Lecture 5

Question 1

What is stereopsis?

Answer 1

Perception of 3D space

Question 2

Images to the OD and OS are on what points? resulting in what?

Answer 2

non-corresponding giving slight retinal disparity resulting in perception of depth.

Question 3

What are the two types of stereopsis?

Answer 3

1. Local/contour/peripheral: two separate contours that can be seen monocularly
2. Global stereopsis: preferred. computer generated patterns obscure the outline of the two objects, you need bifoveal fixation to see object.

Question 4

Titmus test example of what kind of stereopsis?

Answer 4

local or contour.

Question 5

smaller separation means smaller what? and is therefore more difficult to?

Answer 5

smaller disparity and is more difficult to see.

Question 6

which is better, 20 sec of stereo or 300 sec?

Answer 6

20 sec.

Question 7

What is the normal stereo in seconds?

Answer 7

20 sec or better.

Question 8

Random dot E what kind of stereopsis test?

Answer 8

global (therefore patient needs bifoveal fixation to see stereo, no monocular cues).

Question 9

In random dot E, what is the std distance? pass means?

Answer 9

1.5m, pass if they get 4/5, target is presented 5 times.

Question 10

Is random dot E used in eye examinations?

Answer 10

no just screenings.

Question 11

Stereo smile test is best for? How many cards? stnd dist? disadvantage?

Answer 11

children.
6 cards, one blank, one molded, 4 test cards one at 480 sec, 240 sec, 120 sec then 60 sec.
40 cm
EXPENSIVE.

Question 12

Random Dot 2, broken up into what three parts?

Answer 12

A= global stereopsis testing (LEA figures at 400--100 sec of arc)
B/C= local stereopsis testing (circles 400-12.5 circles of arc, this gives you a better level of stereopsis but does not tell you forsure bifoveal fixation, global does). part B used for adults and part C for children.

Question 13

What are some causes of decreased stereopsis?

Answer 13

unequal blur in the eyes (largeer Rx in one)
sstrabismus (no bifoveal fixation, large retinal disparity)
poor fusional ability
fixation disparity (very small strabismus)
idiopathic (unknown)

Question 14

What is the difference between titmus test, random dot E, random dot 2 compared to worth 4 dot?

Answer 14

worth 4 dot tests flat fusion where as the others test higher stereopsis.

Question 15

WHy are global stereo tests preferred over local?

Answer 15

because they have few monocular cues or none. must have bifoveal fixation to see it.

Question 16

random dot 2 used for?

Answer 16

screening or measuring stereo

Question 17

Worth 4 dot is done when?

Answer 17

when stereo is less than 20 sec.

Question 18

stereopsis develops when usually?

Answer 18

around 4-6 months of age.