Induced spherical aberration of the cornea and stress accommodation in children with myopia

Purpose: to study the relationship between spherical aberrations of the cornea induced by orthokeratologic (OK) lenses and accommodation stress and to assess the effectiveness of treating accommodation overstrain with Irifrin BK 2.5 % in myopic patients having either unchanged shape of the cornea or changed shape modified by OK lenses. Material and methods. To study the effect of spherical aberration on the accommodation function in patients with unchanged and changed corneal shape, we formed two groups of high school students with myopia. Group 1 included patients with regular contact vision correction (156 eyes), and Group 2 included those with OK correction (196 eyes). To assess the impact of Irifrin BK 2.5 % on the state of accommodation, we examined 142 students (284 eyes) aged 8 to 19 years with myopia from -0.25 to -9.0 D, with changed and unchanged corneal shape, who were divided into three groups. Group 1 consisted of 52 subjects (104 eyes) with regular contact correction (52 children, 104 eyes), received Irifrin BK 2.5 % daily before bedtime for 30 days. Group 2 consisted of 33 subjects (66 eyes), also with normal contact correction (66 eyes) who were given the same quantity of the drug in the same pattern for 60 days. Group 3 (57 subjects, 114 eyes) with OK correction and varied negative spherical aberration received the drug for 30 days. Results. It was found that the character of spherical aberration in the unchanged corneal shape is different from that changed by OK lens. If the shape is unchanged, in 93.5 % of cases a positive spherical aberration is revealed, so that the share of negative spherical aberration accounts for 6.5 % of cases. In contrast, if the shape of the cornea is changed by OK lenses negative spherical aberration claims 86.7 %, leaving only 13.3 % for positive spherical aberration. A 30-day Irifrin BК treatment of patients with accommodation overstrain in cases of both unchanged and changed corneal shape proved to be more effective than the 60-day course of instillations. However, the treatment of overstrain accommodation with Irifrin BK in patients with OK correction was sufficiently effective for low and moderate negative spherical aberration, whereas in high negative spherical aberration it was noticeably less effective. Conclusion. An interrelation between negative spherical aberration induced by OK lenses with the amplitude and degree of accommodation strain and with the degree of myopia was revealed. It was found that