Biomedical subjects

Jane Gwiazda

Publications and source records attributed to Jane Gwiazda.

12 recordsLinked to original sources

PubMed2006

Evaluating masking in a randomized, double-masked clinical trial in children with myopia.

PURPOSES: The purposes of this study were to evaluate the success of masking in the Correction of Myopia Evaluation Trial (COMET), a study designed as a randomized, double-masked clinical trial comparing the effect of progressive addition lenses (PALs) with single-vision lenses (SVLs) in slowing myopia progression among children and to investigate the impact of unmasking on the treatment effect. METHODS: The success of masking of children and parents was assessed by questionnaires administered after the clinical trial results were reported and before families were informed of their child's lens assignment. Children and parents who correctly guessed their assignment with absolute or "pretty sure" certainty were considered as unmasked. The role of children's age, gender, and ethnicity in unmasking was evaluated using logistic regression. The impact of unmasking on the treatment effect at 3 years was investigated using analysis of variance. The success of masking of the study optometrists was assessed by data collected at the child's follow-up visits. RESULTS: Overall 93% (436 of 469) of the COMET children responded to the questions about lens assignment and certainty. Thirty-seven percent (163 of 436) of children met the criteria for being unmasked with similar results from the parents. The majority (91%) of the 163 "unmasked" children reported that their glasses were the main reason for lens identification. Although children 10 to 11 years at baseline became unmasked more often than did children 6 to 9 years (44% vs. 31%, p = 0.01), there was no difference between boys and girls becoming unmasked (p = 0.2). The treatment effect did not differ between the masked and unmasked children (p = 0.69). The study optometrists became unmasked for five children over the course of 3-year follow up. CONCLUSIONS: Masking was successfully maintained for the study optometrists and the majority (63%) of COMET children. Although some children were able to identify their lens assignment, the primary study outcome was not affected by unmasking.

Child↗

PubMed2005

Relationship of age, sex, and ethnicity with myopia progression and axial elongation in the correction of myopia evaluation trial.

OBJECTIVE: To identify the baseline factors independently related to 3-year myopia progression and axial elongation in COMET. METHODS: A total of 469 children were enrolled, randomly assigned to progressive addition lenses with a + 2.00 diopter (D) addition or to single vision lenses and observed for 3 years. Eligible children were 6 to 11 years old, with spherical equivalent myopia of - 1.25 to - 4.50 D, bilaterally. The primary and secondary outcomes, myopia progression by cycloplegic autorefraction and axial elongation by A-scan ultrasonography, were measured annually. Multiple linear regression was used to adjust for covariates, including treatment. RESULTS: Younger baseline age (6-7 vs 11 years, 8 vs 11 years, and 9 vs 11 years, P<.001; 10 vs 11 years, P = .04), female sex (P = .01), and each ethnic group compared with African Americans (Asian, P = .02; Hispanic, P = .002; mixed, P = .002; white, P = .001) were independently associated with faster 3-year progression. Children aged 6 to 7 years had the fastest progression of all age groups, progressing by a mean (+/- SD) of 1.31 D +/- 0.13 more than children aged 11 years. Females progressed 0.16 D more than the males. Children of mixed, Hispanic, Asian, and white ethnicity progressed more than African American children by 0.49 D +/- 0.16, 0.33 D +/- 0.11, 0.32 D +/- 0.13, 0.27 D +/- 0.08, respectively. Age and ethnicity, but not sex, were independently associated with axial elongation. Among these myopic children, a 0.5 mm increase in axial length was associated with 1 D of myopia progression. CONCLUSIONS: Younger baseline age was the strongest factor independently associated with faster myopic progression and greater axial elongation at 3 years. African American children had less myopic progression and axial elongation than the other ethnic groups.

Age Factors↗

PubMed2005

The association of wavefront aberration and accommodative lag in myopes.

