Adulthood Aging: Normal Effects on Visual Function Goal: Understanding of the normal degradation of numerous visual functions, including the underlying sensory processes, that gradually occur during adulthood. This understanding is necessary for proper clinical examination, diagnosis of age-normal versus pathological change, and patient counseling. Schwartz pages 372 – 378 Optical, neurophysiological and psychological changes combine to detrimentally effect monocular sensory processes. EW8250F07
Transcript
Adulthood Aging: Normal Effects on Visual Function
Goal: Understanding of the normal degradation of numerous visual functions, including the underlying sensory processes, that gradually occur during adulthood. This understanding is necessary for proper clinical examination, diagnosis of age-normal versus pathological change, and patient counseling.
Schwartz pages 372 – 378
Optical, neurophysiological and psychological changes combine to detrimentally effect monocular sensory processes.
Adulthood Aging: Normal Effects on Visual Function
Goal: Understanding of the normal degradation of numerous visual functions, including the underlying sensory processes, that gradually occur during adulthood. This understanding is necessary for proper clinical examination, diagnosis of age-normal versus pathological change, and patient counseling.
Schwartz pages 372 – 378
Optical, neurophysiological and psychological changes combine to detrimentally effect monocular sensory processes.
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Adulthood Aging
There has been understandably less focus on normal aging changes in visual function and enormous focus on eye diseases typically seen in older adults.
Nonetheless, the vision changes produced by the former are often similar, albeit smaller, thus accurate diagnosis requires a working knowledge of these changes.
Age ≥ 85: fastest growing segment of the US population.
Adulthood Aging
There has been understandably less focus on normal aging changes in visual function and enormous focus on eye diseases typically seen in older adults.
Nonetheless, the vision changes produced by the former are often similar, albeit smaller, thus accurate diagnosis requires a working knowledge of these changes.
Age ≥ 85: fastest growing segment of the US population.
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Adulthood Aging: Normal Effects on Visual Function
List of Topics
Optical Changes Pupil, cornea, lens, vitreous
Neurophysiological Changes Retina, cortex
Psychological Changes Criterion
Affected Sensory Processes Dark adaptation, acuity, acuity photostress
Large data spread but does show a decrease in pupil size with age. As expected, the decrease is larger(steeper slope) for very dim lighting.
Very dim lighting, ~3 mm change.
Very bright lighting, ~1 mm change.
Clinical ImplicationsTests and refraction in dim lighting.Advising regarding optimal lighting.Expect a fixed 3–4 mm pupil by ~80.Also pupil reaction speed decreases.
Both iris sphincter and dilator muscles weaken.Increased inhibitory input to EW nucleus (parasympathetic).In total results in miosis and slower constriction and
dilation.Produces symptoms of vision being ‘less bright’, initial
‘dazzle’ to outdoor light and difficult transitioning from light to dark areas.
Both iris sphincter and dilator muscles weaken.Increased inhibitory input to EW nucleus (parasympathetic).In total results in miosis and slower constriction and
dilation.Produces symptoms of vision being ‘less bright’, initial
‘dazzle’ to outdoor light and difficult transitioning from light to dark areas.
Two Benefits:
Reduced pupil-dependent aberrations. Not equal to the detrimental effectsfrom reduced retinal illumination, lens-induced increases in lightscatter, absorption and aberrations, and both retina and cortex aging.
Increased depth of field.Results in less dependence on glasses during high illumination conditions.
Detriment: Reduces retinal illumination thus also VA, CSF, etc.Average pupil size: age 20 = ~5 mm, age 60 = ~3 mm.Retinal Illuminance = Luminance (pupil area) = L(r2).As 2.52 = 6, and 1.52 = 2, retinal illuminance reduces by a factor
of 3.20-year old experiences age 60 trolands via ND 0.48 filter
(log(1/.33)).
Ref-2 Ref-2
}10x factor
3xfactor(~2 lines)
~10 & ~30 trolands
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Adulthood Aging: Decreased Transmittance (T)
Normal sclerosis, largely from UV light absorption, results in
further UV absorption, a yellow appearance, decreased colorperception and decreased retinal illuminance.
