Eye diseases and vision

Blurred vision: causes and treatment


Perception of the depth and remoteness of objects. To understand what is happening in the outside world, it is not enough to identify objects, that is, to determine what we see, hear or touch, it is also important to know where it is. Here we are faced with one of the fundamental problems of perception, namely, the problem of localization - determining the location of objects. This and other problems of perception will be examined by us as an example of vision. There are at least two reasons for this: firstly, the visual analyzer is leading in human life (according to some experts, up to 90% of the processes of information processed by a person are in the visual sensory-perceptual system), and secondly, visual perception is better studied other types of perception.

One of the main issues of perceiving the depth and remoteness of objects is why and due to what we see the world three-dimensional, if we only have a two-dimensional (flat) image of it on the retina? The desire to answer this question led to the search for signs of depth and remoteness - features of the stimulus situation, which allow the observer to determine how far the object is from him and from other objects.

Signs associated with the ratio of images, or projections, of an object to the retina of different eyes, are called binocular signs of depth and remoteness. They exist due to the fact that people, as a rule, see and look with two eyes.

Due to the fact that our eyes are at a certain distance from each other, each eye looks at an object from several different positions. Therefore, each eye sees the same object from a different angle. This difference in directions, or the angle between the axes of vision of two eyes, is called binocular parallax. The sensor system “tracks” this angle, its value serves as a kind of clue, a sign of the distance of the object: a large angle - the object is close, a small angle - the object is far. In this case, the images on the retinas of different eyes are not the same. The difference in retinal imaging is called binocular disparity.

To make sure that each eye receives its image of the subject, conduct the following experiment. Take the cup and hold it in front of you so that the cup handle when looking with both eyes is slightly visible - protrudes from the edge of the cup by half a centimeter. Let the pen be on your right. Now close your right eye. The pen disappeared from sight or, in any case, somewhat “decreased”. Open your right eye and close your left. The pen reappeared.

We can perceive remoteness and depth even with one eye. It is known, for example, that people who are blind in one eye from birth perceive the world in three dimensions. Therefore, there are some signs of remoteness and depth associated with the image taken with one eye. Among these features are usually called linear perspective, superposition, relative size of objects and texture gradient.

The linear perspective as a sign of remoteness reflects the fact that straight lines (for example, rails) seem to converge, moving away from us. We often observe some object inscribed in the coordinates of parallel lines. And if, say, one object is located where parallel lines “converge” to a greater extent than where the other object is located, then it is clear to us that the first of them is located at a greater distance from us (Fig. 11-6 )

What conclusion can we draw about the relative distance from us of two objects, one of which obscures the other? Which one is closer: obscured or obscured? The answer is obvious - blocking. In this case, the sign of superposition was used to assess the distance (Fig. 11-7).

All things being equal, the smaller the projection of the object onto the retina, the more it is perceived. This is due to the geometry of the visual system. The projection of an object located a hundred meters from us is larger than the projection of the exact same object, which is a kilometer away from us (Fig. 11-8). Two objects of the same size - A and B - give different displays on the retina if they are at different distances from the observer.

When we observe a certain surface, such as a pebbled seashore, we can judge the depth of space by the degree of proximity and the size of the homogeneous objects on the surface: the farther away from us a certain point in space, the denser its elements are “packed”. This is an example of a sign of remoteness and depth, which is called the “texture gradient” (Fig. 11-9).

Information about the remoteness of the surrounding objects is also provided to us by our own movement and the movement of the objects surrounding us. The movement leads to the fact that the projection of objects on the retina changes, and closely located objects seem to us moving relatively faster than remote ones, which serves as an additional sign in assessing the distance. Remember the view from the window of a moving train: the sun stands still on the horizon, you can still have time to examine the cars at the barrier, and the trees of the forest belt fly by at a tremendous speed.

Perception of movement. Due to what do we perceive any object as moving? At first glance, the answer to this question can be very simple: this is due to the fact that the projection of an object in motion moves along the retina. But it turns out that this answer is not complete in the sense that moving the projection along the retina is neither a necessary nor sufficient sign of movement.

It is known that an object can be perceived as moving, even if its image does not move along the retina. Imagine that at some distance from each other there are two bulbs. The first one lights up for a short time and goes out, then the second one lights up and goes out too, etc. If the time interval between the lamp ignitions is from 30 to 200 milliseconds, it seems to us that the light strip moves from one point to another. This phenomenon is called the strobe effect. It has long been used in animation and light advertising.

