Transcript Visual Impairment - University of Florida

Visual
Impairment
Medical and Psychosocial
Aspects of Disability
Introduction
• Vision impairment affects a significant proportion of
middle-aged and older Americans
– 1 in 6 adults (17%), age 45 and older, representing
13.5 million Americans, reports some form of vision
impairment even when wearing glasses or contact
lenses
• The prevalence of visual impairments increase with
age
– 15% of people 45-64
– 17% of people 65-74
– 26% of people 75 and older
Factors Affecting Visual
Function and Their Treatment
• Visual Acuity - ability to see "detail"
– Measured using testing distance/letter size
– Normal is 20/20
– Limitation on acuity level is generally determined by
the spacing of the cones
– Treatment: glasses or some form of magnification
• Visual Field - a person's peripheral vision
– Scotoma - loss of vision in an area
• Contrast
• Lighting and Glare
– Often, too much light can be as detrimental as not
enough
Definition of Legal
Blindness
• WHO Definition: Best-corrected visual
acuity of less than 6/120 (<20/400) in the
better-seeing eye.
• US Definition: Best-corrected visual acuity
of 6/60 or worse (<20/200) in the betterseeing eye.
OR
• Peripheral visual field is restricted to 20° or
less in the widest meridian of the better eye
•
(US Definition of Low Vision: best-corrected visual acuity of 6/12
(<20/40) in better-seeing eye.)
Statistics
• In 2000 there were 937,000 blind
Americans older than 40 (0.78%)
• 2,400,000 with low vision (1.98%)
• Thus, there were 3.3 million
Americans aged 40 or more with a
visual impairment in 2000
The Eye Diseases Prevalence Research Group (2004). Causes and prevalence of
visual impairment among adults in the United States. Archives of Ophthalmology,
122, 477-485.
Causes of blindness (best-corrected visual acuity <6/60 [<20/200] in the betterseeing eye) by race/ethnicity
The Eye Diseases Prevalence Research Group, Arch Ophthalmol 2004;122:477-485.
AMD=age-related macular degeneration, DR=diabetic retinopathy
Causes of low vision (best-corrected visual acuity <6/12 [<20/40] in the better-seeing
eye, excluding those who were categorized as being blind by the US definition) by
race/ethnicity
The Eye Diseases Prevalence Research Group, Arch Ophthalmol 2004;122:477-485.
AMD=age-related macular degeneration, DR=diabetic retinopathy
.
Prevalence of Blindness
by Age and Race (US)
White
Black
Hispanic
40-49
0.12
0.18
0.05
50-54
0.10
0.34
0.10
55-59
0.11
0.52
0.16
60-64
0.15
0.81
0.26
65-69
0.23
1.25
0.41
70-74
0.43
1.93
0.64
75-79
0.93
2.96
0.99
>80
6.82
6.85
2.42
Cataracts
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A cataract is opacity or clouding of the
lens that may develop as a result of
aging, trauma, hereditary factors, birth
defects, or diabetes
Cataracts are a normal part of aging
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Prevalence factors
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Approximately 50% of Americans
between 65 and 74 and 70% over
age 75 have cataracts
Caucasians are three times as likely
as African-Americans to develop
cataracts
Smokers have a 60% increase
Those taking medication for gout are
twice as likely to develop cataracts
The greater the progression of the
cataract, the greater the visual
impairment from the effects of glare,
loss of contrast, and decreased visual
acuity
Normally, cataracts are successfully
treated with surgery
Assuming no complications, there
should be no vocational implications
following cataract surgery
No cataract
cataract
Corneal Disease
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The cornea is a structure that is prone to dystrophies, deposition,
noninflammatory progressive thinning (keratoconus), infection, viral
diseases, and trauma
Interference with corneal integrity can result in a blurred or distorted
image on the retina
– May experience severe glare, cloudy vision, and reduced acuity
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Treatment
– Keratoplasty is the primary method of restoring vision for an
individual with a diseased, irregular, or scarred cornea - procedure
involves transplanting a healthy cornea from a compatible donor
– Recently, lasers have been used to treat some corneal problems
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Vocational Implications
– Vocational goals will be dependent on the degree to which the
retinal image is compromised
Macular Degeneration
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Macular degeneration is caused by
degenerative changes to the macular
area of the retina that result in atrophy,
hemorrhage, exudates, fibrovascular
scars, or cyst formations
Risk factors
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Caucasian
Family history
High blood pressure or a history of
hypertension
Light iris color
Smoking
Functional Presentation
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Visually manifested as distortions, a
decrease in the visual acuity, a
decrease in color recognition, a loss
of contrast, or an absolute or relative
area of no vision (scotoma)
Reading may become increasingly
difficult and driving may have to be
discontinued
Macular Degeneration
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Treatment
– Laser treatment can sometimes be used to slow the progression of
the disease
– Other treatments that have been investigated (but not yet
established) include the use of radiation, laser treatment of drusen
(small globular pathological growths formed on optic papilla or on
Descemet's membrane), photodynamic therapy, submacular
surgery, retinal cell transplantation, and the use of vascular
endothelial growth factor
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Vocational Implications
– Driving
– Vision rehabilitation program may be needed before being able to
return to work
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Accommodations/Assistive Technology
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Lenses and magnification devices
Talking books
Bold, felt-tip pens
Talking clocks (and other talking devices and appliances)
Diabetic Retinopathy
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Diabetes accounts for about