Adulthood Aging: Decreased Transmittance (T)
Normal sclerosis, largely from UV light absorption, results in
further UV absorption, a yellow appearance, decreased colorperception and decreased retinal illuminance.
Ref-1
Reduced T beginsat age ~20 (adult).
Visible wavelengths are all absorbed.
Ultraviolet light is maximally absorbed by age ~45 whereasshort visible (blue) wavelengths aresimilarly absorbedby age ~70.
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Adulthood Aging: Decreased Transmittance (T)
Nuclear sclerosis is at most a pre-cursor to nuclear cataract.
Clinical learning involves the lens appearance for cataract diagnosis.
Loss of corneal clarity (small effect) & vitreous debris can decrease T.
Nuclear sclerosis is also shown by changes in index and surface radii:
Adulthood Aging: Decreased Transmittance (T)
Nuclear sclerosis is at most a pre-cursor to nuclear cataract.
Clinical learning involves the lens appearance for cataract diagnosis.
Loss of corneal clarity (small effect) & vitreous debris can decrease T.
Nuclear sclerosis is also shown by changes in index and surface radii:
Ref-1 Large changes by age 40. Anterior radius steepens.Posterior radius steepens.Thus thickness increases.Thus AC depth decreases.Refractive index decreases.Optical density increases.Total lens power decreases.
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Adulthood Aging: Retinal Changes (Physical)
Gradual loss of photoreceptors; rod loss >> cone loss.
Reduced density of foveal cones.
Reduced density of photopigment.
Misalignment or improper orientation of cone outer segment.(Though not shown psychophysically by SCE-I.)
Decrease in membrane resting potential (net hyperpolarized).Could lead to decreased photoreceptor response amplitudes.
Decrease in neurotransmitter levels.
Small but gradual loss of ganglion cells.
Reduced mfERG: optical factors if < age 70 but neural if > age 70
(cone and bipolar cells contribution)
Adulthood Aging: Retinal Changes (Physical)
Gradual loss of photoreceptors; rod loss >> cone loss.
Reduced density of foveal cones.
Reduced density of photopigment.
Misalignment or improper orientation of cone outer segment.(Though not shown psychophysically by SCE-I.)
Decrease in membrane resting potential (net hyperpolarized).Could lead to decreased photoreceptor response amplitudes.
Decrease in neurotransmitter levels.
Small but gradual loss of ganglion cells.
Reduced mfERG: optical factors if < age 70 but neural if > age 70
(cone and bipolar cells contribution)
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Adulthood Aging: Central Changes
Similar to physical changes in the retina…
Small but gradual loss of neurons.
Decrease in neurotransmitter levels, excitatory > inhibitory.
Decrease in amount and weighting of binocular connections.
Decrease in neuron tuning with associated increase in noise.
LGN cell function is unchanged based on monkey physiology. Thus suggesting cortex as the site of major neural changes.
Adulthood Aging: Central Changes
Similar to physical changes in the retina…
Small but gradual loss of neurons.
Decrease in neurotransmitter levels, excitatory > inhibitory.
Decrease in amount and weighting of binocular connections.
Decrease in neuron tuning with associated increase in noise.
LGN cell function is unchanged based on monkey physiology. Thus suggesting cortex as the site of major neural changes.
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Adulthood Aging: Reduced Modulation Transfer Function (MTF)Adulthood Aging: Reduced Modulation Transfer Function (MTF)
Ref-1
Image Contrast
Object Contrast
Reflects optical andneural contributions.
Reduced transfer ofobject contrast forall spatial frequencies.
Higher (worse) absolute threshold: photoreceptor loss (rods > cones).
Slower rate of adaptation: reduced rate of rhodopsin regeneration.
Both of the above: optical changes, e.g. miosis, lens changes.