Accommodative lags, induced by a target at 33 cm (distance-induced condition) and by a -3.0 D lens (lens-induced condition), and wavefront aberrations were measured in 27 young myopic eyes. The accommodative lags and Strehl ratios derived from the wavefront aberrations in myopes were compared with those from 57 emmetropes. Accommodation was measured using a Canon R-1 autorefractor, while aberrations were measured using a psychophysical ray-tracing technique. In accord with previous results, larger accommodative lags were found for the myopes than the emmetropes in both the lens-induced and distance-induced conditions. The mean Strehl ratio was smaller in the myopes (0.079) than the emmetropes (0.091); this difference approached significance (p = 0.055). In addition, for myopes the accommodative lag was significantly correlated with the Strehl ratio in the lens-induced condition (r = -0.45, p < 0.02) and approached significance in the distance-induced condition (r = -0.35, p = 0.07). No significant correlations were found for emmetropes. Possible reasons to account for these results are discussed.

Accommodation, Ocular↗

PubMed2005

Accommodation, accommodative convergence, and response AC/A ratios before and at the onset of myopia in children.

PURPOSE: The purpose of this study was to investigate accommodation, accommodative convergence, and AC/A ratios before and at the onset of myopia in children. METHODS: Refractive error, accommodation, and phorias were measured annually over a period of 3 years in 80 6- to 18-year-old children (mean age at first visit = 11.1 years), including 26 who acquired myopia of at least -0.50 D and 54 who remained emmetropic (-0.25 to + 0.75 D). Refraction was measured by noncycloplegic distance retinoscopy. Concomitant measures of accommodation and phorias were taken for letter targets at 4.0 m and 0.33 m using the Canon R-1 open field-of-view autorefractor with an attached motorized Risley prism and Maddox rod. The accommodation and phoria measurements were used to calculate response AC/A ratios. RESULTS: Compared with children who remained emmetropic, those who became myopic had elevated response AC/A ratios at 1 and 2 years before the onset of myopia, in addition to at onset and 1 year later (t's = -2.97 to -4.04, p < 0.01 at all times). The significantly higher AC/A ratios in the children who became myopic are a result of significantly reduced accommodation. Accommodative convergence was significantly greater in myopes only at onset. CONCLUSIONS: These findings suggest that the abnormal oculomotor factors found before the onset of myopia may contribute to myopigenesis by producing hyperopic retinal defocus when a child is engaged in near-viewing tasks.

Accommodation, Ocular↗

PubMed2005

Myopia progression is specified by a double exponential growth function.

PURPOSE: The purpose of this study was to demonstrate how well a modified Gompertz double exponential growth function delineates the diverse courses of myopia progression found in individual eyes. The function is: R = Re + Rc(0.07295)(a(x - t0)) where the spherical equivalent refractive error at a given age R equals the initial refractive error (Re) plus the overall refractive change (Rc) times a double exponential function with the base (0.07295) representing the proportion of Rc that occurs when maximum acceleration is reached, a is a curvature coefficient, t0 is the age of onset and x is age. METHODS: This function was fit to longitudinal refractive data (spherical equivalents) for both eyes of 36 myopic children. The fits were required to meet a stringent set of criteria, including fitting transitions in and out of myopia progression and having no systematic errors or arbitrary constants. RESULTS: Correlation between values on the refractive function and corresponding data of individual eyes is high (mean r = 0.973 +/- 0.020), the sum of squares between the data and function is low, and all other criteria are met. The rates of refractive change and acceleration were derivable from this function. It has been shown that, if peak acceleration rate is used as a criterion for the onset of myopia progression, then myopization onset starts a year earlier (mean = 8.93 years) than when a -0.50-D onset criterion is used (mean = 9.93 years), and it usually starts before the spherical equivalent reaches zero (mean R = +0.09 D). Age of onset is highly correlated with the duration of myopia progression (r = 0.693), which in turn is correlated with the amount of myopia achieved (r = 0.443). CONCLUSIONS: We demonstrate that the double exponential function delineates the dynamics of myopia progression onset, offset, and the derivatives that describe the mechanisms underlying the growth process that causes myopia and have explained the advantages of this function. The function can be used to more accurately portray the course of individual subject's myopic progression.

Adolescent↗

PubMed2004

Increased accommodation following adaptation to image blur in myopes.

