Internal Astigmatism in Myopes and Non-myopes: Compensation or Constant?

PURPOSE: To examine internal astigmatism (IA) in myopes and non-myopes using a new method to assess compensation of corneal astigmatism (CA) by IA, to look for predictors of high IA in young adult myopes, and to determine if as CA changes IA changes to reduce refractive astigmatism (RA) in an active compensatory process in myopes. METHODS: Right eye keratometry and cycloplegic autorefraction were measured annually over 14 years in 367 myopes and once in 204 non-myopes age- (mean 21.91 ± 1.47 years), gender-, and ethnicity-matched to myopes at year 12. CA and RA at the corneal plane were expressed as J0, J45. IA = RA - CA. Inverse power transformation provided cylinder power and axis of IA for the compensation factor (IA/CA). Analyses included (1) paired and unpaired t-tests (refractive data), (2) chi-square tests (distributions of compensation factor), (3) logistic regression analysis (predictors of high IA), and (4) linear mixed models (time effect on RA, CA, and IA). RESULTS: The magnitude of IAJ0 varied by refractive error (myopes -0.25 ± 0.24 vs. non-myopes -0.32 ± 0.21, p < 0.001). Compensation of CA by IA was poorer in myopes than non-myopes (χ p < 0.001). When matched by CA, compensation remained poorer in myopes than non-myopes (χ all p ≤ 0.04). Within each refractive group, compensation was better when CA was low than high (χ p < 0.001). When CA was low in myopes, high IA (≥1.00D) was less likely (p = 0.01). Longitudinal follow-up of myopes found no evidence for an active compensatory role for IA as CA increased over time. There were differences in IAJ0 by ethnicity over time (p < 0.0001). CONCLUSIONS: In myopic and non-myopic eyes with low amounts of CA, IA may reduce CA's contribution to RA, but IA is not a constant. However, there is no evidence for an active compensatory role for IA reducing CA in myopes.

Visual activity and its association with myopia stabilisation.

PURPOSE: To evaluate the association between outdoor and nearwork activities at baseline and myopia stabilisation by age 15 in the Correction of Myopia Evaluation Trial (COMET). METHODS: Correction of Myopia Evaluation Trial enrolled 469 children (ages: 6-11 years) with spherical equivalent myopia between -1.25 and -4.50 D, who were randomised to progressive addition or single vision lenses and followed for 5 years in their original lenses. At baseline, families recorded the child's outdoor and nearwork activities for 3 days within a week. Weekly hours spent in nearwork and outdoor activities were calculated for each participant. Refractions collected over 11 years were fit using the Gompertz function to determine each participant's myopia stabilisation age. Myopia for each child was then categorized as stable/not stable by age 15. RESULTS: Half (233/469) of participants had usable baseline activity diaries and refraction data that could be fit with the Gompertz function, 59.7% (139/233) had stable myopia by age 15 and 40.3% had myopia that was not yet stable. The frequency of stable myopia was similar for the two categories (median split) of outdoor activities: 60% (71/118) for ≤9.0 hours/week(-1) and 59% (68/115) for >9.0 hours/week(-1) . 56% (64/114) of children reporting >21.0 h of baseline weekly nearwork activity had stable myopia by age 15 compared to 63% (75/119) with ≤21.0 h of near work (adjusted OR = 0.74; 95% CI: 0.43-1.29). Using baseline nearwork as a continuous variable, the multivariable odds ratio for the association between baseline nearwork hours and stabilisation by age 15 is 0.98: 95% CI: 0.96-1.00, a result trending towards significance. CONCLUSION: While time spent in outdoor activities in childhood does not appear to be related to myopia stabilisation by age 15, less near work activity might potentially be associated with myopia stabilisation by that age.

Myopia, contact lens use and self-esteem.

