Dennis W. Siemsen, OD, MHPE Department of Ophthalmology … · 2016-12-12 · • Difficulty seeing...
Transcript of Dennis W. Siemsen, OD, MHPE Department of Ophthalmology … · 2016-12-12 · • Difficulty seeing...
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Dennis W. Siemsen, OD, MHPEDepartment of OphthalmologyMayo Clinic, Rochester [email protected]
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At the end of the presentation the learnerwill:
• Understand the difference between agerelated eye disease and normal aging
• Understand key terms related to eyesand eye health
• Relate changes in vision with potentialpilot performance
Learning objectives
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Changes in visual function (eye)
Changes in visual perception (brain)
It’s pretty easy to describe the first, but wedon’t know enough about the second.
What is “normal” aging?
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Media Opacities
Macular dystrophies and degenerations
Peripheral retinal degenerations
Optic nerve anomalies
Visual cortex (brain) damage
The Complete Guide to Eye Disease(abridged)
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Ocular Anatomy
Neuro-Anatomy
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Normal Vision
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What•Anything that prevents light from reaching
the retina (receptor layer) of the eye•Fuchs’ Corneal Endothelial Dystrophy•Clouding of the front-most layer of the eye
•Cataracts•Cloudy lens behind the pupil•Generally age-associated, but can be
congenital, trauma, or medication related
Media Opacities
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Effect•Generally a hazy view of the world•“Dirty windshield” effect•Light scattering•Worse when viewing bright point sources of
light•Reflected light can by-pass filters and visors
Media Opacities
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Media Opacities
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• Can be dry or wet
• Leading cause of blindness in the USamong persons over 65
• 10 percent of the population over 52, 33percent over 75
• Of those who are not legally blind, 90percent have the dry variety
Age-Related Macular Degeneration
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Effect•Loss of central vision•Peripheral vision is intact•Acuity loss in the range of near perfect to
5/125•Difficulty reading, identifying faces, driving
Age-Related Macular Degeneration
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Age-RelatedMacular Degeneration
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What•Number one cause of new blindness in the
20-74 year old age group•Responsible for 10 percent of the blind
population of the US•Breakdown of retinal vessels leads to
hemorrhage, edema and retinaldetachments
Diabetic Retinopathy
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Effect•Multiple small blind spots from hemorrhage
and laser treatment•Macular edema distorts central vision•Vitreous hemorrhage causes significant
reduction in vision•Retinal detachments can lead to total
blindness
Diabetic Retinopathy
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Diabetic Retinopathy
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What•Hereditary condition which includes:•Progressive visual field loss•Night blindness•Abnormal electro-retinogram
•Characteristic pigmentary pattern•Many syndromes associated with RP
Retinitis Pigmentosa
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Effect•Gradual peripheral vision loss•Cataracts•Ultimate loss of central vision
Retinitis Pigmentosa
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Retinitis Pigmentosa
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Damage to the nerve fibers blocks signalsto the visual center of the brain•Glaucoma•Vascular occlusions•Multiple sclerosis
Optic Nerve Anomalies
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What•Optic nerve atrophy caused by intolerance
to intraocular pressure•Risk factors•Age•Family history•Race•Myopia
Glaucoma
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Glaucoma
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What•Cerebro-vascular events (strokes)•Traumatic Brain Injury (TBI)•Leads to infarct (damage) to brain tissue
that processes the information it gets fromthe eyes
Visual Cortex
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Effect•Minor events•TIA’s•Headaches•Resolving field loss
•Major events•Significant visual field loss•Cortical blindness•Diplopia
Visual Cortex
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Visual Cortex
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• The ability to distinguish between twoobjects in the visual field under varyinglevels of contrast
• Differs from visual acuity; Va assumeshigh contrast
• Affected by cataracts, AMD, small pupils• Even when the optics variables are
removed, there is still an age-relateddecline with age
Spatial Contrast Sensitivity
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Spatial Contrast Sensitivity
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• Difficulty seeing under low light conditions• Some linkage between low light and• Increased risk of falls• Increased risk of car crashes
• Older adults may need 2-3 times morecontrast than a younger observer
• This occurs even when optical factors arecontrolled
• Mechanism is unclear
Scotopic Contrast Sensitivity
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• Very early (1940’s) studies show decreasedlight sensitivity in older adults
• Lens and pupil miosis commonly associated• Recent decade of research suggests more
neural involvement• Rhodopsin (pigment) regeneration is
impaired• 70 YO may take 10 min longer to reach pre-
bleach threshold than 20 YO
Dark Adaptation
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• Slower visual processing speed increases risk ofMV crashes
• Spatial motion of targets is impaired with age
• Visual cortex processing is decreased with age
• Older adults have difficulty ignoring backgroundactivity to identify and react to a figure
• These processing changes affect many everydaytasks
Processing of Time-Varying Targets
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• Aging = slower VP speed
• Contributes to higher order cognitiveprocessing
• Independent of Alzheimer’s or dementia
• This slowing is not inevitable
Visual Processing Speed
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• Is Retraining Possible?
• Does any of this make a difference in thereal world?
Deep thoughts…
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Mostly dating back to the early days of aviationNot much scientific basis“Expert” opinion by Dr. W.H. WilmerKey elements:•Visual acuity•Stereopsis•Refractive error•Two-eyed vision
Newman, SA. Wiley Post and visual standards for pilots. Survey of Ophthalmology 2014
How did we getthe vision regulations we have?
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Visual acuity
Visual field
Binocularity and stereopsis
Contrast sensitivity
Color vision
What are the aspects of vision to beconsidered?
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Theoretically, it should be an indication ofthe ability to see detail
In reality, it measures the ability to see acertain sized letter at a specific distance
How does this translate into pilotperformance?
What are the critical distances for clearvision?
Visual Acuity
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Measures peripheral visionTesting consists of moving a light source of aparticular size and intensity from theperiphery to the center of visionThis can be automated or manually presentedGross tests can detect large defectsStatic vs. dynamic testingHow does visual field affect pilotperformance?
Visual Field
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How do the two eyes work together?Is the vision about the same in both eyes?Levels of binocularity•Simultaneous perception•Bi-ocular vision•Bin-ocular/stereopsisAt what distance does stereopsis have noimpact?How does this affect pilot performance?
Binocularity/Stereopsis
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The ability to detect the margins of one objectwith another
100% contrast is pure black and white
Our world is not 100%
All the standardized test present differentshades of gray
Is color contrast a factor?
How does contrast affect pilot performance?
Contrast Sensitivity
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Many pilot-critical tasks require good colorperception•Signal lights•Runway lights•Cockpit gauges and warning lights•Maps and charts
What does the FAA require?
What is the best way to test this?
Color Vision
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