Vision and Aging Flashcards
what are the changes in the cornea due to aging
- changes shape (usually increase in against the rule astig)
- losses in clarity (resulting in increased scatter)
how does the pupil change with age
diameter decreases w/ age => senile miosis
-decreased pupil diamter means reduced retinal illuminance (T=AxL)
Trolands=pupil area x luminance (cd/m^2)
by the age of 80 how large is the pupil
2-3mm
what are teh advantages of senile miosis
- reduced aberrations (less peripheral aberratoins)
- increased depth of focus
these 2 advantages help maintian object sharpenss
what are the changes in the lens
- optical density increases
2. thickness and rigidity increases
whatundrgoes the most significant age-related changes
lens
the increase in lens optical density results in what?
-for what kind of wavelenth
reduced retinal illumination
for short wavelength lights
the increase in lens size and it becoming harder leads to waht
presby
the retinal illuminace at age 60 is 1/3 of the ret ill at the age of 20 bc of
what does this affect
increased opitcal density of lens and senile miosis
-reduction affects contrast sensitivity, VA, dark adaptation etc
what happens to the vit
collagen fibers of vit deteriroate
=>floaters
floaters increase what
waht does this result in
intra-ocular glare
results in contrast decrease
what happens to the retina
reduction in # of rods and cones
rod count decreases faster than cone count
-photopigment density decreases as well
-photoreceptor transduction decreases
-RPE reduces in number => less melanin molec, incrased intraocular glare => phagocytosis compromised
by the age of 60 there is a ___% dcrease in ganglion cells
30%
the decrease in thickness of layer 1 in V1 suggests waht
neuronal loss at the primary visual cortex
do the elderly experience more diffiuclty dark or light adaptation
dark adaptation: in a dark adapatation curve the rate of dark adapatation decreaes and the abs threshold increases w/ age
what may the cone and rod threshold increase be due to
cone and rod loss throughout adulthood
the slower rate of dark adaptation might be due to..
the slowing of rhodopsin regeneration in aging retina
-in turn this might be due to the aging RPE and the thickening of bruch’s
if senile miosis and less aborption are not taken into consideration in such experiemets, why might they produce similar effects on thresholds
due to reduced retinal ill
by the age of 80, VA is
~20/40
-~1 line per decade after age 60
what makes it difficult to correlate the decrease in VA in decrased cone dnsity
the large inter-observer variability in foveal cone density w/ comparable VA
what makes it difficult to connect the decrease in VA in decreased cone density
the large inter-observer variability in foveal cone desnity
a change in contrast sensitivity function should be expected bc….
VA is a data point on the CSF
the peak sensitivity shifts to lower spatial frequ of what
~4c/deg to ~2c/deg
-reduction in contrast sensitivity for int and high spatial frequ
the loss in high spatial frq can be attricuted to…
optical factors (reduced retinal ill and scattering) and neural factors -an impairment in the parvocellular pathway is most likely the neural cause of decreased contrast sens
why can we not predict the sensitivity at low spatial freq when we know VA
little correlation btwn sensitivities on high and low spatial freq
why do events that appear as separate to young observers might not be perceived as separate for older
-reduction in CFF
reduced retinal illuminace
ferry-porter law
CFF is a data point in the ____ and therefore a reduction in temporal sensitivity is expected
temporal modulation transfer function (TMTF)
temporal sensitivity is reduced at ___ and ____ temporal freq
high and intermeidate
the range of affected temporal freq points towards a deficit in…
magnocellular pathway
what did ball and sekuler use to study motion perception in the elderly
random dot kinetograms
what did ball and sekuler find
older observers were less accurate on judging the direction of motion (3-fold diff)
-motion perception deficit cant be explained by optical factors but it must rather hav e neural basis