PURPOSE: To evaluate whether contact lens (CL) use was associated with self-esteem in myopic children originally enrolled in the Correction of Myopia Evaluation Trial (COMET), that after 5 years continued as an observational study of myopia progression with CL use permitted. METHODS: Usable data at the 6-year visit, one year after CL use was allowed (n = 423/469, age 12-17 years), included questions on CL use, refractive error measurements and self-reported self-esteem in several areas (scholastic/athletic competence, physical appearance, social acceptance, behavioural conduct and global self-worth). Self-esteem, scored from 1 (low) to 4 (high), was measured by the Self-Perception Profile for Children in participants under 14 years or the Self-Perception Profile for Adolescents, in those 14 years and older. Multiple regression analyses were used to evaluate associations between self-esteem and relevant factors identified by univariate analyses (e.g., CL use, gender, ethnicity), while adjusting for baseline self-esteem prior to CL use. RESULTS: Mean (±S.D.) self-esteem scores at the 6-year visit (mean age = 15.3 ± 1.3 years; mean refractive error = -4.6 ± 1.5 D) ranged from 2.74 (± 0.76) on athletic competence to 3.33 (± 0.53) on global self-worth. CL wearers (n = 224) compared to eyeglass wearers (n = 199) were more likely to be female (p < 0.0001). Those who chose to wear CLs had higher social acceptance, athletic competence and behavioural conduct scores (p < 0.05) at baseline compared to eyeglass users. CL users continued to report higher social acceptance scores at the 6-year visit (p = 0.03), after adjusting for baseline scores and other covariates. Ethnicity was also independently associated with social acceptance in the multivariable analyses (p = 0.011); African-Americans had higher scores than Asians, Whites and Hispanics. Age and refractive error were not associated with self-esteem or CL use. CONCLUSIONS: COMET participants who chose to wear CLs after 5 years of eyeglass use had higher self-esteem compared to those who remained in glasses both preceding and following CL use. This suggests that self-esteem may influence the decision to wear CLs and that CLs in turn are associated with higher self-esteem in individuals most likely to wear them.

Alternative methods of refraction: a comparison of three techniques.

PURPOSE: In the developing world, refractive error is a common untreated cause of visual impairment. Lay people may use portable tools to overcome this issue. This study compares three methods of measuring spherical refractive error (SE) performed by a lay technician to a subjective refraction (SR) in a controlled clinical setting and a field trial. METHODS: Fifty subjects from Boston, MA (mean age, 24.3 y ± 1.5) and 50 from Nicaragua (mean age, 40 y ± 13.7) were recruited. Measures (performed on right eye only) included (1) AdSpecs, adjustable spectacles; (2) Focometer, focusable telescope; (3) Predetermined Lens Refraction (PLR), prescripted lens choices; (4) SR. Examiners were masked and techniques randomized. Student t-test compared mean SE determined by each method (95% confidence intervals). AdSpecs repeatability was evaluated by repeating measures of SE and visual acuity (VA). RESULTS: Mean (SD) SE for Boston subjects determined by SR was -2.46 D (3.2). Mean (SD) SE for AdSpecs, Focometer -2.41 D (2.69), -2.80 D (2.82). Among the 30 Boston subjects considered in analyses of PLR data (see Methods), PLR and SR obtained mean (SD) values of -0.65 D (1.36) and -0.41 D (1.67), respectively, a statistically significant difference of -0.24 D (p = 0.046, t = 2.09). Mean PLR SE had greatest deviation from SR, 0.67 D. 20/20 VA was achieved by SR, AdSpecs, Focometer, and PLR in 98, 88, 84, 96% of subjects. Mean (SD) SE for Nicaragua subjects determined by SR was +0.51 D (0.71). Mean (SD) SE for AdSpecs, Focometer, and PLR was +0.68 D (0.83), +0.42 D (1.13), +0.27 D (0.79). Mean PLR SE had the greatest deviation from the SR by 0.24 D, which was a statistically significant difference. 20/20 VA was achieved by SR, AdSpecs, Focometer, and PLR in 78, 66, 66, 88% of subjects. Repeated measures by AdSpecs were highly correlated. CONCLUSIONS: Although the mean value obtained by each technique may be similar to that obtained by SR, substantial and clinically meaningful differences may exist in some individuals; however, where SR is unavailable they could be a feasible alternative.

