Vision: the eye Flashcards
Describe the physical nature of light
Electromagnetic radiation that travels in waves. Speed of light is 299,792,258m/sec
What is a photon?
A particle of light
What is amplitude, wavelength and frequency?
A - Intensity
W - distance between peaks
Frequency (Hz) - number of waves that pass a given point per second
What is the cornea?
Transparent outer coating at the front of the eye (principle means of focus)
What is the sclera?
White opaque outer coating
What is the pupil?
Circular hole in the centre of the iris through which light enters
What is the iris?
Visible through the cornea, coloured
What is the lens?
Transparent focusing element of the eye
What is the retina?
Array of photoreceptors and neural circuitry that covers the back surface of the eye
What is the fovea?
Part of the eye upon which the centre of an image falls
What is the optic nerve?
Bundle of nerve fibres that carry nerve impulses from the retina to the brain
Where is the anterior chamber?
Between the cornea and the iris
Where is the posterior chamber?
Between the iris and the lens
What do both the anterior and posterior chamber contain?
Aqueous
Where is the vitreous chamber?
Behind the lens
What does the vitreous chamber contain?
Vitreous
How does the lens focus on the stimuli?
Lens changes shape to adjust the focus (Accomodation)
What is photo transduction?
Light is detected in the retinal image and is transformed from light energy to electrochemical energy
What are the 2 types of photoreceptors in the retina?
Rods and cones
What are rods?
Responsible for vision at low levels of light, very sensitive to darkness. Have a coarse spatial structure - 120 million located in the peripheral retina
What are cones?
Responsible for vision in bright light and in colour. FIne details - 6 million located in the fovea and the peripheral retina
What is the blind spot?
Point on the retina where the optic nerve leads to the brain so there are no photoreceptors
What is the pathway to the optic nerve?
Light - cornea - pupil - lens - retina - optic nerve