3. Stereoscopic Distortions of Space - Eye Movements and Binocular Vision Summer 2026

Afocal magnifiers can have overall _____ or _____ magnification

spherical; meridional

What are the apparatus used for the study of stereoscopic perception of space?

-the leaf room

-the tilting plane

-the eikonometer target

The leaf room is rich in _____ and _____ contours

vertical; horizontal

The leaf room is _____ to the patient. The patient will have no preconceptions about the shape of the leaf room.

unfamiliar

What magnification effects does the leaf room illustrate?

-horizontal

-overall

-vertical

-oblique

-prism

Leaf Room (Pic)

Leaf Room (Pic)

What is an example of horizontal magnification with a focal magnifier?

3% R x 090

What does an afocal magnifier of 3% R x 090 do?

-meridional magnifier

-induces aniseikonia in the R eye

-image will be stretched horizontally with this magnifier

What is the effect of horizontal magnification via afocal magnifier on the V-M Circle?

Must make β angles smaller in OD to compensate for the magnifier

Magnifiers cause a distortion of _______

distance

With the afocal magnifier (3% R x 090), where will the V-M circle shift?

shift to the right

Which side of the visual field will have to be shifted closer to the patient in order for the field to look flat with an afocal magnifier (3% R x 090)?

Right -- the magnifier tilted the VF to the right

Leaf Room Appearance with Afocal Magnifier -- 3% R x 090 (Pic)

Leaf Room Appearance with Afocal Magnifier -- 3% R x 090 (Pic)

Afocal magnifier axis is 3% R x 090, which meridian is magnified?

horizontal meridian is magnified

With afocal magnifier 3% R x 090, how would the right side of the leaf room appear?

The right side would appear larger and further away d/t the uncrossed disparity

With afocal magnifier 3% R x 090, how would the left side of the leaf room appear?

The left side would appear smaller and closer d/t the crossed disparity

With afocal magnifier 3% L x 090, how would the right side of the leaf room appear?

The right side would appear smaller and closer d/t the crossed disparity

With afocal magnifier 3% L x 090, how would the left side of the leaf room appear?

The left side would appear larger and further away d/t the uncrossed disparity

What is Emmert's Law?

Perceived size varies directly as perceived distance

According to Emmert's Law, you have to rely on the _____ to calculate the size of an object

distance

According to Emmert's Law, a misjudged distance will change what?

the perceived size of the object

If the light of a firefly is misjudged as far away, it will appear (larger/smaller) than actual

larger

IMPORTANT:

Magnification distorts stereoscopic ________

distance

D/t magnification of an object distorting stereoscopic distance to a target, what changes according to Emmert's Law?

the size will change in accordance with Emmert's Law

Does overall magnification (3% ROA) lead to distortions in the leaf room?

No

True or False:

Vertical disparities will negate the effect of lateral disparities in the leaf room

true -- this is why overall magnification does not led to distortion

_____ is induced by vertical disparity

Resizing

When vertical disparities are eliminated d/t resizing effect, what is also eliminated?

horizontal disparity

Characteristics of the Induced Effect

What is the induced effect stimulated by?

detection of vertical disparity

Characteristics of the Induced Effect

Do vertical disparities leading to the induced effect alter the calculation of lateral disparities?

Yes

Characteristics of the Induced Effect

Can be explained as what?

an OVERALL size change -- like a zoom lens would produce

Characteristics of the Induced Effect

Is this global?

Yes -- affects everything in the entire binocular field

Characteristics of the Induced Effect

Limited to what amount of minification?

4%

True or False:

Larger disparities (>4%) still drive the induced effect

True -- but it will be incomplete

After 4% minification of vertical disparity, is the rest ignored?

Yes

Appearance of 3% R x 180 is equal to what other magnification by afocal magnifier?

3% L x 090

Appearance of 3% L x 180 is equal to what other magnification by afocal magnifier?

3% R x 090

What is the appearance of the right side of the leaf room with afocal magnifier 3% R x 180?

The right side would appear smaller and closer d/t the crossed disparity

What is the appearance of the left side of the leaf room with afocal magnifier 3% R x 180?

The left side would appear larger and further away d/t the uncrossed disparity

What is the appearance of the right side of the leaf room with afocal magnifier 3% L x 180?

The right side would appear larger and further away d/t the uncrossed disparity

What is the appearance of the left side of the leaf room with afocal magnifier 3% L x 180?

The left side would appear smaller and closer d/t the crossed disparity

REVIEW: Vertical size difference will trigger what?

resizing of the images

R x 045 and L x 135 will give ______ effects

equal x090 and x180

Stereoscopic Appearance of Plumb Line (Pic)

Stereoscopic Appearance of Plumb Line (Pic)

With afocal magnifier R x 045 and L x 135, what would be the appearance of the top of the leaf room?

The top would appear larger and further away d/t the uncrossed disparity

With afocal magnifier R x 045 and L x 135, what would be the appearance of the bottom of the leaf room?

The bottom would appear smaller and closer d/t the crossed disparity

True or False:

Individual results of afocal magnification can be combined to predict the results of an oblique axis

true -- see pic

True or False:

Prisms will alter how patients see the world

true

When using prisms, where is the IMAGE shifted?

towards the apex of the prism

What are the possible distortions that can be induced by prisms?

