Common Vision Defects
THE EMMETROPIC EYE-ALL DISTANCES
The picture shows what is
known as an "emmetropic" eye, i.e. it has sharply focused vision at
With the aid of its
crystalline lens, the eye can adapt to all distances in much the same way as a
zoom camera lens. This process is known as accommodation.
Myopia or shortsightedness is a condition where the eye is too long in relation to its refractive power. The light rays therefore intersect in front of the retina instead of on it. Blurred vision results. The further away the object observed, the more blurred it appears. Clear vision is limited to nearby objects. Shortsighted therefore means having good near vision but poor distance vision.
appropriate eyeglass lens, a myopic eye can once again enjoy clear vision at all
distances. As you see here, the light rays are slightly diverged in front of the
eye, shifting their point of intersection to the surface of the retina. This
creates the same conditions as those enjoyed by emmetropic eyes, providing the
wearer with excellent vision.
appropriate lens, a hyperopic eye can see clearly again at all distances without
strain. As you see, the light rays are converged in front of the eye, shifting
their point of intersection to the surface of the retina. Accommodation can once
again be used solely for adjusting to different distances.
Astigmatism is a condition where there is a variation in the shape of the cornea. Rays of light pass through the cornea on two planes - vertical and horizontal. In the astigmatic eye one corneal plane is steeper than the other, so that the rays of light do not come together at the same point. One point can be in front of the retina, the other behind. Both can be in front of the retina, etc.
The more unequal the curvature
of the cornea, the more blurred your vision will be.
THE PRESBYOPIC EYE-READING DISTANCE
If you are over 40
and finding it difficult to read because your eyes can no longer focus at short
distances, you may have a condition known as presbyopia.
Sometimes our eyes can feel tired. We may have unexplained headaches and even feel generally fatigued especially following certain visual tasks such as computer use or driving . This can be attributed to our eye muscles not being perfectly balanced in strength between the left and right eyes. Our oculomotor balance tests will measure your muscle 'balance' to ensure your eye are perfectly comfortable at all distances. If not then we can prescribe prism in your spectacles to help relieve symptoms.