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.

Evaluating the Self-esteem of Myopic Children Over a Three-Year Period: The COMET Experience

PURPOSE

The purposes of this study were to evaluate self-esteem over 3 years in the 469 myopic children participating in the Correction of Myopia Evaluation Trial (COMET), and to examine its relationship with lens assignment (progressive addition lenses [PALs] vs. single-vision lenses [SVLs]), myopia progression, and several other ocular and demographic characteristics.

METHODS

Data collection included refractive error measurements, child-reported visual symptoms, attitude toward glasses, adherence, and self-esteem as measured by the Self-Perception Profile for Children (SPPC). A two-way analysis of variance (treatment group x time) was performed to examine whether PAL and SVL wearers differed in self-esteem over time. Multiple regression analyses were used to evaluate associations between self-esteem at follow-up and relevant factors identified by univariate analyses.

RESULTS

Regardless of lens assignment or myopia progression, COMET children reported moderate to high levels of self-esteem at follow-up in the areas of scholastic and athletic competence, physical appearance, social acceptance, behavioral conduct, and global self-worth. Mean scores ranged from 2.87 (+/- 0.68) on athletic competence to 3.40 (+/- 0.56) on global self-worth. Self-esteem changed significantly (p < 0.05) over 3 years in the domains of scholastic competence, social acceptance, and physical appearance. Self-esteem at follow-up was associated with visual symptoms, attitude toward glasses, age, gender, and ethnicity.

CONCLUSIONS

Lens assignment and myopia progression were not associated with self-esteem in the COMET cohort. These children had high levels of self-esteem, suggesting that having myopia does not negatively impact self-esteem. Follow-up reports will monitor self-esteem and related factors in this cohort of myopic children over the course of adolescence and early adulthood.

The intraexaminer and interexaminer repeatability of the alternate cover test using different prism neutralization endpoints

PURPOSE

The alternate cover test (ACT) measures the magnitude of a deviation, but different prism endpoints may be used. This study investigated the intraexaminer and interexaminer repeatability of the ACT using two different prism neutralization endpoints.

METHODS

To determine repeatability of two prism neutralization endpoints (first neutral and midpoint of reversal), two experienced examiners measured near point phoria on 72 subjects. Measurements were repeated with examiners masked to each other and the first results. Paired t-tests were used to assess interexaminer and intraexaminer repeatability and the agreement between different prism endpoints for each examiner within each session. Signed and absolute differences in phoria magnitude were calculated.

RESULTS

For two different test sessions with the same examiner using the same prism neutralization endpoint (intraexaminer repeatability), none were significant except examiner 1 using first neutral (p = 0.038). Average signed differences (ASD's) between two test sessions for each comparison were <0.5 prism diopter (pd) with SD's of </=2.56 pd. Absolute differences ranged from 1.30 to 1.89 pd. When two different examiners used the same prism endpoint within the same session (interexaminer repeatability), there were no significant differences between examiners. ASD's between the two examiners for each comparison were </=0.53 pd with SD's </=2.03 pd. The absolute differences ranged from 1.19 to 1.67 pd. Comparisons of the two different prism endpoints by the same examiner at a single test session were all significantly different (p < 0.005), but the differences (<1 pd between the two endpoints) were not clinically significant. ASD's were <1 pd with SD <2 pd. Absolute differences ranged from 1 to 1.58 pd.

CONCLUSIONS

With experienced examiners, either prism endpoint provides high interexaminer and intraexaminer repeatability (</=0.5 pd). Although the two prism endpoints differ statistically, the differences are not clinically significant.

The relationship between self-esteem of myopic children and ocular and demographic characteristics

PURPOSE

To evaluate self-esteem and its relationship with various ocular and demographic characteristics in 469 myopic children participating in the Correction of Myopia Evaluation Trial (COMET), an ongoing, randomized, multicenter clinical trial designed to evaluate the effects of progressive addition lenses vs. single vision lenses on the progression of juvenile-onset myopia.

METHODS

Baseline data collection included demographic information, refractive error measurements, parent-reported myopia history, child-reported visual symptoms, and self-esteem in several areas (scholastic/athletic competence, physical appearance, social acceptance, behavioral conduct, and global self-worth) as measured by the Self-Perception Profile for Children. Univariate and multiple regression analyses were used to identify factors associated with self-esteem.

RESULTS

The Self-Perception Profile for Children is a reliable measure of self-esteem in COMET children as indicated by the high internal consistency reliabilities (0.74 to 0.81) obtained for the various domains. COMET children's mean self-esteem scores ranged from 2.72 +/- 0.69 for athletic competence to 3.36 +/- 0.56 for global self-worth and were similar to normative samples. Multiple regression analyses showed that less symptomatic children had higher self-esteem in all areas (p < 0.05), except athletic competence, after adjusting for other ocular and demographic characteristics. Self-esteem also varied significantly by age, gender, and ethnicity (p < 0.05).

CONCLUSIONS

Baseline self-esteem is associated with visual symptoms, age, gender, and ethnicity, but not with magnitude of refractive error. Follow-up reports will assess whether there are changes in self-esteem associated with myopia progression and lens assignment.

Interocular suppression produced by rivalry stimuli: a comparison of normal and abnormal binocular vision

This study compares interocular suppression in subjects with early strabismus and/or anisometropia with binocular rivalry suppression in subjects with normal binocular vision. A psychophysical test-probe paradigm was used to measure the changes in luminance-increment detection thresholds associated with periods of phenomenal suppression. In subjects with normal binocular vision, rivalry suppression induced by viewing orthogonally oriented grating pairs produced a distinctive wavelength-dependent change in visual sensitivity; specifically, there was a greater reduction in sensitivity for short (e.g., 450 nm) vs. middle or long wavelength stimuli (e.g., 560 nm). In contrast, subjects with abnormal binocular vision, regardless of the type of early abnormal visual experience, showed more reduction in sensitivity for a 560-nm stimulus than for the short-wavelength, 450-nm stimulus. Moreover, the pattern of sensitivity change in subjects with abnormal binocular vision was the same for suppression induced by either rivalry stimuli or stimuli that would normally promote fusion. The results clearly indicate that interocular suppression in subjects with abnormal binocular vision is qualitatively different from normal binocular rivalry. Evidently, the processes that mediate binocular rivalry are very susceptible to environmental influences during early vision development and can be disrupted easily.

A new version of the TVAS: a validation report

The purpose of this study was to investigate the validity of a revised version of the Test of Visual Analysis Skills (TVAS). Data are presented from testing 198 subjects in two elementary schools with two versions of the TVAS and a second perceptual skills test (VMI). Within-age-group, between-school statistical comparisons strongly support the validity of the revised TVAS.