| Alien-looking word |
Oh, so that's what it
really means... |
| Accommodation |
1. Where you stay
2. A mechanism by which we can get clear sight for both distant
and close objects, by getting the image right on the retina. This
is achieved by the combined action of the extraocular
and ciliary muscles.
|
| Acuity |
A measure of how well you can see fine detail e.g. 20/20 means that
you see very well indeed. In tests of visual acuity, the lighting
and contrast of the font are optimised. Don't worry if you perform
poorly under dim light. |
| Astigmatism |
This one got me confused for a long time. It means that objects
along a certain axis are always blurred, regardless of the viewing
distance. Weird huh? Caused by a warping of the cornea, resulting
in distortion along that axis. |
| Ciliary muscle |
This is a muscle inside your eyeball which changes the shape of
the lens in order to accommodate. |
| Diopter |
A measure of how strong your lenses are, usually denoted by a number
and "D" e.g. 3.00D. |
| Emmetropia |
Perfect eyesight. Warning: if you are emmetropic, leave in 5 seconds
or this web site will explode. |
| Extraocular muscles |
6 external eye muscles that rotate the eyeballs in all directions
(so that you can look at a member of the opposite sex without turning
your head). Some say that they change the shape of the eyeballs in
order to to accommodate, but this old
theory of accommodation has been conclusively dismissed by many scientific
experiments. |
| Glasses |
Vessels from which you drink liquids. A popular kind are used to
contain wine. |
| Hyperopia |
A technical term meaning "long-sightedness". The anti-thesis of
myopia, you can only see far objects clearly. Traditional explanation:
The eyeball is too short. |
| Lenses |
There are two types of lenses, convex and concave. Convex lenses
(also called "minus lenses") diverge light rays while concave ("plus
lenses") converge light rays. These properties of the lenses mean
that they are used respectively for myopia and hyperopia. |
| Myopia |
Also known as "short-sightedness". Means that you can only see near
objects clearly. Don't take it figuratively: having myopia doesn't
mean you are obsessed with the present and can't plan ahead. That
is baloney! Traditional explanation: the eyeball is too long. |
| Presbyopia |
Commonly called "old-age sight". Occurs as a result of a hardening
of the crystalline lens. Often accompanied by stiffening of bones
and joints. |
