Date Published: June 12, 2019
Publisher: Public Library of Science
Author(s): Jaeryung Kim, Dong Hui Lim, Sun Hyup Han, Tae-Young Chung, Hidenaga Kobashi.
To investigate the factors affecting axial length (AXL) growth and myopia progression in orthokeratology.
This prospective, observational study enrolled 28 new orthokeratology lens wearers from a contact lens clinic between March 2016 and March 2017. Among them, 32 eyes of 17 wearers who completed one year of follow-up were finally analyzed. All participants underwent central (C) and peripheral (nasal 30° [N30] and temporal 30° [T30]) AXL measurements as well as central and peripheral refraction, ocular aberrations, and corneal topography at baseline and every posttreatment visit. A generalized estimating equation (GEE) was used to assess the associations between AXL change and all independent variables in both eyes.
The mean central AXL was 24.21 ± 0.60 mm and the mean baseline central spherical equivalent refractive error (SER) was −2.43 ± 0.97 diopters (D). Among all parameters that were significantly associated with AXL change in univariable GEE analyses, the baseline difference in AXL between C and N30 (β = −0.213, p < 0.001), baseline SER (β = −0.040, p < 0.033), posttreatment coma (β = −0.291, p < 0.031), third-order higher-order aberrations (HOAs) (β = −0.482, p < 0.001), and changes in second-order aberrations (β = 0.025, p = 0.027) at one year of follow-up were identified as significant factors in multivariable GEE analysis. The inhibition of AXL elongation and myopia progression in orthokeratology lens wear is significantly associated with the peripheral myopization and asymmetric optical changes mostly induced by third-order HOAs.
Myopia is one of the most common ocular diseases that can present during childhood. The prevalence of myopia has increased over the last few decades , especially in East Asians . The progression of early-onset myopia is usually attributed to axial length (AXL) elongation that is not fully compensated for by a reduction in refractive power of the cornea and crystalline lens [3, 4]. Although myopia is usually adequately corrected by eyeglasses or contact lenses, these treatments cannot prevent AXL elongation. Because high myopia is closely associated with vision-threatening complications such as macular degeneration, retinal detachment, and glaucoma [5, 6], the hindering of myopia progression could potentially benefit children with myopia worldwide by ensuring a decreased risk of these complications.
This study included 32 eyes of 17 orthokeratology lens–treated myopic children. Table 2 presents the main baseline parameters of the children. The age at initial lens wear was 8.63 years ± 0.83 years. The mean logarithm of the minimum angle of resolution uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) were 0.72 ± 0.32 and 0.01 ± 0.02, respectively. The baseline SERs in the central, N30, and T30 gazes were −2.43 ± 0.97 D, −2.17 ± 0.99 D, and −2.63 ± 0.79 D, respectively. The values of parameters at one year of follow-up and the changes of these parameters between baseline and one year of follow-up are presented in Tables 3 and 4. The spherical equivalent refractive error measured by manifest refraction at one year of follow-up was −0.87 ± 0.64 D.
In this study, we demonstrated that the baseline differences in AXL between C and N30 and posttreatment ocular HOAs are significantly associated with AXL growth and myopia progression in orthokeratology. Considering the interindividual variation in myopia progression after orthokeratology wear, our results would be beneficial in the selection of suitable candidates for orthokeratology to inhibit myopic progression as well as correct myopia.