Visual ImpairmentVisual Impairment

Medical and Psychosocial Medical and Psychosocial Aspects of DisabilityAspects of Disability

IntroductionIntroduction

• Vision impairment affects a significant Vision impairment affects a significant proportion of middle-aged and older proportion of middle-aged and older Americans Americans – 1 in 6 adults (17%), age 45 and older, 1 in 6 adults (17%), age 45 and older,

representing 13.5 million Americans, reports representing 13.5 million Americans, reports some form of vision impairment even when some form of vision impairment even when wearing glasses or contact lenses wearing glasses or contact lenses

• The prevalence of visual impairments The prevalence of visual impairments increase with age increase with age – 15% of people 45-64 15% of people 45-64 – 17% of people 65-74 17% of people 65-74 – 26% of people 75 and older 26% of people 75 and older

Factors Affecting Visual Factors Affecting Visual Function and Their TreatmentFunction and Their Treatment

• Visual Acuity - ability to see "detail" Visual Acuity - ability to see "detail" – Measured using testing distance/letter size Measured using testing distance/letter size – Normal is 20/20 Normal is 20/20 – Limitation on acuity level is generally determined by the Limitation on acuity level is generally determined by the

spacing of the cones spacing of the cones – Treatment:  glasses or some form of magnification Treatment:  glasses or some form of magnification

• Visual Field - a person's peripheral vision Visual Field - a person's peripheral vision – Scotoma - loss of vision in an area Scotoma - loss of vision in an area

• Contrast Contrast • Lighting and Glare Lighting and Glare

– Often, too much light can be as detrimental as not Often, too much light can be as detrimental as not enough enough

Definition of Legal BlindnessDefinition of Legal Blindness

• WHO Definition:WHO Definition: Best-corrected visual Best-corrected visual acuity of less than 6/120 (<20/400) in the acuity of less than 6/120 (<20/400) in the better-seeing eye.better-seeing eye.

• US Definition:US Definition: Best-corrected visual Best-corrected visual acuity of 6/60 or worse (acuity of 6/60 or worse (<<20/200) in the 20/200) in the better-seeing eye. better-seeing eye.

OROR • Peripheral visual field is restricted to 20° or Peripheral visual field is restricted to 20° or

less in the widest meridian of the better eyeless in the widest meridian of the better eye • (US Definition of Low Vision: (US Definition of Low Vision: best-corrected visual acuity of 6/12 best-corrected visual acuity of 6/12

(<20/40) in better-seeing eye.)(<20/40) in better-seeing eye.)

StatisticsStatistics

• In 2000 there were 937,000 blind In 2000 there were 937,000 blind Americans older than 40 (0.78%)Americans older than 40 (0.78%)

• 2,400,000 with low vision (1.98%)2,400,000 with low vision (1.98%)

• Thus, there were 3.3 million Thus, there were 3.3 million Americans aged 40 or more with a Americans aged 40 or more with a visual impairment in 2000visual impairment in 2000

The Eye Diseases Prevalence Research Group (2004). Causes and prevalence of The Eye Diseases Prevalence Research Group (2004). Causes and prevalence of visual impairment among adults in the United States. visual impairment among adults in the United States. Archives of Archives of Ophthalmology, 122Ophthalmology, 122, 477-485., 477-485.

The Eye Diseases Prevalence Research Group, Arch Ophthalmol 2004;122:477-485.AMD=age-related macular degeneration, DR=diabetic retinopathy

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;122:477-485.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

Prevalence of Blindness by Prevalence of Blindness by Age and Race (US)Age and Race (US)

WhiteWhite BlackBlack HispanicHispanic

40-4940-49 0.120.12 0.180.18 0.050.05

50-5450-54 0.100.10 0.340.34 0.100.10

55-5955-59 0.110.11 0.520.52 0.160.16

60-6460-64 0.150.15 0.810.81 0.260.26

65-6965-69 0.230.23 1.251.25 0.410.41

70-7470-74 0.430.43 1.931.93 0.640.64

75-7975-79 0.930.93 2.962.96 0.990.99

>>8080 6.826.82 6.856.85 2.422.42

CataractsCataracts• A cataract is opacity or clouding of A cataract is opacity or clouding of

the lens that may develop as a the lens that may develop as a result of aging, trauma, hereditary result of aging, trauma, hereditary factors, birth defects, or diabetes factors, birth defects, or diabetes

• Cataracts are a normal part of Cataracts are a normal part of aging aging

– Approximately 50% of Americans Approximately 50% of Americans between 65 and 74 and 70% over between 65 and 74 and 70% over age 75 have cataracts age 75 have cataracts

