Lecture 6 - Vision I Flashcards
What is refraction?
What affects the degree of refraction?
L6 S4 LO1
Bending of light waves when passing from one medium to another via an angulated surface.
The ratio of the refractive index’s of the different substances determines degree of refraction.
What is refractive index?
L6 S6 LO1
Ratio of the velocity of light in air and another substance.
What is refractive power?
L6 L6 LO1
Measure of how much a lens bends light waves.
What is a diopter?
L6 S6 LO1
Measure of refractive power.
1 diopter = 1m / focal length
What is focal point?
L6 S8 LO1
Point through which all parallel rays of light pass through after going through a lens.
What is the function of the iris?
L6 S13 LO1
Controls the amount of light enters the eye to adjust for brightness of the environment.
Relate emmetropia, hyperopia, and myopia.
L6 S16-17;18 LO1
Emmetropia:
- normal depth of focus
- parallel light rays converge on the retina
- all objects seen clearly
Hyperopia:
- farsightedness; distant objects seen clearly
- parallel light rays converge behind retina
- eye is too short or lens too weak
Myopia:
- nearsightedness
- parallel light rays converge in front of retina
- eye is too long or ciliary muscles are completely relaxed
What is focal length?
L6 S8 LO1
The distance from the center of a lens to the focal point.
What is the maximum visual acuity of the eye to detect two-point sources of light?
L6 S20 LO1
1.5-2 μm
This is related to the average diameter of a cone cell which is 1.5 μm.
How is aqueous humor formed?
Describe the flow of aqueous humor through the eye.
L6 S22 LO1
Formed by the ciliary process. Sodium ions are actively secreted and accompanied by chloride and bicarbonate ions. These ions draw water into the space.
Formation occurs in the posterior chamber and then flows into the anterior chamber. It then flows out through the canal of Schlemm.
What are the different photosensitive pigments of the eye?
L6 S26 LO2
Rods:
-rhodopsin
Cones:
-the different types of options
What are the component molecules of Rhodopsin?
What is rhodopsin broken down into when exposed to light?
How long does it take for rhodopsin to be regenerated?
Rhodopsin = scotopsin + 11-cis retinal
Rhodopsin + light = scotopsin + all-trans retinal
It takes minutes to regenerate rhodopsin.
How does ion flow change when rhodopsin is exposed to light?
L6 S30-31 LO2
Retinal portion of rhodopsin is activated by the decomposition of rhodopsin. This activates a G-protein called transducin which stimulate conversion of cGMP into 5’GMP.
Reduction of cGMP closes sodium channels and the photoreceptor becomes polarized.
