Blur Detection, Depth of Field, and Accommodation in Emmetropic and Hyperopic Children

The induced defocus by Defocus Incorporated Soft Contact lenses is dependent on visual distance and ambient illuminance

PURPOSE

Defocus Incorporated Soft Contact (DISC) lenses, a commonly used type of multifocal lens in clinical practice, may slow down myopia progression by inducing myopic retinal defocus. The purpose of this study was to explore whether the induced defocus across the retina could be affected by visual environments encountered in the real world, such as differences in viewing distance and ambient illuminance.

METHODS

In this cross-over trial, 30 myopic adults wore both DISC lenses and single vision contact (SVC) lenses in random order. An open-view Hartmann-Shack scanning wavefront sensor was used to measure defocus at different retinal locations along the horizontal meridian under four experimental conditions: far target (3 m) and near targets (0.33 m) under scotopic (<1 lux) or photopic (~300 lux) conditions.

RESULTS

The results showed that DISC lenses induced more myopic retinal defocus than SVC lenses in all conditions (all p < 0.05), except for the scotopic near target. In addition, for DISC lenses, the defocus was greater in the photopic than the scotopic conditions for both the far and near targets (both p < 0.05).

CONCLUSION

In conclusion, the retinal defocus induced by these multifocal lenses was dependent on both visual distance and ambient illuminance, indicating that the visual conditions might affect the anti-myopia efficacy of these devices.

Accuracy and stability of accommodation and vergence responses during sustained near tasks in uncorrected hyperopes

This study investigated the accuracy and stability of accommodative and vergence functions in children with and without hyperopia while engaged in two sustained near tasks. The sustained accommodative and vergence characteristics of participants without refractive correction (n = 92, aged 5-10 years) with and without hyperopia (defined as cycloplegic retinoscopy ≥  + 1.00D and less than + 5.00D) were measured using eccentric infrared photorefraction (PowerRef 3; PlusOptix, Germany). Binocular measures of accommodation and eye position were recorded while participants engaged in 2 tasks at 25 cm for 15 min each: (1) reading small print on an Amazon Kindle and (2) watching an animated movie on liquid crystal display screen. Comprehensive visual assessment, including measurement of presenting visual acuity, amplitude of accommodation, and stereoacuity was conducted. The magnitude of accommodative and vergence responses was not related to refractive error (P > 0.05). However, there were inter-task differences in the accuracy and stability of the accommodative responses across refractive groups (P < 0.05). The relationship between accommodation and vergence was not significant in both tasks (P > 0.05). However, increased accommodative and vergence instabilities were associated with total accommodative response (P < 0.05). Despite having greater accommodative demand, uncorrected hyperopes accommodate comparably to emmetropic controls. However, uncorrected hyperopes have increased instabilities in their accommodative and vergence responses, which may adversely impact their visual experience.

Validation of the PowerRef 3 for Measuring Accommodation: Comparison With the Grand Seiko WAM-5500A Autorefractor

Purpose

This validation study examines the PowerRef 3 as a method for measuring accommodation objectively. We assess agreement with refractive measurements obtained simultaneously by the Grand Seiko WAM-5500A autorefractor.

Methods

Refractive measurements were recorded simultaneously using the PowerRef 3 and WAM-5500A in 32 noncyclopleged participants aged 15 to 46 years. Accommodative states were recorded for 10 seconds at six accommodative demands (5 diopters [D], 4 D, 3 D, 2.5 D, 2 D, and 0 D) while participants fixated a high-contrast Maltese cross. WAM-5500A measurements were converted to power in the vertical meridian for comparison with PowerRef 3 data. Dioptric difference values were computed, and agreement was assessed using Bland-Altman plots with 95% limits of agreement (LOA) and intraclass correlation coefficient analyses.

Results

The mean absolute dioptric differences measured 0.14 D or less across accommodative demands. Analyses showed an excellent intraclass correlation coefficient across the tested demands (0.93). Bland-Altman plots indicated a bias of -0.02 D with 95% LOA of -1.03 D to 0.99 D. The 95% LOA was smallest for the 3 D demand (-0.71 D to 0.64 D), and largest at 5 D demand (-1.51 D to 1.30 D).

Conclusions

The mean dioptric differences between the PowerRef 3 and WAM-5500A autorefractor were small and not clinically significant. While some variability in agreement was observed depending on the tested demand, the PowerRef 3 demonstrated good agreement with the WAM-5500A.

