How does this thing called vision function? How do we see? The eye, as is constantly pointed out, operates in many respects like a camera. At this moment you are looking across the room. Perhaps there is a painting on the opposite wall. Perhaps you see an easy chair with a lamp beside it. Whatever it is, for our purposes it constitutes a picture.
Suppose you want to record that picture with a camera. First, you adjust the focal length so that the image is sharp and clear without blurring or distortion on the film. If the object is at a distance, you shorten the focal length. If it is close, you lengthen it. Then you snap the picture. That is, you let light in upon the exposed plate and the picture is taken. You cannot see it, however, until the film has been developed.
How does this compare with the functioning of the eye? The eyeball of a normal eye involuntarily adjusts itself so that the image is focused on the retina (film of the camera). Once again there must be sufficient light to make your picture clear. Once again, if the object is at a distance, the focal length (the distance from the cornea to the retina) is shortened; and vice versa if the object is close. This process of adjustment to far or near sight is called accommodation. the conflicting opinions which exist in regard to its functioning.
Light enters the eye through the small hole in the iris called the pupil, and comes to a focus on the retina where, by a chemical reaction, it is changed from radiant energy into nerve impulses. Sensitive nerve receptors of the retina, which are a part of the optic nerve, carry these impulses to the visual centers in the brain where, with the assistance of memory, imagination, experience and judgment, a picture is developed. That is, the mind interprets the image.
It is, therefore, the brain that sees. The greater the degree of mental control, that is, the better your memory and imagination, the better you see.
When the camera is in the hands of a person who does not understand its functioning, the pictures are unsatisfactory, and so with the eye. If the eye fails to accommodate, as a result of some malfunctioning, it is improperly focused. If it strains to see, the individual begins to suffer from some form of eye trouble.
He goes to an ophthalmologist and, after examination, departs with a pair of glasses. The glasses fix on the individual the trouble which they are supposed to correct, while the underlying cause remains unchanged. Meanwhile, the sight will worsen when the glasses are removed. For instance, a person with 20/70 vision will find, a few weeks after being fitted with glasses, that his vision has degenerated to 20/200 when he removes them.
While many eye troubles are preventable and many more can be vastly alleviated, the only solution that is offered for this appalling condition is to fit the eyes with glasses. There are glasses for young and old, dark glasses and colored glasses, reading glasses and ornate affairs; glasses for the near-sighted and for the far-sighted; glasses for eyestrain and to relieve headache. Glasses for every purpose, indeed, except to get at the cause of the eyestrain. This is how we see.
Suppose you want to record that picture with a camera. First, you adjust the focal length so that the image is sharp and clear without blurring or distortion on the film. If the object is at a distance, you shorten the focal length. If it is close, you lengthen it. Then you snap the picture. That is, you let light in upon the exposed plate and the picture is taken. You cannot see it, however, until the film has been developed.
How does this compare with the functioning of the eye? The eyeball of a normal eye involuntarily adjusts itself so that the image is focused on the retina (film of the camera). Once again there must be sufficient light to make your picture clear. Once again, if the object is at a distance, the focal length (the distance from the cornea to the retina) is shortened; and vice versa if the object is close. This process of adjustment to far or near sight is called accommodation. the conflicting opinions which exist in regard to its functioning.
Light enters the eye through the small hole in the iris called the pupil, and comes to a focus on the retina where, by a chemical reaction, it is changed from radiant energy into nerve impulses. Sensitive nerve receptors of the retina, which are a part of the optic nerve, carry these impulses to the visual centers in the brain where, with the assistance of memory, imagination, experience and judgment, a picture is developed. That is, the mind interprets the image.
It is, therefore, the brain that sees. The greater the degree of mental control, that is, the better your memory and imagination, the better you see.
When the camera is in the hands of a person who does not understand its functioning, the pictures are unsatisfactory, and so with the eye. If the eye fails to accommodate, as a result of some malfunctioning, it is improperly focused. If it strains to see, the individual begins to suffer from some form of eye trouble.
He goes to an ophthalmologist and, after examination, departs with a pair of glasses. The glasses fix on the individual the trouble which they are supposed to correct, while the underlying cause remains unchanged. Meanwhile, the sight will worsen when the glasses are removed. For instance, a person with 20/70 vision will find, a few weeks after being fitted with glasses, that his vision has degenerated to 20/200 when he removes them.
While many eye troubles are preventable and many more can be vastly alleviated, the only solution that is offered for this appalling condition is to fit the eyes with glasses. There are glasses for young and old, dark glasses and colored glasses, reading glasses and ornate affairs; glasses for the near-sighted and for the far-sighted; glasses for eyestrain and to relieve headache. Glasses for every purpose, indeed, except to get at the cause of the eyestrain. This is how we see.
0 comments:
Post a Comment