Adulthood Aging: Reduced Dark Adaptation
Mechanisms underlying upward shift of function:
Higher (worse) absolute threshold: photoreceptor loss (rods > cones).
Slower rate of adaptation: reduced rate of rhodopsin regeneration.
Both of the above: optical changes, e.g. miosis, lens changes.
Ref-2
Aged adults have more difficulty adapting to dark conditions than to light conditions.
Elevated thresholdsthroughout function
Maximum elevation:Cone portion 1 log unit Rod portion 2+ log unit
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Adulthood Aging: Reduced Visual Acuity
Normal acuity is maintained until age 65 – 70, then declines.From age 65 the link between VA and pathology is more
difficult.
Adulthood Aging: Reduced Visual Acuity
Normal acuity is maintained until age 65 – 70, then declines.From age 65 the link between VA and pathology is more
difficult.
Ref-2
20/16
20/20
20/25
20/32
20/40
20/50
20/20, age ~65
20/25, age ~70
20/32, age ~75
Other studiesfind less loss:~1 line/decade.
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Adulthood Aging: Reduced Visual Acuity
VA is a threshold measure so all optical and neural factors contribute.
Reflected in effects of both reduced illumination and letter contrast:
Marked VA reduction before age 65 – 70 that continues proportionally.
Adulthood Aging: Reduced Visual Acuity
VA is a threshold measure so all optical and neural factors contribute.
Reflected in effects of both reduced illumination and letter contrast:
Marked VA reduction before age 65 – 70 that continues proportionally.
Ref-3
Ref-2
High Contrast and Luminance
High Contrast, Low Luminance
Low Contrast and Luminance
Slightly unequal age onset and rateof decline.
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Adulthood Aging: Reduced Visual Acuity
VA test conditions / reason that older adults are very sensitive to:
Luminance level / retinal illuminanceLetter contrast / CSFLetter spacing / crowdingCriterion / conservativeNumber of letters per size / guessingIncrement size of letters / if subnormal VA
Improper testing often results in false VA loss in older adults.
LogMar chart resolves some of these conditions.
Adulthood Aging: Reduced Visual Acuity
VA test conditions / reason that older adults are very sensitive to:
Luminance level / retinal illuminanceLetter contrast / CSFLetter spacing / crowdingCriterion / conservativeNumber of letters per size / guessingIncrement size of letters / if subnormal VA
Improper testing often results in false VA loss in older adults.
LogMar chart resolves some of these conditions.
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Adulthood Aging: Reduced Photostress Recovery Time
Procedure: exposure to bright, diffuse light then wait for best VA.Results: age ≥ 60 shows non-linear increase in recovery time.Results: ~ 13–90 second recoveries; glare response to 20/200.
Adulthood Aging: Reduced Photostress Recovery Time
Procedure: exposure to bright, diffuse light then wait for best VA.Results: age ≥ 60 shows non-linear increase in recovery time.Results: ~ 13–90 second recoveries; glare response to 20/200.
Ref-3
MechanismReduced letter contrast due to increased light scatter from miosisand lens changes.
Adulthood changes do not result in the CSF of youth.Normal CSF, age 18–39.
Youth CSF, age 8–15.reduced at all but highspatial frequencies.
Adulthood CSF, age 45–66.Expect with further aging:Continued reduction of intermediate and high sf,and preservation of low sf.
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Adulthood Aging: Reduced Spatial CSF
Selected sensitivity loss suggests parvocellular > magnocellular loss.Also because this loss occurs under photopic and mesopic conditions.
(Early age loss: increased aberrations & decreased retinal illuminance.)
Adulthood Aging: Reduced Spatial CSF
Selected sensitivity loss suggests parvocellular > magnocellular loss.Also because this loss occurs under photopic and mesopic conditions.
(Early age loss: increased aberrations & decreased retinal illuminance.)
Ref-2
Ref-7
Parvocellularcomponent
Magnocellular component
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Adulthood Aging: Reduced Temporal CSF
Shown for all temporal frequencies.
Also, reduced high temporal frequency cut-off (CFF).
