Refractive disorders in children

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

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

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

While low-grade hyperopia is a physiological type of refraction for young children, high-grade hyperopia, myopia, and astigmatism not only cause visual impairment (blurring), but also provoke the development of strabismus and amblyopia. Transient refractive disorders, especially astigmatism, occur in the first year of a child's life.

Various methods are used to study refractive errors in young children.

Visual acuity screening

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

Autorefractometry

Autorefractometry is only advisable in the presence of cycloplegia; in other cases, the method is uninformative.

Photorefractometry

Photorefractometry is performed using photographic equipment. The method makes it possible to evaluate refractive disorder by the nature of the image of the light source reflected from the eye. There are two methods of photorefractometry.

1. On-axis photorefractometry. Several images are taken to assess refractive error, but in most cases off-axis photorefractometry is preferred over this method.
2. Off-axis photorefractometry. No more than one or two images are required to assess refractive errors. That is why this method is more common, especially for screening. The main disadvantage of both methods is the need for cycloplegia to detect small refractive errors (especially with hypermetropic refraction).

Refraction

To this day, the main method for identifying refractive disorders in children is the study of subjective and objective refraction.

Methods of refraction research

Several methods are used to assess refractive disorders. Some studies are conducted under conditions of drug-induced accommodation paralysis, others - without the use of cycloplegic drugs.

Studies without the use of cycloplegic agents

1. Subjective refraction is examined in a dark room. Positive lenses are placed in front of the eye, which prevents accommodation from being activated. The examination always begins with stronger positive lenses, gradually reducing their optical power.
2. Fixation at a distance. The examiner controls the child's fixation at a distance, achieving relaxation of accommodation. This technique has proven itself as an effective method for studying refraction in children.
3. Dynamic retinoscopy. It is one of the main methods of refraction research. It is performed in a darkened room.

Studies under cycloplegia

In most cases, accurate determination of refraction in children is possible only under conditions of drug-induced accommodation paralysis. For this purpose, one of the cycloplegic drugs is instilled into the child. 1.0.5% or 1% atropine solution is instilled one to three times a day for 3 days before the examination. 2.1% cyclopentolate solution is instilled twice at 10-minute intervals directly on the day of the examination. Refraction is examined approximately 30-40 minutes after instillations. 3.1% tropicamide solution is instilled twice at 10-minute intervals directly on the day of the examination. Refraction is examined approximately 30 minutes later. Despite the fact that tropicamide effectively dilates the pupil, the drug does not provide complete cycloplegia, and therefore its use is limited. For children under 6 months of age, use a 0.5% solution of cyclopentolate or a 0.5% solution of tropicamide.

Refractive errors

Subjective research methods

The main problem that arises when studying subjective refraction is the impossibility of controlling accommodation. The most common error that is possible when using this method is overdiagnosis of myopia. Some authors claim that in 10-15% of cases there is overcorrection of myopia.

Retinoscopy technique

Although retinoscopy is the most objective method for determining refraction, it also has its limitations. The short anterior-posterior axis of the infant eye is the cause of hyperopia overdiagnosis in the first months of life, despite attempts to reduce the working distance during the examination. A shift from the center of only 10-15° during off-axis retinoscopy contributes to overdiagnosis of both the frequency of astigmatism and its degree.

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