Minus-lens-stimulated accommodative amplitude decreases sigmoidally with age: a study of objectively measured accommodative amplitudes from age 3

BCLA CLEAR Presbyopia: Evaluation and diagnosis

It is important to be able to measure the range of clear focus in clinical practice to advise on presbyopia correction techniques and to optimise the correction power. Both subjective and objective techniques are necessary: subjective techniques (such as patient reported outcome questionnaires and defocus curves) assess the impact of presbyopia on a patient and how the combination of residual objective accommodation and their natural DoF work for them; objective techniques (such as autorefraction, corneal topography and lens imaging) allow the clinician to understand how well a technique is working optically and whether it is the right choice or how adjustments can be made to optimise performance. Techniques to assess visual performance and adverse effects must be carefully conducted to gain a reliable end-point, considering the target size, contrast and illumination. Objective techniques are generally more reliable, can help to explain unexpected subjective results and imaging can be a powerful communication tool with patients. A clear diagnosis, excluding factors such as binocular vision issues or digital eye strain that can also cause similar symptoms, is critical for the patient to understand and adapt to presbyopia. Some corrective options are more permanent, such as implanted inlays / intraocular lenses or laser refractive surgery, so the optics can be trialled with contact lenses in advance (including differences between the eyes) to better communicate with the patient how the optics will work for them so they can make an informed choice.

Clinical Evaluation Of a 0.05 D-step Binocular Wavefront Optometer in Young Adults in China

CLINICAL RELEVANCE

Myopia has become a public health priority as its prevalence increases worldwide, and in clinical practice, the precise evaluation of refraction errors is necessary.

BACKGROUND

This study aimed to compare objective and subjective refraction measured by a binocular wavefront optometer (BWFOM) in adults with conventional objective and subjective refractions measured by an optometrist.

METHODS

This cross-sectional study included 119 eyes of 119 participants (34 men and 85 women; mean age:27.5 ± 6.3 years). Refractive errors were measured using BWFOM and conventional methods, with and without cycloplegia. The mean outcome measures were spherical power, cylindrical power, and spherical equivalence (SE). The agreement test was assessed using a two-tailed paired t-test and Bland - Altman plots.

RESULTS

Under noncycloplegic conditions, there were no significant differences in the objective SE between BWFOM and Nidek. Significant differences in subjective SE were observed between BWFOM and conventional subjective refraction (-5.79 ± 1.86 vs -5.65 ± 1.75 D, P < 0.01). Under cycloplegic conditions, the mean objective SE was significantly different between BWFOM and Nidek (-5.70 ± 1.76 vs -5.50 ± 1.83 D, P < 0.001); the mean subjective SE was significantly different between BWFOM and conventional subjective refractions (-5.52 ± 1.77 vs -5.62 ± 1.79 D, P < 0.001). The Bland - Altman plots revealed mean percentages of 95.38% and 95.17% for the points within the limits of agreement between BWFOM and conventional measurements and those between noncycloplegic and cycloplegic refractions, respectively.

CONCLUSION

The BWFOM is a new device that measures both objective and subjective refraction. It is more convenient and faster to obtain a proper prescription at a 0.05-D interval. The subjective refraction results of the BWFOM and the conventional subjective refraction were in good agreement.

Digital device viewing behaviour in children

INTRODUCTION

Habitual viewing behaviour is widely believed to be an important contributing factor to the onset and progression of myopia and may be task dependent. The purpose of this study was to quantify the habitual viewing distance of children performing five different tasks on a smartphone digital device.

METHODS

The real-time viewing distance in 38 children with their habitual correction was measured using software (MyopiaApp) on a handheld (Google Pixel 3) device. Five tasks were performed in a randomised sequence: playing a game, watching video in a light (680 lux) and dark (5.5 lux) environment and reading small (8 pt) and large (16 pt) text. ANCOVA statistical analysis was used to evaluate the effect of task, group (myope vs. non-myope) and arm length on the median relative viewing distance.

RESULTS

Arm length was not correlated with viewing distance in any of the tasks, and there was no significant difference in viewing distance between any of the tasks. Specifically, a two-way mixed ANCOVA indicated that task, refractive group (myopic vs. non-myopic), age and arm length, as well as all two-way interactions were not significantly associated with viewing distance. Overall, 60% of the total variance in viewing distance was accounted for by individual differences.

CONCLUSIONS

The average handheld viewing distance was similar across a variety of everyday tasks in a representative sample of myopic and emmetropic children. Neither arm length, age nor refractive group were associated with viewing distance in any of the tasks. Importantly, myopic children of a given size did not hold the smartphone digital device at a different distance for any task than their equally sized non-myopic peers. However, both groups exhibited high inter-individual variability in mean viewing distance, indicating some subjects performed all tasks at further distances while other subjects used at nearer distances.

Comparison of proximal and minus lens autorefraction techniques to measure monocular accommodative amplitude

SIGNIFICANCE

This study provides a faster method for objectively measuring accommodative amplitude with an open-field autorefractor in a research setting.

PURPOSE

Objective measures of accommodative amplitude with an autorefractor take time because of the numerous stimulus demands tested. This study compares protocols using different amounts and types of demands to shorten the process.

METHODS

One hundred participants were recruited for four age bins (5 to 9, 10 to 14, 15 to 19, and 20 to 24 years) and monocular amplitude measured with an autorefractor using three protocols: proximal, proximal-lens (letter), and proximal-lens (picture). For proximal, measurements were taken as participants viewed a 0.9 mm "E" placed at 13 demands (40 to 3.3 cm = 2.5 to 30 D). The other protocols used a target (either the "E" or a detailed picture) placed at 33 and 12.5 cm followed by 12.5 cm with a series of lenses (-2, -4, and -5.5 D). Adjustments were made for lens effectivity for the three lens conditions, which were thus 9.6, 11.1, and 12.0 D for individuals without additional spectacle lenses. Accommodative amplitude was defined as the greatest response measured with each technique. One-way analysis of variance was used to compare group mean amplitudes across protocols and differences between letter protocols by age bin.

RESULTS

Amplitudes were significantly different between protocols (p < 0.001), with proximal having higher amplitudes (mean ± standard deviation, 8.04 ± 1.70 D) compared with both proximal-lens protocols (letter, 7.48 ± 1.42 D; picture, 7.43 ± 1.42 D) by post hoc Tukey analysis. Differences in amplitude between the proximal and proximal-lens (letter) protocol were different by age group (p = 0 .003), with the youngest group having larger differences (1.14 ± 1.58 D) than the oldest groups (0.17 ± 0.58 and 0.29 ± 0.48 D, respectively) by post hoc Tukey analysis.

CONCLUSIONS

The proximal-lens protocols took less time and identified the maximum accommodative amplitude in participants aged 15 to 24 years; however, they may underestimate true amplitude in younger children.

Objective and subjective assessment of accommodative insufficiency

SIGNIFICANCE

A variety of subjective and objective procedures are available to measure the amplitude of accommodation. However, it is unclear whether the standard criterion of Hofstetter's minimum minus 2 D can be used to diagnose accommodative insufficiency with each of these techniques.

PURPOSE

The use of objective dynamic retinoscopy and three subjective techniques to diagnosis accommodative insufficiency was examined.

METHODS

A total of 632 subjects between 8 and 19 years of age were enrolled. Accommodative lag, monocular accommodative facility, and subjective (push-up, modified push-down, and minus lens) and objective (dynamic retinoscopy) amplitude of accommodation were quantified. Accommodative insufficiency was diagnosed based on Hofstetter's minimum minus 2 D for each subjective method, as well as adding an additional subjective criterion (either accommodative lag exceeding 0.75 D or monocular accommodative facility falling below the age-expected norms).

RESULTS

The prevalence of accommodative insufficiency was lowest and highest with the push-up (7.9 and 1%) and dynamic retinoscopy (94 and 12%) procedures when measured without and with the additional subjective criteria, respectively. Comparing the validity of dynamic retinoscopy against the traditional criterion, moderate to low sensitivity and high specificity were found. However, adding the additional subjective criteria improved the findings with moderate to high sensitivity and high specificity. Using a cutoff for dynamic retinoscopy of 7.50 D showed moderate diagnostic accuracy based on likelihood ratios.

CONCLUSIONS

It is clear that a revised definition of accommodative insufficiency is required, which must include the method of assessing accommodation. The various objective and subjective methods for quantifying the amplitude of accommodation are not interchangeable, and subjective assessment does not provide a valid measure of the accommodative response.

