Binocular Vision: Lecture 8: Anomalous Retinal Correspondence

Question 1

As a clinician, what is the best way to tell if a patient has normal retinal correspondence?

Answer 1

1. Good Stereopsis

Question 2

If a patient develops strabismus who has normal Binocular vision and normal correspondence, what will result?

Answer 2

1. Perception of Visual Confusion, where 2 foveal images are seen superimposed on each other, and diplopia

Question 3

1. In ARC, will the 2 foveas correspond to each other?
   a. So, Stimuli at each fovea are perceived at what locations?
   i. Is this similar to what we see with visual confusion seen w/normal correspondence?
   ii. What does it produce?

Answer 3

1. NO!
   a. at Distinctly different locations
   i. No. It’s the opposite
   ii. Binocular Rivalry

Question 4

1. In ARC, the fovea of the fixating eye corresponds to what region?
   a. Why is this?
2. ARC allows for what?
   a. although without what?

Answer 4

1. to a nonfoveal region of the deviating, strabismic eye
   a. so that under binocular viewing conditions, the fovea of the fixating and the nonfoveal area of the deviating eye will BOTH be stimulated by the object of regard.
2. a LOW grade of simultaneous binocular vision
   a. w/o significant global stereopsis

Question 5

1. The Sensitive Period for Retinal Disparity starts at what age?
   a. When does Peak of integration hit?
   b. and the sensitive period gradually declines up to what age?
2. During this time period, what is REFINED?
   a. What can also be developed?

Answer 5

1. 4 months
   a. 2 years of age
   b. 9 years
2. NRC
   a. HARC

Question 6

1. In a child, a newly developed ARC: it gradually becomes possible/impossible to reverse.
   a. Why?
2. If a child has a Large Angle Exotropia or Deep Amblyopia in the deviated eye, there is a possibility for ABSENCE of what?

Answer 6

1. Impossible
   a. Due to the Sensitive Period
2. of Retinal Correspondence

Question 7

Harmonious Retinal Correspondence

1. What is it?
2. The patient w/strabismus and HARC will generally perceive the world in what kind of spatial sense?

Answer 7

1. a Precise shift in corresponding points that matches the angle of the strabismic deviation
2. a Normal Spatial Sense, w/o Diplopia or Confusion

Question 8

Hering-Bielschowsky Afterimage Test

1. How is this test done?
2. If patient has normal correspondence between the foveas, then what will happen?

Answer 8

1. a Vertical line afterimage is placed on the fovea of 1 eye by a bright strobe light form a camera flash. A Horizontal Line Afterimage is then flashed onto the fovea of the other eye.
2. the Vertical and horizontal line afterimages will be perceived as superimposed and will be recognized as a cross.

Question 9

After-image test for ARC

1. LE (Vertical line Flash stimuli) and RE (Horizontal line Flash Stimuli)
   a. After-images: If patient doesn’t have Eccentric Fixation, the 2 monocular images will be centered on the R and L Foveolas. So what is seen w/Normal Correspondence?
   b. What if the 2 foveolas do not correspond?

Answer 9

1. a. Binocular after images will appear perfectly aligned

b. the two line after images will appear mis-registered

Question 10

Maddox Rod Test

1. Eso-phoria (or tropia): Line will be seen where?
2. Exophoria (tropia)?

Answer 10

1. Vertical line to the RIGHT of the dot
2. Vertical line to the LEFT of the dot.

(Maddox rod lines will be held over the right eye)

Question 11

Hess-Lancaster Test (1)

1. What does it measure?
2. Patients wear what?
3. What do patients see in each eye?
4. If the patient has NRC?

Answer 11

1. Subjective Angle of Strabismus
2. Anaglyphic (red-green) glasses w/the red filter in front of the right eye and face a large white screen in a relatively darkened room
3. Patient sees a green circle w/the left eye and a Red Annulus w/the Right Eye. Fusion is suspended cuz of the Dissimilar images seen by each EYE.
4. the 2 test stimuli will be located on the screen in the locations in which the two foveas project

Question 12

Hess-Lancaster Test (2)

1. The examiner projects a green circle from a hand-held torch onto the screen. The patient then projects what?
2. Patient is then asked to place the Red Annulus around or to superimpose it on what?
3. If a Patient has a RIGHT ESOTROPIA, where will the Red Annulus be placed?

Answer 12

1. a Red Annulus of Light onto the Screen
2. on the Examiner’s green circle
3. the red annulus will be placed to the LEFT of the GREEN CIRCLE

Question 13

1. What is the Objective Angle of Strabismus?
2. What is the Subjective Angle of Strabismus?
3. In Normal Retinal Correspondence, what is the size of the ANGLES?
   a. What about Anomalous Retinal Correspondence?
   i. What is this DIFFERENCE CALLED?

