Spherical Equivalent of Eye Refraction

The spherical equivalent of the refraction of the eye is the arithmetic average of the refractive index in diopters of astigmatic eyes along the two main meridians, which are measured using skiascopy.

Spherical equivalent refraction is a measure of the eye's astigmatism and is used to determine the degree of refractive error and its effect on visual function. Normally, the eye has an ideal spherical shape, but if there is astigmatism, its shape is distorted. At the same time, refractive indexes along the two main meridians may differ from each other.

To measure the spherical equivalent of refraction, a skiascopic examination is used, in which the pupil is looked at through special lenses of different powers. After this, the arithmetic mean value of the refractive index is determined for each of the main meridians of the eye.

Normally, the spherical equivalent of refraction should be no more than 0.5 diopters. If the indicator exceeds this value, this can lead to a decrease in visual acuity and the appearance of distortions in the image.

It is important to note that spherical equivalent refraction is only one of many parameters that is taken into account when determining the degree of astigmatism. For example, the shape and location of the main meridians, as well as the degree of astigmatism for each of the meridians, are also taken into account.

Thus, the spherical equivalent of refraction plays an important role in determining the degree of refractive error of the eyes and can help in choosing the correct vision correction for the patient.