Precision Concussion Management: Approaches to Quantifying Head Injury Severity and Recovery

Mitigating the substantial public health impact of concussion is a particularly difficult challenge. This is partly because concussion is a highly prevalent condition, and diagnosis is predominantly symptom-based. Much of contemporary concussion management relies on symptom interpretation and accurate reporting by patients. These types of reports may be influenced by a variety of factors for each individual, such as preexisting mental health conditions, headache disorders, and sleep conditions, among other factors. This can all be contributory to non-specific and potentially misleading clinical manifestations in the aftermath of a concussion. This review aimed to conduct an examination of the existing literature on emerging approaches for objectively evaluating potential concussion, as well as to highlight current gaps in understanding where further research is necessary. Objective assessments of visual and ocular motor concussion symptoms, specialized imaging techniques, and tissue-based concentrations of specific biomarkers have all shown promise for specifically characterizing diffuse brain injuries, and will be important to the future of concussion diagnosis and management. The consolidation of these approaches into a comprehensive examination progression will be the next horizon for increased precision in concussion diagnosis and treatment.

Estimation of Crystalline Lens Material Properties From Patient Accommodation Data and Finite Element Models

Purpose

The mechanical properties of the crystalline lens are related to its optical function of accommodation, and their changes with age are one of the potential causes for presbyopia. We estimated the mechanical parameters of the crystalline lens using quantitative optical coherence tomography (OCT) imaging and wavefront sensing data from accommodating participants and computer modeling.

Methods

Full-lens shape data (from quantitative swept-source OCT and eigenlens representation) and optical power data (from Hartmann-Shack wavefront sensor) were obtained from 11 participants (22-30 years old) for relaxed accommodation at infinity and -4.5 D accommodative demand. Finite element models of lens, capsular bag, zonulae, and ciliary body were constructed using measured lens geometry and literature data, assuming a 60-mN radial force. An inverse modeling scheme was used to determine the shear moduli of the nucleus and cortex of the lens, such that the simulated deformed (maximally stretched) lens matched the participant's lens at -4.5 D.

Results

The shear moduli of the nucleus and cortex were 1.62 ± 1.32 and 8.18 ± 5.63 kPa, on average, respectively. The shear modulus of the nucleus was lower than that of the cortex for all participants evaluated. The average of the two moduli per participant was statistically significantly correlated with age (R2 = 0.76, P = 0.0049).

Conclusions

In vivo imaging and mechanical modeling of the crystalline lens allow estimations of the crystalline lens' mechanical properties. Differences between nuclear and cortical moduli and their dependency with age appear to be critical in accommodative function and likely in its impairment in presbyopia.

A Review of Lens Biomechanical Contributions to Presbyopia

Purpose: Presbyopia-the progressive loss of near focus with age-is primarily a result of changes in lens biomechanics. In particular, the shape of the ocular lens in the absence of zonular tension changes significantly throughout adulthood. Contributors to this change in shape are changes in lens biomechanical properties, continuous volumetric growth lens, and possibly remodeling of the lens capsule. Knowledge in this area is growing rapidly, so the purpose of this mini-review was to summarize and synthesize these gains.Methods: We review the recent literature in this field.Results: The mechanisms governing age-related changes in biomechanical properties remains unknown. We have recently shown that lens growth may be driven by zonular tension. The same mechanobiological mechanism driving lens growth may also lead to remodeling of the capsule, though this remains to be demonstrated.Conclusions: This mini-review focuses on identifying mechanisms which cause these age-related changes, suggesting future work which may elucidate these mechanisms, and briefly discusses ongoing efforts to develop a non-surgical approach for therapeutic management of presbyopia. We also propose a simple model linking lens growth and biomechanical properties.

Automated segmentation of the ciliary muscle in OCT images using fully convolutional networks

Quantifying shape changes in the ciliary muscle during accommodation is essential in understanding the potential role of the ciliary muscle in presbyopia. The ciliary muscle can be imaged in-vivo using OCT but quantifying the ciliary muscle shape from these images has been challenging both due to the low contrast of the images at the apex of the ciliary muscle and the tedious work of segmenting the ciliary muscle shape. We present an automatic-segmentation tool for OCT images of the ciliary muscle using fully convolutional networks. A study using a dataset of 1,039 images shows that the trained fully convolutional network can successfully segment ciliary muscle images and quantify ciliary muscle thickness changes during accommodation. The study also shows that EfficientNet outperforms other current backbones of the literature.

Comparison of the Amplitude of Accommodation Measured Using a New-Generation Closed-Field Autorefractor with Conventional Subjective Methods

Purpose: This study aims to compare and assess the agreement of the objective amplitude of accommodation (AA) measured using a new-generation closed-field autorefractor with conventional subjective methods. Methods: In total, 84 healthy individuals with an age range of 19 to 50 years participated in this cross-sectional study. AA was measured objectively with a Nidek autorefractor (AR-1a; Nidek Co., Ltd., Tokyo, Japan) and subjectively using push-up (PU) and minus-lens (ML) methods in a random order. Comparison between different methods was performed using repeated-measures analysis of variance and the Bonferroni test for pairwise comparisons. In addition to the Pearson correlation, the Bland and Altman method and the intraclass correlation coefficient were used to determine the agreement between the three techniques. Only the right-eye results were used for analysis. Results: AA measured using the Nidek autorefractor (3.43 ± 1.94 D) was significantly lower than that measured with PU (7.67 ± 2.38 D; p < 0.001) and ML (7.60 ± 2.81 D; p < 0.001) methods. The difference between the subjective methods was not significant statistically (p = 1.0). The correlation for Nidek measurements and PU and ML methods was moderate (r = 0.5502 and r = 0.6832, respectively), while it was strong when comparing subjective methods (r = 0.7821). The limits of agreement for Nidek vs. PU, Nidek vs. ML, and PU vs. ML methods were −8.28 to −0.23 D, −8.19 to −0.15 D, and −3.38 to 3.51 D, respectively. Conclusions: There was a moderate agreement between AA obtained with subjective methods and objective Nidek measurements. The objective AA measurements obtained with a new Nidek autorefractor were significantly lower than subjective measurements.

Study of the Immediate Effects of Autostereoscopic 3D Visual Training on the Accommodative Functions of Myopes

Purpose

Stereoscopic viewing has an impact on ocular dynamics, but its effects on accommodative functions are not fully understood, especially for autostereoscopic viewing. This study aimed to investigate the changes in dynamic accommodative response, accommodative amplitude, and accommodative facility of myopes after autostereoscopic visual training.

Methods

We enrolled 46 adults (men = 22 and women = 24; age = 21.5 ± 2.5 [range = 18–25] years, spherical equivalent: −4.52 ± 1.89 [−8.88 to −1.75] diopters [D]) who visited the Eye & ENT Hospital of Fudan University. The study population was randomly divided into three-dimensional (3D) and two-dimensional (2D) viewing groups to watch an 11-minute training video displayed in 3D or 2D mode. Dynamic accommodative response, accommodative facility, and accommodative amplitude were measured before, during, and immediately after the training. Accommodative lag and the variability of accommodation were also analyzed. Visual fatigue was evaluated subjectively using a questionnaire.

Results

Accommodative lag decreased from 0.54 ± 0.29 D to 0.42 ± 0.32 D (P = 0.004), whereas accommodative facility increased from 10.83 ± 4.55 cycles per minute (cpm) to 13.15 ± 5.25 cpm (P < 0.001) in the 3D group. In the 2D group, there was no significant change in the accommodative lag (P = 0.163) or facility (P = 0.975), but a decrease in accommodative amplitude was observed (from 13.88 ± 3.17 D to 12.71 ± 2.23 D, P = 0.013). In the 3D group, the accommodative response changed with the simulated target distance. Visual fatigue was relatively mild in both groups.

Conclusions

The immediate impact of autostereoscopic training included a decrease in the accommodative lag and an increase in the accommodative facility. However, the long-term effects of autostereoscopic training require further exploration.

Effect of Cycloplegia on Refractive Error Measure in Chinese School Students

PURPOSE

To determine differences in cycloplegic vs. non-cycloplegic refractive error and factors associated with these differences in Chinese school students.

METHOD

In this cross-sectional school-based study, refractive error was measured in school students using a NIDEK autorefractor before and after administration of 0.5% tropicamide. Spherical equivalent (SER) in diopters (D) was calculated as sphere plus half cylinder. SER differences before vs. after cycloplegia were evaluated using mean, standard deviation (SD), 95% limits of agreement. Univariable and multivariable regression models were used to determine factors associated with SER differences.

