Vision and Aging (sensory) Flashcards
Why does pupil size decrease as we age?
Due to greater IRIS DILATOR atrophy vs iris sphincter atrophy
NOTE: this causes an INC in Depth of Focus (refract in 0.50 to 1.00 steps bc won’t notice small steps)
NOTE: this also DEC retinal illumination (iris causes a slight decrease retinal illumination, but NOT as much as yellowing of the lens)
What happens when the lens increases in size as we age?
- INC in optical density from INC in axial dimension
- DEC retinal illuminance
- INC in density/size causes MYOPIC shift
- INC in size/stiffening contributes to onset of presbyopia
- Lens opacities INC light scatter & reduces contrast of retinal image
What aging changes occur to corneal clarity and sensitivity?
Clarity: INC peripheral haze as we grow that eventually moves centrally due to endothelial cell loss
Sensitivity: loss of sensitivity due to endothelial cell loss –> therefore GAT is easier
What happens to the index of the vitreous as we age?
It increases –> might be responsible for hyperopic shift?
NOTE: syneresis occurs as we age.
How does refractive error generally change between 40-70 years old?
Hyperopic shift!!!!!
Myopia DECREASES
How does refractive error generally change >70 years old?
Myopic shift (prob due to lens change)
What happens to astigmatism as we age?
It INCREASES
NOTE: corneal astigmatism stays constant with age HOWEVER, lenticular astigmatism INCREASES in ATR
Research shows what happens to EOM fibers with age?
They atrophy
Therefore, versions become slower
What happens to dark adaption with age?
Overall loss of dark adaptation sensitivity & slower rates of dark adaptation
NOTE: this is due to ROD PR LOSS & some rod outer segment enlargement. The rate is lower because rhodopsin regeneration is slower (may be related to INC thickness of Bruch’s membrane)
Light detection thresholds will not be as good due to what?
Reduced CONVERGENCE
But VA decrease due to INC convergence at the fovea
What happens with high contrast VA with age?
Does not fall off … it has a threshold that is MORE robust with age than other psychophysical properties
In low vision, greater than how many lines of difference btwn high and low contrast VA is a red flag for poor contrast?
2 lines
NOTE: after 70 contrast VA starts to get worse
Young people only take ~10 sec to recover from glare. How long does it take a 90 year old to do the same task?
1 minute
With cataracts removed what does the fundus appear to look like now?
Blue-ish hue
When does effective VF decrease for older pts?
Multi-tasking
NOTE: useful VF declines with age –> reduced speed of visual processing, reduced ability to divide attention, reduced salience of the target against its background