Another example of an illusory movement is the effect of induced movement. Each of us saw the moon moving against the backdrop of clouds. Of course, not the moon moves, but the clouds driven by the wind. The moon practically does not move along the retina, but is perceived as moving, the clouds move relative to ourselves, but are perceived as motionless. It turns out that moving along the retina is not only an optional attribute of motion perception, but also insufficient. In general, it is human nature to attribute the movement to that of two objects, which is perceived by the figure against the background of the other. Background - this is what surrounds, includes, is large in relation to another object, perceived, respectively, as a figure.

To confirm the above position, the following experiment was carried out. The subjects sitting in a dark room were presented with a luminous rectangular frame, inside of which was a luminous circle. In fact, the frame moved to the right, and the circle stood still. Nevertheless, the subjects believed that this circle moves to the left, and the frame stands still (Fig. 11-10).

If moving an object along the retina is not a necessary and sufficient sign of movement, then what mechanisms can explain the perception of movement? First, psychophysiologists have discovered the existence of special brain cells responsible for the perception of movement, and each type of cell responds better to certain directions and speed of movement. Secondly, the movement of an object is perceived and evaluated better in the case of relative movement, i.e., when it moves on a structured (inhomogeneous) field compared with the case of movement on a dark or uniform field. In other words, when only an object (absolute movement) is in the field of view, errors in the perception of movement are more likely. Thirdly, feedback is involved in the perception of movement - signals informing about the movement of our eyes and head: everyone, probably, has caught himself repeatedly that he is following his eyes with a moving object.

Perception of form. To perceive an object, it is not enough to see where it is and where it is moving, it is desirable to know what kind of object it is, that is, to identify it. The perception of the shape of an object is an essential aspect of its identification. For example, in order to perceive a dog, it is first necessary to note that this is something standing on four legs, having a tail and an elongated muzzle. Of course, color and size are also important, but shape is still crucial in the process of identifying and recognizing objects.

Perception researchers have wondered if there are some elementary form elements into which objects of any configuration can be decomposed. Perhaps the perception of form is built similarly to the collection of a certain machine: a holistic image is built from individual parts. The works of two famous physiologists (Hubel D. H., Wiesel T. N., 1959, 1979) suggest that the above position is not meaningless. Hubel and Wiesel examined the activity of individual cells of the cerebral cortex in response to the presentation of various stimuli. They found a certain selectivity of certain cells in relation to certain visual elements. For example, one cell may not respond or hardly respond to horizontal lines, but respond to vertical lines, and the other, on the contrary, only respond to horizontal lines. Such cells have been called feature detectors. In addition, Hubel and Wiesel discovered cells that responded to more complex combinations of shapes: for example, only to right-angles.

Along with information coming from below, from individual signs, there is a flow of information from above, namely, starting the process of identifying an object, a person forms a set of perceptual hypotheses, expectations and attitudes, which generally increase the efficiency of the recognition process, limiting the search area decisions, but at the same time can lead to various kinds of misunderstandings and errors when expectations and attitudes diverge significantly from the true state of things (Arbib M., 1976, U. Nayser, 1981, Edelman J., Mountcastle V., 1981, Natadze R. G., 1 960, Uznadze D. H., 1961).

The division of a certain group of objects into separate objects or the selection of its individual components in a group of objects is called perceptual segregation. The initial stage of perceptual segregation is the isolation of a figure from the background. In familiar situations, we do not pay attention to this, but the first thing to do when perceiving some visual information is to decide what to consider as a figure and what as a background. There are some features of visual stimulation that in themselves help the perceptual system to distinguish a figure from a background: a background usually includes a figure, it contains fewer details and distinctive features compared to a figure. Let's turn to fig. 11-11. In this case, we have no doubt about where the figure is and where the background is: the visual information itself suggests that something relatively more connected and clearly defined (a bright spot) is a figure.

However, it would be wrong to explain the process of isolating a figure from the background only by stimulation features. This can be clearly demonstrated by the example of the perception of dual images, or images with an mutually reversible figure and background (Fig. 11-12)

Fig. 11-12. Reversible figure and background: profiles or a vase

When we look at this image, we alternately see either a vase, or two human profiles, at any one time one. Such traps make you wonder, due to what, under normal conditions of existence, do we consistently and fairly steadily take one object for a figure and another for a background? Studies show (Weisstein N., Wong E., 1986) that the perception of an object as a figure is associated with a relatively more detailed analysis of information compared to the perception of an object as a background, in other words, a figure is what we currently focus on Attention.

In one of the experiments, the subjects were shown for a short time vertical or slightly inclined lines against the background of the classic image “profile or vase” (Fig. 11-13). Moreover, the lines were presented in one of three positions: A, B or C. The task of the subjects was quite simple: to answer whether the line is vertical or slightly inclined. The results showed that the percentage of correct answers was relatively higher when the line was in the area that was currently perceived by the subject as a figure. In those moments when the subject saw the vase, the location of the line at point B led to more correct answers compared to the location options at points A or C, on the contrary, when the subject saw the profiles, the answers were more accurate when located at points A or C.

