2015 Binocular Vision & Retinal Correspondence

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Information about 2015 Binocular Vision & Retinal Correspondence

Published on September 14, 2015

Author: AlvinaPaulineSantiag

Source: slideshare.net

1. I. Binocular Vision and Retinal Correspondence II. Amblyopia Alvina Pauline D. Santiago, MD Pediatric Ophthalmology & Adult Strabismus Basic Course Lectures in Ophthalmology Sentro Oftalmologico Jose Rizal Philippine General Hospital September 2015

2. Binocular Vision & Retinal Correspondence

3. Theories of Binocular Vision  Correspondence & disparity  sensory binocular cooperation based on correspondence & disparity  single visual impression, no depth  binocular rivalry: diplopia  horizontal disparity: depth within Panum’s fusional space

4. Terms  Horopter  locus of all object pts imaged on corresponding retinal elements at a given fixation distance  Panum’s fusional space or area of SBV  region in front of and at the back of the horopter that still allows SBV  allows depth perception

5.  Horopter  Elliptical line that stimulate corresponding points on the retina  Panum’s fusional space  Area in front and behind horopter where objects stimulate non correspondings points and yet are still fusible as one retinal image Figure from Wright’s Pediatirc Ophthalmology

6. Physiologic diplopia  Uncrossed diplopia  Crossed diplopia Figure from Wright’s Pediatirc Ophthalmology

7. Theories of Binocular Vision  Neurophysiologic theory  visual stimuli from retina to visual cortex modified and coded  only 25% binocularly driven cells are stimulated equally; 75% graded influence from R & L eye  Macaque monkey: Ar 18; Rhesus: Ar 17-18  Lost binocular neurons do not recover

8. Binocular Vision  Reduced panorama of vision  Upright position  Frontal eye position  Visuomotor tasks improved  Depth perception  Orientation of body to environment

9. Visual Pathway From Adler’s Physiology of the Eye

10. Development of Visual Acuity From Cybersight.org: Compilation of behavioral data from different studies showing the development of binocular grating acuity in humans over the first 5 postnatal years. (From Teller DY, Movshon JA: Visual development. Vision Res 26:1483, 1986.)

11. Macula Development  Fine visual discrimination characteristic of high VA require sharply focused small objects as appropriate stimuli http://www.macuhealth.com

12. Amblyoscope or haploscope From Rosenbaum & Santiago Clinical Strabismus Management

13. Amblyoscope  2 mirrors at elbow that reflect images from picture slides  arms may be moved to align targets on each fovea From Rosenbaum & Santiago Clinical Strabismus Management

14. Amblyoscope  Subjective angle  amount in degrees the examiner must move amblyoscope arms for patient to see 2 pictures as superimposed  during binocular viewing conditions  Objective angle

15. Amblyoscope  Subjective angle  Objective angle  deviation measured by alternate prism cover test  during monocular viewing conditions

16. Amblyoscope  Angle of anomaly  displacement of the true fovea from pseudofovea  zero if NRC; subjective = objective angle  (+) if alternate cover test (objective angle) is not equal to subjective angle

17. Worth’s level of fusion  First degree (simultaneous perception)  Dissimilar targets presented  Perceived at the same time in the same visual direction  Second degree  Third degree

18. Worth’s level of fusion  First degree (simultaneous perception)  Second degree (flat fusion)  similar targets with dissimilar components (monocular suppression checks)  Third degree

19. Worth’s level of fusion  First degree (simultaneous perception)  Second degree (flat fusion)  Third degree (stereopsis)  Same targets as 2nd degree + disparity

20.  First degree  simultaneous perception  2nd degree  flat fusion  3rd degree  Stereopsis From Rosenbaum & Santiago Clinical Strabismus Management

21. Normal retinal correspondence  RE: circle  LE: black dot  Orthotropic  Black dot in circle From Wright’s Pediatric Ophthalmology

22. Normal retinal correspondence  Organization of visual space is such that the visual direction of each fovea is the same  Angle of anomaly = 0  Patients with NRC always use fovea as center of reference

23. NRC, with strabismus  To see black dot in circle, need to move arms of amblyoscope total of 40 PD From Wright’s Pediatric Ophthalmology