RESULTS

Among 3604 students, 3450 (95.7%) provided data for analysis. Mean age (SD) was 9.7 (3.6) years. The mean SER (SD) was -1.12 (1.97) D before cycloplegia, and -0.20 (2.19) D after cycloplegia, with a mean difference of 0.92 D (95% limits of agreement: -0.93 to 2.78 D). Among 196 eyes with non-cycloplegic SER -6.0 D or worse (e.g., met high myopia definition), 71.4% had cycloplegic SER -6.0 D or worse, and among 3607 eyes with non-cycloplegic SER -0.5 D or worse (e.g., met myopia definition), 62.1% eyes had cycloplegic SER -0.5 D or worse. Cycloplegic SER was more correlated with axial length than non-cycloplegic SER (Pearson r = 0.82 vs. 0.72, p < .0001). In multivariable analysis, larger SER differences were associated with more hyperopic refractive error and smaller axial length (all p < .0001).

CONCLUSION

Non-cycloplegic refractive error overestimates myopia by approximately one diopter. This overestimation increases with more hyperopic refractive error and smaller axial length. Non-cycloplegic refractive error should not be used for evaluating pediatric myopia.

ABBREVIATIONS

BCVA = best corrected visual acuity; D = diopter; SD = standard deviation; SE = standard error; SER = spherical equivalent; CI = confidence interval.

Increasing incidence and risk factors for divergence insufficiency esotropia

PURPOSE

To document the increasing incidence of divergence insufficiency (DI) esotropia and to identify risk factors for DI.

METHODS

All patients with a diagnosis of esotropia seen by one provider (DLG) over 41 years were identified from the medical record. Patients with onset of strabismus before age 10 years or with prior strabismus surgery were excluded. Cases of esotropia associated with thyroid eye disease, scleral buckles, trauma, neurological diseases, or atypical misalignment were included but not labeled as DI regardless of the distance versus near deviation. The remaining patients, whatever the original diagnosis, were retrospectively categorized as having, or not having, DI, using a uniform criterion: distance esotropia ≥5^Δ more than near esotropia.

RESULTS

The percentage of DI patients among acquired esotropia patients increased significantly between the first and second half of the 41-year period, from 11.8% to 29.4% (P < 0.001). Multivariate logistic regression identified advancing age and the use of progressive addition lenses as risk factors for the development of DI.

CONCLUSIONS

The incidence of DI is increasing. DI's association with age and progressive addition lenses may help us to understand its etiology and to decrease the prevalence of this condition in the future.

A validated finite element model to reproduce Helmholtz's theory of accommodation: a powerful tool to investigate presbyopia

PURPOSE

To reproduce human in vivo accommodation numerically. For that purpose, a finite element model specific for a 29-year-old subject was designed. Once the proposed numerical model was validated, the decrease in accommodative amplitude with age was simulated according to data available in the literature.

METHODS

In contrast with previous studies, the non-accommodated eye condition was the reference configuration. Consequently, two aspects were specifically highlighted: contraction of the ciliary muscle, which was simulated by a continuum electro-mechanical model and incorporation of initial lens capsule stresses, which allowed the lens to become accommodated after releasing the resting zonular tension.

RESULTS

The morphological changes and contraction of the ciliary muscle were calibrated accurately according to the experimental data from the literature. All dynamic optical and biometric lens measurements validated the model. With the proposed numerical model, presbyopia was successfully simulated.

CONCLUSIONS

The most widespread theory of accommodation, proposed by Helmholtz, was simulated accurately. Assuming the same initial stresses in the lens capsule over time, stiffening of the lens nucleus is the main cause of presbyopia.

Feasibility of optical quality analysis system for the objective assessment of accommodation insufficiency: a phase 1 study

PURPOSE

To assess differences in a new objective metric obtained with a double-pass technique between a group with accommodation insufficiency (AI) and a control group and to explore the diagnostic capabilities of this new tool in comparison to conventional procedures.

METHODS

Retrospective cross-sectional case-control phase 1 study. Two groups with ages ranging from 8 to 18 years were recruited: AI and control group. The diagnostic criterion of AI was based on monocular accommodative amplitude (AA), 2 D below Hofstetter's calculation for minimum AA, and monocular accommodative facility (MAF), failing with minus lens and cut-off at ≤ 6 cycles per minute. Accommodative response with a double pass device (HD Analyzer, Visiometrics) was measured, performing an evaluation from +1.00 D to -3.50D (-0.5D steps), offering the width of the profile at 50% (WP) in minutes of arc.

RESULTS

Differences were found between groups for the AA, MAF and MEM retinoscopy (p < 0.0001, p < 0.001, p = 0.037). The discriminative capacity of MEM retinoscopy for AI diagnosis was significant and the cut-off that maximized the sensitivity and specificity was > 0.5 D. Considering WP 50% in different points, the discriminative AI diagnosis capacities for the points of 2.0 D and 2.50 D were significant (ROC-AUC 0.78; p = 0.03 and p = 0.02).

CONCLUSIONS

Double-pass system metric differed between patients with AI and control group, therefore the aim of a Phase I study was achieved. Further steps with higher sample sizes are required to evidence if the system really provides any advantage versus conventional methods in the diagnosis of AI.

Optimal allocation of quantized human eye depth perception for multi-focal 3D display design

Creating immersive 3D stereoscopic, autostereoscopic, and lightfield experiences are becoming the center point of optical design of future head mounted displays and lightfield displays. However, despite the advancement in 3D and light field displays, there is no consensus on what are the necessary quantized depth levels for such emerging displays at stereoscopic or monocular modalities. Here we start from psychophysical theories and work toward defining and prioritizing quantized levels of depth that would saturate the human depth perception. We propose a general optimization framework, which locates the depth levels in a globally optimal way for band limited displays. While the original problem is computationally intractable, we manage to find a tractable reformulation as maximally covering a region of interest with a selection of hypographs corresponding to the monocular depth of field profiles. The results indicate that on average 1731 stereoscopic and 7 monocular depth levels (distributed optimally from 25 cm to infinity) would saturate the visual depth perception. Such that adding further depth levels adds negligible improvement. Also the first 3 depth levels should be allocated at (148), then (83, 170), then (53, 90, 170) distances respectively from the face plane to minimize the monocular error in the entire population. The study further discusses the 3D spatial profile of the quantized stereoscopic and monocular depth levels. The study provides fundamental guidelines for designing optimal near eye displays, light-field monitors, and 3D screens.

Age Effect on Treatment Responses to 0.05%, 0.025%, and 0.01% Atropine: Low-Concentration Atropine for Myopia Progression Study

PURPOSE

To investigate the effect of age at treatment and other factors on treatment response to atropine in the Low-Concentration Atropine for Myopia Progression (LAMP) Study.

DESIGN

Secondary analysis from a randomized trial.

PARTICIPANTS

Three hundred fifty children aged 4 to 12 years who originally were assigned to receive 0.05%, 0.025%, or 0.01% atropine or placebo once daily, and who completed 2 years of the LAMP Study, were included. In the second year, the placebo group was switched to the 0.05% atropine group.

METHODS

Potential predictive factors for change in spherical equivalent (SE) and axial length (AL) over 2 years were evaluated by generalized estimating equations in each treatment group. Evaluated factors included age at treatment, gender, baseline refraction, parental myopia, time outdoors, diopter hours of near work, and treatment compliance. Estimated mean values and 95% confidence intervals (CIs) of change in SE and AL over 2 years also were generated.

MAIN OUTCOME MEASURES

Factors associated with SE change and AL change over 2 years were the primary outcome measures. Associated factors during the first year were secondary outcome measures.

RESULTS

In 0.05%, 0.025%, and 0.01% atropine groups, younger age was the only factor associated with SE progression (coefficient of 0.14, 0.15, and 0.20, respectively) and AL elongation (coefficient of -0.10, -0.11, and -0.12, respectively) over 2 years; the younger the age, the poorer the response. At each year of age from 4 to 12 years across the treatment groups, higher-concentration atropine showed a better treatment response, following a concentration-dependent effect (P_trend <0.05 for each age group). In addition, the mean SE progression in 6-year-old children receiving 0.05% atropine (-0.90 diopter [D]; 95% CI, -0.99 to -0.82) was similar to that of 8-year-old children receiving 0.025% atropine (-0.89 D; 95% CI, -0.94 to -0.83) and 10-year-old children receiving 0.01% atropine (-0.92 D; 95% CI, -0.99 to -0.85). All concentrations were well tolerated in all age groups.

CONCLUSIONS

Younger age is associated with poor treatment response to low-concentration atropine at 0.05%, 0.025%, and 0.01%. Among concentrations studied, younger children required the highest 0.05% concentration to achieve similar reduction in myopic progression as older children receiving lower concentrations.