Prolonged exposure to blurred images produces perceptual adaptation (M. A. Webster, M. A., Georgeson, & S. M. Webster, 2002). The purpose of this study is to test whether in addition to the reported change in perceived blur there is also a change in accommodation. Young adult (aged 18 to 31 years) myopic (n = 23) and emmetropic (n = 17) subjects participated in the study. Myopes were tested with contact lenses and had corrected monocular visual acuity of 20/20 or better. Accommodation was measured binocularly with a PowerRefractor, an eccentric infrared photorefractor. Accommodation for a near target (high-contrast text at 0.33 m) was measured for 2 min before and immediately after 3 min of blur exposure. Blur was induced using 0.2 Bangerter diffusing filters in front of both eyes. In addition, accommodation was measured for a far target (high-contrast letters at 4.0 m) before and after the near measurements, with each subject's initial far readings used as a baseline for calculating the accommodative responses at near. Compared to the pre-adaptation level, myopes showed a significant (p < .01) increase in the near accommodative response after 3 min of blur adaptation, while accommodation to the near target in emmetropes did not change. In a second experiment using monocular viewing, the increase of accommodation found in myopes was shown to occur during the period of blur exposure. The refractive group differences in the accommodative response may be related to differences in the habitual response to image clarity between myopes and emmetropes under normal viewing conditions.

Accommodation, Ocular↗

PubMed2004

Comparison of spherical equivalent refraction and astigmatism measured with three different models of autorefractors.

PURPOSE: The purpose of this study was to compare refractions measured with three different autorefractors. METHODS: The refractive error of each eye of 50 adults aged 17 to 59 years (mean, 30.5 years) was measured without cycloplegia using the Canon R-1 and two newer instruments, the Grand Seiko WR-5100K and the Nidek ARK 700-A. For the first two, an isolated line of 20/100 letters on an ETDRS chart at 4.0 m served as a target, whereas for the Nidek, the subject looked at a picture of a balloon in the instrument. Five readings were taken for each eye, and the data (sphere, negative cylinder power, and axis) were analyzed using Fourier decomposition of the power profile. Each reading was broken down into the spherical equivalent (M) and two Jackson crossed-cylinder vectors, J0 and J45. Right-eye results are reported. RESULTS: The mean spherical equivalent refraction measured by the Canon R-1 was -2.44 D. Measurements from the Grand Seiko were more hyperopic (mean M, -2.01 D), whereas those from the Nidek were more myopic (mean M, -2.66 D). Correlation of M for each pair of autorefractors was 0.99. For J0, the Canon was more minus than the other two instruments by 0.15 D compared with the Nidek and 0.13 D with the Grand Seiko, and on this component, the correlation of the Canon with each of the other two was 0.87. Mean J0 values for the Nidek and Grand Seiko were similar, 0.05 D and 0.03 D, respectively, and mean J45 values were 0.04 D for both instruments. Correlations were 0.97 between these two autorefractors for each of the two components. J45 measured by the Canon was more positive than the other two by 0.06 D. For J45, the correlation of the Canon with the Grand Seiko was 0.40 and with the Nidek was 0.38. In 92% of the eyes, the absolute difference in cylinder power between the Grand Seiko and the Nidek was < or =0.25 D. Only 42% of the differences between the Canon and the Grand Seiko and 40% of the differences between the Canon and the Nidek were this small. CONCLUSIONS: The Canon provided more myopic readings than the Grand Seiko and more hyperopic readings than the Nidek. The Canon measured more astigmatism that did not correlate well with the other instruments, whereas measurements of astigmatism taken by the Nidek and the Grand Seiko showed good agreement. If the Grand Seiko is used in place of the older Canon, the differences in spherical equivalent and astigmatism must be considered.

Adolescent↗

PubMed2003

Change in corneal shape and corneal wave-front aberrations with accommodation.

This study investigated the change in corneal curvature and corneal wave-front aberrations with accommodation. The corneal curvature of the right eyes of 12 young adults was measured using a corneal topography system, while subjects fixated far (4.0 m) and near (0.2 m) targets with their left eyes. Convergence was controlled. Both the mean corneal radius at the vertex and the shape parameter significantly increased from the far to the near viewing condition. No significant change in root mean square of wave-front aberrations with accommodation was observed for the group, but there was individual variation in the change of wave-front aberration. A significant mean change for the group in both x-axis coma and spherical aberration was found. The change in corneal surface with accommodation suggests an increase in peripheral curvature with flattening at the vertex.