24. Difficulties in Testing NRC and strabismus  If with dense large regional suppression, no subjective angle, difficult to superimpose images  If monofixator, use targets for peripheral retina

25. Harmonious ARC  subjective angle = 0  measured under binocular conditions  Pseudofovea compensates for angle of deviation  No subjective misalignment From Wright’s Pediatric Ophthalmology

26. Unharmonious ARC  pseudofovea does not compensate fully for angle of deviation  Angle of anomaly = objective angle - subjective angle From Wright’s Pediatric Ophthalmology

27. Amblyoscope  Measures fusional vergenge amplitudes  Angle of deviation  Area of suppression  Retinal correspondence  Torsion  Instrument convergence

28. Terms  Retinal correspondence  single vision: hallmark  ARC vs NRC  Retinal disparity & rivalry:  diplopia and visual confusion

29. Abnormalities of binocular vision  Diplopia  Visual confusion  Suppression  Horror fusionis  Anomalous retinal correspondence

30. Diplopia vs Visual Confusion  Diplopia  Object of interest seen by fovea of one eye and peripheral retina of the other eye  Visual confusion  Fovea of both eyes (or corresponding retinal points) sees 2 objects of interest interpreted as coming from the same point in space

31. Diplopia vs Visual Confusion From Rosenbaum & Santiago Clinical Strabismus Management

32. Suppression  Suppression: alteration of visual sensation that results in inhibition or prevention of one eye’s image from reaching consciousness  Physiologic suppression prevents physiologic diplopia from reaching consciousness

33. Central vs peripheral suppression  Central:  pathologic extension of retinal rivalry  prevents foveal image of deviating eye from being perceived  Peripheral:  Prevents awareness of the image on peripheral retina (2nd image)

34. Suppression Scotoma Esotropia Exotropia From Rosenbaum & Santiago Clinical Strabismus Management

35. Monocular vs Alternating suppression  Monocular: unidirectional  Dominant eye always predominate over image from deviating eye  Alternating: bidirectional  Suppression switches between the two eyes

36. Facultative vs Obligatory Suppression  Facultative  Present only when eyes are deviated  Obligatory  Present at all times, whether eyes are deviated or aligned

37. Amblyopia

38. Definition: Amblyopia  Etymology: dullness of vision  Greek:  amblyos = dull  Stem: ops = vision  Observer (MD) sees nothing, and the patient sees very little  von Graefe

39. Definition  Unilateral or bilateral decrease in VA caused by pattern vision deprivation or abnormal binocular interaction for which no cause can be detected by physical examination, and which in appropriate cases, reversible by therapeutic measures  von Noorden

40. Prevalence  Approximately 2-2.5% of general population has amblyopia  Military Recruits 1-3.2%  Preschool children 0.5-3.5%  Ophthalmic patients 4-5.3%

41. Basic Mechanisms  Abnormal binocular interaction  Foveal pattern vision deprivation  Combination of both

42. Susceptible Period  Most sensitive first 2-3 years  Decreases until age 6- 7 years  complete visual maturation  retinocortical pathways and visual centers resistant to abnormal visual input From Adler’s Physiology of the Eye

43. Classification  Reversible (functional)  Strabismic amblyopia  Anisometropic / ametropic amblyopia  Visual deprivation amblyopia  Idiopathic amblyopia  Toxic / Nutritional amblyopia  Irreversible (organic)  Amblyopia in nystagmus  Other ocular pathologies

44. Strabismic Amblyopia  Higher prevalence in ET than XT because of nasotemporal asymmetry of retinocortical projections  ET: fovea of deviating eye competes with strong temporal field  XT: fovea competes with weaker nasal field

45. Strabismic Amblyopia  always unilateral,  caused by active inhibition of retinocortical pathway originating from fovea of deviating eye due to visual confusion  lack of adequate stimulation of the fovea  Duration of strabismus rather than age at time strabismus develops correlates more closely with amblyopia

46. Sensory Adaptations  Double vision: diplopia  obj of interest seen by fovea of one eye and peripheral retina of other eye  Visual confusion  fovea of each eye sees 2 different obj interpreted by brain to be in the same visual direction

