Senescence of Vision:

1
Senescence of Vision What visual functions
decline with age? (VA, CS, Fields, CFF, Glare,
Color Vision) What are the causes of these
visual losses? Optics decreased transmittance,
increased scatter, increased aberrations, pupil
miosis, presbyopia. Neural reduced
photoreceptors and post-receptoral neurons,
reduced neural connectivity (e.g. due to reduced
neuro-transmitters).
There has been, and continue to be a rapid
expansion of the older population (over 84 group
has increased by 3,000 since 1900). Most older
Americans live independently and rely on vision
to maintain this independence.
2
Visual Acuity Declines with Age
Snellen Acuity
3
Neural contribution
There is only a small loss in CS for gratings
generated by laser interferometry (by-pass
optics) ? neural function in older visual systems
is not the main contributor to reduced visual
function. Thus, loss of cortical neurons and
photoreceptors has only a small impact on spatial
vision at high light levels.
Light sensitivity (not optically limited)
declines by 0.04 Log units per decade
photopically, and 0.08 log units per decade
scotopically (sensitivity drops by 50 after 37
years). Again, neural loss seems small, but
larger scotopically.
4
Increased Aberrations of older eyes
1.0
The optical MTF of the young eye is significantly
superior to the older eyes for same size pupils
4-mm pupil diameter
0.8
Young normal eye
Mean of 5 older subjects
0.6
MTF
0.4
0.2
0.0
30
40
0
20
10
Spatial Frequency (c/deg)
5
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6
But older eyes have smaller pupils, and
aberrations ? with pupil size
Young normal group (6.5 mm pupil)
Middle-aged group (5.5 mm pupil)
Old group (4.5 mm pupil)
The natural miosis seems to help counteract for
the increase in aberrations with age.
7
Optical Changes in Older Eyes
Decreased Elesticity Decreased transmittance Incre
ased Scatter Increased Aberration
Increased reflectance
Pupil miosis
The patient suffers from increased forward
scatter, but the clinician sees the increased
back scatter. Although related, knowing back
scatter does not determine forward scatter.
Old Eye
Young Eye
8
Disability Glare measured with Brightness
Acuity Tester (BAT), or the Berkeley Glare Test.
Reduced visual function while glare glare source
is on.
Brightness Acuity Tester
Berkeley Glare Tester
eye
A B C D
E F G H
A B C D E F G H I J K L M N O P
Glare Source
Bright Glare

Source
Patient view
A B C D
E F G H
9
Lenticular changes recorded in the art work of an
aging Monet
78 years
Developing cataract
58 years
OD
85 years old, with aphakic right eye (with
posterior capsule removed due to post surgical
opacification) Monet could see striking color
differences between his two eyes
OS
aphakic
phakic
10
High contrast, high luminance acuity is LEAST
affected by aging
11
Disability Glare increases dramatically in older
eyes. Notice that the median AND the variability
increase with age. Notice the bimodal
distribution of scatter in older eyes (those with
and those without clear plastic lenses).
Most significant impact of increased forward
scatter will be in night driving conditions
(light from oncoming headlights is scattered onto
the retina region that is imaging the road ahead,
and thus reducing contrast of road targets).
12
Glare recovery (photo-stress test) is
dramatically slowed in older eyes. Again, notice
the increased Variance.
Young trichromatic adults rarely make any erros
on the D-15 test, but older subjects start to
make a large number of errors.
Recovery of criterion VA can take 3 minutes
instead of lt10 seconds.
fail
pass
13
There is a significant reduction in CFF from 55
to below 35 in some older eyes, some of this is
likely due to reduced retinal illuminance
(remember the Ferry-Porter law)
Although the standard field of view for
supra-threshold stimuli remians quite large even
at very old ages, the attentional field (Useful
Filed of View or UFOV) decreases dramatically.
When a cognitively demanding foveal task is added
to the visual field test (e.g. count number of
times the fixation light turns off and on),
fields can drop to zero (e.g. 25 of 90 have
zero UFOV!!). UFOV was developed to examine the
real world visual fields, which are
particularly important for driving.
Standard VF
UFOV
Age (years)
60
70
80
90