Translational Relevance

The PowerRef 3 may be used to obtain objective measures of accommodation both monocularly and binocularly and provides a more flexible method, especially in pediatric populations.

Repeatability of the Accommodative Response Measured by the Grand Seiko Autorefractor in Children With and Without Amblyopia and Adults

PURPOSE

To assess test-retest repeatability of the accommodative response (AR) in children with and without amblyopia and adults using the Grand Seiko autorefractor.

DESIGN

Prospective reliability assessment.

METHODS

Test-retest of accommodation was obtained while participants viewed 20/150 sized letters at 33 cm using the Grand Seiko autorefractor in children 5 to <11 years with amblyopia (n=24) and without amblyopia (n=36), and adults 18 to <35 years (n=34). Bland-Altman 95% limits of agreement (LOA) and intraclass correlation coefficients (ICCs) were used to assess repeatability and reliability. The AR between the fellow and amblyopic eyes of children with amblyopia and eye 1 and eye 2 of the visually normal participants was assessed using group comparisons.

RESULTS

The 95% LOA of the AR was greatest in the amblyopic eyes (-1.25 diopters [D], 1.62 D) of children with amblyopia. The 95% LOA were similar between the fellow eyes (-0.88 D, 0.74 D) of children with amblyopia and both eyes of the children without amblyopia (eye 1: -0.68 D, 0.71 D; eye 2: -0.59 D, 0.70 D) and the adults (eye 1: 95% LOA = -0.49 D, 0.45 D; eye 2: LOA = -0.66 D, 0.67 D). ICCs revealed the Grand Seiko autorefractor as a reliable instrument for measuring AR.

CONCLUSIONS

The Grand Seiko autorefractor was more repeatable and reliable when measuring the AR in children and adults without amblyopia than in the amblyopic eye in children with amblyopia. It is recommended that multiple measures of the AR be obtained in amblyopic eyes to improve the precision of measures.

The Impact of Hyperopia on Academic Performance Among Children: A Systematic Review

PURPOSE

To assess the impact of uncorrected hyperopia and hyperopic spectacle correction on children's academic performance.

DESIGN

Systematic review and meta-analysis.

METHODS

We searched 9 electronic databases from inception to July 26, 2021, for studies assessing associations between hyperopia and academic performance. There were no restrictions on language, publication date, or geographic location. A quality checklist was applied. Random-effects models estimated pooled effect size as a standardized mean difference (SMD) in 4 outcome domains: cognitive skills, educational performance, reading skills, and reading speed. (PROSPERO registration: CRD-42021268972).

RESULTS

Twenty-five studies (21 observational and 4 interventional) out of 3415 met the inclusion criteria. No full-scale randomized trials were identified. Meta-analyses of the 5 studies revealed a small but significant adverse effect on educational performance in uncorrected hyperopic compared to emmetropic children {SMD -0.18 [95% confidence interval (CI), -0.27 to -0.09]; P < 0.001, 4 studies} and a moderate negative effect on reading skills in uncorrected hyperopic compared to emmetropic children [SMD -0.46 (95% CI, -0.90 to -0.03); P = 0.036, 3 studies]. Reading skills were significantly worse in hyperopic than myopic children [SMD -0.29 (95% CI, -0.43 to -0.15); P < 0.001, 1 study]. Qualitative analysis on 10 (52.6%) of 19 studies excluded from meta-analysis found a significant (P < 0.05) association between uncorrected hyperopia and impaired academic performance. Two interventional studies found hyperopic spectacle correction significantly improved reading speed (P < 0.05).

CONCLUSIONS

Evidence indicates that uncorrected hyperopia is associated with poor academic performance. Given the limitations of current methodologies, further research is needed to evaluate the impact on academic performance of providing hyperopic correction.

Fluctuations of Steady-State Accommodation Is a Marker for Screening Spasm of Near Reflex

Purpose

To determine the utility of root mean squared (RMS) deviations of steady-state accommodation as a noncycloplegic marker for spasm of near reflex (SNR) vis-à-vis regular refractive errors.

Methods

Binocular steady-state responses of accommodation, pupil, and vergence of 20 patients with accommodative spasm subtype of SNR (SNR-A; 9-23 years) and 91 with regular refractive errors (29 emmetropes, 41 myopes, 21 hyperopes; 19-38 years) was recorded in the uncorrected refractive error state for 120 seconds using a dynamic (50 frames per second), infrared photorefractor. Mean and RMS deviation of raw data was calculated for three 20-second-long epochs and their diagnostic utility was determined using standard ROC curves.

