Binocular Vision: Lecture 11: Aniseikonia

Question 1

Geometric Effect

1. An Afocal Meridional Magnifier AXIS 90 is PLACED in front of an EYE. Where does its MAGNIFICATION OCCUR (along what meridian)?
   a. And the Perceived Apparent FRONTOPARALLEL Plane is what?
2. The Difference in Horizontal Image Sizes b/w the 2 eyes Introduces what?
   a. What does it NOT AFFECT?

Answer 1

1. Along the Horizontal Meridian
   a. ROTATED about the FIXATION POINT
2. Horizontal Binocular Disparities
   a. But it DOES NOT AFFECT MONOCULAR CUES (optical Effect)

Question 2

1. With a Magnifier axis 90 in front of the RIGHT EYE, what happens to the HOROPTER?
   a. And the Apparent Fronto-Parallel Plane rotates where?

Answer 2

1. it ROTATES TOWARDS the RIGHT EYE (Clockwise)

a. in the OPPOSITE DIRECTION, AWAY from the right Eye (so Counterclockwise)

Question 3

1. The Degree of rotation or tilting of the Visual Space is Determined by what Eqn?
2. Depth Information obtained from the Binocular Cues CONFLICTS with what?

Answer 3

1. tana = (M-1)/(M+1) * (d/a)

M = Mag of size lens

d = Viewing distance

a = 1/2 IPD

2. with the Depth Information of the Monocular Cues

Question 4

1. The Tilt and Distortion of the Visual World induced by UNIOCULAR MAGNIFICATION is MADE MORE APPARENT IN WHAT?
   a. What is this?
2. What happens to the ENTIRE ROOM when a MAGNIFIER is PLACED BEFORE ONE EYE?

Answer 4

1. The LEAF ROOM
   a. It’s a room where the walls, floor, and ceiling are COVERED with LEAVES to help obscure MONOCUlAR CUES TO DEPTH
2. the entire room LOOKS TILTED and DISTORTED

Question 5

1. With an Axis 90 AFOCAL MAGNIFIER on the Right Eye, which WALL APPEARS FARTHER AWAY?
   a. This is due to what?
   b. The Size of the LEAVES ARE ALSO LARGER on what side of the room causing this illusion?
2. Only what Disparities are there to produce a perception of Depth?

Answer 5

1. the RIGHT WALL APPEARS FARTHER AWAY than the Left wall
   a. due to the TILTING of the Apparent Frontoparallel Plane in the Geometric Effect
   b. on the RIGHT SIDE WALL
2. Only HORIZONTAL DISPARITIES

Question 6

1. With an Axis 180 Meridional Lens, it will PRODUCE NO CHANGE to the HOROPTER. However, the World will STILL BE TILTED. What is this called?
   a. Why does this happen?
   i. We get no perception of what?

Answer 6

1. the INDUCED EFFECT
   a. When an axis 180 meridional magnifier is placed in FRONT of the RIGHT EYE, its IMAGE is MAGNIFIED VERTICALLY!
   i. No STEREOSCOPIC PERCEPTION

Question 7

1. When one Eye’s Image is Uniformly Magnified in the Horizontal and Vertical meridians, what Effects are generated?
2. So if you uniformly Magnify an Image in ONE eye by a SMALL AMOUNT, what effect will it have on the ORIENTATION of the Apparent Frontoparallel Plane?
   a. Why?
   b. However, what MAY BE DIFFICULT?

Answer 7

1. BOTH GEOMETRIC and INDUCED EFFECTS are generated!
2. It will have LITTLE or NO EFFECT
   a. Because the Geometric (linear line on graph) and the Induced (Curvy line) effects will CANCEL EACH OTHER OUT!
   b. FUSION MAY BE DIFFICULT!

Question 8

1. For every DIOPTER of REFRACTIVE DIFFERENCE b/w the 2 EYES, there is ABOUT what % of RELATIVE MAGNIFICATION DIFFERENCE b/w the IMAGES of the 2 eyes?
2. The Induced Effect Breaks down with Magnification GREATER than About what % of UNCORRECTED GEOMETRIC EFFECT?
3. Mag. Difference GREATER than what % will Produce Difficulties with FUSION?
4. Oblique Mag. Introduces what?
   a. What is this?