Accommodative lag by autorefraction and two dynamic retinoscopy methods.

PURPOSE: To evaluate two clinical procedures, Monocular Estimate Method (MEM) and Nott retinoscopy, for detecting accommodative lags 1.00 diopter (D) or greater in children as identified by an open-field autorefractor. METHODS: One hundred sixty-eight children 8 to <12 years old with low myopia, normal visual acuity, and no strabismus participated as part of an ancillary study within the screening process for a randomized trial. Accommodative response to a 3.00 D demand was first assessed by MEM and Nott retinoscopy, viewing binocularly with spherocylindrical refractive error corrected, with testing order randomized and each performed by a different masked examiner. The response was then determined viewing monocularly with spherical equivalent refractive error corrected, using an open-field autorefractor, which was the gold standard used for eligibility for the clinical trial. Sensitivity and specificity for accommodative lags of 1.00 D or more were calculated for each retinoscopy method compared to the autorefractor. RESULTS: One hundred sixteen (69%) of the 168 children had accommodative lag of 1.00 D or more by autorefraction. MEM identified 66 children identified by autorefraction for a sensitivity of 57% (95% CI = 47 to 66%) and a specificity of 63% (95% CI = 49 to 76%). Nott retinoscopy identified 35 children for a sensitivity of 30% (95% CI = 22 to 39%) and a specificity of 81% (95% CI = 67 to 90%). Analysis of receiver operating characteristic curves constructed for MEM and for Nott retinoscopy failed to reveal alternate cut points that would improve the combination of sensitivity and specificity for identifying accommodative lag > or =1.00 D as defined by autorefraction. CONCLUSIONS: Neither MEM nor Nott retinoscopy provided adequate sensitivity and specificity to identify myopic children with accommodative lag > or =1.00 D as determined by autorefraction. A variety of methodological differences between the techniques may contribute to the modest to poor agreement.

Detection of Strabismus by Non-Health Care Professionals in an Ethnically Diverse Set of Images.

IMPORTANCE: Understanding the criteria for when strabismus becomes detectable by non-health care professionals could influence the goals for determining the success of surgical intervention and how patients with such misalignments are counseled. OBJECTIVE: To examine the magnitude at which strabismus is detectable by lay observers in an ethnically diverse set of images. DESIGN, SETTING, AND PARTICIPANTS: Photographs of 12 ethnically diverse models (black, white, and Asian) were simulated to have strabismus from esotropia of 21 prism diopters (∆) to exotropia of 21∆. From July 1, 2007, to October, 1, 2008, images were presented to 120 non-health care professionals aged 21 years or older from the general community in Boston, Massachusetts, who were asked whether strabismus was present. Analysis was conducted from November 1, 2008, to March 31, 2009. MAIN OUTCOMES AND MEASURES: The threshold angle for detecting strabismus to enable 70% of lay observers to make a positive determination whether strabismus is present. RESULTS: In white and black models, the threshold allowing a 70% positive detection rate was higher for esotropia than for exotropia (P < .001 for both). For white models, the threshold was 23.2∆ (95% CI, 21.0∆ to 26.5∆) for esotropia and 13.5∆ (95% CI, 12.5∆ to 14.6∆) for exotropia. For black models, the threshold was 20.8∆ (95% CI, 19.2∆ to 22.2∆) for esotropia and 16.3∆ (95% CI, 15.5∆ to 17.2∆) for exotropia. Asian models showed an opposite trend, with the threshold allowing a 70% positive detection rate for esotropia (14.3∆; 95% CI, 13.2∆ to 15.7∆) being lower than that for exotropia (20.9∆; 95% CI, 18.0∆ to 24.6∆) (P < .001). CONCLUSIONS AND RELEVANCE: Esotropia was easier for lay observers to detect than exotropia in Asian models, and exotropia was easier to detect than esotropia in white and black models. This information should be considered when managing patients who have concerns about the social significance of their strabismus. Future studies should include diverse individuals and make an effort to account for individual factors that may alter the perception of strabismus.

