Vision

Best Corrected Vision

the sharpest, clearest vision attainable by the client, under the nest circumstances, using vision out of the best eye with standard corrective lenses (glasses or contact lenses)

Low Vision

best corrected visual acuity less than 20/40 in the better seeing eye

Near Normal Vision (Mild Vision Loss)

20/30 to 20/60

Moderate Low Vision (Moderate Visual Impairment)

20/70 to 20/160

Severe Low Vision (Severe Visual Impairment)

20/200 or worse

Profound Low Vision (Profound Visual Impairment)

20/500 to 20/1000

Near Total Low Vision (Near Total Visual Impairment)

< 20/1000

Total Blindness (Total Visual Impairment)

no light perception

Blindness

best corrected visual acuity of 20/200 or worse in the better seeing eye

Distance Visual Acuity

ability to discriminate small details while far away from an object

Near Visual Acuity

ability to discriminate details at close range

Visual Field

side vision decreases with age

glaucoma, retinitis pigmentosa, stroke can cause impairment

eyelid ptosis can impair vision

may not see people around them, cars passing by

may not be aware of the problem because loss occurs gradually

Light/Dark Adaptations and Sensitivity

difficulty driving at night

shifting from dark to bright headlights, streetlights, turning on the lights in the middle of the night, etc

difficulty driving through tunnels

decreased light sensitivity

increased lumination needs

Contrast Sensitivity

capacity to distinguish between objects similar in color

affects distance judgement (tailgating, hitting the curb)

may not see faded lane markers or others in dark clothing at night

older adults needs 3x more contrast to distinguish targets from background (deficits is worse in low light)

deficits common with cataracts and Parkinson’s disease

Presbyopia

los of elasticity in culinary muscle and suspensory ligament

difficult with near vision

Age Related Macular Degeneration

impacts reading and driving: identifying details of faces, words, and letters

safety and falls

dry and wet

Macula

for central vision and seeing details sharply

Age Related Macular Degeneration (Dry)

thinning, white/yellow deposits of fatty protein

fuzzy, blurred spot in central vision, decreased visual acuity

Age Related Macular Degeneration (Wet)

growth of abnormal blood vessels

whiteout or dark blurriness in central vision

straight lines look wavy

decreased intensity of color brightness

Diabetic Retinopathy

uncontrolled diabetes that lead to damaged retinal capillaries (leaking fluid into macula, poor blood flow, growing blood vessels, hemorrhaging blood vessels)

changes: decreased near and distance vision, scotomas (spots) in vision

difficulty driving (night), reading, preparing meds, testing glucose, mobility

Glaucoma

buildup of excess fluid that leads to pressure of the optic nerve

peripheral blindness and tunnel vision

bumping into objects

difficulty of reading walking and driving

Cataracts

buildup of lens protein leading to cloudiness, blurriness, faded colors, halos of light

Retinal Tear/Retinal Detachment

occurs when the retina is pulled away from they from the back of eye

symptoms: sudden onset of new or a lot of floaters, flashes of light, dark shadow/curtain in the peripheral or central vision

treatment: laser surgery, freezing to seal tears, reattachment

Agumentation

reinforcing/strengthening existing sensory pathways that the person already has available

Alternative Pathway

using other sensory systems to convey information

often done when the primary pathway is so impaired that no useful information can be gleaned from it