The effect of spatially-related environmental risk factors in visual scenes on myopia

Interaction of retinal electrophysiology and novel orthokeratology lens use on myopia control efficacy in children

AIMS

The relationship between retinal electrophysiological function and myopia progression was evaluated in school-aged children wearing Breath-O-Correct Orthokeratology (OK) lenses compared with those wearing single vision (SV) lenses over 24 months.

METHODS

In this randomised, single-blind, parallel controlled trial, children aged 8-12 years with -1.00 to -4.00 D of myopia were recruited. Retinal function was evaluated using global-flash multifocal electroretinography at baseline before OK or SV treatment. Axial length was evaluated at 6-month intervals up to 24 months. The main outcome measures were axial elongation (AE) between groups and the interactive effect of baseline retinal function.

RESULTS

A total of 70 children (43 OK, 9.8±1.3 years; 27 SV, 9.5±1.4 years) completed the 2-year study and were included in the analysis. The 2-year normalised AE was 0.37±0.37 mm in the OK group and 0.60±0.41 mm in the SV group, respectively. For children in the SV group, the amplitude of the central inner retinal response was negatively correlated with axial length elongation (p=0.03). In contrast, this relationship between retinal electrophysiology and AE was not observed in OK group, indicating that they were independent of each other in children treated with OK (p=0.33).

CONCLUSION

A weak retinal electrophysiological response was a risk factor for rapid AE in SV controls. However, OK treatment can lower this risk factor and significantly reduce AE in school-aged children.

Lower indoor spatial frequency increases the risk of myopia in children

BACKGROUND/AIMS

Animal models have shown that the absence of high-frequency visual information can precipitate the onset of myopia, but this relationship remains unclear in humans. This study aims to explore the association between the spatial frequency content of the visual environment and myopia in children.

METHODS

Images from the rooms of children and their frequently visited outdoor areas were taken by their parents and collected by the researcher through questionnaires. The spatial frequency was quantified using Matlab. Cycloplegic refraction was used to measure the spherical equivalent (SE), and IOL Master was used to measure axial length (AL) and corneal radius (CR). AL/CR ratio was calculated.

RESULTS

The study included 566 children with an average age of (8.04±1.47) years, of which 270 were girls (47.7%), and the average SE was (0.70±1.21) D. Image analysis revealed that indoor spatial frequency slope was lower than that of the outdoor environment (-1.43±0.18 vs -1.11±0.23, p<0.001). There were 79 myopic individuals (14.0%). Images from indoor content of myopic children had a lower spatial frequency slope than non-myopic children (-1.47±0.16 vs 1.43±0.18, p=0.03) while there was no significant difference in outdoor spatial frequency slope. Regression analysis indicated that the indoor spatial frequency slope was positively associated with SE value (β=0.60, p=0.02) and inversely related to myopia (OR=0.24, p<0.05).

CONCLUSION

The spatial frequency of the outdoor environment is significantly higher than that of the indoor environment. Indoor spatial frequency is related to children's refractive status, with lower indoor spatial frequency being associated with a higher degree of myopia.

Spatial frequency of environments and myopia: A systematic review on associated evidence and underlying mechanisms

PURPOSE

Previous animal studies have found a relationship between spatial frequency and myopia. New research in humans suggest that reduced high spatial content of the visual environment may be a contributing factor for myopia development. This study aims to review the literature and elucidate the potential biological mechanisms linking spatial frequency and myopia.

METHODS

A systematic search was conducted across PubMed and Web of Science databases. The studies published from their inception to August 2024 that have explored the connection between spatial frequency and myopia. Only full-text articles in English were included. PRISMA was used for data validity.

RESULTS

A total of 13 articles were included in this review, comprising seven animal model studies, four population-based studies, one pictorial analysis and one study on research design. Epidemiological evidence is comparatively limited and has only begun to emerge in recent years. Mid- to high spatial frequencies were found to play an important role in the emmetropization process of the eye. Low spatial frequencies can increase the risk of myopia incidence. Furthermore, the potential mechanisms of how spatial frequency affects myopia are summarized as visual information processing characteristics, eye accommodation function and eye movements, contrast sensitivity and relevant molecules involved in the pathway.

CONCLUSION

The evidence suggests that indoor spatial frequency may be related to the development of myopia. Further studies are warranted to understand if the incorporation of changes in indoor environments is helpful in the prevention and control of myopia.

Binocular Visual Deficits at Low to High Spatial Frequency in Intermittent Exotropia After Surgery

Purpose

To investigate binocular visual deficits at low to high spatial frequencies in patients with intermittent exotropia (IXT) after surgical correction, using the binocular orientation combination task.