Accommodation, Ocular↗

PubMed2003

A randomized clinical trial of progressive addition lenses versus single vision lenses on the progression of myopia in children.

PURPOSE: The purpose of the Correction of Myopia Evaluation Trial (COMET) was to evaluate the effect of progressive addition lenses (PALs) compared with single vision lenses (SVLs) on the progression of juvenile-onset myopia. METHODS: COMET enrolled 469 children (ages 6-11 years) with myopia between -1.25 and -4.50 D spherical equivalent. The children were recruited at four colleges of optometry in the United States and were ethnically diverse. They were randomly assigned to receive either PALs with a +2.00 addition (n = 235) or SVLs (n = 234), the conventional spectacle treatment for myopia, and were followed for 3 years. The primary outcome measure was progression of myopia, as determined by autorefraction after cycloplegia with 2 drops of 1% tropicamide at each annual visit. The secondary outcome measure was change in axial length of the eyes, as assessed by A-scan ultrasonography. Child-based analyses (i.e., the mean of the two eyes) were used. Results were adjusted for important covariates, by using multiple linear regression. RESULTS: Of the 469 children (mean age at baseline, 9.3 +/- 1.3 years), 462 (98.5%) completed the 3-year visit. Mean (+/-SE) 3-year increases in myopia (spherical equivalent) were -1.28 +/- 0.06 D in the PAL group and -1.48 +/- 0.06 D in the SVL group. The 3-year difference in progression of 0.20 +/- 0.08 D between the two groups was statistically significant (P = 0.004). The treatment effect was observed primarily in the first year. The number of prescription changes differed significantly by treatment group only in the first year. At 6 months, 17% of the PAL group versus 30% of the SVL group needed a prescription change (P = 0.0007), and, at 1 year, 43% of the PAL group versus 59% of the SVL group required a prescription change (P = 0.002). Interaction analyses identified a significantly larger treatment effect of PALs in children with lower versus higher baseline accommodative response at near (P = 0.03) and with lower versus higher baseline myopia (P = 0.04). Mean (+/- SE) increases in the axial length of eyes of children in the PAL and SVL groups, respectively, were: 0.64 +/- 0.02 mm and 0.75 +/- 0.02 mm, with a statistically significant 3-year mean difference of 0.11 +/- 0.03 mm (P = 0.0002). Mean changes in axial length correlated with those in refractive error (r = 0.86 for PAL and 0.89 for SVL). CONCLUSIONS: Use of PALs compared with SVLs slowed the progression of myopia in COMET children by a small, statistically significant amount only during the first year. The size of the treatment effect remained similar and significant for the next 2 years. The results provide some support for the COMET rationale-that is, a role for defocus in progression of myopia. The small magnitude of the effect does not warrant a change in clinical practice.

Child↗

PubMed2003

Repeatability of ETDRS visual acuity in children.

PURPOSE: To evaluate repeatability of the best corrected log minimum angle of resolution (MAR) Early-Treatment Diabetic Retinopathy Study (ETDRS) acuity in a group of 6- to 11-year old children with myopia. METHODS: Best corrected monocular visual acuity (VA) of a subset of children (n = 86) enrolled in the Correction of Myopia Evaluation Trial (COMET; mean spherical equivalent refractive error -2.35 D with no more than 1.25 D astigmatism) was measured at baseline and 1 month later with ETDRS logMAR charts. Children started with logMAR 0.4 (6/15 or 20/50) and read each letter on all subsequent lines until they missed all letters in 1 line. RESULTS: At baseline, the mean best corrected logMAR VA was 0.003 +/- 0.076 (6/6 or 20/20 +/- 3.8 letters) in the right eye and 0.008 +/- 0.059 (6/6 or 20/20 +/- 2.95 letters) in the left eye. The signed difference between VA measured at baseline and that measured at 1 month was not significantly different from zero in either eye. Repeatability was not associated with age, but a small, statistically significant association with gender was detected in the left eye, with boys approximately 2 letters more variable than girls. The kappa statistic (agreement within 1 line) was good to excellent. CONCLUSIONS: Based on the 95% limits of agreement, the criterion for a statistically significant change in VA is no more than +/-0.15 logMAR (or +/-8 letters). This value is similar to those reported for adults and indicates that logMAR VA provides a repeatable measure of acuity in children.