• Prevalence factors Prevalence factors – Caucasians are three times as likely Caucasians are three times as likely

as African-Americans to develop as African-Americans to develop cataracts cataracts

– Smokers have a 60% increase Smokers have a 60% increase – Those taking medication for gout Those taking medication for gout

are twice as likely to develop are twice as likely to develop cataracts cataracts

• The greater the progression of the The greater the progression of the cataract, the greater the visual cataract, the greater the visual impairment from the effects of impairment from the effects of glare, loss of contrast, and glare, loss of contrast, and decreased visual acuity decreased visual acuity

• Normally, cataracts are Normally, cataracts are successfully treated with surgery successfully treated with surgery

• Assuming no complications, there Assuming no complications, there should be no vocational should be no vocational implications following cataract implications following cataract surgery surgery

No cataract cataract

Corneal DiseaseCorneal Disease

• The cornea is a structure that is prone to dystrophies, deposition, The cornea is a structure that is prone to dystrophies, deposition, noninflammatory progressive thinning (keratoconus), infection, noninflammatory progressive thinning (keratoconus), infection, viral diseases, and trauma viral diseases, and trauma

• Interference with corneal integrity can result in a blurred or Interference with corneal integrity can result in a blurred or distorted image on the retina distorted image on the retina – May experience severe glare, cloudy vision, and reduced acuity May experience severe glare, cloudy vision, and reduced acuity

• Treatment Treatment – Keratoplasty is the primary method of restoring vision for an individual Keratoplasty is the primary method of restoring vision for an individual

with a diseased, irregular, or scarred cornea - procedure involves with a diseased, irregular, or scarred cornea - procedure involves transplanting a healthy cornea from a compatible donor transplanting a healthy cornea from a compatible donor

– Recently, lasers have been used to treat some corneal problems Recently, lasers have been used to treat some corneal problems • Vocational Implications Vocational Implications

– Vocational goals will be dependent on the degree to which the retinal Vocational goals will be dependent on the degree to which the retinal image is compromised image is compromised

Macular DegenerationMacular Degeneration

• Macular degeneration is caused by Macular degeneration is caused by degenerative changes to the macular degenerative changes to the macular area of the retina that result in area of the retina that result in atrophy, hemorrhage, exudates, atrophy, hemorrhage, exudates, fibrovascular scars, or cyst formations fibrovascular scars, or cyst formations

• Risk factors Risk factors – Caucasian Caucasian – Family history Family history – High blood pressure or a history of High blood pressure or a history of

hypertension hypertension – Light iris color Light iris color – Smoking Smoking

• Functional Presentation Functional Presentation – Visually manifested as distortions, a Visually manifested as distortions, a

decrease in the visual acuity, a decrease in the visual acuity, a decrease in color recognition, a loss of decrease in color recognition, a loss of contrast, or an absolute or relative area contrast, or an absolute or relative area of no vision (scotoma) of no vision (scotoma)

– Reading may become increasingly Reading may become increasingly difficult and driving may have to be difficult and driving may have to be discontinued discontinued

Macular DegenerationMacular Degeneration

• Treatment Treatment – Laser treatment can sometimes be used to slow the progression of Laser treatment can sometimes be used to slow the progression of

the disease the disease – Other treatments that have been investigated (but not yet Other treatments that have been investigated (but not yet

established) include the use of radiation, laser treatment of drusen established) include the use of radiation, laser treatment of drusen (small globular pathological growths formed on optic papilla or on (small globular pathological growths formed on optic papilla or on Descemet's membrane), photodynamic therapy, submacular Descemet's membrane), photodynamic therapy, submacular surgery, retinal cell transplantation, and the use of vascular surgery, retinal cell transplantation, and the use of vascular endothelial growth factor endothelial growth factor

• Vocational Implications Vocational Implications – Driving Driving – Vision rehabilitation program may be needed before being able to Vision rehabilitation program may be needed before being able to

return to work return to work • Accommodations/Assistive Technology Accommodations/Assistive Technology

– Lenses and magnification devices Lenses and magnification devices – Talking books Talking books – Bold, felt-tip pens Bold, felt-tip pens – Talking clocks (and other talking devices and appliances) Talking clocks (and other talking devices and appliances)

Diabetic RetinopathyDiabetic Retinopathy

• Diabetes accounts for about Diabetes accounts for about 5,000 new cases of blindness 5,000 new cases of blindness each year and people with each year and people with diabetes have a 25 times greater diabetes have a 25 times greater risk for blindness than the general risk for blindness than the general population population – Approximately 40% of people with Approximately 40% of people with

diabetes have diabetic diabetes have diabetic retinopathy retinopathy

• Functional Presentation Functional Presentation – Fluctuating or severely decreased Fluctuating or severely decreased

visual acuity visual acuity – Problems due to glare, reduced Problems due to glare, reduced

contrast sensitivity, and various contrast sensitivity, and various types of visual field problems types of visual field problems