Thus likely involves parvocellular and magnocellular neurons…
With a contribution from decreased retinal illuminance.
Adulthood Aging: Reduced Temporal CSF
Shown for all temporal frequencies.
Also, reduced high temporal frequency cut-off (CFF).
Thus likely involves parvocellular and magnocellular neurons…
With a contribution from decreased retinal illuminance.
Ref-7
Entire function shiftsdown and in.
Parvo = filled symbolsMagno = open symbols
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Adulthood Aging: Reduced Color Discrimination
Shift towards blue-yellow (tritan) deficit.Primarily due to increased absorption by the lens.Secondary contribution from decreased retinal illumination.Secondary contribution from UV light induced retina damage.Minimal contribution from cone loss or photopigment change.
Adulthood Aging: Reduced Color Discrimination
Shift towards blue-yellow (tritan) deficit.Primarily due to increased absorption by the lens.Secondary contribution from decreased retinal illumination.Secondary contribution from UV light induced retina damage.Minimal contribution from cone loss or photopigment change.
Ref-3
D-15 failure Is very high from age 65.
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Adulthood Aging: Reduced Color SensitivityAdulthood Aging: Reduced Color Sensitivity
Ref-5
Blue and violet lightshow the greatest rateof reduced sensitivity(> 2 log unit change).40%–50% of reductionis due to lens sclerosis.Remaining reductiondue to retinal change:damage > cone loss.
Red and white lightshow ~ equal ratesof reduced sensitivity(~ 0.5 log unit change).
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Adulthood Aging: Reduced Limits of Visual Field (VF)
VF continually decreases at 1–3 degrees per decade.
This rate is only slightly increased by adulthood aging.
Example:Widest horizontal VF extent: 170–180 degrees.Horizontal extent could reduce at age ≥ 70 to 130–140
degrees.
Mechanism is both optical (degraded retinal image) and neural.
MechanismDecreased elasticity of thecrystalline lens capsule >>reduced ciliary body andzonular fibers function.
Push Up MethodContaminated by angularmagnification, depth of field, and subjective response.
Stigmatoscopy MethodNot affected by depth of field. Other two factors remain.Uses a point source conjugate to the retina to measureaccommodative change for aseparate accommodation target.
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Adulthood Aging: Reduced Motion Detection and Discrimination
Increase in the minimum displacement to detect coherent motion (Dmin).
Decrease in the accuracy of discriminating direction of coherent motion.
Loss of direction discrimination is worse than that for motion detection.
Supported by macaque physiology showing age-related reduction in directional tuning by V1 neurons.
Adulthood Aging: Reduced Motion Detection and Discrimination
Increase in the minimum displacement to detect coherent motion (Dmin).
Decrease in the accuracy of discriminating direction of coherent motion.
Loss of direction discrimination is worse than that for motion detection.
Supported by macaque physiology showing age-related reduction in directional tuning by V1 neurons.
Ref-3
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Adulthood Aging: Reduced Motion Detection and Discrimination
Mechanism is neural as both psychophysical and physiological studies used stimuli greatly above threshold (contrast & spatial frequency).
Likely involvement of area MT or even higher-order motion areas.
Adulthood Aging: Stiles Crawford Effect of the First Kind (SCE-I)
Remains constant.
Original study participants repeated at age 60s: no changes.
Would change in response to pathology affecting pupil position.
Apparently does not change in response to age-related aberrations.
Adulthood Aging: Stiles Crawford Effect of the First Kind (SCE-I)
Remains constant.
Original study participants repeated at age 60s: no changes.
Would change in response to pathology affecting pupil position.
Apparently does not change in response to age-related aberrations.
Ref-3
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Adulthood Aging: Reduced Stereoacuity
Stereoacuity is the highest level of depth perception.It is a binocular rather than monocular process…But it requires optimal VA, cortical processing and eye
alignment.
Adulthood Aging: Reduced Stereoacuity
Stereoacuity is the highest level of depth perception.It is a binocular rather than monocular process…But it requires optimal VA, cortical processing and eye
alignment.