Images of perception are characterized by integrity. This means that they present some coherent picture, image of an object or event. We do not perceive the tree outside the window as a collection of oval objects of green color, located against the background of black thick vertical lines and thin black lines, most of which are at a slight slope. We see a tree: trunk, branches and leaves. This peculiarity of perception was especially emphasized by representatives of the school of gestalt psychology, the main thesis of which was that mental images, and in particular images of perception, are more than a simple sum of elements. The image of perception is a certain organization of stimuli. The question arises: due to what it becomes possible to combine the individual elements of stimulation into a holistic image, in other words, due to what mechanisms does perceptual grouping occur? Why, for example, do we perceive the image in Fig. 11-14 as three pairs of vertical lines, and not just as six vertical lines?

Gestalt psychologists have formulated a number of principles to which perceptual organization (grouping) obeys. One of these principles is proximity: the closer the two elements are to each other, the more we tend to group them together in perception. The action of this principle can explain the perception of the image in Fig. 14 as three pairs of vertical lines: the first and second, third and fourth, fifth and sixth lines are in close proximity to each other, so we tend to group them, that is, to perceive them as an integral object.

Another principle of grouping is the similarity: similar objects are combined into a single image. For example, we group stars with asterisks based on their similarities with each other and therefore we see not just a collection of zeros and stars, but a triangle of stars (Fig. 11-15).

Elements that form a smooth, continuous contour are perceived as a single figure - are grouped. This principle is called a good continuation, or continuity. The line segments in Fig. 11-16 are grouped so that A combines with D, and C with B, not A with B and C with D, because the first pairs form a smooth contour with each other.

Fig. 11-16. Good sequel as a principle of perceptual grouping

If the outline of the figure has gaps, then we tend to fill them, as it were, to supplement the figure to a certain holistic image. This principle is called isolation. For example, in fig. 11-17 we see a triangle, despite the gaps in its contour.

It is interesting that we can see the contour where in reality it is not there. Look at the pic. 11-18. You clearly see the white triangle with its top up. Moreover, this white triangle is perceived as more white than the background. In fact, there is no triangle as such, in addition, the imaginary triangle is not whiter than the background. This phenomenon is called the “subjective contour effect” (Kanizsa G., 1976). According to many researchers of perception, the principles of closure and good continuation are at the heart of the subjective contour phenomenon.

At the initial stage of the development of gestalt psychology, its representatives (Koehler W., 1947) insisted that perceptual organization is simply a function of the stimulus, the result of processes going from the bottom up. However, further studies have shown that factors such as the experience of the subject, his installation, have a significant impact on the organization of stimulus information.

In order to understand what kind of object is in the field of attention, the individual must not only separate it from the background, combine the elements into a certain integral image, but also attribute this image to a certain category, the type of objects previously perceived by it. The process of assigning perceptual images to a certain category is called the process of identification, or pattern recognition.

Interestingly, a person has the ability to easily recognize even highly altered images. It is quite difficult to create a program for computer recognition of handwritten text, and in most cases a person understands hand-written text without much difficulty. In addition, we perceive the shape of the book as a rectangle, despite the fact that at a certain angle of view, the reflection on the retina has the shape of a trapezoid. We recognize a familiar melody even if it is played on another instrument or in a different key. Phenomena of this kind served the Gestalt psychologists as one of the main arguments in favor of the fact that the image of perception is not reducible to the sum of its parts.

But, as in the case of other processes of perception, pattern recognition cannot be explained only by the features of the stimulus situation. The “influence from above” also has significance: the effects of experience, attitudes, personality traits of the perceiver, etc. For example, the effect of the influence of attitudes on pattern recognition can be demonstrated by the following experiment (Leeper R. W., 1935).

The critical stimulus material in this experiment was an ambiguous picture (Fig. 11-19, a), in which one can alternately see either a young woman who has slightly turned away from the observer, or an old woman in profile.

Before demonstrating an ambiguous picture, one group of subjects was shown an unambiguous image of a young woman (Fig. 11-19, b), and the other group was shown an unambiguous image of an old woman (Fig. 11-19, c). It turned out that the subjects of the first group saw a young woman in an ambiguous picture, and the subjects of the second group saw an old woman. The identification of the image was influenced by the installation formed earlier.

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Reasons Why Vision Was Blurred

The list will help you identify the cause of blurred vision and identify the most common symptoms.

- Astigmatism or myopia. Astigmatism is a disorder that makes you hard to see near and far. The consequence of the second pathological condition is blurry vision away. They not only blur the vision, but also distort it as a whole.