Zone of Clear Single Binocular Vision in Myopic Orthokeratology

PURPOSE

To examine the zone of clear single binocular vision (ZCSBV) in myopic children and young adults after 12 months of orthokeratology (OK) wear, in comparison with single-vision soft contact lens (SCL) wear.

METHODS

Twelve children (8-16 years) and 8 adults (18-29 years) were assessed with a series of near-point binocular vision tests when myopia was corrected using single-vision SCLs and again after 1 and 12 months of OK wear, and axial length was measured. The ZCSBV was constructed for baseline SCL wear and after 12 months of OK wear.

RESULTS

After 1 month of OK wear, increased accommodative responses were noted in children (C) and adults (A) as increased binocular amplitude (C:P=0.03, A:P=0.04) and reduced accommodative lag (C:P=0.01, A:P=0.01). Divergence reserves improved after 1 month in both groups (P<0.04), and a near exophoric shift was evident at 12 months (C:P=0.01, A:P=0.04). All changes at 1 month maintained stability at 12 months. An increase in accommodation and vergence responses without reduction in range resulted in an expansion of the ZCSBV in both age groups. Axial length did not significantly change in either children (P=0.25) or adults (P=0.72).

CONCLUSION

In both pediatric and young adult myopes, the ZCSBV expands toward a more divergent, increased accommodation response in OK compared with SCL wear. This occurs without a corresponding loss of convergence or accommodation deactivation, indicating improved depth of focus. These findings are relevant to visual acceptance and possible mechanisms of OK's efficacy for myopia control.

A randomised clinical trial of multifocal contact lenses and contact lens discomfort

PURPOSE

To determine how multifocal contact lenses affect contact lens discomfort.

METHODS

This randomised, participant-masked, crossover clinical trial fitted 84 uncomfortable soft contact lens wearers (30-40 years old) with single vision and multifocal contact lenses. Contact lens discomfort was assessed using the Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8).

RESULTS

There was no difference between multifocal and single vision survey scores (p = 0.08). There was an interaction between lens type and age group (p = 0.05). CLDEQ-8 scores with the single vision lens were less symptomatic than multifocal scores in participants <35 years old (p = 0.01). Single vision and multifocal scores for the older age group were not different. Subjectively, those in the <35 year-old age group preferred the single vision lens for intermediate (p = 0.02), distance (p = 0.003), and overall vision (p = 0.002). In the ≥35 year-old age group, no lens was significantly preferred for vision.

CONCLUSIONS

Participants in the younger age group had more favourable wearing experiences with the single vision lens compared to the multifocal lens. The older age group, however, had similar wearing experiences with both lens types. While younger contact lens wearers may prefer the wearing experience with single vision lenses, some uncomfortable contact lens wearers approaching 40 years old may benefit from wearing a multifocal contact lens sooner in life than is typically practised.

The Effect of Retinal Illuminance on the Subjective Amplitude of Accommodation

SIGNIFICANCE

We show that the amplitude of accommodation decreases with retinal illumination even under photopic reading conditions and a constant pupil size. This result provides a basis for clinical approaches that are not based on an optical explanation.

PURPOSE

We investigated the effect of retinal illuminance on the amplitude of accommodation while the pupil of the eye remained constant.

METHODS

The amplitudes of accommodation of 10 young subjects (from 20 to 38 years of age) and that of 10 presbyopic subjects (from 45 to 54 years of age) were measured subjectively through an artificial pupil of 5 mm using a Badal optometer and for four values of retinal illuminance: 222, 821, 2138, and 5074 trolands. Phenylephrine was instilled to all the subjects to ensure that their natural pupil was greater than the artificial one in all experimental runs. Linear mixed-effects model for repeated measures with age and log luminance as covariates were used to check whether changes in amplitude of accommodation with retinal illumination were statistically significant.

RESULTS

In the range of illuminances tested, the amplitude of accommodation decreased on average from 6.34 to 4.35 D in the young subjects and from 1.69 to 1.04 D in the presbyopic subjects. Illuminance was associated with the amplitude of accommodation in both young and presbyopic groups, with P < .01.

CONCLUSIONS

The reduction in the amplitude of accommodation with target illumination (a phenomenon named night presbyopia) under photopic light conditions is not only due to a reduction in the depth of focus as a consequence of pupil dilation; it is strongly affected by the decrease of retinal illumination.

Optical and imaging properties of a novel multi-segment spectacle lens designed to slow myopia progression

PURPOSE

High sampling density optical metrology combined with pupil- and image-plane numerical analyses were applied to evaluate a novel spectacle lens containing multiple small zones designed to slow myopia progression.

METHODS

High-resolution aberrometry (ClearWave, www.lumetrics.com) was used to sample wavefront slopes of a novel spectacle lens, Defocus Incorporated Multiple Segments (DIMS) (www.hoya.com), incorporating many small, positive-powered lenslets in its periphery. Using wavefront slope and error maps, custom MATLAB software ('Indiana Wavefront Analyzer') was used to compute image-plane point-spread functions (PSF), modulation transfer functions (MTF), simulated images and power distributions created by the dual-focus optic for different pupil sizes and target vergences.

RESULTS

Outside of a central 10 mm zone containing single distance optical power, a hexagonal array of small 1 mm lenslets with nearest-neighbour separations of 0.5 mm were distributed over the lens periphery. Sagittal and curvature-based measures of optical power imperfectly captured the consistent +3.50 D add produced by the lenslets. Image plane simulations revealed multiple PSFs and poor image quality at the lenslet focal plane. Blur at the distance optic focal plane was consistent with a combination of diffraction blur from the distance optic and the approximately +3.50 D of defocus from the 1 mm diameter near optic zones.

CONCLUSION

Converging the defocused beams generated by the multiple small (1 mm diameter) lenslets to a blurred image at the distance focal plane produced a blur magnitude determined by the small lenslet diameter and not the overall pupil diameter. The distance optic located in between the near-add lenslets determines the limits of the optical quality achievable by the lens. When compared to the optics of a traditional concentric-zone dual-focus contact lens, the optics of the DIMS lens generates higher-contrast images at low spatial frequencies (<7 cycles per degree), but lower-contrast at high spatial frequencies.

Repeatability of the amplitude of accommodation measured by a new generation autorefractor

Significance

This is the first study to validate the repeatability of objective measurements of amplitude of accommodation (AA) using the TONOREF III (NIDEK Co., Ltd., Japan), which can measure the AA in 30 seconds.

Purpose

To evaluate the repeatability of objective measurements of AA using the TONOREF III and explored the association between objectively measured AA and factors, including age, sex, spherical equivalent, baseline pupil size and pupil size change during accommodation.

Methods

This cross-sectional study recruited 35 healthy subjects aged 26 to 52 years. The Bland-Altman method and intraclass correlation coefficients (ICCs) were used to assess the repeatability of TONOREF III measurements. The relationships between AA and age, sex, baseline pupil size, changes in pupil size (ΔPS) during accommodation were analyzed using linear regression for univariate and multivariate analysis.

Results

The mean difference in AA (ΔAA) between two sessions of TONOREF III measurements was 0.23 D (95% CI: -1.07 to +1.53 D), while no significant correlation was found between the mean and ΔAA (p = .14). The ICCs of the TONOREF III was 0.96. Age, sex, and ΔPS during accommodation were significant factors affecting the AA in multivariate analysis.

Conclusions

The repeatability of objective AA measurements using the TONOREF III was good. Measuring AA using the TONOREF^TM III in clinical practice is feasible.

Sources of error in clinical measurement of the amplitude of accommodation

Measurement of the amplitude of accommodation is established as a procedure in a routine optometric eye examination. However, clinical methods of measurement of this basic optical function have several sources of error. They are numerous and diverse, and include depth of focus, reaction time, instrument design, specification of the measurement end-point, specification of the reference point of measurement, measurement conditions, consideration of refractive error, and psychological factors. Several of these sources of inaccuracy are composed of multiple sub-sources, and many of the sub-sources influence the common methods of measurement of amplitude of accommodation. Consideration of these sources of measurement error casts doubt on the reliability of the results of measurement, on the validity of established normative values that have been produced using these methods, and on the value of reports of the results of surgery designed to restore accommodation. Clinicians can reduce the effects of some of the sources of error by modifying techniques of measurement with existing methods, but a new method may further improve accuracy.

Impact of monovision on dynamic accommodation of early presbyopes

PURPOSE

To examine the impact of monovision on dynamic changes in accommodation, pupil responses, spherical aberration and resultant image quality in early presbyopes.

