Correction of poor vision

Correction of poor vision is based on strengthening the visual image due to:

• improvement of image quality;
• magnification of the image on the retina;
• expansion of the field of view.

Means of help are chosen individually, depending on the nature of the pathology of the organ of vision, anatomical-optical characteristics and other ophthalmological parameters.

The expansion of the "tunnel" field of vision is effective at a sufficiently high acute central vision; carried out with the help of reverse telescopes and negative lenses of high refractions.

Improvement of image quality is achieved due to the correction of amethropy and astigmatism, the use of diaphragms, spectral filters, creating optimal levels of illumination. With ametropia, which is noted in 98% of visually impaired children, they use eyeglasses or contact correction in the distance. Special therapeutic light filters are effective in 95% of cases. They protect the structure of the eye from the damaging effect of UV radiation, provide increased visual acuity, contrast, create optimal levels of illumination, reduce light scattering in the environment of the eye, contribute to the prevention of visual complications. They use them with glasses to the distance and for reading, while working with a computer. The choice of the optimal filter is influenced not only by the basic, but also by the accompanying ophthalmopathology, the type of visual work, the conditions of illumination.

Diaphragms increase the resolving power of the eye in non-occlusive opacities of optical media. The use of chromatic spectacle correction and diaphragm can significantly increase visual acuity, however in most cases it is insufficient for the most difficult visual task - reading.

The main way to improve the perception of the visual image is to increase its retinal image in order to connect the functioning paracentral and peripheral parts of the retina to work.

Remote objects are better distinguished by the use of afocal telescopic systems of Galilean or Kepler type of different power, which are divided into telescopic glasses, monoculars and binoculars. Children prefer to use portable monoculars 2,5-5-fold increase, focusing objects from infinity to 1 m. The need to improve distance vision arises mainly during the period of obtaining general or special education, with orientation.

The most difficult visual task is reading. Magnifying agents used to improve vision near: gyrocopy goggles of mono- and binocular use, magnifiers of different powers and designs, telescopic goggles and electronic video magnifiers.

Hyperoculars - glasses with positive spherical or spheroprismatic lenses (so-called magnifying glasses) - one of the main means of helping children with low vision, with the exception of people with myopia. Leaving hands and working space free, they can increase the observed object up to 5 times. With visual acuity above 0.15, glasses often serve as the most sought after augmentation tool.

Wider indications for use are loupes of various design solutions with an increase of 1.5-12 times. With a weak accommodation, aphakia preferred overhead or support loops. However, the higher the magnification, the narrower the lens diameter and, correspondingly, the smaller the letters in the field of view. To expand the visible field, two types of magnifiers are combined: hyperaculars (which can also be used for writing) and magnifiers.

More complicated in use telescopic glasses children do not use because of significant limitations of the field of view, unaesthetic appearance, significant dimensions; glasses, in addition, are not effective in oculomotor pathology (nystagmus, strabismus).

Modern electronic video magnifiers contain many attractive features for visually impaired people: large visible field size, sufficient depth of field, stable working distance and precise focusing. A wide range of magnifications (5-40 times) makes it possible to distinguish a book font with a visual acuity of 0.01-0.02. At work it is possible to use contact and glasses correction, light filters, to observe correct posture, to carry out an eccentric fixation of a gaze, to connect to seeing worse a seeing eye. The inversion of the image of letters, adjustable brightness, contrast provide comfortable conditions for people with photophobia, and requiring higher levels of illumination. In cases of uneven visual acuity on two eyes, the device can provide acceptable conditions for the second eye to perceive information. However, the reading speed is constrained by a limited number of letters on the screen of the monitor (although their number in the field of view is greater than when using loops of equal magnification). Reduces the speed of reading the delay in the appearance of a clear image of letters on the monitor while moving the camera along the line; discoordination of eye movements during reading (from left to right) and "running" line on the screen (from right to left); time costs for translating text manually from line to line. In this regard, videoimplifiers recommend children with a significant decrease in vision: from 0.02 to 0.1-0.12, with a reading speed of no higher than 500-600 z / min.

Children easily adapt to new situations and quickly learn to use optical devices. In addition to correction of visual acuity, improvement of oculomotor activity is necessary, development of eye-hand coordination. Careful examination of the central area of the field of vision can help in choosing the most optimal position of the book with fixation of the text by the retina with the highest resolution or with a sufficiently wide field. The purpose of various means of special care, in addition, depends on the child's age, his somatic pathology, the presence and severity of neuropsychiatric disorders. Children up to 5-6 years of age generally need tools for improving image quality: glasses, contact, intraocular lenses, spectral filters; to consider closely located objects may require second glasses, 2-4 Dpts stronger than the points in the distance. The help of parents, educators, teachers is important. When enrolling in school, they use other magnifying aids: support or overhead magnifiers of large diameter. In addition to improving the perception of small objects, magnifying glasses prevent a reduction in working distance, which is important for preventing deformation of the chest and spine in children. The need for magnifiers increases throughout the entire study period: the visual load is increased, the training font is reduced, the disease may progress. In adolescence, children more often use telescopes in the distance, the age-related decrease in the amount of accommodation requires stronger magnifiers when reading and writing. They use computers more actively, when working with which bifocals are often used. Adolescents show more personal initiative in mastering the means of increasing communication, receiving various visual information.

Special correction of the visually impaired is effective throughout the lifetime of a child with a disability and serves as one of the main components of a complex of rehabilitation measures for education, rational employment and for raising the standard of living.

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