Development of Vernier acuity in childhood

PURPOSE: To measure Vernier acuity and resolution development after 3 years of age. METHODS: Observers were 39 children with normal vision (aged 3 to 12 years), 10 adult observers with normal vision (aged 19 to 24 years), and 7 adults with amblyopia. Vernier acuity and resolution were measured using uncrowded static stimuli and a 3AFC psychophysical paradigm. Curve fitting was used to estimate A2, the age at which thresholds are twice asymptotic levels. RESULTS: Vernier acuity was hyperacute (i.e., finger than predicted from foveal cone size or spacing) in 3- to 4-year-old observers, but developed later (A2 = 5.6 +/- 1.5 years) than resolution acuity (A2 = 2.2 +/- 0.9 years). CONCLUSIONS: Children's Vernier thresholds are poorer than would be predicted solely from their decreased foveal photon capture. Therefore cortical immaturity may play a role in children's relative position acuity deficit. R/V ratios (resolution/Vernier thresholds) for the youngest age group are similar to those for adult nonstrabismic amblyopes, but better than for strabismic amblyopes

Visibility of motion in infant vernier displays, using adult subjects

Motion is frequently incorporated in stimuli used for psychophysical testing of vernier acuity in infants and young children. In such stimuli, detection of the vernier offset is necessary in order to perceive the motion. Research described in this report tested whether the perception of a vernier offset is sufficient to signal the stimulus motion in adults. We measured how motion detectability changed as a function of vernier offset for two adult subjects, using a stimulus similar to that employed by other authors to measure vernier acuity in infants and children. Motion visibility varied with offset size, achieving a detectability of motion (d') of 0.95 (comparable to two-alternative forced-choice thresholds) at stimulus offsets of 16-19 s arc. In comparison to the motion, the stimulus offset itself was much easier to see, being detectable on 95-100% of trials with the smallest offset, 6.6 s arc. This distinction, between the visibility of motion and the visibility of the vernier offset itself, should be considered when interpreting vernier results using such displays, especially in infants and children for whom motion may be the attractive cue

Age-Related Changes in Accommodative Dynamics from Preschool to Adulthood

Specific aspects of accommodative dynamics are shown to change with age from preschool to adulthood, whereas other aspects remain stable over these ages in response to a range of near stimulus demands

Static and Dynamic Measurements of Accommodation in Individuals with Down Syndrome

Dynamic measurements of accommodation in subjects with Down syndrome (DS) demonstrated that primarily motor aspects of accommodation did not differ from those of controls; however, combined sensory and motor aspects were poorer in subjects with DS. These findings suggest that poor accommodative accuracy in individuals with DS may be predominantly related to sensory deficits

Longitudinal changes in corneal curvature and its relationship to axial length in the Correction of Myopia Evaluation Trial (COMET) cohort

Purpose: To describe longitudinal changes in corneal curvature (CC) and axial length (AL) over 14 years, and to explore the relationship between AL and CC, and the axial length/corneal radius (AL/CR) ratio. Methods: In total 469, 6 to <12-year-old, children were enrolled in COMET. Measurements of refractive error, CC (D), CR (mm), and ocular component dimensions including AL were gathered annually. Linear mixed models were used to evaluate longitudinal changes adjusting for covariates (gender, ethnicity, lens type, baseline age and baseline refraction). The Pearson correlation coefficient between AL and CC was computed at each visit. Results: There was a slight but significant (p < 0.0001) flattening in CC over 14 years. At all visits females had significantly steeper CC than males (overall difference = 0.53 D, p < 0.0001). Caucasians had the steepest CC, and Hispanics the flattest (p = 0.001). The correlation between AL and CC was −0.70 (p < 0.0001) at baseline (mean age = 9.3 years) and decreased to −0.53 (p < 0.0001) at the 14-year visit (mean age = 24.1 years). The average AL/CR ratio was 3.15 at baseline and increased to 3.31 at the 14-year visit. The correlation between the magnitude of myopia and AL/CR ratio was significantly higher (p < 0.0001) at each visit than the correlation between myopia and AL alone. Conclusions: Differences in average corneal curvature by age, gender, and ethnicity observed in early childhood remain consistent as myopia progresses and stabilizes. This study also demonstrates increases in the AL/CR ratio as myopia progresses and then stabilizes, supporting observations from previous cross-sectional data

A Randomized Trial of the Effect of Soft Contact Lenses on Myopia Progression in Children

Purpose: Soft contact lenses have been reported to increase the progression of myopia. The purpose of this study was to determine whether soft contact lenses affect the progression of myopia in children. Methods: Children between the ages of 8 and 11 years with −1.00 to −6.00 D myopia and less than 1.00 D astigmatism were randomly assigned to wear soft contact lenses (n = 247) or spectacles (n = 237) for 3 years. Refractive error and corneal curvatures were measured annually by cycloplegic autorefraction, and axial length was measured annually by A-scan ultrasound. Multilevel modeling was used to compare the rate of change of refractive error, corneal curvature, and axial length between spectacle and contact lens wearers. Results: There was a statistically significant interaction between time and treatment for myopia progression (P = 0.002); the average rate of change was 0.06 D per year greater for contact lens wearers than spectacle wearers. After 3 years, the adjusted difference between contact lens wearers and spectacle wearers was not statistically significant (95% confidence interval [CI] = −0.46 to 0.02). There was no difference between the two treatment groups with respect to change in axial length (ANCOVA, P = 0.37) or change in the steepest corneal curvature (ANCOVA, P = 0.72). Conclusions: These data provide reassurance to eye care practitioners concerned with the phenomenon of “myopic creep.” Soft contact lens wear by children does not cause a clinically relevant increase in axial length, corneal curvature, or myopia relative to spectacle lens wear. (ClinicalTrials.gov, NCT00522288.)Vision Science