Answer 13

1. It’s the ANGLE b/w the FOVEAS LINES of SIGHT as measured by the Objective Cover Testing
2. It’s the SEPARATION B/w Imaged in the 2 eyes, as seen by Subjective Superimposition of Half-Views in an Amblyoscope.
3. They’re EQUAL
   a. The Angles differ
   i. ANGLE of ANOMALY

Question 14

Angles

1. Angle H: What is it?
   a. How is it measured?
2. Angle S: What is it?
   a. What does it measure?
3. Angle A: What is it?
   a. In normal Correspondence?
4. In Anomalous Correspondence, are these angles equal?

Answer 14

1. Objective Angle of Strabismus
   a. measured using the CT w/Loose Prisms (this is the ANGLE of DEVIATION for the Eyeball itself)
2. Subjective Angle of Strabismus
   a. using the SAME principles as the von Graffe test or by measuring the perceived angle of diplopia
3. Angle of Anomaly
   a. Angle H (objective angle) and Angle S (Subjective Angle) are EQUAL

4 NO!. The difference b/w them is the angle of Anomaly. Thus, ANGLE A = (Angle H - Angle S)

Question 15

Mechanisms of ARC

1. SENSORY THEORY: what is it?
2. A Patient w/a CONSTANT angle of Strabismus is MOST likely to give this sensory mechanism the opportunity to adapt to what?

Answer 15

1. correspondence changes related to some unknown but purely sensory processes as a sensory adaptation to the Strabismus; Sensory shift takes time to generate
2. to the STRABISMUS

Question 16

Mechanisms of ARC (2)

1. Does the Sensory Theory adequately explain the presence of Anomalous Correspondence that occurs in Pts w/INTERMITTENT STRABISMUS, Variable-Angle Strabismus, or the Covariation phenomenon often seen in these cases?
2. Covariation Refers to what phenomenon?

Answer 16

1. NO!

2. the Apparent Coexistence of BOTH Normal and ANOMALOUS Correspondence in the SAME individual with STRABISMUS

Question 17

Mechanisms of ARC (3)

1. The MOST COMMON form can be observed in cases of Intermittent Exotropia of the Divergence-Excess Type
2. What happens if Multiple tests of correspondence are performed on the same STRABISMIC PATIENT?

Answer 17

1. Anomalous Retinal Correspondence is Seen when the Strabismus is Manifest, but NORMAL correspondence is seen when the EYES ARE FUSED
2. Normal Correspondence may be seen on SOME TESTS and ANOMALOUS Correspondence on others

Question 18

Mechanisms of ARC (4)

1. Motor Theory: What is it?

Answer 18

1. Change in correspondence is registered w/the Oculomotor System, Produces BOTH an EYE MOVEMENT and a CHANGE in RETINAL CORRESPONDENCE

Question 19

Mechanisms of ARC (5)

1. ABNORMAL DISPARITY VERGENCE STIMULUS DETECTION: What is ARC thought to be?
   a. Anomalous disparity vergence system produces eye movements yielding what?

Answer 19

1. ARC is thought to be the NEUROPHYSIOLOGICAL DYSFUNCTION that causes the STRABISMUS.
   a. Motor Fusion b/w what are clinically observed as Anomalous Retinal Points, Producing Strabismus

Question 20

Mechanisms of ARC (6)

1. Will an Adult who develops Strabismus have Anomalous Correspondence or Suppression?
2. Do people with ARC retain the Neurophysioloy needed to also maintain normal retinal correspondence?

Answer 20

1. NO!

2. Most People with ARC do.

Question 21

Unharmonious Retinal Correspondence

1. After adaptation to HARC, when a person undergoes Surgery for for HETEROPHORIA how are the eyes sitting?
2. Is the ARC fulfilling the function?
3. The Diplopia produced by UARC is usually suppressed by when?

Answer 21

1. The EYES are almost STRAIGHT, but the AC now produces Diplopia
2. Not anymore, for which it is developed and is now unharmonious. (UARC)
3. Within 24 Hrs

Question 22

Charactericstics of the following

1. Normal Correspondence
2. Anomalous Correspondence
3. Harmonious Anomalous Correspondence
4. Unharmonious Anomalous Correspondence
5. Paradoxical a.c., Type I
6. Paradoxical a.c., Type II

Answer 22

1. Angle H = Angle S; Angle A = 0
2. Angle H DOES NOT EQUAL ANGLE S
3. Angle S = 0. Angle A = Angle H
4. Angle S Angle H; Angle S Angle H; Angle A