Answer 8

1. 1.4%
2. 5-7% (or maybe he was trying to say that this is uncorrected geometric effect)
3. 7%
4. Cyclodisparity
   a. VERTICAL LINES are SEEN as TILTED TOWARD the MERIDIAN of MAGNIFICATION

Question 9

1. What is it: A Percept that the world is tilted about the Horizontal meridian, with the Visual Field SKEWED so that its top is tilted away from you and the bottom TOWARD you, or VICE VERSA?
2. DECLINATION: It’s the TILT of what Meridian of the images?
3. If the Magnification is in MERIDIAN 45 (axis 135) in the LEFT EYE, and Meridian 135 (Axis 45) in the RIGHT Eye, How does the leaf room look?

Answer 9

1. INCLINATION/DECLINATION EFFECT
2. of the VERTICAL MERIDIANS
3. The upper part of the Leaf Room looks LARGER and FARTHER AWAY, with the Meridians of Magnification Reversed b/w the 2 Eyes, the OPPOSITE EFFECT OCCURS

Question 10

1. Is it possible to ignore binocular cues and just use monocular cues?
2. Magnification along the Meridian 45 degrees in the Right Eye, and along 135 Degrees in the Left Eye, will do what to the Fronto-parallel plane?

Answer 10

1. Yes.

2. it Produces a TILT in the UPPER Part of the FRONTO-PARALLEL plane TOWARDS the SUBJECT!

Question 11

Knapp’s Law

1. Refrative Anisometropes will have ANISEIKONIA introduced if CORRECTED by what?
   a. Refractive Myopic Anisometropes will experience what?
   b. Refractive Hyperopes will experience what?
2. Uncorrected Axial Ametropia Produces an Image Size Much different from that of the Emmetropic Eye.
   a. Size in Hyperopia?
   b. Size in Myopia?

Answer 11

1. by Spectacle Lenses
   a. Image Minification
   b. Image Magnification
2. a. Smaller
   b. Larger

Question 12

1. In Axial Anisometropia, Knapp’s Law says what?
   a. If Anisometropia is AXIAL, you should correct the PATIENT with what?
2. With Refractive Anisometropia, Knapp’s Law says that a Refractive correction in the CORNEAL PLANE will result in what?
   a. If anisometropia is refractive, how should it be corrected?

Answer 12

1. that a SPECTACLE CORRECTION Placed in the Eye’s Anterior Focal Plane will Result IN NO ANISEIKONIA!
   a. Correct Pt with SPECTACLES instead of Contact Lenses
2. in Minimal Aniseikonia
   a. Correct persons with CONTACT LENSES!

Question 13

1. In Normal Subjects, the perceived spacing of Penlights EQUALS that of the Perceived Spacing b/w what?
   a. In Aniseikonia, the two spacings are what?

Answer 13

1. b/w the STREAKS of Light

a. they’re Unequal

Question 14

1. This is a Specialized Stereoscope whose target allows Quantification of the Tilting of the Frontoparallel Plane in Aniseikonia. What is it?

Answer 14

1. SPACE EIKONOMETER

Question 15

1. The Change in the Nonuniform Magnification Factor (H) of the Horopter can be explained FULLY by what?
   a. And not by what?
2. BASE-OUT Prisms cause Visual Space to do what?
   a. The corresponding Horopter change is for the Horopter to do what?
3. And Base-In?

Answer 15

1. by the NONUNIFORM OPTICAL EFFECTS of the PRISMS
   a. and Not by Neural changes in the arrangement of Corresponding Points
2. to CURVE CONCAVE TOWARDS the VIEWER
   a. for the horopter to BOW OUT away from the Observer
3. causes visual space to CURVE MORE AWAY and the Horopter to Curve Convex

Question 16

Adaptation to Lenses and Prisms

1. In Free Space and Natural Viewing Conditions, Subjects SHOWED Greater Adaptation with what Effect Being NEUTRALIZED?
   a. How long did each take to neutralize?
   b. Studies of Short-term Adaptation to Aniseikonia showed that the Adaptation Process starts really quickly, after about how long?
2. The adaptation could be accounted for by psychological factors like what?

Answer 16

1. with the Geometric Effect being Neutralized
   a. Geometric Effect: 3-4 Days

Induced Effect: 5-6 Days

b. After only about 20 MINUTES
2. like Increased Reliance on Monocular Depth Cues, Especially Perspective, to determine the Location of Objects in Space

Question 17

1. What percent of EMMETROPES have NEURAL ANISEIKONIA of AT LEAST 0.8%
2. Clinical Symptoms of Aniseikonia (headaches or Asthenopia) can occur with only what % of Magnification Differences?
3. Aniseikonia beyond what % begins to influence Stereoscopic thresholds?
4. Aniseikonia in what % range, is Incompatible with Binocular Vision?

Answer 17

1. 40%
2. 1-2%
3. 5%
4. 20% (commonly found in pts with Aphakia corrected with Spectacle Lenses)