The relationship between accommodative and binocular function with myopia progression in myopic children undergoing orthokeratology.

PURPOSE: To determine the relationship between changes in accommodative and binocular function with myopia progression in myopic children over a two-year follow-up period, and to determine when changes in visual functions stabilized after switching from spectacles to orthokeratology (Ortho-K). METHODS: This prospective, self-controlled study followed thirty-six participants (aged 8-14 years) for two years after they switched from spectacles to Ortho-K. Accommodative and binocular function were assessed prior to and 1, 3, 6, 12, 18 and 24 months after commencing Ortho-K. Measurements included accommodative amplitude, accommodative response, accommodative facility, accommodative convergence/accommodation (AC/A), ocular alignment, positive relative accommodation (PRA), negative relative accommodation (NRA), horizontal vergence range, reading ability and stereoacuity. Myopia progression was quantified by the change in axial length. RESULTS: Ocular alignment, monocular and binocular accommodative facility, and PRA stabilized after 1 month. The distance blur point in the convergence range, the distance break and recovery point in the divergence range, accommodative amplitude, calculated AC/A, stereoacuity and reading ability stabilized within 6 months. After two years of Ortho-K, NRA significantly increased (p = 0.044), while it showed no significant difference after one-year of lens wear (p = 0.49). The distance break point in the convergence range showed no significant difference (p = 0.20), but significantly decreased after one-year (p = 0.005). There were no significant correlations between the change in axial length with changes in accommodative or binocular function (p > 0.05). CONCLUSION: Accommodative and binocular function changed significantly after switching from spectacles to Ortho-K and most of the parameters stabilized within the first 6 months. There was no association between the change in accommodative or binocular function and myopia progression.

The effects of base curve aspheric orthokeratology lenses on corneal topography and peripheral refraction: A randomized prospective trial.

BACKGROUND: To investigate the effects of orthokeratology (ortho-k) lenses with aspheric and spherical base curve designs on corneal refractive power (CRP) and peripheral refraction. METHODS: Children aged 8 to 12 years with myopia between -0.75 D to -4.00 D, astigmatism ≤1.00 D, and corneal astigmatism ≤1.50 D were randomly assigned to the base curve aspheric (BCA) and base curve spherical (BCS) ortho-k lens groups. CRP was assessed for the central 8 mm cornea along horizontal and vertical meridians, and peripheral refraction was measured at 10°, 20°, and 30° along the nasal and temporal retina. Primary measurements included relative corneal refractive power change (RCRPC) and relative peripheral refraction change (RPRC). RESULTS: The 3-month results of the 33 and 29 subjects (right eye only) in the BCA and BCS groups, respectively, were obtained. Nonsignificant differences were found in the baseline data between the two groups (p > 0.05). At the 3-month follow-up visit, the mean RCRPC in the BCA group (2.08 ± 0.65 D) was significantly greater than that in the BCS group (1.32 ± 0.81 D) (F1,51 = 25.25, p < 0.001). The BCA group (-1.82 ± 0.65 D) exhibited a larger absolute RPRC than the BCS group (-0.98 ± 0.54 D) (F1,57 = 33.73, p < 0.001). CONCLUSIONS: It was found that the BCA ortho-k lens resulted in a more aspheric treatment zone and a more myopic relative peripheral refraction (RPR) along the horizontal meridian. The more myopic RPR was contributed by a more hyperopic central refraction and a more myopic peripheral refraction in the BCA group.

Accommodation and binocular vision changes after wearing orthokeratology lens in 8- to 14-year-old myopic children.

PURPOSE: The study aimed to observe and analyze the dynamic accommodation and binocular vision changes in myopic children after they switched from spectacles to orthokeratology (ortho-k) lenses. METHODS: Thirty-six myopic children aged 8-14 years were enrolled in this prospective, self-controlled study from West China Hospital. General information was gathered, and examinations were performed at baseline and at 1, 3, 6, and 12 months after switching to ortho-k lenses. The examination included assessments of distance/near visual acuity, distance/near horizontal and vertical ocular alignment, distance/near horizontal vergence range, accommodative amplitude, monocular/binocular accommodative facility, accommodative response, positive and negative relative accommodation (PRA/NRA), accommodation convergence/accommodation (AC/A), stereopsis, and reading ability. RESULTS: After the children switched to ortho-k lenses, distance and near ocular alignment showed an exophoric shift (distance: p = 0.001, near: p = 0.002), and the horizontal vergence range decreased by different degrees (convergence: distance blur point (p = 0.002), distance break point (p = 0.005), near blur point (p = 0.011), near break point (p = 0.043); divergence: distance break point (p < 0.001), distance recover point (p < 0.001), near recover point (p = 0.005)). The stereopsis ability (p < 0.001), monocular/binocular accommodative facility (p < 0.001), and PRA (p = 0.010) increased. The accommodative lag (p < 0.001), accommodative amplitude (p < 0.001), and calculated and gradient AC/A (calculated: p = 0.001, gradient: p = 0.025) decreased. The adjusted horizontal and vertical reading times and their ratio decreased (all p < 0.001). CONCLUSION: The subjects showed distance and near exophoric shifts after switching to ortho-k lenses; improvements in accommodative function, stereopsis, and ocular motility; and a decrease in the binocular horizontal vergence range. The relationships between these changes and the ortho-k myopic control effects require further investigation.

Relationship between higher-order aberrations and myopia progression in schoolchildren: a retrospective study.

AIM: To investigate the relationship between higher-order aberration (HOA) and myopic progression in school children. METHODS: Between April 23, 2011 and August 29, 2011 in the children's myopia outpatient clinic of the West China Hospital of Sichuan University, 148 eyes of 74 schoolchildren were reviewed. HOAs for a 6-mm pupil were measured with an aberrometer. Myopic progression rate was defined according to the change in spherical equivalent refraction (SER) divided by the time span (years). Subjects with myopic progression rate of ≥0.50 diopters (D) were classified as the 'fast' group and the subjects with myopic progression rate of <0.50D were classified as the 'slow' group. A retrospective study was conducted to compare HOA between the two groups, using root mean square (RMS) values and Zernike coefficients. RESULTS: The RMS values of HOA (t=2.316, P=0.02), HOA without Z4 (0) (t=2.224, P=0.03), third-order aberrations (t'=2.62, P=0.01), and coma (t'=2.49, P=0.01) were significantly higher in the fast group than those in the slow group. The individual Zernike coefficients of Z3 (-1) (t=-2.072, P=0.04) and Z5 (1) (Z =-2.627, P=0.01) displayed statistically significant differences between the two groups. Significant correlations were found between the RMS values of HOA (r=0.193, P=0.019), RMS values of HOA without Z4 (0) (r=0.23, P =0.005), RMS values of coma (r=0.235, P=0.004), RMS values of third-order aberrations (r=0.243, P =0.003), and the progression rate. CONCLUSION: Our results provide evidence of a relationship between HOA and myopic progression. In a future prospective longitudinal study, we aim to verify whether HOA is a risk factor for myopic progression.