- Cataract - more common in people over the age of 60 years. Sometimes it has no symptoms. In the latter case, it causes clouding of the cornea, proper vision, sensitivity to light, double vision and progressive blurred vision.

- One of the many symptoms of an imbalance in blood sugar can be blurred vision. You must be vigilant if you suffer from this disease, as it can lead to much more serious vision problems, such as blindness. Weight loss and increased appetite, palpitations, high blood pressure, tremors, and blurred vision are the most common symptoms of this disorder that affects the thyroid gland.

- Multiple sclerosis - this neurodegenerative disorder is often accompanied by numerous vision problems, including blurred vision. It can also cause problems with the bladder, changes in sensitivity, etc.

- Hypoglycemia, a condition when blood sugar suddenly drops, this can lead not only to blurred vision, but also to second types of disturbances, confusion, double vision, loss of concentration, anxiety, heart palpitations and trembling. Other signs of this condition are nausea, sensitivity to light, eye pain, and vomiting. It is worth noting that migraines can have the same symptoms.

- High blood pressure and glaucoma. If you have hypertension or eye pressure (glaucoma), you may experience vision problems. In addition, both diseases cause additional problems, such as loss of consciousness, complete or partial loss of vision, tachycardia, etc.

What to do if you have blurred vision

If you often feel any of the above symptoms, it is very important to see a doctor immediately. If they occur sometimes, pay attention to our tips: reduce stress. This will help you lower your blood pressure and nervousness. So you will be calmer and your vision will improve.

- Hypertension is one of the worst enemies of your eyes. If you have eye pressure, it is also worth getting rid of stress. Work to reduce anger and anxiety so that they do not affect your well-being.

- If you work in front of a computer or laptop monitor for a long time, your eyes may get tired, and this will cause blurry vision.

In this case, you should:

  • Stay sitting and close your eyes for a minute.
  • Another option: stand up, raise your index finger in front of your face and slowly zoom in and out, watching his eyes. After that, do the same, but move your finger to the right, and then to the left, like a pendulum. You should only move your eyes, not your head.
  • Focusing and defocusing. Select an object and look closely, focusing on it. Then try to defocus the attention from the object and see what is around it.

- One of the reasons why ours vision became blurry - this is the inability to focus on something specific, because every day we get hundreds of incentives. Therefore, watch your attention.

- Watch out for food. Try to eat right, exclude foods that do not give you anything besides empty calories (sweets, flour products, alcohol, finished products, etc.) A complete list of foods that are harmful to humans can be found on specialized diet websites and watch videos on the Internet about nutrition from leading fitness experts, experts in the field of nutrition. Smoking is also better to quit

Of course, you already know that water is the best ally, thanks to which the eyes remain hydrated. In addition, it can help remove toxins that have accumulated in the body and threaten to harm the liver - an organ that is directly associated with the eyes.

If your vision is blurry or blurred, try eating low fat foods and avoiding fried foods. Drink tea daily and eat steamed or partially boiled vegetables (primarily broccoli, spinach and chard) with whole grain rice.

Do not eat fatty meat or dairy products. You will make the choice in favor of lean meat and if you like dairy products, then eat homemade cottage cheese cooked on your own. Recipes can be found on the Internet.

At the same time, you should increase the intake of vitamins A and C. You will find them in citrus fruits, carrots, papaya and broccoli. Lead a healthy lifestyle.

- Increase the size of the letters on the computer screen so as not to move it closer to the eyes, do not read if there is not enough light (natural light is better than artificial light), keep at least one meter from the television screen.

- Wear sunglasses when going out for lunch or returning home.

- Also, it is good to spend time in the countryside or in nature, for example, in a village or on the beach. So you can train your eyes. Just as in the case of panoramic photography, the eyes need to rest from the simultaneous contemplation of such a large number of objects, in particular colors and bright neon lights.

3 comments for “Blurred Vision: Causes and Treatment”

Astigmatism can also be described as a visual impairment, the main symptom of which is a blurred image. The cornea of ​​the eye with astigmatism does not have a spherical shape, its meridians have different radii of curvature. We can say that in a healthy eye, the shape of the cornea resembles the surface of a ball. While the shape of the cornea of ​​an astigmatic eye resembles the surface of a rugby ball.

Treatment depends on the causes of this condition. It is imperative to normalize nutrition and daily routines. Particular attention should be paid to the workplace and proper lighting. It is necessary to minimize the load on vision and on the body as a whole. If there is a doctor’s recommendation, it’s worth using glasses or lenses to correct vision, take medications to improve eye nutrition, and perform specialized sets of exercises.

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