Methods

Thirteen patients whose IXT has been aligned surgically (17 ± 4.8 years old; 7 females) and 13 normal individuals (21.8 ± 2.5 years old; 6 females) were recruited. All participants had normal or corrected-to-normal visual acuity. The IXT patients had undergone surgery at least one month prior to the study and achieved successful eye alignment post-surgery. We measured participants' balance points (BPs), defined as the interocular contrast ratio (nondominant eye/dominant eye) when both eyes contributed equally to binocular combination, using the binocular orientation combination task at three spatial frequencies (0.5, 4.0, and 8.0 cycles/degree). The absolute values of log10(BP) (i.e., |logBP|) and the area under of the |logBP| versus spatial frequency curve were used to quantify the extent of binocular imbalance.

Results

Surgery aligned the eye position of patients with IXT, with a postoperative exodeviation of -4.92 ± 4.29 prism diopters at distance. Participants' |logBP| values showed significant differences between groups, F(1,24) = 9.175, P = 0.006, and across spatial frequencies, F(2,48) = 7.127, P = 0.002. However, the interaction between group and spatial frequency was not significant, F(2,48) = 0.379, P = 0.687.

Conclusions

Patients whose IXT has been alighted surgically experience binocular imbalance across a wide range of spatial frequencies, with greater binocular imbalance occurring at high spatial frequencies than low spatial frequencies.

Development of the University of Houston near work, environment, activity, and refraction (UH NEAR) survey for myopia

CLINICAL RELEVANCE

There is a need to better elucidate demographic and behavioural factors that are contributing to the rising prevalence of myopia. Doing so will aid in developing evidence-based recommendations for behavioural modifications to prevent onset and slow progression of myopia in children.

BACKGROUND

The contributions of environmental and behavioural factors in myopia remain unclear. The goal of this work was to provide a standardised survey to better understand risk factors for myopia.

METHODS

Development of the survey was carried out in 4 phases. In phase 1, three methods (direct, lay terms, and indirect) of parental reporting for the presence of myopia in their child were investigated through a questionnaire (N = 109) to determine sensitivity and specificity. The best method determined from phase 1 was used in phase 2, where questions regarding demographics, ocular history, and visual behaviour were compiled and refined. In phase 3, the survey was administered to focus groups of parents (N = 9). In phase 4, a scoring system was developed.

RESULTS

The highest sensitivity for parental reporting for myopia of their child was the indirect method (0.84), and the lowest sensitivity was the direct method (0.41). The highest specificity was the direct method (0.86), once excluding the 'do not know' responses, and the lowest specificity was the indirect method (0.53). The direct method yielded a 53.2% 'do not know' response rate, 50.5% for the lay method, and 1.8% for the indirect method. Time to complete the survey was 10:09 ± 2:45 minutes.

CONCLUSION

This study provides a comprehensive and up-to-date myopia risk factor survey that can be utilised by researchers and clinicians. Parents found the survey to be easy to understand and relatively quick to answer, and the scoring system allows quantification of behaviours across different categories using provided equations.

Prevalence of refractive error in Nigerian children

Refractive errors can have profound effects on children. Cost and logistics prohibit national population-based studies and global data do not accurately reflect the burden among Nigerian children. This systematic review and meta-analysis aim to provide pooled prevalence and pattern of refractive error in Nigerian children. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The protocol for this study was pre-specified and registered on the International Prospective Register of Systematic Review (registration number ID: CRD42022303419). A systematic search of PubMed, EMBASE, Scopus, CINAHL Cochrane Library, African Journal Online, and African Index Medicus databases, was done for school-based, or population-based studies on refractive error prevalence in Nigerian children younger than 18 years of age or school children in pre-tertiary institutions. Quality-effect model was used to calculate weighted prevalence, odds ratio, and corresponding 95% confidence interval. Twenty-eight school-based studies including 34,866 children were identified. No population-based studies were found. The pooled prevalence of refractive error in Nigerian children was 5.9% (3.6-8.7%) and varied between regions and with the definition of refractive error used in the studies. The number of children needed to be screened to detect one case of refractive error was 15 (9-21). The odds of refractive error was higher in girls (odds ratio: 1.3 {1.1 to 1.5}), children >10 years (odds ratio: 1.7 {1.3 to 2.2}), and urban residents (odds ratio: 2.0 {1.6 to 2.5}). The high prevalence of refractive error in Nigerian children substantiates the value of screening school children for refractive error, particularly targeting urban and older children. Research is needed to refine case definitions and improve screening protocol. Population-based studies are needed to define the prevalence of refractive error in communities. The epidemiologic and methodological challenges in conducting prevalence reviews is discussed.

Lifestyle Factors in Myopic Spanish Children

BACKGROUND

Childhood myopia represents a global concern with increasing prevalence in recent decades. Lifestyle factors significantly impact myopia.