Child↗

PubMed2003

Wave-front aberrations in the anterior corneal surface and the whole eye.

In order to investigate the sources of wave-front aberrations in the human eye, we have measured the aberrations of the anterior cornea and the whole eye using a topographic system and a psychophysical wave-front sensor. We have also calculated the aberrations for the internal optics of both eyes of 45 young subjects (aged 9 to 29 years). The mean rms for the anterior cornea was similar to that for the internal optics and thewhole eye when astigmatism was included, but less than that for both the internal optics and the whole eye with astigmatism removed. For eyes with low whole-eye rms values, mean rms for the anterior cornea was greater than that for the whole eye, suggesting that the anterior corneal aberration is partially compensated by the internal optics of the eye to produce the low whole-eye rms. For eyes with larger whole-eye rms values, the rms values for both the anterior cornea and the internal optics were less than that for the whole eye. Thus the aberrations for the two elements tend to be primarily additive. This pattern exists whether or not astigmatism was included in the wave-front aberration rms. For individual Zernike terms, astigmatism and spherical aberration in the anterior cornea were partially compensated by internal optics, while some other Zernike terms showed addition between the anterior cornea and internal optics. Individual eyes show different combinations of compensation and addition across different Zernike terms. Our data suggest that the reported loss of internal compensation for anterior corneal aberrations in elderly eyes with large whole-eye aberrations [J. Opt. Soc. Am. A 19, 137 (2002)] may also occur in young eyes.

Adolescent↗

PubMed2002

Baseline refractive and ocular component measures of children enrolled in the correction of myopia evaluation trial (COMET).

PURPOSE: To describe baseline refractive and ocular component measures in children with myopia enrolled in the Correction of Myopia Evaluation Trial (COMET). COMET is a multicenter, randomized clinical trial to evaluate whether progressive-addition lenses slow the progression of juvenile-onset myopia compared with single-vision lenses. METHODS: Four hundred sixty-nine children with myopia between -1.25 and -4.50 D spherical equivalent and without eye or systemic conditions known to affect refractive development were recruited from four geographically and ethnically diverse communities in the United States. Their ages were 6 to 11 years inclusive, and 52% were girls. The main outcome measure for the overall trial is progression of myopia determined by cycloplegic autorefraction after inducement of cycloplegia with 2 drops of 1% tropicamide. Axial length, the secondary outcome measure, was assessed by ultrasonography. The distance correction was determined by subjective methods before cycloplegia, with noncycloplegic autorefraction values as the starting point. RESULTS: Because data were similar in both eyes, they are reported for the right eye only. The mean spherical equivalent measured by cycloplegic autorefraction was -2.38 +/- 0.81 D. Young children had significantly less myopia than older children (P = 0.03), but the amount of myopia did not differ by gender or ethnicity. Mean axial dimensions were 4.0 +/- 0.2 mm (anterior chamber), 3.4 +/- 0.2 mm (lens), 16.8 +/- 0.7 mm (vitreous chamber), and 24.1 +/- 0.7 mm (axial length). Girls' eyes had significantly shorter axial length than boys' (P < 0.0001). Mean corneal radii were 7.73 +/- 0.25 mm (horizontal) and 7.59 +/- 0.24 mm (vertical). Ninety-five percent of the eyes had a ratio of axial length to corneal radius higher than 3.0. CONCLUSIONS: These baseline measures provide cross-sectional data on a large group of ethnically diverse children with myopia. Refractive and axial component dimensions are consistent with data in other studies showing that myopic eyes have longer vitreous chambers than emmetropic eyes. The measures reported herein will serve as a basis for examining changes that occur over a minimum of 3 years of follow-up of children enrolled in COMET.

Accommodation, Ocular↗