METHODS

Refractive state, pupil size and spherical aberration levels were monitored in nine early presbyopes who exhibited some accommodation (40-50 years, mean = 42 ± 2.37 years) using a Shack-Hartmann aberrometer as a binocularly viewed stimulus stepped closer (from 2 m to 40 cm), or farther (from 40 cm to 2 m). Comparison data from two fully presbyopic (i.e. non-accommodating) subjects (ages 46 and 61 years) and two young adults (ages 26 and 29 years) were also collected. Each subject was fit with four different refractive strategies: (1) both eyes corrected for 2 m, (2) both eyes corrected for 40 cm, (3) monovision with the measured right eye corrected for 2 m and, (4) monovision with the right eye corrected for 40 cm. Monochromatic image quality was quantified using the AreaMTF metric.

RESULTS

When fit with monovision, the largest number of early presbyopes produce an accommodative response dominated by the right eye correction (distance or near) as the stimulus is abruptly changed from the retinal conjugate plane of one eye to that of the other eye. However, the accommodative responses in some early presbyopes were always dominated by the distance corrected eye, the near corrected eye, or by convergence. When the stimulus approached, the near corrected eye experienced high image quality only if there was no accommodative response. However, reduced image quality was observed if an accommodative response was initiated. Neither accommodation nor pupil response latencies were longer with monovision corrections compared with bilateral distance corrections (p > 0.05). In the early presbyopes, spherical aberration was reduced during near viewing, but primarily due to pupil miosis and not lens shape changes.

CONCLUSION

As the stimulus was abruptly changed from the retinal conjugate plane of the distance corrected eye to that of the near corrected eye, most early presbyopes fit with monovision accommodated, which resulted in a decline, not an increase in image quality in the near corrected eye. These results reveal a non-optimal accommodative strategy in early presbyopes fit with monovision.

Comparison of Dynamic Retinoscopy and Autorefraction for Measurement of Accommodative Amplitude

SIGNIFICANCE

This study promotes the use of dynamic retinoscopy to obtain objective measures of accommodative amplitude (AA) in the clinical setting in lieu of the subjective push-up technique.

PURPOSE

This study compared the agreement between open-field autorefraction and a modified dynamic retinoscopy for the objective measurement of AA.

METHODS

Accommodative amplitude was measured using two objective techniques for subjects aged 5 to 60 years. Test order was randomized and monocular AA was measured as subjects viewed printed letters 0.9 mm in height with their dominant eye and distance refraction. For retinoscopy, subjects held a near rod and viewed the target at the nearest (most proximal) point of clear vision. The examiner then performed dynamic retinoscopy along the horizontal meridian and identified the physical location of neutrality of the reflex, which was converted to AA in diopters. Autorefraction was performed obtaining repeated measures of refraction beginning from a target demand of 2.5 D and increasing in discrete steps until there was no subsequent increase in accommodative response. Refractions were converted to power in the horizontal meridian and expressed as accommodation in diopters with the maximal value termed the AA. Distance overrefractions were measured for both techniques to adjust AA for any uncorrected refractive error. Difference versus mean analysis was used to compare agreement between tests.

RESULTS

The 95% limits of agreement between techniques were calculated after removal of two young outliers who responded poorly to one of the techniques. The overall mean difference for 95 subjects was 0.02 ± 0.97 D, with limits of agreement spanning -1.87 to 1.92 D. No significant linear relationship between the magnitude of the AA and the differences between techniques was observed.

CONCLUSIONS

Agreement between dynamic retinoscopy and open-field autorefraction was less than 2 D with no systematic bias, suggesting that dynamic retinoscopy may be a suitable clinical technique to measure objective AA.

Accommodative insufficiency in a student population in Iran

PURPOSE

To determine the prevalence of accommodative insufficiency (AI) and its relation with age, gender, and refractive errors in a college-age student population in Iran.

METHODS

The present study was conducted cross-sectionally in 2017. All students had optometric tests including measurement of visual acuity, objective and subjective refraction, as well as binocular vision and accommodative examinations. Amplitude of accommodation was measured with the Donders' push-up method using the Royal Air Force (RAF) rule. Monocular accommodative facility was measured with ±2.00diopter flipper lenses. The accommodative response was tested using dynamic retinoscopy with the monocular estimation method (MEM).

RESULTS

The prevalence of AI in the studied population was 4.07% (95% CI: 2.61-5.52). The rate was 6.04% (95% CI: 3.58-8.50) in females and 2.01% (95% CI: 0.53-3.48) in males, and logistic regression showed a significantly higher odds of AI in females (OR=3.14, 95% CI: 1.33-7.45, p-value=0.009). The prevalence of AI was 2.59% (95% CI: 0.55-7.56) in the 18-19-year-old age group and 4.08% (95% CI: 0.09-8.07) in the 24-25-year-old group (p-value=0.848). The prevalence of AI among emmetropic, myopic, and hyperopic individuals was 3.74% (95% CI: 1.88-5.61), 4.44% (95% CI: 2.07-6.81), and 5.26% (95% CI: 4.79-16.32), respectively (p-value=0.869). In the multiple regression model, only gender showed significant relationship with AI (Odds ratio=3.14, 95% CI: 1.33-7.45; p-values=0.009).

CONCLUSION

The prevalence of AI in the present study is lower than the most prevalence rates reported in previous studies. In the present study, gender and AI showed a strong association, such that AI prevalence was significantly higher in females than males.

Validity of the +1.50 plus lens screening test as a predictor of uncorrected moderate hyperopia

PURPOSE

Screening for uncorrected hyperopia in school children is important given its association with poorer visual function and academic performance. However, standard distance visual acuity screening may not detect low to moderate hyperopia. The plus lens test is used to screen for hyperopia in many school screening protocols, but has not been well validated. The current study investigated the effectiveness of the plus lens test to identify hyperopia in school children.

METHODS

Participants included Grade 2 school children. Monocular distance visual acuity (logMAR letter chart) was measured unaided, and then through a +1.50D lens, known as the plus lens test. Cycloplegic refraction was undertaken to classify moderate hyperopia (≥+2.00D). Sensitivity, specificity, positive predictive values (PPV) and negative predictive values (NPV) were calculated for commonly used cut-offs for the plus lens test: 6/6, 6/9 and less than two lines difference between unaided acuity and acuity through the plus lens test.

RESULTS

The sample included 59 children (mean age 7.2 ± 0.4 years). Fourteen (24%) children were classified as having uncorrected hyperopia. The sensitivity and specificity of the +1.50 plus lens test for identifying hyperopia were 0% and 98% respectively for a 6/6 cut-off, 29% and 91% for 6/9 cut-off, and 50% and 76% for a <2 line reduction between unaided acuity and acuity through the plus lens test. Receiver Operating Curve (ROC) analysis revealed area under curves of 0.69 based on acuity through the plus lens test, and 0.65 for a reduction in acuity through the plus lens test.

CONCLUSIONS

The plus lens test has low sensitivity for detecting uncorrected hyperopia using traditional cut-offs of 6/9 or better. This raises questions about the role of the plus lens test in school screening batteries.

Accommodation and age-dependent eye model based on in vivo measurements

PURPOSE

To develop a flexible model of the average eye that incorporates changes with age and accommodation in all optical parameters, including entrance pupil diameter, under photopic, natural, environmental conditions.

METHODS

We collated retrospective in vivo measurements of all optical parameters, including entrance pupil diameter. Ray-tracing was used to calculate the wavefront aberrations of the eye model as a function of age, stimulus vergence and pupil diameter. These aberrations were used to calculate objective refraction using paraxial curvature matching. This was also done for several stimulus positions to calculate the accommodation response/stimulus curve.

RESULTS

The model predicts a hyperopic change in distance refraction as the eye ages (+0.22D every 10 years) between 20 and 65 years. The slope of the accommodation response/stimulus curve was 0.72 for a 25 years-old subject, with little change between 20 and 45 years. A trend to a more negative value of primary spherical aberration as the eye accommodates is predicted for all ages (20-50 years). When accommodation is relaxed, a slight increase in primary spherical aberration (0.008μm every 10 years) between 20 and 65 years is predicted, for an age-dependent entrance pupil diameter ranging between 3.58mm (20 years) and 3.05mm (65 years). Results match reasonably well with studies performed in real eyes, except that spherical aberration is systematically slightly negative as compared with the practical data.

CONCLUSIONS

The proposed eye model is able to predict changes in objective refraction and accommodation response. It has the potential to be a useful design and testing tool for devices (e.g. intraocular lenses or contact lenses) designed to correct the eye's optical errors.

