Intro to Low Vision Flashcards
About how many people are blind?
39 million
About what percentage of all visual impairment can be avoided or cured?
80%
What is the leading cause of visual impairment worldwide?
Uncorrected refractive errors
What is the leading cause of blindness in middle and low income countries?
Cataracts
What is considered being visually impaired?
About 20/70 or worse Peripheral vision loss Scotomas Diplopia Distortions Central vision loss Loss in contrast sensitivity Depth perception problems Visual perception problems Extreme photophobia
What are the 3 leading causes of visual impairment in the United States?
AMD
Diabetic retinopathy
Glaucoma
What is low vision?
Reduced vision not correctable by glasses, contacts, medicine or surgery
What problems are included under the title, “visual impairment”?
Reduced visual acuity Contrast sensitivity Visual field loss Photophobia Diplopia Visual distortion Visual perceptual difficulties
What is a visual disorder?
Anatomical change caused by diseases of the eye
- They may not affect a person’s function
What is a visual impairment?
A functional loss that results from a visual disorder
-Ex. Reduced visual acuity, constricted peripheral field, photophobia…
What is a visual disability?
Limitations in a person’s skills and abilities
What are some examples of visual disabilities?
Inability to: read, write, drive, self-care, travel, managing finances, seeing people’s faces, preparing meals
What is a visual handicap?
Phychosocial and economic consequences of vision loss, as well as environmental barriers
What is the definition of legal blindness in the US?
Best corrected VA is 20/200 or worse in the better eye, OR peripheral vision less than 20 degrees in the better eye
What is considered low vision?
Best corrected VA of 20/70
Less than 20 degrees of peripheral field
Total blindness is also known as what?
No light perception
What is low vision rehab?
Teaching patients to use their remaining vision and/or other senses effectively and efficiently by modifying activities that have become difficult due to vision loss
How does LV rehab optimize the patients existing vision?
Prescribed optical devices Adaptive technology Non-optical aids Absorptive filters Rehab techniques
What are some of the different things done in a VR exam vs. as standard exam?
Detailed functional case history Obtain VA differently Trial frame refraction Central field test Contrast sensitivity Optical device testing
How do you greet a person with visual impairment?
Introduce yourself
Ask if they would like assistance
Speak clearly
Use appropriate voice leve
How do you make someone unsteady more comfortable when acting as a sighted guide?
Bend your arm so they have something more sturdy to hang on to
What is the goal of distance visual acuity?
To obtain the best measurable acuity
What isn’t allowed in low vision if they can’t see the biggest letter on the chart?
Using your fingers as the target
What is the gole standard for low vision distance VA charts?
ETDRS
Which test can measure up to 20/800?
Feinbloom chart
What are the disadvantages of the feinbloom chart?
Variable number of optotypes per page
Variable spacing between optotypes
In which unit does ETDRS measure VA?
Meters
In which units does Feinbloom measure VA?
Feet
In M notation, what does the visual acuity equal?
Test distance/letter size
How are extrapolations of measurements noted?
In parentheses
What is the mathematical calculation for VA?
Test distance/letter size
What is the most common goal for patients with vision loss?
Reading
Can you use a reduced Snellen notation if the test difference is less than 40 cm?
Nope - it doesn’t allow you to extrapolate for various distances
Where should near VA be measured for a patient with low vision?
At the patient’s preferred working distance (it may not be 40 cm) *record in M units, not reduced Snellen
How many minutes of arc is 1M at 1 meter?
5 min arc
1M is equal to what point font?
8pt
8 point font is equivalent to what Snellen size?
20/50
How do you convert from Snellen to point?
Divide by 6
How do you convert from point to Meters?
Divide by 8
How do you convert from Meters to Snellen?
Multiply by 50
What are the static peripheral field tests used in Low Vision?
Confrontation fields
Humphrey automated perimetry
Octopus perimetry
What are the kinetic peripheral field tests used in low vision?
Tangent screen
Humphrey SSA kinetic test
Goldmann perimetry
Octopus perimetry
What are the central field tests used in low vision?
Amsler grid
Humphrey automated perimetry
California Central visual field test
Octopus perimetry
What is the gold standard contrast sensitivity chart?
Pelli-Robson contrast sensitivity chart
You should select lenses for trial frame refraction based on what?
JND - Just Noticeable Difference
What is JND?
The minimum lens change that a patient can appreciate
What is the Kestenbaum formula?
Reciprocal of distance vision
