Refractive disorders in children

Refraction of the eye depends on the state of the four structures and their interaction:

1. optical power of the cornea;
2. depth of anterior chamber;
3. optical power of the lens (its thickness and curvature);
4. length of anterior-posterior axis of the eye.

Changes in one or more of these parameters cause a refractive disorder. For example, excessive growth of the eyeball in the antero-posterior direction leads to the occurrence of myopic refraction.

While low-grade hypermetropia is a physiological type of refraction for younger children, a high degree of hypermetropia, myopia and astigmatism lead not only to visual impairment (fogging), but to the appearance of strabismus and amblyopia. In the first year of the child's life there are transient refractive disorders, especially astigmatism.

To study refractive disorders in young children apply different methods.

Screening for visual acuity

With the standard screening technique, the main goal is to identify amblyopia or gross refractive anomalies. Unfortunately, this method is not effective in children under 3-4 years of age.

Autorefractometry

Carrying out of autorefractometry is expedient only against cycloplegia, in other cases the method is not very informative.

Photorefractometry

Photorefractometry is carried out using photographic technique. The method makes it possible to evaluate the refractive error by the nature of the image of the light source reflected from the eye. There are two ways of photorefractometry.

1. Axial photorefractometry. To assess refractive error, several photographs are taken, but in most cases this method is preferred to off-axis photorefractometry.
2. Off-axis photorefractometry. To assess the violation of refraction, no more than one or two photographs are required. This is why this technique is more common, especially when conducting screening. The main disadvantage of both methods is the need for cycloplegia to detect small refractive defects (especially with hypermetropic refraction).

Refraction

To detect refractive disorders in children to this day, the main method is to study subjective and objective refraction.

Methods for the study of refraction

Several methods are used to assess refractive error. Some studies are conducted in conditions of pharmacological paralysis of accommodation, others - without the use of cyclophilic drugs.

Studies without the use of cycloplegic drugs

1. Subjective refraction is examined in a dark room. Before the eye put positive lenses, which prevents the inclusion of accommodation. Research always begins with stronger positive lenses, gradually reducing their optical strength.
2. Fixing into the distance. The researcher controls the child's fixation in the distance, seeking relaxation of accommodation. This technique has proved to be an effective method of studying refraction in children.
3. Dynamic retinoscopy. It is one of the main methods of investigating refraction. Carried out in a darkened room.

Research in conditions of cycloplegia

In most cases, the precise definition of refraction in children is possible only in conditions of drug-induced paralysis of accommodation. For this, one of the cycloplegic drugs is instilled in the child. 1.0.5% or 1% atropine solution is instilled one to three times a day 3 days before the study. 2.1% solution of cyclopentolate is instilled twice with an interval of 10 minutes directly on the day of examination. Refraction is examined after about 30-40 minutes after instillation. 3.1% solution of tropicamide is instilled twice with an interval of 10 minutes directly on the day of the examination. Refraction is examined after about 30 minutes. Despite the fact that tropicamide effectively dilates the pupil, the drug does not provide full cycloplegia, and therefore its use is limited. For children less than 6 months of age, use a 0.5% solution of cyclopentolate or a 0.5% solution of tropicamide.

Refractive disorders

Subjective methods of research

The main problem arising in the study of subjective refraction is the impossibility of exercising control over accommodation. The most common mistake, possible with the use of this technique, is hyperdiagnosis of myopia. Some authors assert that in 10-15% of cases there is hypercompression of myopia.

Technique of retinoscopy

Although retinoscopy is the most objective method of determining refraction, it also has its limitations. The short anterior-posterior axis of the infant's eye is the cause of hyperdiagnosis of hypermetropia in the first months of the child's life, despite attempts to reduce the working distance during the study. Displacement from the center of only 10-15 ° in the process of off-axis retinoscopy promotes overdiagnosis as the frequency of astigmatism, and its degree.

[1], [2], [3], [4], [5], [6]