– May have transient episodes of May have transient episodes of diplopia diplopia

Diabetic RetinopathyDiabetic Retinopathy

• Vocational Implications Vocational Implications – Rehabilitation considerations must Rehabilitation considerations must

include not only vision but also the include not only vision but also the effect of diabetes on other systems effect of diabetes on other systems

• Accommodations/Assistive Accommodations/Assistive Technology Technology – Low-vision devices Low-vision devices – Prisms to correct transitory diplopia Prisms to correct transitory diplopia

GlaucomaGlaucoma• If left untreated, results in the destruction of the If left untreated, results in the destruction of the

peripheral retina peripheral retina • Basically three types of glaucoma Basically three types of glaucoma

– Chronic open-angle glaucoma:  elevated pressure over Chronic open-angle glaucoma:  elevated pressure over time eventually affects the optic nerve and visual field time eventually affects the optic nerve and visual field

– Acute (closed-angle) glaucoma:  rapid increase or Acute (closed-angle) glaucoma:  rapid increase or spiking of the intraocular pressure that may be spiking of the intraocular pressure that may be accompanied by intense pain and even nausea or accompanied by intense pain and even nausea or vomiting vomiting

– Low-tension glaucoma:  may be caused by a decrease Low-tension glaucoma:  may be caused by a decrease in blood flow to the optic nerve in blood flow to the optic nerve

• Over a period of time, especially if left Over a period of time, especially if left untreated, irreversible optic nerve and visual untreated, irreversible optic nerve and visual field damage will occur, impairing night vision, field damage will occur, impairing night vision, visual acuity, mobility, and reading skillsvisual acuity, mobility, and reading skills

GlaucomaGlaucoma

• Treatment Treatment – Medications that decrease production of aqueous humor or Medications that decrease production of aqueous humor or

facilitate outflow of fluid facilitate outflow of fluid – Laser surgery to create drainage holes Laser surgery to create drainage holes – Other surgery procedures to assist with drainage Other surgery procedures to assist with drainage

• Vocational Implications Vocational Implications – Progressive loss of vision may result in difficulty in performing Progressive loss of vision may result in difficulty in performing

one's job one's job • Accommodations/Assistive Technology Accommodations/Assistive Technology

– Low-vision devices, including spectacles, hand and stand Low-vision devices, including spectacles, hand and stand magnifiers, closed circuit TV, and lighting magnifiers, closed circuit TV, and lighting

– Absorptive lenses enhance the apparent brightness of the Absorptive lenses enhance the apparent brightness of the scene and often aid in mobility scene and often aid in mobility

– Modifications in the work space may be required, with high Modifications in the work space may be required, with high technology, including voice-output devices technology, including voice-output devices

AlbinismAlbinism

• Albinism is a trait that is inherited through autosomal Albinism is a trait that is inherited through autosomal recessive or sex-linked transmission and results in recessive or sex-linked transmission and results in characteristics that affect the pigmentation of the skin and characteristics that affect the pigmentation of the skin and hair as well as the iris and retina hair as well as the iris and retina

• Persons with albinism have a decrease in visual acuity due Persons with albinism have a decrease in visual acuity due to macular aplasia to macular aplasia

• Treatment consists of corrective spectacle lenses as well as Treatment consists of corrective spectacle lenses as well as absorptive lenses to reduce light sensitivity absorptive lenses to reduce light sensitivity

• Vocational Implications Vocational Implications – Similar to other types of visual impairments Similar to other types of visual impairments – Need to pay attention to exposure to sunlight Need to pay attention to exposure to sunlight

• Accommodations/Assistive Technology Accommodations/Assistive Technology – Low-vision devices, including strong microscopic reading Low-vision devices, including strong microscopic reading

lenses, magnifiers, absorptive lenses, and telescopic lenses lenses, magnifiers, absorptive lenses, and telescopic lenses

Retinitis PigmentosaRetinitis Pigmentosa

• A progressive eye disease that A progressive eye disease that affects the pigmentary layer of affects the pigmentary layer of the retina, and most commonly the retina, and most commonly affects the periphery or affects the periphery or midperiphery of the retina midperiphery of the retina

• Most common cause of inherited Most common cause of inherited blindness blindness

• In addition, 30% of people with RP In addition, 30% of people with RP report some degree of hearing report some degree of hearing loss loss

