Incorrectly selected lenses: causes of poor near vision

Symptoms

Reference! Deterioration of near vision and its simultaneous improvement at long distances is called hypermetropia.

If these changes are associated with age-related degenerative processes in the tissues of the eye, age-related presbyopia is diagnosed.

This disorder is accompanied by the following symptoms :

• When stress is placed on the organs of vision (reading, working at the computer), fatigue and headaches may appear ;
• develops , when, along with a deterioration in the quality of vision, the eyes that see worse may cease to function fully;
• the closer the objects in question are, the more blurred their outlines are ;
• after prolonged eye strain, may appear .

The stronger the degree of farsightedness, the more pronounced the symptoms will be.

In the most severe cases, a person without glasses or contact lenses cannot see objects at arm's length at all.

Controlling depth of field in the camera

It is the aperture value that most influences the depth of field of a photo. But there are two more points on which the depth of field depends. This is the focal length and the distance to the subject.

Once you understand from your own experience how the above-mentioned factors can affect a photo, learn how to combine them correctly, you will immediately understand how to change the depth of field and how to create a composition with the desired depth of field.

Now we propose to consider these three points in order of their importance for the final result. What does depth of field depend on?

What diseases can cause a person to have difficulty seeing up close?

Deterioration of near vision in itself is already called “hypermetropia”.

Note! This pathology can manifest itself against the background of certain ailments, one of which is a violation of accommodation.

The eye can no longer focus on objects at different distances due to atrophic processes in the tissues of the lens.

Deterioration of vision at close distances may be associated with the development of the following ophthalmological diseases:

1. Retinal detachment. The retina is an element located at the back of the eye. Light reflected from visible objects is focused on it, and this information is transmitted in the form of an image to the brain. In a detachment, the retina separates from the choroid to which it is tightly attached.
2. Macular degeneration. The disease is a lesion of the “macula” – the area of ​​the retina where the largest number of photoreceptors is concentrated.
3. Retinal and vitreous tears.
4. Diabetic retinopathy. A disease of the vascular system of the eyes, in which atherosclerotic changes develop in the capillaries. As a result, the blood supply to the optic nerve and retina is disrupted and the person begins to see worse.

Farsightedness often develops against the background of cataracts (pathology of the lens).

It is worth noting! When diseased, the lens loses its natural transparency and ceases to fully perform the work of a lens, making normal focusing of vision impossible.

Hard to see up close

This condition is called farsightedness. There is an opinion that patients who have poor close vision can clearly see objects that are at a great distance from them. This is wrong. In most cases, farsighted people have blurred vision both far and near.

Hypermetropia, as this ophthalmological disease is also called, occurs due to the focus of the image falling behind the retina. The normal length of the organ of vision is 23.5 mm. The size of the farsighted eye is 20 mm.

Treatment at home

It is impossible to correct poor vision at home; you can only reduce the tension of the eye muscles. To do this, you can prepare and take a folk remedy:

1. 1. Pour 24 g of eyebright into 0.5 liters of boiling water.
2. 2. Strain through cheesecloth.
3. 3. Drink 100 ml four times a day.

Visual impairment due to farsightedness can be treated with exercises that are recommended to be performed 2 times a day:

1. 1. Move your eyes from side to side, up and down 5 times.
2. 2. Attach a dark mark (1x1 cm) to the window. Stand a meter away from her, look through the glass, catching your gaze on the mark. The image behind the mark must be clear. Repeat three times, after each repetition blink 5 times.
3. 3. Take the watch and glance at the numbers 12, 3, 6, 9. Repeat 3 times, and then perform the exercise counterclockwise.
4. 4. Imagine that in front of your eyes there are the number 8, geometric shapes, a star, and outline each one.

Recourse

When visiting an ophthalmology clinic, a patient with poor vision will be offered a diagnostic test. In case of farsightedness, glasses with positive diopters are prescribed.

Upon reaching 18 years of age or in the absence of contraindications, the patient is offered a laser correction procedure. People with a high degree of farsightedness (plus 20 diopters) are implanted with phakic lenses.

Causes of poor vision at close distances

The risk group mainly includes people aged 35 years and older.

At this age, the cornea begins to lose its elasticity and cannot focus light normally.

The disorder can occur at a younger age, and even in small children.

But in them such problems are caused exclusively by physiological disorders and often go away with age, when the eye tissues are finally formed.

It has been proven that deterioration of near vision may be a consequence of a genetic predisposition to such disorders in the tissues of the eyes.