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.

Limited change in anisometropia and aniso-axial length over 13 years in myopic children enrolled in the Correction of Myopia Evaluation Trial.

PURPOSE: We investigated changes in anisometropia and aniso-axial length with myopia progression in the Correction of Myopia Evaluation Trial (COMET) cohort. METHODS: Of 469 myopic children, 6 to <12 years old, enrolled in COMET, 358 were followed for 13 years. Cycloplegic autorefraction and axial length (AL) in each eye were measured annually. The COMET eligibility required anisometropia (interocular difference in spherical equivalent refraction) of ≤ 1.00 diopter (D). For each child, a linear regression line was fit to anisometropia data by visit, and the regression slope b was used as the rate of change. Logistic regression was applied to identify factors for significant changes in anisometropia (b ≥ 0.05 D/y, or a cumulative increase in anisometropia ≥ 0.50 D over 10 years). Similar analyses were applied to aniso-AL. RESULTS: A total of 358/469 (76.3%) children had refractions at baseline and the 13-year visit. The mean (SD) amount of anisometropia increased from 0.24 D (0.22 D) at baseline to 0.49 D (0.46 D) at the 13-year visit. A total of 319/358 (89.1%) had slopes |b| < 0.05 D/y and 39 (10.9%) had slopes |b| ≥ 0.05 D/y, with only one negative slope. Similarly, 334/358 (93.3%) children had little change in aniso-AL over time. The correlation between changes in anisometropia and aniso-AL over 13 years was 0.39 (P < 0.001). The correlation between changes in anisometropia and myopia progression was significant (r = -0.36, P < 0.001). No correlation was found between baseline anisometropia and myopia progression (r = -0.02, P = 0.68). CONCLUSIONS: Myopia and axial length progressed at a similar rate in both eyes for most children in COMET during the period of fast progression and eventual stabilization. These results may be more generalizable to school-aged myopic children with limited anisometropia at baseline. (ClinicalTrials.gov number, NCT00000113.).

Minimal angle horizontal strabismus detectable by lay observers.

PURPOSE: Patients with socially significant strabismus may be at risk for certain psychosocial consequences. However, the magnitude at which strabismus becomes socially significant is ill defined. Suggested criteria for socially significant strabismus can be found in the literature, but they are rarely, if ever, referenced. The purpose of this study is to further define the magnitude at which strabismus becomes socially significant according to lay observers. METHODS: Strabismus was simulated using photo manipulation and off-center fixation. Horizontal deviations were created in 3Delta steps up to 24Delta. One model was used for all photos. The photos were presented in random order to non-health care professionals (N = 58). Participants were instructed to view each picture and determine: "yes, this person has an eye turn" or "no, this person does not have an eye turn." A chi test was used for analysis. RESULTS.: There was an increase in the likelihood of strabismus detection as the size of the angle increased for exotropia and esotropia. Overall, exotropia was easier to identify than esotropia. For esotropia, a dramatic increase in detectability occurred between 9Delta (47.41% detection; p = 0.001) and 12Delta (67.24% detection; p = 0.001), with 70% detection being achieved at 14.5Delta. A significant increase in detection of exotropia occurred between 6Delta (60.34% detection; p = 0.001) and 9Delta (77.59% detection; p = 0.001), with 70% detection achieved at 8Delta. CONCLUSIONS: Our results suggest that exotropia is easier for lay observers to detect than esotropia, with the critical magnitude (70% detection) being 14.5Delta for esotropia and 8Delta for exotropia. This refutes generally accepted beliefs that esotropia is easier to detect than exotropia. Additional studies are needed to look at the effect of ethnicity, sex, and age. Multiple models should be used to reduce the possible influence of distinct facial characteristics and increase the generalizability of the results.