Stereotests for Stereoacuity Flashcards
What is stereoacuity measured in?
Seconds of arc “
What is gross stereoacuity and fine stereoacuity in minutes of arc?
3,000” (gross) and 10” (fine)
What are the qualitative tests for stereoacuity?
Lang 2-pen test & synoptophore slides
What are the quantitative tests for steroacuity?
- Random Dot Tests (TNO, Randot, Randor Pre-School Steroacuity, Distance Stero Randot and Lang I & II)
- Polarised Contoured Vectograph (Wirt)
- Real-Depth Tests (Frisby Near, FNS and Frisby Davis Distance, FD2)
What are random dot tests?
Include TNO, Randot, Randor Pre-School, Distance Stereo Randot and Lang I & II
Dots which form the stereo-shape are duplicated and shifted horizontally to create a disparity. The fusion of dots creates a stereo-effect and tests for global stereopsis and is less susceptible to monocular cues.
What are real-depth tests of stereoacuity?
Frisby Near and Frisby-Davis Distance
They’re truer to life but monocular cues can be an issue if care isn’t taken when presenting
What distance are the near sterotests?
40cm or 16 inches
What must you be aware of when presenting sterotests?
- Near at 40cm/16 inches
- Correct plane to the eyes and in good illumination, either in primary position, perpendicular or at reading
- No leading questions
- Inconclusive or unusual results warrants another test
- To be aware of not presenting monocular cues by head movements or moving the test
What are the benefits of using stereograms for stereotests?
- Less monocular cues
- Often need to have glasses on (not Lang)
- Cue conflict can affect blur
What are the benefits of using real-depth tests for stereotests?
- ‘Real life’
- Monocular cues
- No glasses needed
What must you consider for choosing stereotests?
- Monocular Cues
- Disparity Range
- Presentation
- Fine vs. Coarse Texture
How do monocular cues affect stereotests?
- Aid recognition (enhance BSV)
- TNO contoured butterfly is more readily seen even with abnormal BSV
How does disparity range affect stereotests?
Tests vary as to the range of stereoacuities that they assess; normal stereogram disparity is approximately 60” and real objects are approximately 10”
Wirt fly is really good for patients with poor stereoacuity as it measures gross stereopsis
How does presentation affect stereotests?
The ease and repeatability of presentation is important and you can’t learn FNS and FD2 but things like the Lang are quick and portable.
The understanding and age is important to picking stereotests. FNS and FD2 both have monocular cues that you can use to teach the task.
Randot, Lang and Wirt have animals that children like
How does Fine vs. Coarse Texture affect stereotests?
Stereotests can help identify poor VA; the Frisby (FNS) has a chunky texture. TNO has fine textures so some can’t appreciate the stereo effect as unable to resolve the texture (dots) BUT passing the test is a good indicator of normal visual system and so is considered the ‘gold standard’
What’s the gold standard sterotest?
TNO
What glasses do you wear for TNO?
Red-Green
What does the Randot look like?
Had a bunch of circles; 3 within a crowding bar and then has cartoon images below on the left side. Then on the right-side is a random dot task. Has a way of checking suppression on the R-L. Answers are on the back. Can sometimes see a shape is distorted without having stereoacuity. Wear polarised glasses
What test has a way of checking suppression?
Randot
What does the Randot Pre-School Stereoacuity test look like?
There are 3 books, start with book 1 and then, if able to pass this go on to book 2 but if fail then move on to book 3.
It’s a case of matching which of the squares on the right are shown with the key on the Left
What does the Distance Randot Stereotest look like?
This is conducted at 3m but some will do it 4m for a distance test.
Has the seconds or arc (“) under each image and is a pure random dot test
Have to use polaroid glasses
Must hold straight on as if tilted = doesn’t work
What does the Lang I & II look like?
- Random dots using cylinders for dissociation
- Good for children as only has 3 pictures and thus 3 levels of stereoacuity
- Portable
- Can use on individuals as pre-verbal
- II is harder than I; read the lowest number disparity for each image as this shows the hardest level
What does the Lang Stereopad look like?
Designed to have movement of the images so that the individual cannot learn via rote learning what they should be expected to see.
What does the Wirt Stereotest look like?
It’s polaroid contoured vectograph with polaroid glasses and doesn’t rely on dissociation of random dots
There is a latency for getting the fly further out from the page. Helpful for someone with abnormal BSV as it gives the contours and they know how a fly looks.
It’s an easy-to-use test
However, as not random dot abnormal BSV can see the distortion and there are some monocular cues so have to ensure they’re seeing depth and not just something that looks “different”
On the left are dot and cartoon animal pictures