Interesting fact! According to statistics, certain ethnic groups are more predisposed to such disorders: North American Indians, Pacific Islanders and African Americans.

Depth of field in photography: separating the subject from the background

As we have already found out, the optimal depth of field contributes to an excellent visual effect - the separation of the subject from the background. The photo gains volume, the background is blurred, the subject attracts the viewer’s attention - in general, an excellent formula for success.

But you shouldn’t completely erase the background; it doesn’t look organic everywhere. It may turn out that you destroy a beautiful location and turn it into a sparse, spotted background that will resemble a studio photo for a school yearbook. When the background is “readable” (that is, you can visualize where the shoot is taking place), it adds a special ambiance to the photo that can make your photo more successful. Remember, when you want to highlight an object in the frame, think about how to achieve depth of field.

Possible complications

Hypermetropia develops relatively slowly and its symptoms are always clearly visible , which allows you to start treatment on time and avoid serious consequences.

But if the therapy is incorrect or the main preference is given to traditional methods of treatment, the following serious pathologies may develop :

• glaucoma;
• blepharitis, keratitis and conjunctivitis of a non-infectious nature;
• concomitant strabismus;
• amblyopia (lazy eye syndrome).

Treatment must begin as early as possible and the therapeutic course will depend entirely on the diagnostic results and the causes of the disease.

Diaphragm

The effect of aperture on depth of field is what you need to pay attention to first.

And now a lyrical digression for beginners, so if you know where the aperture is in the camera and how to use it, then you can safely skip this passage of text.

The aperture in a digital camera is the “hole” that allows light to pass through to your camera’s sensor. By using your aperture skillfully, you can take beautiful shots with excellent exposure. Also, using this simple hole you can adjust the background blur.

How to adjust the aperture on a camera? The aperture is designated by the letter f, next to which there are always numbers. So, to open the aperture, you need to set a lower number, and to close it, you need to do exactly the opposite.

Now let's talk about the connection between the aperture and the depth of field. Everything here is extremely simple: an open aperture means a shallow depth of field. Closed gives greater depth of field.

The maximum aperture value in a camera directly depends on the lens of your camera. Some allow you to set the aperture to 2.0 or even 1.2. True, such values ​​will complicate your work.

How to determine depth of field? Of course, there are various formulas by which you can calculate the ideal depth of field, but we recommend using an online calculator.

What to do: treatment approaches

What to do if you encounter this symptom and near vision becomes poor? If near vision deteriorates, treatment is prescribed depending on the cause of the disorder and the severity of farsightedness, as well as the age of the patient.

Keep in mind! Options range from conservative therapy (in mild cases) to surgical intervention.

General approach

Conservative treatment in this case includes the use of corrective optics .

Moreover, if farsightedness is slight, you can wear glasses or contact lenses only when performing activities that require visual concentration (reading, watching TV, working on a computer).

In childhood, the tissues of the eye are still quite elastic, and instead of such auxiliary means, you can try to get rid of refractive errors with the help of special eye exercises.

If the examination reveals farsightedness of more than +3 diopters, you cannot do without constantly wearing corrective glasses or lenses.

Additionally, computer-based treatment can be used.

If this combination does not produce results, surgical or laser treatment is prescribed.

Surgical treatment

The following surgical options are possible:

• laser correction;
• laser thermokeratoplasty (the cornea is affected by thermal radio waves, as a result of which the shape of the cornea changes and, accordingly, its refractive characteristics);
• lensectomy (removal of a poorly functioning lens and its replacement with an artificial implant, mainly relevant for age-related visual impairment);
• keratoplasty (replacement of a clouded area of ​​the cornea);
• lens implantation, in which the organ is not removed, but the lens is installed directly in front of the lens;
• radial keratotomy (applying incisions to the cornea that help correct its refractive power);
• thermokeratocoagulation (spot treatment of the cornea with a needle heated to a certain temperature).

Each method has its own indications, different effectiveness and rehabilitation period. The choice of treatment method depends on the results of a preliminary examination of the patient.

Image depth of field

You need to remember that even the most seemingly harmless mistake made when focusing can greatly ruin your photo. And at the same time, it will be absolutely unimportant whether you shot a portrait or captured a full-length model. The lack of sharpness of the photo is very noticeable, so much so that even those who do not have knowledge of the rules of photography can notice it.

How to use depth of field when shooting close-ups? The answer is simple - focus on the eyes. In any portrait, the eyes are an indicator of sharpness, and when they are out of focus, your photo loses a lot.

