1. Medical and Psychosocial Aspects of Disability
Visual Impairment
Medical and Psychosocial Aspects of Disability

2. 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

3. 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

4. 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 better-seeing 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.)

5. 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,

6. Causes of blindness (best-corrected visual acuity <6/60 [<20/200] in the better-seeing eye) by race/ethnicity
The Eye Diseases Prevalence Research Group, Arch Ophthalmol 2004;122:
AMD=age-related macular degeneration, DR=diabetic retinopathy

7. 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:
AMD=age-related macular degeneration, DR=diabetic retinopathy .

8. 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
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

10. Cataracts No cataract cataract
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
Approximately 50% of Americans between 65 and 74 and 70% over age 75 have cataracts
Prevalence factors
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

11. Corneal Disease
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
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
Vocational Implications
Vocational goals will be dependent on the degree to which the retinal image is compromised

12. Macular Degeneration
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
Caucasian
Family history
High blood pressure or a history of hypertension
Light iris color
Smoking
Functional Presentation
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

13. Macular Degeneration Treatment Vocational Implications
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
Vocational Implications
Driving
Vision rehabilitation program may be needed before being able to return to work
Accommodations/Assistive Technology
Lenses and magnification devices
Talking books
Bold, felt-tip pens
Talking clocks (and other talking devices and appliances)

14. Diabetic Retinopathy
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
Approximately 40% of people with diabetes have diabetic retinopathy
Functional Presentation
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

15. 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

16. 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

17. Glaucoma Treatment Vocational Implications
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
Vocational Implications
Progressive loss of vision may result in difficulty in performing one's job
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

18. Albinism
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
Accommodations/Assistive Technology
Low-vision devices, including strong microscopic reading lenses, magnifiers, absorptive lenses, and telescopic lenses

19. Retinitis Pigmentosa
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
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

20. Retinitis Pigmentosa Treatment Vocational Implications
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
Vocational Implications
Individuals with severe progressive visual field loss should not contemplate occupations that will necessitate driving
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

21. 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

22. General Vocational Implications
Transportation issues need to be considered
Safety issues need to be considered

23. Resources
The National Society to Prevent Blindness (
Prevent Blindness America (
Prevent Blindness Florida (
American Academy of Opthamology (
Glaucoma Research Foundation (
Lighthouse International (
AMD Alliance International (
National Eye Institute (
National RP Foundation (
Research to Prevent Blindness (
The Rehabilitation Research and Training Center on Blindness and Low Vision (
Florida Division of Blind Services (
JAN's webpage (