47. Diplopia vs Visual Confusion From Rosenbaum & Santiago Clinical Strabismus Management

48. Suppression Scotoma Esotropia Exotropia From Rosenbaum & Santiago Clinical Strabismus Management

49. Lateral Geniculate Nucleus in Strabismic Amblyopia NORMAL Figure from Wright’s Pediatirc Ophthalmology

50. Other Associations  Eccentric Fixation  Anomalous Correspondence  Loss of fusion  Retinal disparity and rivalry  Crowding phenomenon  Smooth pursuit asymmetry

51. Amblyopia vs Suppression  Both occur to eliminate visual confusion from dissimilar retinal images  Suppression occurs only under binocular conditions  Amblyopia persists after closure of fixating eye

52. Anisometropic Amblyopia  Active inhibition of fovea  Eliminate sensory interference caused by superimposition of a focused and defocused image (abnormal binocular interaction)  Aniseikonia may be a factor  Foveal pattern vision deprivation

53. Visual Deprivation Amblyopia  Disuse or understimulation of retina  Unilateral more severe than bilateral  Both pattern vision deprivation and abnormal binocular interaction are factors in monocular  Only pattern vision deprivation in binocular

54. Mechanism of Ambyopia Causes AbN binoc Form interaction Deprivation Strabismus + - Anisometropia + + Visual Deprivation Unilateral + + Bilateral - +

55. Organic Amblyopia  Superimposed functional component can be improved with amblyopia therapy  Wrong orientation of retinal receptors?  Changes in lateral geniculate nucleus and striate cortex

56. Diagnosis  Fixation preference  but many normal patients have fixation preference  Crossed fixation  does not always imply absence of amblyopia

57. Figure from Wright’s Pediatirc Ophthalmology

58. Figure from Wright’s Pediatirc Ophthalmology

59. 10 PD Base Up Test Figure from Wright’s Pediatirc Ophthalmology

60. Diagnosis  Visual acuity  difference in acuity in 2 eyes  but certain small difference exist in normal population  difference of 2 lines for most clinical purposes

61. Amblyopia Therapy  Occlusion or patching even in nystagmus  1 week per year of life then reevaluate  does not signify end of therapy  evaluate occlusion amblyopia  Full time vs part time  Role of tapering

62. Amblyopia Therapy  3-6 weeks in older child because of school  Rationale:  force to use the bad eye  allows neural circuitry to be reestablished

63. Patch with Eyeglasses

64. Alternative to Patching  Penalization  Atropine (Hunter, Johns Hopkins protocol)  Optical penalization (over plus: fogging)  Neutral density filters  Blurring better eye by any means

65. Factors Affecting Recovery  Stage of maturity of visual connections at which abnormal visual experience began  Type of abnormal visual experience  amblyopia more common in ET than XT  may be related to nasotemporal asymmetry (stronger temporal hemifield)

66. Factors Affecting Recovery  Duration of deprivation  Age at which treatment was started  Compliance  Neurologic status  Psychological and psychosocial considerations

67. Problems with Amblyopia Therapy  Patient compliance & acceptance  Parental understanding of rationale  Parent-child dynamics  Poor follow-up  Smart children memorize charts!  Differing methods of assessment  When to stop patching?

68. Results of Treatment  Single optotype improves more rapidly than line acuity  Crowding has prognostic value  Single E acuity represents true potential  Different charts, different results

69. Visual Acuity Prediction From Adler’s Physiology of the Eye

70. Normalization of fixation Figure from von Noorden’s Binocular Vision

71. Timing of Surgery  Maximize amblyopia treatment prior to straightening eyes  Enhances fusion-lock  More practical to start patching, continue even after surgery

72. References  Rosenbaum & Santiago: Clinical Strabismus Management  Von Noorden: Binocular Vision and Ocular Motility  Wright: Pediatric Ophthalmology and Strabismus  Taylor:Pediatric Ophthalmology  Nelson:Pediatric Ophthalmology  Moses & Hart:Adler’s Physiology of the Eye  PEDIG Amblyopia Studies

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