Prevention

Deterioration of near vision is a refractive problem that occurs due to problems with focusing.

Remember! Prevention of such a disorder mainly comes down to maintaining the correct working conditions, under which the visual organs will not overwork and get tired:

• Proper lighting must be provided in the workplace ;
• in order to avoid the development of an accommodation spasm, you should not read in poor lighting or lying down , and when working at a computer, the distance from the monitor to the eyes should be 50-60 centimeters;
• Every hour and a half of working with the computer, you need to take five-minute breaks , during which it is advisable to perform an independent massage of the eyeballs. It is enough to massage your closed eyelids with your palms for 1-2 minutes.

Can't see into the distance

Visual impairment when a person cannot see into the distance (far away objects) is called myopia or myopia. The disease tends to progress; if left untreated, the patient ceases to distinguish objects nearby.

With this diagnosis, the image is located in the plane in front of the retina. With myopia, the size of the eyeball reaches 30 mm.

How to fix it at home

A popular remedy for myopia is apricot remedy. It should be consumed twice a day, 24 g, with plenty of water. You can take this remedy constantly, and prepare it at home like this:

1. 1. Grind the apricot and mix with walnuts in a 1:1 ratio (you can take 100 g of each ingredient).
2. 2. Add liquid honey (12 g).
3. 3. Mix thoroughly.

The method of reading with one eye has become widely effective in the treatment of myopia. To do this you need to:

1. 1. Cover one eye with a sheet of paper.
2. 2. Read a newspaper or book at the greatest distance from your eyes.
3. 3. Every 5 minutes, bring the subject of reading half closer several times.

This procedure provides massage to the lens of the eye. Reading time using this method is 15 minutes. If one eye sees worse than the other, then the duration of reading with the first can be increased to half an hour.

Exercises suitable for people with farsightedness also help with myopia, as they help relax the eye muscles.

Diagnostic methods

Diagnosis of visual impairment is carried out using the following methods:

1. Checking visual acuity using the table. With the use of appropriate glasses, normal visual acuity can be achieved. However, this diagnostic method is biased.
2. Computerized visual acuity measurements can detect farsightedness and other refractive errors. The advantage of this examination is the detection of the degree of astigmatism.
3. Impact on the ciliary muscle with eye drops. Their action is associated with muscle relaxation. In this case, a person sees practically nothing up close. Computer diagnostics allows you to accurately determine the degree of visual impairment.
4. Skiascopy allows you to observe the movements of shadows as light passes through the cornea. For this purpose, a light beam and a skiascopic ruler are used.
5. Ultrasound. This diagnostic method allows you to determine the length of the eyeball.
6. Tomography of the cornea allows you to determine its thickness. With farsightedness, it is usually greater.

Focal length

How to reduce depth of field? Increase your lens focal length!

Given: Aperture value 8.0, object at a distance of two meters.

Solution:

To summarize: if you need to slightly blur the background while maintaining the same aperture value, simply use a long lens.

What causes night blindness?

Doctors identify several causes and risk factors for the occurrence of pathology:

• genetic predisposition;
• depletion of the body due to poor nutrition, malnutrition and lack of vitamins A, B2 and PP;
• eye diseases (glaucoma, myopia, retinal detachment, cataracts);
• pregnancy;
• eye injuries;
• anemia;
• severe infectious diseases suffered in adulthood (measles, rubella, chickenpox);
• strabismus;
• hard physical labor;
• sudden hormonal disruptions.

There are many reasons; only a specialist can determine the true one. It is important to establish it, since night blindness is rarely an independent disease. It often accompanies a more dangerous pathology.

Lens depth of field

In fact, only long depth of field lenses with a good lens (such as Canon's "L" series) can provide good sharpness in all conditions. For example, the Canon 24-105 L IS and Canon 600 f4 L IS provide excellent clarity even at f/4.

Depth of field effect

You can also select an object in a photograph during processing. Any, even the simplest editor has a blur brush. Take a brush and carefully, gently blur the desired areas. This way you can create a more artistic effect and can be as creative as you like.

Distance to object

Here, shallow depth of field is achieved by the distance between you and your subject. The closer, the shallower the depth. How to increase depth of field? It's simple - move away from the object.

As you might have guessed, shallow depth of field blur in macro photography will present some challenges. If we have a focal length of 60 mm, an aperture value of f/22 and a distance to the object, for example, fifteen centimeters, then the resulting depth of field will be 0.33 cm, that is, only 3.3 mm.