theory that the refractive errors caused by deformations of the eyeball leads naturally to the conclusion that they are immutable condition and that the normal refraction - is also a kind of permanent state.Since this theory is widely regarded as the true, it is not surprising to find that the normal eye is considered to be a perfect mechanism, which is always in good working condition.Whether familiar or unfamiliar person to the object in question, it is sufficient or insufficient lighting, pleasant or unpleasant surroundings and even in the presence of bodily stress or disease is considered that the normal eye should always have a normal refraction and normal sight.In fact, the facts do not conform to such a point of view, and because they are conveniently attributed to the lack of the ciliary muscle, or if such an explanation does not fit, generally ignored.
However, when we understand how the shape of the eyeball is regulated outer muscles and it instantly responds to their effect, is easy to see th
Similarly, I have not found a single pair of eyes with a constant or fixed value of refractive error.All people with refractive errors and often during the day and night there are times when their vision becomes normal, and their myopia, hyperopia or astigmatism completely disappear.It may also vary and the shape of the anomaly - myopia turns even hyperopia, and astigmatism becomes one form to another.
Of the several thousand students surveyed in the course of the year, more than half had normal eyes with perfect for a certain time vision, but none of them had perfect vision in each eye throughout the day.Their vision could be good in the morning and worse in the afternoon or vice versa.Many children could read one Snellen test, having perfect vision, but could well see another.Many could also read some letters of the alphabet, but could not identify others of similar size and with similar conditions.The degree of degradation in such cases lying within wide limits and is from 1/3 to 1/10 or less of the norm.The duration of such a state is also varied.In some circumstances it could last for a few minutes, in other circumstances it might interfere with the student to see the blackboard for days, weeks or even longer this time.Exposure to this state to such an extent were often class all students.
similar condition was observed and infants.Most researchers found infants hyperopia.Some found their myopia.My own research shows that the refraction of the eye in infants is constantly changing.Thus, one child under atropine tested for 4 consecutive days, beginning two hours after birth.In both eyes was pour in a three-percent solution of atropine.Pupils at the same time expanded to the maximum.There were other physiological symptoms of atropine application.The first survey showed the state of mixed astigmatism.On the second day we found difficult hyperopic astigmatism, and the third - complex myopic astigmatism.The fourth day of the survey showed normal vision, and the next-myopia.Similar changes were observed in many other cases.
What is true for children and babies, it is equally true for adults of all ages.People older than 70 years suffer from the loss of varying degrees, and in such cases the retinoscope always shows any error of refraction.One man eighty years old with normal eyes and normal vision is usually observed periods of vision loss that lasted from a few minutes to half an hour or more.Retinoscopy in such moments always showed myopia in diopters and 4 above.
During sleep the refractive condition of the eye is often, if not always, with a deviation from the norm.People whose refraction is normal when they are awake, during sleep there is myopia, hyperopia or astigmatism.Maybe so, if they have any refractive error during wakefulness, they increase during sleep.This is the reason that people wake up to the eyes, tired more than at any other time, and even with severe headaches.When a person is under the influence of ether or chloroform, or for any other reason falls into unconsciousness position also appear or increase refractive error.
When the eye regards an unfamiliar object is always an error of refraction.An example of this is known to all, eyestrain when placing pictures or other exhibits in the museum.Children with normal eyes that can accurately read the small characters in a quarter of an inch in height of ten feet always have difficulties in reading unfamiliar entries on the board, despite the fact that in this letter can have a height of two inches.Unfamiliar geographical map or even any geographical map has the same effect.I have never seen such a child, or a teacher who could look at a map from a distance, without becoming short-sighted.Gothic blamed when something that he supposedly leads to poor vision and the emergence of the imaginary "German" of the disease.But if a German child attempts to read Latin script, he immediately becomes temporarily hyperopic.Gothic or Greek fonts, or Chinese characters will have the same effect on the child and any other person who is used to the Latin script.Professor Hermann Kohno of Breslau rejected the idea that the gothic tiring for the eyes.On the contrary, he finds "pleasant after a long monotone reading of the Latin text, return to our beloved Gothic."Since the Gothic was more familiar to him than other fonts, he found it less tiring for the eyes.Children, learning reading, writing, drawing or embroidery, always suffer from poor eyesight due to unknown lines or objects with which they work.
sudden flash of light, rapid or unexpected changes in illumination have most likely lead to a deterioration of the normal eye, which in some cases lasts for weeks and months.
Noise is also a frequent cause of visual impairment in the normal eye.When an unexpected loud noise is heard, all the people see clearly.Familiar sounds do not impair vision, while strangers always do.Rural children from quiet schools may suffer from poor vision for a long time after moving in a bustling city.At school, they can not cope with their studies because their vision is impaired.It would, of course, obvious injustice on the part of teachers and others to scold, punish or humiliate such children.
In terms of physical or mental discomfort, such as pain, cough, fever, discomfort due to heat or cold, depression, anger or excitement in the normal eye is always an error of refraction, and in the eye, where they already exist, anomaly increases.
Due to the refraction of the eye of impermanence there is a lot of accidents.When people on the street hit by a car or tram, often it happens due to the fact that they suffer a temporary loss of vision.Rail, air and sea disasters, death during military maneuvers, and so on. N. Often occur due to the fault of any person suffering from a temporary loss of vision.
The same reason explains to a large degree, and confusion, which notice any dealing with this issue in the statistics reflecting the frequency of occurrence of various refractive errors.As I understand it, never taken into account the fact that the results of such studies are highly dependent on the conditions in which they were held.You can take the best eyes in the world and test them so that their owner will not be able to enlist in the army.Conversely, the check may be carried out so that the eyes that are clearly abnormal original vision for a few minutes required to test to reach normal vision and can perfectly read the test card.