• Functional Presentation Functional Presentation – Night vision and peripheral vision Night vision and peripheral vision

go hand in hand - the more go hand in hand - the more advanced the RP, the greater loss advanced the RP, the greater loss of peripheral vision and the more of peripheral vision and the more difficult to travel difficult to travel

– Reading becomes more and more Reading becomes more and more difficult as the visual field difficult as the visual field becomes small becomes small

– Glare or light sensitivity is Glare or light sensitivity is frequently associated with RP frequently associated with RP

Retinitis PigmentosaRetinitis Pigmentosa

• Treatment Treatment – At present, no medical or surgical treatments are known to At present, no medical or surgical treatments are known to

stop or decrease the progression of RP stop or decrease the progression of RP – Refractive corrections are necessary, along with absorptive Refractive corrections are necessary, along with absorptive

lenses to cut down the glare or light sensitivity lenses to cut down the glare or light sensitivity – Contrast-enhancing lenses may be beneficial in enhancing Contrast-enhancing lenses may be beneficial in enhancing

performance and reducing adaptation times between performance and reducing adaptation times between outdoors and indoors outdoors and indoors

• Vocational Implications Vocational Implications – Individuals with severe progressive visual field loss should Individuals with severe progressive visual field loss should

not contemplate occupations that will necessitate driving not contemplate occupations that will necessitate driving • Accommodations/Assistive Technology Accommodations/Assistive Technology

– Closed-circuit TV to enable the person to control the Closed-circuit TV to enable the person to control the brightness and contrast of the image viewed brightness and contrast of the image viewed

– Prism lenses to increase the awareness of the periphery Prism lenses to increase the awareness of the periphery – The Nightsope might be able to be used for mobility under The Nightsope might be able to be used for mobility under

dim illumination dim illumination – Mobility devices, such as a traveling cane, special laser Mobility devices, such as a traveling cane, special laser

cane, sensory device, or Seeing Eye dogcane, sensory device, or Seeing Eye dog

Peripheral Visual Field Loss Peripheral Visual Field Loss from Strokes or Tumors from Strokes or Tumors

• A person who has a stroke or tumor can be left A person who has a stroke or tumor can be left with a resultant visual field loss with a resultant visual field loss

• In addition, can affect perception of visual form, In addition, can affect perception of visual form, color, object meaning, recognition, and attention color, object meaning, recognition, and attention

• May also be disorders of the visual system such May also be disorders of the visual system such as hallucinations as hallucinations

• Vocational Implications - driving Vocational Implications - driving • Accommodations/Assistive Technology Accommodations/Assistive Technology

– Prisms to enhance spatial awareness Prisms to enhance spatial awareness – Mirrors to facilitate peripheral field awareness Mirrors to facilitate peripheral field awareness – Low-vision devices Low-vision devices

General Vocational General Vocational ImplicationsImplications

• Transportation issues need to be Transportation issues need to be considered considered

• Safety issues need to be considered Safety issues need to be considered

ResourcesResources

• The National Society to Prevent Blindness The National Society to Prevent Blindness (www.eyeinfo.org/national.html) (www.eyeinfo.org/national.html)

• Prevent Blindness America (http://www.preventblindness.org/) Prevent Blindness America (http://www.preventblindness.org/) • Prevent Blindness Florida (www.preventblindness.org/florida/) Prevent Blindness Florida (www.preventblindness.org/florida/) • American Academy of Opthamology (http://www.aao.org/) American Academy of Opthamology (http://www.aao.org/) • Glaucoma Research Foundation (http://www.glaucoma.org/) Glaucoma Research Foundation (http://www.glaucoma.org/) • Lighthouse International (http://www.lighthouse.org/) Lighthouse International (http://www.lighthouse.org/) • AMD Alliance International (http://www.amdalliance.org/) AMD Alliance International (http://www.amdalliance.org/) • National Eye Institute (http://www.nei.nih.gov/) National Eye Institute (http://www.nei.nih.gov/) • National RP Foundation (www.rpsa.org.za/training.htm) National RP Foundation (www.rpsa.org.za/training.htm) • Research to Prevent Blindness (http://www.rpbusa.org/) Research to Prevent Blindness (http://www.rpbusa.org/) • The Rehabilitation Research and Training Center on Blindness and The Rehabilitation Research and Training Center on Blindness and

Low Vision (http://www.blind.msstate.edu/) Low Vision (http://www.blind.msstate.edu/) • Florida Division of Blind Services (www.state.fl.us/dbs/index.shtml) Florida Division of Blind Services (www.state.fl.us/dbs/index.shtml) • JAN's webpage (www.jan.wvu.edu/media/sight.html) JAN's webpage (www.jan.wvu.edu/media/sight.html)