The influence of constant slight myopic defocus prescribed in the binocular and alternating monocular spectacle formats on the onset and progression of myopia in the children

Abstract

Objective. To elucidate the long-term influence of constant slight myopic defocus prescribed in the binocular and the alternating monocular spectacle formats on the dynamics of refraction and its components in the children. Material and methods. The study involved 129 children (258 eyes) at the age varying from 5 to 12 years. The patients were divided into four groups. Group 1 was comprised of 48 children at the age of 5-8 years presenting with emmetropia and risk factors of the development of myopia. Group 2 consisted of 46 children at the age from 7 to 11 years with slight myopia between -0.75 and -2.25 D to whom the alternating continuous wearing of two pairs of spectacles was prescribed. The first control group was composed of 15 children (30 eyes) at the age from 6 to 9 (mean 7.5 ± 1.4) years presenting with pseudomyopia without correction. The second control group was comprised of 20 children (40 eyes) at the age from 7 to 12 (mean 9.7 ± 1.2) years having slight myopia and wearing conventional spectacle correction. Results. The children of group 1subjected to constant slight myopic defocus during one month experienced a shift of refraction toward hypermetropia attributable to the thinning of the lens and deepening of the anterior chamber. None of the children in this group developed myopia during the follow-up period of up to 9 years. In the patients of group 2, refraction remained unaltered during either 4 years (81.8% of the cases) or 7 years (66.6% of the cases). An insignificant increase in the length of the antero-posterior axis was documented in these children along with the significant increase of the horizontal diameter (HD) of the eyeball. The dynamic observation of the children of both control groups during 3 years has demonstrated the strengthening of cycloplegic refraction associated with the significant increase of the length of the antero-posterior axis and the insignificant increase of the transverse diameter of the eyeball. Conclusion. The permanent slight myopic defocusing of the image in the binocular spectacle format slows down the growth of the eyes and the shift of refraction toward myopia in the children with mild hypermetropia, emmetropia, and slight myopia. The proposed method for alternating monolateral constant slight myopic defocus inhibits progression of myopia in 81.8% of the children presenting with mild myopia during 4 years and in 66.6% of them during 7 years.