Observation and Testing for Vision Impairment Flashcards
What are the 3 main types of vision?
Photopic vision
Mesopic vision
Scotopic vision
What is photopic vision? 3
-Cone photoreceptors/color vision
-Resolves fine detail 20/20 or better: high acuity
-Functions only in good illumination
What is Mesopic vision? 3
-Both rods and cones function over a wide range of light at simultaneous levels
-Intermediate levels of chromatic function
simultaneously.
-Twilight or dusk occurs in a mixed rod/cone mode
What is scotopic vision? 5
-Uses rod photoreceptors
-Occurs in very low light levels
-Exhibits poorer quality vision
-Is limited by resolution (usually 20/200 or less) for acuity
-Provides ability to discriminate only shades of black and white
When going from day to night what types of vision are being used? 3
photopic to mesopic to scoptic vision
What vision type is happening when their is no significant light source?
Pure scotopic vision
Are rods or cones more sensitive at lower levels of light?
rods
What are the parameters of ocular functions? 6
-Macula function
-Provides binocular vision
-Visual acuity (VA) better than 20/200
-Central vision less than 10 degrees
-Stereopsis
-Color vision
What basic visual function test are included in the Activities of Daily Living (ADL)? 5
-Acuity test
-Stereopisis
-Color Perception
-Visual Field
-Muscle balance
What does an acuity test check? 3
-Monocular and binocular vision
-Both distance and near visual acuity
-With and without correction
Why do we perform visual screenings? 2
- Analyze anatomic and structural changes caused by disease or
injury. - To find relationship of these functional changes to the visual
requirements of (ADL) or specific
occupational requirements
What are the reasons for the specific types of vision testing? 4
- Functional Vision
- Binocular Vision
- Monocular Vision
- Contrast Sensitivity
What does functional testing check for? 3
-how the eyes and the visual system function
-If organ functions are reduced, they are referred to as
impairments
-Cerebral vision impairments may cause abnormal vision
How does binocular vision help us? 3
-Makes hard-to-see objects easier to detect,
-Enlarges the total field of view
-Improves a person’s capacity to distinguish small
differences in depth.
If organ function is reduced what is it refferred to as?
an impairment
If someone only uses monocular vision what condition could they be suffering with? 5
-Suppression
-Amblyopia
-Tropia
-Disease
-Trauma
What does contrast sensitivity test for?
Determines the lowest contrast level that can be detected by a person for a given size target
What is one of the most common tests for contrast sensitvity?
Pelli-Robson
What does the Pelli-Robson use in the test to check for contrast sensitivity?
Uses letters with sharp edges that are more like actual objects.
What is the standard test for visual acuity?
Snellen Chart
what does the snellen chart measure for?
resolution of fine detail at
high contrast.
what does stereopsis measure for?
depth perception with book and 3D glasses
what is the colour perception test called?
ishihara’s test
In what situation other than someone being colour blind could they fail the color test?
low visual acuity (20/50 or less)
