression . Procedure: The patient wears a green lens in front of the left eye And a red lens in front of the right eye The patient then views a box with four lights ; one red , two green and one white

31. If BSV is present all four lights are seen. If all four lights are seen in the presence of a manifest deviation, harmonious ARC is present. If two red lights are seen , left suppression is present . If three green lights are seen , right suppression is present. If two red and three green lights are seen , diplopia is present. If the green and red lights alternate , alternating suppression is present. Results

32. This is a test for detecting BSV , ARC or suppression . Each lens have fine striations which convert a point source of light into a line, as with the Maddox rod . Procedure: The two lenses are placed at 45°and 135° in front of each eye and the patient fixates a small light source . Each eye perceives an oblique line of light , perpendicular to that perceived by the fellow eye. Dissimilar images are thus presented to each eye under binocular viewing conditions . BAGOLINI STRIATED GLASSES

33. If the two streaks intersect at their centers in the form of an oblique cross ( an X ), the patient has BSV if the eyes are straight , or harmonious ARC in the presence of manifest strabismus . If the two lines are seen but they do not form a cross , diplopia is present . If only one streak is seen , there is no simultaneous perception and suppression is present . If a small gap is seen in one of the streaks , a central suppression scotoma ( as found in microtropia ) is present . R esults:

34. TNO test A booklet consisting of 7 plates Viewed with red- green spectacles Each plates contain various shape (squares, dots, crosses) created by computer generated random dot analgyphs Analgyphs is a stereogram in which two disparate views are printed in red and green on white background The eye looking through the red filter sees only green picture as black The eye looking through the green filter sees the red picture as black Two views fuse to give a stereoscopic effect 480- 15 sec of arc No monocular clues 3/30/2024 PRESENTATION TITLE 41

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36. Frisby test Assess fine stereopsis Degree of disparity ranges from 600 to 15 seconds of arc S tereogram consists of 3 plates each containing 4 squares of small random shape The three plates are of differing thickness, 6mm, 3mm and 1.5mm (55, 170, 340sec of arc , 40cm viewing distance) By adjusting the viewing distance, the test can give a disparity of 600 to 15 sec of arc One of the squares contain one hidden circle which is seen disparately. Doesn’t require use of polarized glasses 3/30/2024 PRESENTATION TITLE 43

37. Titmus test 1) WIRT FLY TEST Assess gross stereopsis Utilizes the principle of vectograph Useful in young children Made up by 2 plates in the form of booklet The plates are reviewed with polaroid glasses The right side of booklet – large housefly with threshold 3000 sec of arc Stereoscopic ,will reach above the plate (child is encouraged to pick up the tip of the wings between finger and thumb). Performed at a distance of 16 inches (40cm) 3/30/2024 PRESENTATION TITLE 44

38. 2) Animal test Assess fine stereopsis 3 rows of 5 animals each 1 animal from each row is imaged disparately (appear forward). In each row, one of the animals imaged in two eyes is printed heavily (misleading clue) 3/30/2024 PRESENTATION TITLE 45

39. 3) Circles test Consist of 9 squares Each containing 4 circles arranged in the form of a lozenge Only 1 of the circle in each square is disparately imaged at random 3/30/2024 PRESENTATION TITLE 46

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41. Lang stereotest Targets are made up of fine vertical lines which are seen alternatively by each eye when focused through built in cylindrical lens elements Lang I: Disparity = Car 550", Star 600", Cat 1200" Lang II: Disparity = Moon 200", Car 400", Elephant 600", Star monocular visible Unique feature – No polaroid glasses need to be worn for viewing the test plate 3/30/2024 PRESENTATION TITLE 48

42. Synopthore Synopthore compensates for the angle of squint and allows stimuli to be presented to both eyes simultaneously Used to investigate the potential for binocular functions in the presence of manifest squint and useful in assessing young children It can detect suppression and ARC 3/30/2024 PRESENTATION TITLE 49

43. Two pencil test Gross stereopsis Examiner holds the pencil vertically in front of patients eye Patient touch the upper tip of pencil Having stereopsis – Pass test with BE open One eye closed – patient fails the test Disparity range : 3000-5000 secs of arc 3/30/2024 PRESENTATION TITLE 50

44. Conclu sion BSV is not inborn,but develops in the first decade of life Abnormal visual experience results in poor or no BSV R e v ers i ble on l y i f i n ter vened i n the plastic peri o d of development A good understan d ing o f m echa n ism o f BS V is fundamental in successive treatment of its anamolies

45. References Reference Adler’s physiology of eye: clinical application , 10th Ed. St Louis: Mosby, 2003. Khurana A. K.: Theory and Practise of Squint and Orthoptics; first ed AAO Pediatric Ophthalmology and strabismus 2022- 2023

46. MCQ 1 Requirements for Binocular Single Vision include Normal retinal correspondence Good vision in one eye Precise coordination of the eyes at all times Ability of fusional areas of brain to fuse slightly dissimilar images Normal macular function

47. MCQ 1 Requirements for Binocular Single Vision include Normal retinal correspondence T Good vision in one eye F Precise coordination of the eyes at all times T Ability of fusional areas of brain to fuse slightly dissimilar images T Normal macular function T

48. MCQ 2 In Binocular vision Only points on the horopter fall on the corresponding retinal points Points in front of the horopter will stimulate binasal retina Points outside the horopter is perceived doubly The Pannum’s fusional area is wider in the centre than periphery Sensory fusion refers to the cortical integration of images perceived by the two eyes

49. MCQ 2 In Binocular vision Only points on the horopter fall on the corresponding retinal points T Points in front of the horopter will stimulate binasal retina F Points outside the horopter is perceived doubly T The Pannum’s fusional area is wider in the centre than periphery F Sensory fusion refers to the cortical integration of images perceived by the two eyes T

50. MCQ 3 Advantages of binocular single vision include A larger field of vision Elimination of blind spot Better binocular visual acuity Accurate depth perception Multiple mental impression

51. MCQ 3 Advantages of binocular single vision include A larger field of vision T Elimination of blind spot T Better binocular visual acuity T Accurate depth perception T Multiple mental impression F

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