The Eye
Different parts of the eye are responsible for different things. The
sclera is the tough, white outer layer of the eye and it protects
the eye. When the sclera wraps around the front it becomes
transparent and is called the cornea. The cornea is transparent to
allow light in and is also important for changing direction of light
rays coming into the eye to make sure they are focused on the
retina. The optic disc is the area where the optic nerve leaves the
eye and a blind spot.
Accommodation of the eye
To focus on far away objects the ciliary muscles relax and the suspensory ligaments are
pulled tight. This makes the lens flat and thin. This means the lens only slightly refracts the
light, so it is focused on the retina. When focusing on closer objects, the ciliary muscles
contract, which means the suspensory ligaments slacken. This leads to the lens becoming
shorter and thicker which means the lens refracts the light a lot more, so it is focused on the
retina.
In bright light, the circular muscles contract and the radial muscles relax (they are an
antagonistic pair) and this causes the pupil to constrict. The pupil does this to allow less light
in to protect the rods and cones. In dim light, the circular muscles relax and the radial
muscles contract. This causes the pupil to dilate, and it does this to try and get more light in.
Myopia and Hyperopia
Myopia means a person can see close objects clearly, however distant objects are blurred.
Light is focused in front of the retina, so the images that land on the retina are blurry and
out of focus. This could be caused by a particularly long eyeball or an overly curved lens. The
most common way of treating myopia is by wearing glasses with a concave lens which
spreads out the light from distant objects before it reaches the eye. This means the thicker
lens can bring it into perfect focus on the retina.
Hyperopia is when a person can see distant objects clearly, however close objects appear
blurry. This could be caused by a short eyeball or an overly flat or thin lens. As a result, the
lens cannot refract the rays of light strongly enough which leads to the light being focused
behind the retina so the image that lands on the retina is blurry or out of focus. A way to fix
this is to wear glasses with a convex lens. This brings the light rays together before they
reach the eye which means the thinner lens can now focus them exactly on the retina to
give a clear image.
Technology in treatments for the eye
The development of technology in recent years has led to several treatments for problems
with the eye:
Different parts of the eye are responsible for different things. The
sclera is the tough, white outer layer of the eye and it protects
the eye. When the sclera wraps around the front it becomes
transparent and is called the cornea. The cornea is transparent to
allow light in and is also important for changing direction of light
rays coming into the eye to make sure they are focused on the
retina. The optic disc is the area where the optic nerve leaves the
eye and a blind spot.
Accommodation of the eye
To focus on far away objects the ciliary muscles relax and the suspensory ligaments are
pulled tight. This makes the lens flat and thin. This means the lens only slightly refracts the
light, so it is focused on the retina. When focusing on closer objects, the ciliary muscles
contract, which means the suspensory ligaments slacken. This leads to the lens becoming
shorter and thicker which means the lens refracts the light a lot more, so it is focused on the
retina.
In bright light, the circular muscles contract and the radial muscles relax (they are an
antagonistic pair) and this causes the pupil to constrict. The pupil does this to allow less light
in to protect the rods and cones. In dim light, the circular muscles relax and the radial
muscles contract. This causes the pupil to dilate, and it does this to try and get more light in.
Myopia and Hyperopia
Myopia means a person can see close objects clearly, however distant objects are blurred.
Light is focused in front of the retina, so the images that land on the retina are blurry and
out of focus. This could be caused by a particularly long eyeball or an overly curved lens. The
most common way of treating myopia is by wearing glasses with a concave lens which
spreads out the light from distant objects before it reaches the eye. This means the thicker
lens can bring it into perfect focus on the retina.
Hyperopia is when a person can see distant objects clearly, however close objects appear
blurry. This could be caused by a short eyeball or an overly flat or thin lens. As a result, the
lens cannot refract the rays of light strongly enough which leads to the light being focused
behind the retina so the image that lands on the retina is blurry or out of focus. A way to fix
this is to wear glasses with a convex lens. This brings the light rays together before they
reach the eye which means the thinner lens can now focus them exactly on the retina to
give a clear image.
Technology in treatments for the eye
The development of technology in recent years has led to several treatments for problems
with the eye:
