Glossary
A
B
C
D
E
F
G
H
I
J
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M
N
O
P
Q
R
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A
- accommodation
- the changing of lens curvature to focus images onto retina
- action potential
- nerve impulse; transmission of a temporary voltage change down a nerve fibre
- adaptation
- the ability of the eye to respond to new environmental light conditions
- aqueous humour
- a clear fluid in the space between the cornea and the lens
B
- Bates, William
- an opthalmologist who disagreed on the use of eyeglasses and preferred patients to do eye exercises to improve vision
- bleaching
- a process during which retinene splits from opsin when light strikes on photopigments
C
- camera eyes
- eyes in structural similarity to a camera, able to control light entry into eye, with lens to refract light... e.g. human eyes
- cataract
- a disease in which the eye lens turns cloudy and vision is blurred
- choroid
- a pigmented tissue with a blood vessels network; part of the vascular coat between the sclera and retina
- ciliary body
- a thickening of the anterior part of the vascular coat; contains muscles which can change the thickness of lens in accommodation
- compound eye
- the eye of an insect; made up of units of ommatidium, each pointing in a slightly different direction to form a mosaic image. (see ommatidium)
- cone
- a cone-shaped light sensitive pigment containing iodopsin present in retina
- conjunctiva
- a membrane covering the cornea and lining the inner side of the eyelids; usually transparent
- cornea
- the transparent anterior part of the outermost fibrous coat; refracts light into the eye
D
- diabetic retinopathy
- a complication of diabetes which causes damage to the retina
- dioptric media
- the structures through which light refracts to reach the retina
- dry eye
- an eye disease in which not enough tears is produced
E
- extrinsic / extraocular muscles
- the six muscles external to the eye, mainly for moving the eye to different directions
F
G
- glaucoma
- an eye disease in which the internal pressure in the eye is too high and vision is impaired
H
- hyperopia
- far-sightedness; a visual defect in which the eye's refractive power is not enough; images are formed behind the retina so they appeared blurred.
I
- illusions
- the situation when what our senses perceive is different from the actual reality
- iodopsin
- the photopigment in cones responsible for colour vision, with higher threshold intensity than rhodopsin
- iris
- a circular, coloured piece of membrane; contains muscles which regulate the size of an opening called the pupil
J
K
L
- lacrimal system
- a system of glands and ducts, to produce and drain away tears
- lens
- a transparent, biconvex and elastic body situated behind the iris, involved in focusing
M
- myopia
- near-sightedness; a visual defect in which the eye's refractive power is too great; images are formed in front of the retina so they appeared blurred.
N
O
- ocellus
- a "simple eye" in an insect
- ommatidium
- a light sensitive unit of a compound eye in an insect, with the cuticle and a crystalline cone acting as lens
P
- pupil
- an opening in the iris for light to pass into the eye
- pupillary reflex
- an involuntary response of iris muscles to change the pupil size for regulating the amount of light entry into the eye
Q
R
- retina
- the innermost tunic in the wall of the eyeball, multilayered and contains light sensitive cells and nerve fibres
- retinal detachment
- an eye disease in which the retina separates from the back of the eye
- rhodopsin
- the photopigment in rods which has low threshold intensity, useful for detecting dim light
- rod
- a rod-shaped light sensitive cell containing rhodopsin present in retina
S
- sclera
- the tough, opague tissue which made up a large proportion of the outermost fibrous coat; mainly for protection of the eye and anchorage of muscles
- stereoscopic vision
- the ability of the eye to see objects as three-dimensional
- strabismus
- an eye disease in which only one eye is focused and the other is misaligned
- stigma
- the light sensitive eyespot in Euglena
T
- threshold intensity
- the minimum intensity level and duration of a stimuli needed to evoke a response
- Trichromatic theory
- a suggested theory of how the three types of cones can help differentiate colours
- tunic
- one of the three layers in the wall of the eyeball
U
- uvea
- the other name for 'vascular coat' --- choroid, ciliary body, iris
- uveitis
- the inflammation of the uvea
V
- vitreous body
- a transparent, gel-like body behind the lens and in front of the retina; helps maintain shape of the eye
W
X
Y
Z
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