What causes excessive strain on the eyes.

Tired eyes or asthenopia

as ophthalmologists call this condition, it manifests itself in the form of subjective symptoms of visual fatigue. In this case, the patient may complain about:

• decreased visual acuity (feeling of a “veil” or “fog” before the eyes);
• the appearance of vagueness or intermittency of the objects in question;
• feeling of “sand” in the eyes;
• redness of the eyes;
• photophobia or dark adaptation disorder;
• difficulty or impossibility of quickly focusing when changing your gaze from a close distance to an object in the distance and vice versa;
• headache;

The main diagnostic criterion for asthenopia is an increase in the above-described complaints during intense visual stress (working on a computer, working with documents, reading or needlework). In this case, all relevant symptoms may significantly decrease or disappear completely during rest.

Asthenopia

Both adults and children are susceptible. Moreover, this disorder most often affects children of middle and high school age, as well as students. That is, all those categories of the population performing any work related to visual stress for a long time.

And so the main causes and risk factors for the development of asthenopia are:

• reading or any visual work in low light;
• working at the computer or watching TV for a long time;
• long periods of driving, especially at dusk and at night;
• work associated with constant visual strain, for example, work with small details (embroidery, jeweler’s work and other similar industries);
• improper correction of ametropia (myopia, farsightedness or astigmatism);
• general diseases, in particular endocrine ones;
• intoxication;

Types of asthenopia:

• Muscular asthenopia. Associated with weakness of convergence i.e. dynamic focusing of both eyes on the fixed object. This can be difficult if the eye muscles are weak.)
• Accommodative asthenopia. Accommodation is the physiological process of changing the refractive power of the eye during visual perception of objects located at different distances from it. The accommodative apparatus of the eye includes: smooth muscle fibers of the ciliary muscle, fibers of the zonular ligament, choroid and lens. Any disturbances in the functioning of these structures can contribute to a decrease in the reserve of accommodation and cause certain asthenopic complaints.
• Mixed asthenopia occurs with a combined disorder of convergence and accommodation.
• Nervous asthenopia can be associated with stress or various mental disorders. 
• Symptomatic asthenopia occurs with various pathologies of the eye and nearby organs and disappears when the underlying disease is cured (1).

Muscular asthenopia most often occurs with uncorrected myopia, farsightedness, presbyopia (age-related farsightedness) or astigmatism.

Asthenopic complaints can also occur with initially incorrectly selected glasses or contact lenses. Or it is possible that myopia or presbyopia has progressed, and the patient continues to use old glasses that are no longer suitable for him in terms of diopter.

Muscular asthenopia can also occur against the background of general diseases that affect the rectus ocular muscles, for example, endocrine diseases (thyrotoxicosis), myasthenia gravis or myositis.

With myopia, work at close distances occurs with increased accommodation, which is carried out with the help of the internal rectus muscles. With strabismus, asthenopia occurs due to fatigue due to the desire to overcome the deviation of the eyes.

Causes accommodative asthenopia – spasm of accommodation, inadequate correction of farsightedness and astigmatism, ocular and general pathology leading to weakness of the ciliary muscle, for example, inflammatory and degenerative diseases of the eye. When working at close range, accommodation tension is required, which is carried out with the help of the ciliary muscles.

Diagnosis of asthenopia:

• Determination of visual acuity with and without correction
• Skiascopy for narrow and wide pupils (more often in children).
• Refractometry with a narrow and wide pupil.
• Determination of the strabismus angle using the Hirschberg method and synoptophore;
• Determination of the nature of vision using a four-point test;
• Measuring the accommodation reserve – an opaque screen is placed in front of one eye and the other is asked to read the text at a distance of 33 cm. Then negative lenses with increasing strength are placed in front of it and allowed to “get used to” for some time. The strongest lens, with which the text can still be read, is considered a reserve of accommodation. At 20-30 years old it is equal to 10 diopters, after 40 years it decreases.
• Determination of fusion reserves is carried out using a synoptophore. In this case, two parts of the image are connected together, then they begin to separate the halves of the drawings and subjectively determine when the eye begins to perceive the image as 2 different ones. Normally, positive reserves (convergent) are 15-25 degrees, and negative reserves (divergent) are 3-5 degrees. With asthenopia they are reduced. Can also be determined using prismatic lenses.

Treatment of asthenopia.

Treatment of asthenopia, as a rule, is long-term and largely depends on the patient’s desire and mood for recovery. The main method is correctly selected correction of ametropia with glasses or contact lenses. Treatment of the cause of asthenopia, including extraocular pathology, is mandatory. To relieve spasm of accommodation and relax the ciliary muscle, short-acting mydriatics are instilled, 1 drop every day or every other day at night for a month.

Hardware treatment methods are used to train the reserves of positive accommodation and convergence. This is achieved by using lenses of varying strengths, prisms and special simulators (2).

Hardware and computer methods for treating amblyopia:

• Synoptophore helps train and develop fusional reserves (the ability to merge visual images from both eyes into a single image).
• Laser stimulation relaxes the ciliary muscle. 
• The accomodo trainer affects accommodation when looking both near and far, and can also be used at home. 
• Various computer programs. To relieve eye fatigue and prevent the development of computer syndrome – EyeDefender, Safe eyes, RELAX. If there is myopia, hypermetropia or strabismus, then EYE, Strabismus, Blade, Flower, Crosses, Contour, etc. (3).

Hardware treatment gives especially good results in children.

Prevention of the development of asthenopia:

• Correct and timely correction of refractive errors (myopia, farsightedness, astigmatism).
• Compliance with the work and rest regime regarding the eyes. After every hour of eye strain, you need to take breaks. At this time, you can do eye exercises.
• Adequate local and general lighting of the workplace.
• The use of special perforated glasses relieves the stress of accommodation.
• Taking vitamins or dietary supplements for the eyes and a proper, balanced diet in general.
• Sports and fitness activities.

The prognosis for asthenopia with timely treatment and compliance with all prevention rules is favorable.

1. “Binocular functions in ametropia” Shapovalov S.L., Milyavsky T.I., Ignatieva S.A., Kornyushina T.A. St. Petersburg 2014

2. “Complex treatment of accommodative disorders in acquired myopia” Zharov V.V., Egorov A.V., Konkova L.V., Moscow 2008.

3. “Functional treatment of concomitant strabismus” Goncharova S.A., Panteleev G.V., Moscow 2004.