Low Vision Flashcards
What is low vision?
Uncorrectable reduced vision meaning vision cannot be improved by glasses/contacts
A person with low vision may still be able to use the visual system for reading but the standard size, contrast, or spacing are inadequate.
How does the PALS Survey define low vision?
Difficulty seeing someone from 12 feet or in reading a newspaper despite corrective lenses
What is blindness?
Very significant vision loss requiring alternative sensory pathway enhancements (auditory, tactile)
For a blind person, the visual system does not provide a useful input channel for reading or mobility. For individuals who are blind, alternative sensory pathways of either audition (hearing) or touch (feeling) must be used to provide input.
How is visual acuity measured?
Measured by determining the refractive index of the eye, typically using the Snellen Chart
How is the Snellen Chart scored?
Fraction measured in feet- You/Normal seeing person
Ex: 20/20 normal vision
20/10 better than normal
20/40 worse than normal
What is visual accommodation?
The process by which the ciliary muscles change the curvature of the lens and hence the focal point of the eye
What is normal visual accommodation?
For a person less than 20 years of age with normal visual accommodation, the eye can accommodate for an object located at about 4 inches.
Ability to accommodate decreases as an individual ages.
- At 50, the eye cannot accommodate to objects closer than 12 inche.
Give an example of accommodative insufficiency.
For example, if a person is using a keyboard device with a visual display, the separation of these two system components may require constant accommodation as visual gaze is directed at the keyboard and then at the display and back to the keyboard. Appropriate placement of the keyboard and visual display can reduce the amount of accommodation that is required and can result in significantly improved overall system performance.
What is accommodative insuffieciency?
Many types of disabilities affect accommodation; limitations in accommodation are referred to as accommodative insufficiency, which can be a significant factor when ATs are used.
What is the normal range of peripheral vision?
With the head and eyes fixed on a central point, normal range of peripheral vision in the right eye is 70º to the left and 104º to the right.
If eyes allowed to rotate with head remaining fixed, it is 166º to each side of central point.
What diseases/injuries affect visual field?
CP, TBI, diseases affecting eye and visual system
KNOW FIELD CUTS
Unilateral is also called anopia
What causes congenital blindness?
Optical nerve lesions main cause in high income countries
In low-income countries additional causes include corneal scarring from measles, vitamin A deficiency, the use of harmful traditional eye remedies, and ophthalmia neonatorum.
Retinopathy of prematurity is an important cause in middle-income countries.
Cataract, congenital abnormalities, and hereditary retinal dystrophies are significant causes in all countries.
What is age related macular degeneration?
Most common cause of blindness in seniors
It occurs most frequently in individuals over 65, beginning in one eye and progressing gradually to both eyes.
ARMD primarily affects the central vision with the peripheral vision being preserved. As it progresses, the size of the impaired central field gradually increases.
What are the types of ARMD?
There are two types of ARMD: dry, or atrophic, and wet, or endovascular.
- The dry form is much more common, but the wet form accounts for 80% to 90% of the cases of ARMD- related blindness.
What is galucoma?
Glaucoma is a group of eye diseases caused by increased intraocular pressure that damages the optic nerve.
It is most common in individuals over 60 y/o.
The effect on vision of glaucoma is loss of the peripheral visual field.
In early stages there are treatments that can prevent further vision loss.
What is cataracts?
A cataract is a clouding of the lens of the eye that results in blurred vision.
The most common treatment is surgical replacement of the lens with an artificial lens.
What are different diabetic eye diseases?
Diabetic retinopathy, cataracts, and glaucoma
What is diabetic retinopathy?
Diabetic retinopathy is the most common type of eye disease that accompanies diabetes and is a leading cause of blindness.
It is caused by changes in the blood vessels of the eye that affect the blood supply to the retina.
The result is loss of parts of the visual field seen as black areas at random points.
What is Dynavision therapy?
Ortho for ROM
Neuro - CVA, TBI, midline, visual scanning
Attention deficit disorders
Visual field therapy
Keep head still and click lit up buttons
What is the purpose of vision rehab?
Purpose is not to get back your sight,
but to regain your ability to do the everyday activities that have been affected by the loss of vision
Typical impairments from macular degeneration
Reading
Driving
Watching TV
Computer
Seeing faces
Writing checks
Impairments from vision loss
Shopping
- price tags, labels
Hobbies
- crafts, playing cards
ADLs
- foot on plate, plugging in appliances, setting appliances
- using phone
Trouble walking
- increased risk of falls
Goals of vision rehab
Adjustment to vision loss (augmentation ie. Magnifier)
Functional: maximize remaining vision with devices and training
Emotional: LV patients are at 20x greater risk of depression
Also inform patients about community resources available
Central field loss and eccentric viewing (EV)
Train patients to move their eyes in a consistent way to look around their blind spot
Lighting for LV
Want to be as close to natural daylight as possible
Special lamps
High intensity flashlights
Be aware of glare
Inc. lighting = Inc. glare
Use directional light, with shade, from the side
Lighting assessment for LV
Evaluate current lighting
Light meter assessment of specific work areas
Demonstrate various types of light/globes
Types of light
Daylight
Incandescent - light bulb
Fluorescent
Halogen - old school
How to control glare
Macular degeneration patients benefits from Blue Blocker lenses:
Indoor glare control: Yellow or light amber lenses
Outdoor glare control: Orange or brown lenses
What is OT’s role in vision rehab?
Eccentric view training
Device training
Adaptive strategies
Home visits and modifications
Fall prevention
Magnifier
The larger the magnifier the weaker it is.
Over the counter (+6 diopters or 2X) vs. LV magnifiers (up to +56 diopters or 14X)
- Hand held mags
- LED illuminated
Traditional: Stand magnifiers
- Makrolux (2.2x, 3.6X)
- Scribolux (2.8X)
- Menas Lux (3.0X)
Video magnifier
- Closed Circuit Television (CCTV)
> Closed Circuit Television$2000 to $3000
- Topaz by Freedom Scientific
- Clearview by Optelec
- Merlin by Enhanced Vision
Types of video magnifiers that read to you
DaVinci by Enhanced Vision
Clear View + Speech by Optelec
Prodigy Duo 2 in 1 by Humanware
Handheld video magnifiers
Pebble HD 4.3 by Enhanced Vision
Smartlux Digital by Eschenbach
Ruby by Freedom Scientific
What is the Mobilux Digital Magnifier by Eschenbach?
Magnification range from 3x to 6x
High definition LED screen feels like a regular magnifier
What are computer adaptations for LV
Large print keyboard
Operating system accessibility options
- Computer glasses
- Large print software
- Zoom text
- Jaws
Adaptations for communication
Large print phone
Bold line paper, felt tip pens
Types of limitations in LV and aids to correct them
- intensity - glasses
- frequency/wavelength - color filters or varying contrast
- field limitation - use lenses that widen the field