Ref-3
85 arc sec criteria is not strict.
Reduction beginsat age ~50.That is, prior to normal reductionof visual acuity.Thus hinting atother mechanisms.
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Adulthood Aging: Normal Effects on Visual Function
Patient counseling regarding avoidance of disability glare.
Patient counseling regarding upcoming changes in vision.
Variable aging rates and the continuum of age-normal to pathology found for many conditions (e.g. cataract & macular degeneration) often make diagnosis rather arbitrary. Clinical experience develops consistency in accurate diagnoses.
Adulthood Aging: Clinical Relevance
Acknowledging that people age at different rates, expecteds enable…
Proper examination methods, including lighting, and sequence.
Proper diagnosis of age-normal or early pathologic conditions.
Patient counseling regarding avoidance of disability glare.
Patient counseling regarding upcoming changes in vision.
Variable aging rates and the continuum of age-normal to pathology found for many conditions (e.g. cataract & macular degeneration) often make diagnosis rather arbitrary. Clinical experience develops consistency in accurate diagnoses.
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Adulthood Aging: References
1. Atchison, D., & Smith, G. (2000). Optics of the human eye. Butterworth-Heinemann, Oxford.
2. Norton, T., Corliss, D., & Bailey, J., Eds. (2002). The psychophysical measurement of visual function. Butterworth-Heinemann, MA.
3. Schwartz, S. (2004). Visual perception: a clinical orientation. 3rd Ed. McGraw-Hill Companies, Inc., NY.
4. Chalupa, L., & Werner, J., Eds. (2004). The visual neurosciences. MIT Press, MA.
5. Rosenbloom, A., & Morgan, M., Eds. (1993). Vision and aging. 2nd Ed. Butterworth-Heinemann, MA.
6. Gescheider, G. (1997). Psychophysics: The Fundamentals. 3rd Ed. Lawrence Erlbaum Associates, Inc., NJ.
7. Wandell, B. (1995). Foundations of vision. Sinauer Associates, MA.
8. Grosvner, T. (2006). The aging eye: problems that affect acuity and contrast sensitivity. Pacific University College of Optometry, http://www.opt.pacificu.edu/ce/catalog/165554-GO/AgeAcuity.html.
9. Bruce, V., Green, P., & Georgeson, M. (2003). Visual perception: physiology, psychology and ecology. 4th Ed. Psychology Press, NY.
Adulthood Aging: References
1. Atchison, D., & Smith, G. (2000). Optics of the human eye. Butterworth-Heinemann, Oxford.
2. Norton, T., Corliss, D., & Bailey, J., Eds. (2002). The psychophysical measurement of visual function. Butterworth-Heinemann, MA.
3. Schwartz, S. (2004). Visual perception: a clinical orientation. 3rd Ed. McGraw-Hill Companies, Inc., NY.
4. Chalupa, L., & Werner, J., Eds. (2004). The visual neurosciences. MIT Press, MA.
5. Rosenbloom, A., & Morgan, M., Eds. (1993). Vision and aging. 2nd Ed. Butterworth-Heinemann, MA.
6. Gescheider, G. (1997). Psychophysics: The Fundamentals. 3rd Ed. Lawrence Erlbaum Associates, Inc., NJ.
7. Wandell, B. (1995). Foundations of vision. Sinauer Associates, MA.
8. Grosvner, T. (2006). The aging eye: problems that affect acuity and contrast sensitivity. Pacific University College of Optometry, http://www.opt.pacificu.edu/ce/catalog/165554-GO/AgeAcuity.html.
9. Bruce, V., Green, P., & Georgeson, M. (2003). Visual perception: physiology, psychology and ecology. 4th Ed. Psychology Press, NY.Adulthood Aging sample final exam questions: 2006 Final & NBEO ‘07 Review (EW).Adulthood Aging sample final exam questions: 2006 Final & NBEO ‘07 Review (EW).