Results

RMS deviations of accommodation increased with mean refractive error in SNR-A (y = -0.23x + 0.38; r2 = 0.69; P < 0.001) and regular refractive error (y = -0.02x + 0.10; r2 = 0.14; P = 0.002) cohorts, albeit with steeper slope and higher y-intercept in the former rather than the latter cohort. RMS deviation of 0.19D reliably distinguished SNR-A from regular refractive errors with a sensitivity and specificity of 95.2% and 92.2%, respectively [mean (±1 SEM) area under ROC curve: 0.98 ± 0.01]. The sensitivity, specificity, and area under ROC curve for RMS deviations of pupil (66.7%, 80%, and 0.70 ± 0.09) and vergence (52.4%, 84.6%, and 0.68 ± 0.08) were smaller than accommodation.

Conclusions

RMS deviations of steady-state accommodation is a robust noncycloplegic marker for differentiating SNR-A from regular refractive errors. Pupil and vergence fluctuations have limited utility in this regard.

Translational Relevance

RMS deviations of accommodation may be easily obtained using commercial photorefractors, and the cut-off values reported herein may be implemented to identify SNR-A during refractive error screening.

Impact of Visual Cues on the Magnitude and Variability of the Accommodative Response in Children With Emmetropia and Uncorrected Hyperopia and Adults

Purpose

We investigated the effect of blur and disparity cues on accommodative accuracy (lag) and variability (time [RMS] and frequency domain [LFC]) in the developing visual system.

Methods

A total of 59 children (3–9 years, spherical equivalent refractive error [RE] = −0.3– +4.91 diopters [D]) and 10 adults (23–31 years, RE = −0.37–+1.15D) participated. Accommodation was measured in the right eye for 1 minute at 100 and 33 cm using photorefraction (25 Hz) for three conditions: blur + disparity (binocular, 20/50 optotypes), blur-only (monocular, 20/50 optotypes), disparity-only (binocular, difference-of-Gaussian stimulus). The effect blur and disparity cues have on accommodative accuracy, RMS, and LFC was assessed.

Results

Lag, RMS, and LFC increased (P < 0.001) from 100 to 33 cm for each condition in children and adults. In children, accommodation was most accurate and stable when blur and disparity cues remained in the stimulus and became significantly less accurate and more variable (P < 0.001) when blur or disparity cues were removed at 33 cm. In adults, accommodation was significantly less accurate and more variable only when blur was removed from the stimulus (P < 0.022). Children with RE matched to adults had less accurate and more variable accommodative responses at near than adults when cues were removed (P ≤ 0.02).

Conclusions

In children and adults, an increase in RMS and LFC is related to an increase in accommodative lag. Children's accommodative systems do not compensate as efficiently as adults when blur and disparity cues are removed, suggesting children <10 years old do not have a mature afferent visual pathway.

Is blur sensitivity altered in children with progressive myopia?

School aged children with progressive myopia show large accommodative lags to blur only cue which is suggestive of a large depth of focus (DOF). While DOF measures are lacking in this age group, their blur detection and discrimination capacities appear to be similar to their non-myopic peers. Accordingly, the current study quantified DOF and blur detection ability in progressive myopic children showing large accommodative lags compared to their non-myopic peers and adults. Blur sensitivity measures were taken from 12 children (8-13 years, 6 myopes and 6 emmetropes) and 6 adults (20-35 years). DOF was quantified using step changes in the lens induced defocus while the subjects viewed a high contrast target through a Badal lens at either 2 or 4D demand. Blur detection thresholds (BDT) were tested using a similar high contrast target in a 2-alternate forced-choice paradigm (2AFC) at both the demands. In addition to the large accommodative lags, micro fluctuations and DOF were significantly larger in myopic children compared to the other groups. However, BDTs were similar across the three groups. When limited to blur cues, the findings of a large DOF coupled with large response lags suggests that myopes are less sensitive to retinal defocus. However, in agreement to a previous study, refractive error had no influence on their BDTs suggesting that the reduced sensitivity to the defocus in a myopic eye appears to be compensated by some form of an adjustment in the higher visual processes to preserve the subjective percept even with a poor retinal image quality.