Accommodation in Early Presbyopes Fit with Bilateral or Unilateral Near Add

SIGNIFICANCE

When fit with monovision, most early presbyopes (aged 40 to 50 years) accommodated to near objects by focusing the distance corrected eye, leaving the near corrected eye myopically defocused with reduced image quality. A few were able to switch focus to the near corrected eye retaining a consistently focused image in one eye over a wider range of distances.

PURPOSE

The aim of this study was to examine accommodation behavior, pupil responses, and resultant image quality of early presbyopes fit with either bilateral or unilateral (monovision) near adds.

METHODS

Accommodative response and pupil size of 19 subjects (27 to 60 years), including 13 early presbyopes (40 to 50 years), were measured using an aberrometer as a binocularly viewed 20/40 letter E was moved from 2 m to 20 cm. Each subject was fit with different refractive strategies: bilateral distance correction, bilateral +2 diopters (D) near add, and unilateral +2 D near add placed over the measured right eye or unmeasured left eye. Monochromatic image quality was quantified using the Visual Strehl ratio metric.

RESULTS

With bilateral +2 D near add, all early presbyopes mostly refrained from accommodating (gain = 0.22 D/D) until the target approached closer than the 50-cm far point, and they then accommodated accurately until their maximum accommodative amplitude was reached. With monovision, most (10 of 13 early presbyopes) accommodated to focus the distance corrected eye, leaving the near corrected eye myopically defocused with reduced image quality. As stimulus distance became closer than their distance corrected eye's near point, they continued to exert maximum accommodation. Only two early presbyopes relaxed their accommodation to "switch" focus to the near corrected eye as target distance was reduced, and these two did not experience bilateral drop in image quality as stimulus distance became closer than the near point of the distance corrected eye.

CONCLUSIONS

Our data suggest that many early presbyopes will not initially adopt an accommodation strategy that optimizes image quality with monovision, but consistently accommodate to focus the distance corrected eye.

Comparison of the amplitude of accommodation determined subjectively and objectively in South African university students

Background: Historically, two clinical methods have been used for measuring the amplitude of accommodation, which are the push-up and minus lens methods. However, it has been documented that the push-up method overestimates amplitude of accommodation, while the minus lens method underestimates it.Aim: The purpose of this study was to compare subjective and objective procedures for determining the monocular amplitude of accommodation in young optometry students.Setting: The study was conducted in the optometry clinic at the university.Methods: Amplitude of accommodation was measured on 45 optometry students (17 males and 28 females, whose ages ranged from 21 to 27 years) using the push-up, push-down, minus lens, modified dynamic retinoscopy and Pascal dynamic retinoscopy methods. Data were collected by three different examiners in this study. One examiner measured all the subjective tests, while another examiner measured the modified dynamic retinoscopy. The third examiner measured the Pascal heterodynamic retinoscopy.Results: The highest amplitude of accommodation was obtained using the push-up method (10.23 ± 1.67 D), while the minus lens method gave the lowest subjective finding (8.43 ± 1.68 D). However, the subjective methods generally produced comparable results. Both retinoscopic methods showed the lowest mean amplitude of accommodation of approximately 6.50 ± 1.40 D. However, there was a high correlation between the various methods.Conclusion: The push-up and push-down methods overestimate the true amplitude of accommodation because of the relative magnification, while the minus lens method creates an abnormal viewing environment in which the target is stationary but the stimulus becomes increasingly minified. Subjective amplitude of accommodation is an inadequate measure to assess any true accommodation because it fails to differentiate between passive depth of focus and an active accommodative power change in the eye. Therefore, subjective measurement of the amplitude of accommodation may suggest that accommodation is present when it is not. Further research is needed to further validate dynamic retinoscopy as the optimal or best possible routine clinical method to assess the true amplitude of accommodation.

Visual, musculoskeletal and balance symptoms in individuals with visual impairment

BACKGROUND

Visual impairment is globally among the most prevalent disabilities. Research concerning the health consequences of visual deficits is challenged by confounding effects of age, because visual impairment becomes more prevalent with age. This study investigates the influence of visual deficits on visual, musculoskeletal and balance symptoms in adults with and without visual impairment, while controlling for age effects.

METHODS

Thirty-nine patients with visual impairment, aged 18-72 years, were compared to 37 age-matched controls with normal vision, allocated to two age groups: < 45 and ≥ 45 years. Self-reported symptoms were measured using the Visual, Musculoskeletal and Balance Symptoms Questionnaire and compared with demographic and optometric variables.

RESULTS

In total, patients with visual impairment reported more symptoms than age-matched normally sighted controls. Younger adults in the control group were almost free from symptoms, whereas younger adults with visual impairment reported levels of symptoms equal to older adults with visual impairment. Multiple logistic regression modelling identified use of eyeglasses, magnifying aids and presence of anisometropia to be the most influential risk factors for reporting visual, musculoskeletal and balance symptoms, with accentuated influence on balance symptoms.

CONCLUSIONS

People with visual impairments and people with age-related normal visual deficits are both predisposed to report visual, musculoskeletal and balance symptoms relative to people without visual defects or need for eye-wear correction. Age-related variations in symptoms were observed in the control groups but not in the visual impairment groups, with younger visual impairment patients reporting as many symptoms as older visual impairment patients. These findings indicate a need for a wider interdisciplinary perspective on eye care concerning people with visual impairment and people with need for habitual daily use of eye wear correction.

Maximum human objectively measured pharmacologically stimulated accommodative amplitude

Purpose

To measure the maximum, objectively measured, accommodative amplitude, produced by pharmacologic stimulation.

Methods

Thirty-seven healthy subjects were enrolled, with a mean age of 20.2±1.1 years, corrected visual acuity of 20/20, and mean spherical equivalent refraction (SER) =-0.83±1.60 diopters. For each subject, the right pupil was dilated with phenylephrine 10%. After 30 minutes, the pupil was measured, the left eye was patched, and the right eye was autorefracted. Pilocarpine 4% was then instilled in the right eye, followed by phenylephrine. At 45 minutes after the pilocarpine, autorefraction and pupil size were again measured.

Results

Mean pupil size pre- and postpilocarpine was 8.0±0.8 mm and 4.4±1.9 mm, respectively. Pre- and postpilocarpine, the mean SER was -0.83±1.60 and -10.55±4.26 diopters, respectively. The mean pilocarpine-induced accommodative amplitude was 9.73±3.64 diopters. Five subjects had accommodative amplitudes ≥14.00 diopters. Accommodative amplitude was not significantly related to baseline SER (p-value =0.24), pre- or postpilocarpine pupil size (p-values =0.13 and 0.74), or change in pupil size (p-value =0.37). Iris color did not statistically significantly affect accommodative amplitude (p-value =0.83).

Conclusion

Following topically applied pilocarpine, the induced objectively measured accommodation in the young eye is greater than or equal to the reported subjectively measured voluntary maximum accommodative amplitude.

Attention and Visual Motor Integration in Young Children with Uncorrected Hyperopia

SIGNIFICANCE

Among 4- and 5-year-old children, deficits in measures of attention, visual-motor integration (VMI) and visual perception (VP) are associated with moderate, uncorrected hyperopia (3 to 6 diopters [D]) accompanied by reduced near visual function (near visual acuity worse than 20/40 or stereoacuity worse than 240 seconds of arc).

PURPOSE

To compare attention, visual motor, and visual perceptual skills in uncorrected hyperopes and emmetropes attending preschool or kindergarten and evaluate their associations with visual function.

METHODS

Participants were 4 and 5 years of age with either hyperopia (≥3 to ≤6 D, astigmatism ≤1.5 D, anisometropia ≤1 D) or emmetropia (hyperopia ≤1 D; astigmatism, anisometropia, and myopia each <1 D), without amblyopia or strabismus. Examiners masked to refractive status administered tests of attention (sustained, receptive, and expressive), VMI, and VP. Binocular visual acuity, stereoacuity, and accommodative accuracy were also assessed at near. Analyses were adjusted for age, sex, race/ethnicity, and parent's/caregiver's education.