5,000 new cases of blindness
each year and people with
diabetes have a 25 times greater
risk for blindness than the general
population
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Approximately 40% of people
with diabetes have diabetic
retinopathy
Functional Presentation
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Fluctuating or severely
decreased visual acuity
Problems due to glare, reduced
contrast sensitivity, and various
types of visual field problems
May have transient episodes of
diplopia
Diabetic Retinopathy
• Vocational Implications
– Rehabilitation considerations must
include not only vision but also the
effect of diabetes on other systems
• Accommodations/Assistive
Technology
– Low-vision devices
– Prisms to correct transitory diplopia
Glaucoma
• If left untreated, results in the destruction of the
peripheral retina
• Basically three types of glaucoma
– Chronic open-angle glaucoma: elevated pressure
over time eventually affects the optic nerve and visual
field
– Acute (closed-angle) glaucoma: rapid increase or
spiking of the intraocular pressure that may be
accompanied by intense pain and even nausea or
vomiting
– Low-tension glaucoma: may be caused by a
decrease in blood flow to the optic nerve
• Over a period of time, especially if left untreated,
irreversible optic nerve and visual field damage will
occur, impairing night vision, visual acuity, mobility, and
reading skills
Glaucoma
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Treatment
– Medications that decrease production of aqueous humor or
facilitate outflow of fluid
– Laser surgery to create drainage holes
– Other surgery procedures to assist with drainage
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Vocational Implications
– Progressive loss of vision may result in difficulty in
performing one's job
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Accommodations/Assistive Technology
– Low-vision devices, including spectacles, hand and stand
magnifiers, closed circuit TV, and lighting
– Absorptive lenses enhance the apparent brightness of the
scene and often aid in mobility
– Modifications in the work space may be required, with high
technology, including voice-output devices
Albinism
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Albinism is a trait that is inherited through autosomal
recessive or sex-linked transmission and results in
characteristics that affect the pigmentation of the skin and
hair as well as the iris and retina
Persons with albinism have a decrease in visual acuity due
to macular aplasia
Treatment consists of corrective spectacle lenses as well as
absorptive lenses to reduce light sensitivity
Vocational Implications
– Similar to other types of visual impairments
– Need to pay attention to exposure to sunlight
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Accommodations/Assistive Technology
– Low-vision devices, including strong microscopic reading
lenses, magnifiers, absorptive lenses, and telescopic lenses
Retinitis Pigmentosa
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A progressive eye disease that
affects the pigmentary layer of the
retina, and most commonly affects
the periphery or midperiphery of
the retina
Most common cause of inherited
blindness
In addition, 30% of people with
RP report some degree of hearing
loss
Functional Presentation
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Night vision and peripheral
vision go hand in hand - the
more advanced the RP, the
greater loss of peripheral vision
and the more difficult to travel
Reading becomes more and
more difficult as the visual field
becomes small
Glare or light sensitivity is
frequently associated with RP
Retinitis Pigmentosa
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Treatment
– At present, no medical or surgical treatments are known to stop or
decrease the progression of RP
– Refractive corrections are necessary, along with absorptive lenses
to cut down the glare or light sensitivity
– Contrast-enhancing lenses may be beneficial in enhancing
performance and reducing adaptation times between outdoors and
indoors
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Vocational Implications
– Individuals with severe progressive visual field loss should not
contemplate occupations that will necessitate driving
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Accommodations/Assistive Technology
– Closed-circuit TV to enable the person to control the brightness and
contrast of the image viewed
– Prism lenses to increase the awareness of the periphery
– The Nightsope might be able to be used for mobility under dim
illumination
– Mobility devices, such as a traveling cane, special laser cane,
sensory device, or Seeing Eye dog
Peripheral Visual Field Loss
from Strokes or Tumors
• A person who has a stroke or tumor can be left with a
resultant visual field loss
• In addition, can affect perception of visual form, color,
object meaning, recognition, and attention
• May also be disorders of the visual system such as
hallucinations
• Vocational Implications - driving
• Accommodations/Assistive Technology
– Prisms to enhance spatial awareness
– Mirrors to facilitate peripheral field awareness
– Low-vision devices
General Vocational
Implications
• Transportation issues need to be
considered
• Safety issues need to be considered
Resources
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The National Society to Prevent Blindness
(www.eyeinfo.org/national.html)
Prevent Blindness America (http://www.preventblindness.org/)
Prevent Blindness Florida (www.preventblindness.org/florida/)
American Academy of Opthamology (http://www.aao.org/)
Glaucoma Research Foundation (http://www.glaucoma.org/)
Lighthouse International (http://www.lighthouse.org/)
AMD Alliance International (http://www.amdalliance.org/)
National Eye Institute (http://www.nei.nih.gov/)
National RP Foundation (www.rpsa.org.za/training.htm)
Research to Prevent Blindness (http://www.rpbusa.org/)
The Rehabilitation Research and Training Center on Blindness and
Low Vision (http://www.blind.msstate.edu/)
Florida Division of Blind Services (www.state.fl.us/dbs/index.shtml)
JAN's webpage (www.jan.wvu.edu/media/sight.html)