The Eye (Conclusion)

“Those who love peace must learn to organise as effectively as those who love war.”

– Martin Luther King Jr

INTERESTING THOUGHT, isn’t it? Hello, students. Once again we meet to share knowledge. Although we are not together physically, that does not mean that we are not interacting with each other. Remember that even as I am doing my part, you also need to do yours. Are you thinking that you do not know what your part is? Your part is to read over the material in order to ensure that you learn it to the point where you can use it to answer any question that you may be asked! When you can answer all questions without any problem, you would have succeeded in doing your part!

This week, we will complete our study of the eye; we will do this by continuing to look at eye defects. Previously, we looked at accommodation; remember what this is? It is the ability of the lens to change its shape automatically to focus near and distant objects. However, unfortunately, as we age we lose this ability. The lens harden and become less flexible so they cannot change shape (become fat) to view near objects. This means that older people lose the ability to read easily. They can no longer grab a book or a newspaper and read! I am sure you must have noticed certain individuals (Grandma, Grandpa and those over 40-year-old teachers who are in denial) holding a book or the newspaper at arm’s length in order to decipher the words. Fortunately, this loss of accommodation can be corrected using eyeglasses specially designed for reading; the individual does not experience difficulty with the other visual aspects of his or her life.

If the person is short-sighted, then the ophthalmologist will prescribe bifocals or transition lenses. These types of lenses will help the individual to view both near and distant objects more readily.

ASTIGMATISM

This occurs when there is an irregular curvature of the lens or the cornea. This causes light reaching the eye to be in focus in one plane but not in others. Astigmatism is corrected with the use of cylindrical lenses. If the individual is also long- or short-sighted, the lenses would have to be designed to correct this additional defect.

CATARACT

The individual is said to have a cataract when the lens become opaque. This prevents light from passing through the lens (it is no longer translucent) and since light is the stimulus to which the eye responds, it means that the person will not be able to see objects clearly. The individual’s sight can be improved by removing the defective lens and replacing it with an intraocular lens. There are some instances when the condition is treated using eyeglasses with very strong convex lenses.

GLAUCOMA

■ This occurs when too much fluid gathers in front of the lens, causing a build-up of pressure in the aqueous humour.

■ The increased pressure distorts the lens and can damage the optic nerve.

■ The person’s vision becomes poor and the individual may experience sightless areas in the field of vision. This can lead to blindness if the disease is not treated.

■ Early detected glaucoma can be treated with medication. A tube can also be inserted into the eye to assist in the draining of the fluid.

The likelihood of an individual having glaucoma increases with age, and also if the individual is diabetic. The disease does not display obvious symptoms and requires yearly testing for early detection. Unfortunately, people of African origin have the tendency to develop glaucoma.

ADVANTAGES OF HAVING TWO EYES

Humans and other animals have binocular vision. Our eyes are in the front of our heads; because of this, the field of vision for each eye is similar but not identical. The brain interprets the two fields of vision so only one image is seen. In doing this, the brain helps us to appreciate the size, shape, depth and distance of the image. This helps us to form a three-dimensional picture of the object. Even though there is some overlapping of the two fields of vision, our two eyes are still able to give us a wide range of vision.

I hope you enjoyed our study of the eye and that right now you have a better understanding of how your body functions, and that you have been equipped to answer any question on the eye that you might see on the exam paper. Have a good week until we meet again!