Sensory impairment

Question 1

Describe the visual process

Answer 1

Light enters the cornea and passes through the aqueous humor which supplies nutrients to the lens
Light continues through the lens
Both the cornea and lens focus light on the central fovea of the macula within the retina
In the retina, light is converted into chemical and electrical impulses a sent through the optic nerve
The retina and brain constitute the central nervous system
The brain then translates these impulses into “sight”

Question 2

Tear secretion in aging

Answer 2

Decreases with aging

Leads to eye irritation and discomfort

Can damage the cornea

Question 3

Describe extraocular changes with age

Answer 3

Eyelids lose elasticity

Entropion – muscles of the lower lid turn inward

Ectropion – lower lid turns outward

Goblet cells produce less mucin

Question 4

Describe age related changes to cornea and anterior chamber

Answer 4

Senile arcus – gray to silver ring at junction of cornea and iris composed of calcium and cholesterol salts. There is no clinical significance

Cornea surface becomes rough facing the anterior chamber and pigments collects causing decreased visual acuity

Anterior chamber becomes smaller due to thickening lens.
There are little canals at the edges of the chamber that control volume and movement of fluid in the anterior chamber.

Resorption of the fluid is less efficient and this leads to increased intraocular pressure

Question 5

Describe changes to lens and pupil

Answer 5

The lens becomes thicker, heavier and stiffer starting around 40.

Changes in color perception and glare becomes a problem

Pupil becomes smaller and less responsive to light.

Ciliary body muscle loses tone.

Question 6

Describe function of cones and rods in retina

Answer 6

Cones
stimulated by large amount of photons in bright light
color experience
concentrated in the fovea producing high visual acuity
Rods
extremely sensitive and can be stimulated by one photon
help in low light levels – cannot see color at low light
Cones and rods are distributed evenly throughout the rest of the retina

Question 7

Describe intraocular changes in photoreceptors with aging

Answer 7

Rods decline by 30% over a lifetime causing blurred vision in periphery

Cones remain stable

Retinal ganglion cell (RGC) bodies decrease over a lifetime

The axons of the RGC becomes vulnerable to due to light induced damage, oxidative stress, and metabolic stress

Optic nerve becomes thicker causing impaired exchange of nutrients and metabolites resulting in accumulation of proteins.