-asymmetric magnification (base-apical magnification)

-curvature of lines perpendicular to the base-apex

-rotation of lines parallel to the base-apex

-overall magnification

Asymmetric magnification will increase towards the (base/apex) of a prism

apex

Prism Image Formation (Pic)

Prism Image Formation (Pic)

REVIEW: Magnification will increase towards the (base/apex) of a prism

apex

When using BO prism, the back wall of the leaf room may look (convex/concave)

concave

When using BI prism, the back wall of the leaf room may look (convex/concave)

concex

Vertical contours will be bowed towards the (apex/base) of the prism

base

Tilting Plane Apparatus (Pic)

Tilting Plane Apparatus (Pic)

What is the mechanism behind the tilting plane apparatus?

-A device used to quantify stereoscopic spatial distortions

-The patient will tilt the plane until it is a fronto-parallel plane that appears to be flat.

What types of targets are included in a tilting plane apparatus?

-ink splatter

-vertical lines

-oblique cross

The Space Eikonometer (Pic)

The Space Eikonometer (Pic)

Is the space eikonometer made anymore?

No

What is the space eikonomter used for?

measuring image size differences in aniseikonia

The Space Eikonomter is a _________

Brewster stereoscope

What is the Space Eikonometer target?

4 vertical lines & 1 oblique cross in the center

What effects can be induced by the afocal magnifiers of the Space Eikonometer?

-x090

-overall

-x180

-oblique

What is the effect of R x 090 on the Space Eikonometer?

-Will induce horizontal magnification of the target.

-Uncrossed disparity of the R side of the target (farther)

-Crossed disparity of the L side of the target (closer)

What is the effect of R.O.A. on the Space Eikonometer?

-Right overall magnification

-Uncrossed disparity of the R vertical lines of the target (farther)

-Crossed disparity of the L vertical lines of the target (closer)

-The oblique lines do not have any disparity

Is there any induced effect for the Space Eikonometer?

There is no induced effect because the vertical disparities are NOT strong enough.

What is the effect of R x 180 on the Space Eikonometer?

-This will NOT create an induced effect

-Vertical lines have no disparity

-R Oblique lines will have crossed disparity (cross closer)

-L Oblique lines will have uncrossed disparity (cross farther)

What is the Oblique Effect on the Space Eikonometer when R x 045; L x 135?

See pic

What are cyclotorsional eye movements?

rotations of the eyes about the lines of fixation

What are conjugate cyclotorsional eye movements?

-cyclotorsional eye movements in the same direction

-compensate for tilts of the head or body

What are disjunctive cyclotorsional eye movements?

-cyclotorsional eye movements in opposite directions

-compensate for inclinations of objects relative to the head

Cyclofusional eye movements will influence what?

stereoscopic distortions

Target inclination stimulates what?

cyclofusion

When R x 045; L x 135, what is the effect on the oblique cross of the Space Eikonometer?

Oblique meridional magnifiers have NO apparent effect on this target

When R x 045; L x 135, what is the effect on the vertical lines of the Space Eikonometer?

Eyes will totally eliminate declination & NO INCLINATION WILL BE SEEN d/t cyclofusion

If the outer two lines are inclined, what is this disparity stimulus for?

stimulus for a cyclofusional eye movement to the majority of the lines

If the outer two lines are inclined and this is a stimulus for a cyclofusional eye movement, what will be the result of this?

The center line will be inclined as a result of the excyclofusional eye movement to the majority of the lines

What is the result of R x 045; L x 135 on an oblique cross with three vertical lines (such as the Eikonometer target)?

-Excyclofusional eye movement

-Outside vertical lines will have no disparity

-Oblique cross will have crossed disparity at the top; uncrossed disparity at the bottom

R x 045; L x 135 Target (Pic)

R x 045; L x 135 Target (Pic)

What is the result of R x 135; L x 045 on an oblique cross with three vertical lines (such as the Eikonometer target)?

-Incyclofusional eye movement

-Outside vertical lines will have no disparity

-Oblique cross will have uncrossed disparity at the top; crossed disparity at the bottom

R x 135; L x 045 Target (Pic)

R x 135; L x 045 Target (Pic)

Eikonometer Targets (Pic)

Eikonometer Targets (Pic)

Review of Eikonometer Targets Effects

Axis 90 magnification

Lines and crosses will have disparities

Review of Eikonometer Targets Effects

Overall magnification

only the lines will have disparity

Review of Eikonometer Targets Effects

axis 180 magnification

only the cross will have disparity (direction is opposite of axis 90)

Review of Eikonometer Targets Effects

oblique magnification

only the cross will have disparity (direction is opposite leaf room)

Does the eikonometer target produce an induced effect?

No -- distortions are not qualitatively different above 3-4% magnification

Does the eikonometer give distinctive distortion for each magnification effect?

Yes -- R x 090 is NOT the same effect of L x 180 like the leaf room

What is the declination of vertical lines with the Space Eikonometer?

zero

Oblique magnifiers distort only the ________

oblique cross