RESULTS

Two hundred forty-four hyperopes (mean, +3.8 ± [SD] 0.8 D) and 248 emmetropes (+0.5 ± 0.5 D) completed testing. Mean sustained attention score was worse in hyperopes compared with emmetropes (mean difference, -4.1; P < .001 for 3 to 6 D). Mean Receptive Attention score was worse in 4 to 6 D hyperopes compared with emmetropes (by -2.6, P = .01). Hyperopes with reduced near visual acuity (20/40 or worse) had worse scores than emmetropes (-6.4, P < .001 for sustained attention; -3.0, P = .004 for Receptive Attention; -0.7, P = .006 for VMI; -1.3, P = .008 for VP). Hyperopes with stereoacuity of 240 seconds of arc or worse scored significantly worse than emmetropes (-6.7, P < .001 for sustained attention; -3.4, P = .03 for Expressive Attention; -2.2, P = .03 for Receptive Attention; -0.7, P = .01 for VMI; -1.7, P < .001 for VP). Overall, hyperopes with better near visual function generally performed similarly to emmetropes.

CONCLUSIONS

Moderately hyperopic children were found to have deficits in measures of attention. Hyperopic children with reduced near visual function also had lower scores on VMI and VP than emmetropic children.

Accommodation and Phoria in Children Wearing Multifocal Contact Lenses

PURPOSE

To determine the effect of multifocal contact lenses on accommodation and phoria in children.

METHODS

This was a prospective, non-dispensing, randomized, crossover, single-visit study. Myopic children with normal accommodation and binocularity and no history of myopia control treatment were enrolled and fitted with CooperVision Biofinity single vision (SV) and multifocal (MF, +2.50D center distance add) contact lenses. Accommodative responses (photorefraction) and phorias (modified Thorington) were measured at four distances (>3 m, 100 cm, 40 cm, 25 cm). Secondary measures included high- and low-contrast logMAR acuity, accommodative amplitude, and facility. Differences between contact lens designs were analyzed using repeated measures regression and paired t-tests.

RESULTS

A total of 16 subjects, aged 10 to 15 years, completed the study. There was a small decrease in high (SV: -0.08, MF: +0.01) and low illumination (SV: -0.03, MF: +0.08) (both P < .01) visual acuity, and contrast sensitivity (SV: 2.0, MF: 1.9 log units, P = .015) with multifocals. Subjects were more exophoric at 40 cm (SV: -0.41, MF: -2.06 Δ) and 25 cm (SV: -0.83, MF: -4.30 Δ) (both P < .01). With multifocals, subjects had decreased accommodative responses at distance (SV: -0.04; MF: -0.37D, P = .02), 100 cm (SV: +0.37; MF: -0.35D, P < .01), 40 cm (SV: +1.82; MF: +0.62D, P < .01), and 25 cm (SV: +3.38; MF: +1.75D, P < .01). There were no significant differences in accommodative amplitude (P = .66) or facility (P = .54).

CONCLUSIONS

Children wearing multifocal contact lenses exhibited reduced accommodative responses and more exophoria at increasingly higher accommodative demands than with single vision contact lenses. This suggests that children may be relaxing their accommodation and using the positive addition or increased depth of focus from added spherical aberration of the multifocals. Further studies are needed to evaluate other lens designs, different amounts of positive addition and aberrations, and long-term adaptation to lenses.

The Response AC/A Ratio Before and After the Onset of Myopia

Purpose

To investigate the ratio of accommodative convergence per diopter of accommodative response (AC/A ratio) before, during, and after myopia onset.

Methods

Subjects were 698 children aged 6 to 14 years who became myopic and 430 emmetropic children participating in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error. Refractive error was measured using cycloplegic autorefraction, near work by parent survey, and the AC/A ratio by simultaneously monitoring convergence and accommodative response. The response AC/A ratios of children who became myopic were compared with age-, sex-, and ethnicity-matched model estimates for emmetropic children from 5 years before through 5 years after the onset of myopia.

Results

The response AC/A ratio was not significantly different between the two groups 5 years before onset, then increased monotonically in children who became myopic until reaching a plateau at myopia onset of about 7 Δ/D compared to about 4 Δ/D for children who remained emmetropic (differences between groups significant at P < 0.01 from 4 years before onset through 5 years after onset). A higher AC/A ratio was associated with greater accommodative lag but not with the rate of myopia progression regardless of the level of near work.

Conclusions

An increasing AC/A ratio is an early sign of becoming myopic, is related to greater accommodative lag, but does not affect the rate of myopia progression. The association with accommodative lag suggests that the AC/A ratio increase is from greater neural effort needed per diopter of accommodation rather than change in the accommodative convergence crosslink gain relationship.

Does Hofstetter's equation predict the real amplitude of accommodation in children?

PURPOSE

The aim was to determine the distribution and associated factors of accommodative amplitude (AA) in six- to 12-year-old children and compare the results with those calculated using Hofstetter's formula.

METHODS

In a cross-sectional study in 2015, random sampling was done from urban and rural populations of Shahroud, northern Iran. Participating schoolchildren were examined for manifest, cycloplegic and subjective refraction, as well as uncorrected vision and visual acuity. The AA was measured with Donders' push-up method using a ruler. The near point of convergence (NPC) was also measured.

RESULTS

Of the 6,624 selected children, 5,620 participated in the study and after applying the exclusion criteria, the final analyses were done on data from 5,444 schoolchildren. The mean age of the final sample was 9.24 ± 1.71 years (from six to 12 years) and 53.6 per cent (n = 2,919) were boys. Mean measured AA was 14.44 D (95 per cent confidence interval [CI]: 14.33-14.55). In all age groups, the mean measured AA was less than the predicted mean value calculated with the Hofstetter's equation. Mean measured AA was 14.44 D (95 per cent CI: 14.28-14.59) and 14.45 D (95 per cent CI: 14.29-14.6) in boys and girls, respectively (p = 0.926). AA significantly declined with age (coefficient: -0.18, 95 per cent CI: -0.23 to -0.12, p < 0.001). Mean AA in emmetropic, myopic and hyperopic children was 14.31 D, 17.30 D and 14.87 D, respectively. Older age (coefficient = -0.18), living in rural areas (coefficient = -0.48) and NPC (coefficient = 0.47) inversely related with AA and higher AA was associated with a shift of the spherical equivalent refraction toward myopia (coefficient = -0.41).

CONCLUSION

The differences among groups with different types of refractive error and high AA in children with myopia are important findings of this study. The results of the present study suggest that Hofstetter's formula provides inaccurate AA estimates in children and thus, the interpretation of this index requires further population-based studies in different racial and ethnic groups.

Accommodative amplitude using the minus lens at different near distances

Purpose:

The purpose of this study was to compare the mean findings and the repeatability of the minus lens (ML) amplitude of accommodation (AA) at 33 cm and 40 cm.

Materials and Methods:

AA was measured from the dominant eye of 120 fully corrected subjects using the ML procedure when viewing the target at both 33 and 40 cm. Each measurement was repeated between 24 and 48 hours after the first trial.

Results:

Mean AA when tested at 33 cm and 40 cm was 10.20 diopter (D) (standard deviation [SD] =1.24) and 8.85 D (SD = 1.23), respectively (P < 0.001). The limits of agreement of the measured amplitude calculated with taking into account of the replicates at 33 and 40 cm were − 0.19 (95% confidence interval [CI]: −0.34 to −0.04) and 2.53 (95% CI: 2.38 to 2.68), respectively. The repeatability of testing at the two distances 33 and 40 cm was ± 1.24 and ± 0.99, respectively. In addition, the retest reliability of measured amplitude using the intraclass correlation coefficient was 0.87 (95% CI: 0.789–0.920) at 33 cm and 0.91 (95% CI: 0.872–0.945) at 40 cm.

Conclusion:

There is no agreement in the obtained amplitude at the two measurement distances. Testing the ML AA at 40 cm may be superior given that a lower repeatability coefficient was observed. However, it is unclear whether the larger amplitude measured at 33 cm reflects a larger increase in accommodation (greater proximity effect) or a decrease in the ability to perceive the first slight sustained blur.

Cycloplegic Refraction in Hyperopic Children: Effectiveness of a 0.5% Tropicamide and 0.5% Phenylephrine Addition to 1% Cyclopentolate Regimen

Purpose

To evaluate the effectiveness of a cycloplegic regimen using 0.5% tropicamide and 0.5% phenylephrine (Tropherine, Hanmi Pharm), in addition to 1% cyclopentolate, in hyperopic children.

Methods

The medical records of hyperopic patients below the age of 14 years who had undergone cycloplegic retinoscopy were retrospectively reviewed. Cycloplegic refractions were performed using one of two cycloplegic regimens. Regimen 1 was a Tropherine-added regimen comprising the administration of one drop of 1% cyclopentolate followed by two to three drops of Tropherine added at 15-minute intervals. Regimen 2 was a cyclopentolate-only regimen comprising the administration of three to four drops of 1% cyclopentolate at 15-minute intervals. The mean difference between noncycloplegic and cycloplegic refraction was compared between the two regimens.

Results

A total of 308 eyes of 308 hyperopic children were included. The mean difference (±standard deviation) in the spherical equivalent (SE) between cycloplegic and noncycloplegic refraction was significantly larger in regimen 2 than in regimen 1, with values of +1.70 ± 1.03 diopters (D) and +1.25 ± 0.89 D, respectively (p=0.001). The SE change after cycloplegia was significantly different between the two regimens only in patients aged 5 years or younger (p=0.001), particularly in those with high hyperopia with an SE ≥5 D (p=0.005) or fully accommodative esotropia (p=0.009). There was no significant difference between the two regimens in patients older than 5 years, regardless of the presence of high hyperopia or fully accommodative esotropia.

Conclusions

The Tropherine-added regimen exerted a weaker cycloplegic effect than the cyclopentolate-only regimen, particularly in children under the age of 5 years with high hyperopia or fully accommodative esotropia. However, the difference in refraction between the two regimens was small. A Tropherine-added regimen can be effective in hyperopic children, with less associated discomfort than the instillation of cyclopentolate.

Interaction of aberrations, diffraction, and quantal fluctuations determine the impact of pupil size on visual quality

Our purpose is to develop a computational approach that jointly assesses the impact of stimulus luminance and pupil size on visual quality. We compared traditional optical measures of image quality and those that incorporate the impact of retinal illuminance dependent neural contrast sensitivity. Visually weighted image quality was calculated for a presbyopic model eye with representative levels of chromatic and monochromatic aberrations as pupil diameter was varied from 7 to 1 mm, stimulus luminance varied from 2000 to 0.1  cd/m², and defocus varied from 0 to -2 diopters. The model included the effects of quantal fluctuations on neural contrast sensitivity. We tested the model's predictions for five cycles per degree gratings by measuring contrast sensitivity at 5  cyc/deg. Unlike the traditional Strehl ratio and the visually weighted area under the modulation transfer function, the visual Strehl ratio derived from the optical transfer function was able to capture the combined impact of optics and quantal noise on visual quality. In a well-focused eye, provided retinal illuminance is held constant as pupil size varies, visual image quality scales approximately as the square root of illuminance because of quantum fluctuations, but optimum pupil size is essentially independent of retinal illuminance and quantum fluctuations. Conversely, when stimulus luminance is held constant (and therefore illuminance varies with pupil size), optimum pupil size increases as luminance decreases, thereby compensating partially for increased quantum fluctuations. However, in the presence of -1 and -2 diopters of defocus and at high photopic levels where Weber's law operates, optical aberrations and diffraction dominate image quality and pupil optimization. Similar behavior was observed in human observers viewing sinusoidal gratings. Optimum pupil size increases as stimulus luminance drops for the well-focused eye, and the benefits of small pupils for improving defocused image quality remain throughout the photopic and mesopic ranges. However, restricting pupils to <2  mm will cause significant reductions in the best focus vision at low photopic and mesopic luminances.

Prevalence and Risk Factors for Refractive Error in Adult Chinese Americans: The Chinese American Eye Study

PURPOSE

To estimate the prevalence of refractive errors in adult Chinese Americans, and to evaluate factors associated with myopia and high myopia.

DESIGN

A population-based, cross-sectional study.

METHODS

Chinese Americans 50 years and older residing in Monterey Park, California, were recruited. Noncycloplegic automated refraction with supplemental subjective refraction was performed. Myopia, high myopia, hyperopia, and high hyperopia were defined as a spherical equivalent of <-0.5 diopter (D), <-5.0 D, >+0.5 D, and ≥+3.0 D, respectively. Astigmatism and high astigmatism were defined as a cylinder of >0.5 D and >2.25 D, respectively. Risk factor assessment was guided by a conceptual model.

RESULTS

Data from 4144 participants were analyzed. The overall prevalence of myopia, high myopia, hyperopia, high hyperopia, astigmatism, and high astigmatism in the right eye was 35.1% (95% confidence interval, 33.6%-36.6%), 7.4% (6.6%-8.3%), 40.2% (38.7%-41.8%), 2.7% (2.2%-3.3%), 45.6% (44.1%-47.2%), and 3.7% (3.1%-4.3%), respectively. The prevalence of myopia and high myopia was lower among older individuals (P < .05). Reversed age trends were observed for the other refractive errors (P < .05). There was no sex difference in the prevalence of refractive errors, except for a higher prevalence of hyperopia among female subjects (P = .010). Age, acculturation, education, income, marital status, birth country, history of ocular disease, nonocular comorbidities, and recent eye examination were associated with prevalence of myopia. All of these factors, except for acculturation, were also associated with high myopia.

CONCLUSIONS

Our data present the first population-based estimates of the prevalence of refractive errors among adult Chinese Americans. Compared with whites, Hispanics, and blacks, Chinese Americans have a higher burden of myopia, high myopia, and astigmatism.

Comparison of measured with calculated amplitude of accommodation in Nigerian children aged six to 16 years

PURPOSE

Amplitude of accommodation varies with race and ethnicity and Hofstetter's equations are commonly used in Nigeria to calculate expected amplitude of accommodation for clinical purposes. The aim of this study was to present normative values for amplitude of accommodation for Nigerian children and to compare the measured values with those calculated using Hofstetter's equations.

METHODS

A total of 688 children aged six to 16 years from three selected cities in Nigeria were included in the study. Push-up technique was employed to measure the amplitude of accommodation. The measured values were compared with the calculated values (Hofstetter's equations) using the paired t-test and Bland and Altman plots.

RESULTS

The measured amplitude of accommodation for the subjects ranged from 8.00 to 25.00 D with a mean of 15.88 ± 3.46 D. The calculated minimum amplitude of accommodation ranged from 11.00 to 13.50 D with a mean of 12.09 ± 0.55 D and the calculated average amplitude of accommodation ranged from 13.17 to 16.50 D with a mean of 14.62 ± 0.73 D. The calculated maximum amplitude of accommodation ranged from 18.60 to 22.60 D with a mean of 20.34 ± 0.88 D. The t-test indicated a significant difference between the measured and calculated minimum, average and maximum amplitudes of accommodation (p < 0.0001). Also, the Bland-Altman plot suggested that there was a lack of agreement between the measured and calculated amplitudes of accommodation.

CONCLUSION

The mean values of amplitude of accommodation in this study are different from those reported in the literature. Also, the measured values differed from the calculated values using Hofstetter's equation. This suggests that the use of Hosftetter's equations to predict amplitude of accommodation may not be accurate for Nigerian children.

Comparison of three monocular methods for measuring accommodative stimulus-response curves

PURPOSE

The aim was to evaluate the repeatability of dynamic measurement of the accommodative stimulus-response curve (ASRC) at three different dioptric speeds using a modified instrument and its agreement with two other methods.

METHODS

Twenty-nine adults (23.5 ± 2.0 years) were enrolled in the study. ASRC was measured monocularly using three methods: dynamic and static measurement using a motorised Badal system mounted on an open-field auto-refractor (WAM-5500, Grand Seiko Co., Ltd, Japan) and the minus lens technique. Dynamic measurements were conducted at three dioptric stimulus speeds to simulate continuous stimuli for ASRC (0.25, 0.40 and 0.55 D/s), with three repetitions for each speed. All three types of ASRCs were fitted with third-degree polynomial equations. The slope and objective accommodative amplitude of the ASRC were analysed.

RESULTS

The repeatability of objective accommodative amplitude worsened as the speed of the stimuli increased. The repeatability of the slope was best at a speed of 0.40 D/s and worst at 0.55 D/s. The measurement method significantly influenced the objective accommodative amplitude values and slope (both, p < 0.001). The minus lens technique yielded the highest amplitude of accommodation (6.21 ± 0.84 D) and steepest slope (1.11 ± 0.14), followed by the static Badal method (5.60 ± 0.83 D and 0.89 ± 0.09 D). The objective accommodative amplitude decreased with increasing speed during dynamic measurements. There was no difference between the slopes at 0.25 D and 0.40 D/s (p > 0.05) and the slope was lowest at 0.55 D/s.

CONCLUSION

The accommodative stimulus-response curve values are method-dependent and the significant differences between three methods used to determine the ASRC based on slope and accommodative amplitude indicate that these methods are non-interchangeable. Using dynamic measurements, accommodative behaviour varies with the speed of dioptric-change of the stimulus. A speed of 0.40 D/s appears to be the best compromise in terms of time, results and repeatability for dynamic ASRC measurement.