AIM

To evaluate lifestyle factors in myopic children from a metropolitan area in Europe.

METHODS

This was a descriptive study including myopic subjects aged 4-18 years. Patient demographic and clinical data were collected, including cycloplegic refraction in spherical equivalent refraction (SER) and axial length (AL). In addition, a questionnaire on lifestyle factors was conducted between September 2022 and April 2023.

RESULTS

A total of 321 myopic children were included, aged 10.72 ± 3.05 years, of whom 51.4% were boys, with SER -2.25 ± 1.9 D and AL 24.54 ± 0.98 mm. The mean age of myopia onset was 7.69 ± 3.05 years. A total of 59.8% had family history of myopia. Those children who had <2 h/day of screen time (on weekdays) presented SER -2 ± 1.91 D, compared to those who had >2 h/day, SER: -2.50 ±1.88 D (p = 0.009). Children who spent <2 h/day doing near work after school were less myopic compared to those who spent >2 h/day (SER: -1.75 ± 1.83 vs. SER: -2.75 ± 1.82, respectively, p = 0.03). However, no significant association was observed between SER and AL and time spent outdoors nor between SER and AL and academic performance (p > 0.05).

CONCLUSIONS

Screen time and near-work time appear to be lifestyle factors related to myopia.

Effects of virtual distant viewing technology on preventing nearwork-induced ocular parameter changes

Purpose

This study investigates whether virtual distant viewing technology can prevent nearwork-induced ocular parameter changes.

Methods

Twenty-six volunteers read a textbook on one day and the same content on a virtual distant viewing display on another day based on a randomization sequence, with both reading sessions at 33 cm for 4 hours. Visual acuity, diopter, ocular biology, visual fatigue, and accommodative function before and after the nearwork, as well as the number of pages read, were recorded.

Results

After 4 hours of nearwork in the textbook group, the spherical equivalent refraction decreased from -3.13 ± 2.65 D to -3.32 ± 2.70 D (P < 0.001), corneal thickness decreased from 531.6 ± 33.5 μm to 528.9 ± 33.0 μm (P = 0.015), anterior chamber depth decreased from 3.65 ± 0.35 mm to 3.60 ± 0.30 mm (P = 0.002), accommodative facility increased from 15.1 ± 3.5 to 16.4 ± 3.9 (P = 0.018), and subjective visual fatigue increased from 14.0 ± 9.2 to 19.3 ± 7.6 (P = 0.002); no significant changes were seen in the other parameters. In the virtual distant viewing group, the spherical equivalent refraction (from -3.17 ± 2.60 D to -3.11 ± 2.73 D, P = 0.427), corneal thickness (from 531.9 ± 32.8 μm to 529.7 ± 33.2 μm, P = 0.054), and anterior chamber depth (from 3.67 ± 0.35 mm to 3.69 ± 0.32 mm, P = 0.331) did not show significant changes, whereas accommodative facility increased from 14.7 ± 5.8 to 15.9 ± 5.5 (P = 0.042) and subjective visual fatigue increased from 13.5 ± 8.4 to 18.9 ± 8.6 (P = 0.002). In addition, choroidal thickness (from 217.7 ± 76.0 μm to 243.0 ± 85.0 μm, P = 0.043), positive relative accommodation (from -2.32 ± 1.07 D to -2.85 ± 0.89 D, P = 0.007), and amplitude of accommodation (from 7.26 ± 1.41 D to 7.89 ± 1.69 D, P = 0.022) also significantly increased in the virtual distant viewing group. The textbook group and the virtual distant viewing group read 176.0 ± 133.1 pages and 188.0 ± 102.0 pages, respectively, and there was no significant difference between the two groups (P = 0.708).

Conclusion

Virtual distant viewing technology can prevent the increase in myopia degree due to nearwork and improve accommodation function without increasing visual fatigue.

Kinematic characteristics of gait with different myopia: a cross-sectional study

Background

Myopia, a condition affecting approximately one-quarter of the world' s population, has been projected to double in prevalence by the year 2050. It can have an impact on postural control during walking and can increase the risk of falls and injuries.

Objective

(1) To examine the abnormal performance of postural control during walking in male college students who used convex lenses for myopia intervention from a kinematic perspective; (2) to establish theoretical foundation for preventing falls and injuries in the myopic population.

Methods

A total of 22 male college students participated in this study. The center of gravity (COG), the percentage of gait cycle (PGC) and the joint angle(JT) were collected as indications of postural control during walking. A quantitative analysis was conducted using a One-Way Repeated Measures ANOVA to examine the variations among the three groups.

Results

During myopic interventions, (1) the range of vertical COG changes is significant to be greater compared with normal vision (P < 0.05). (2) there was an significant increase in the PGC in single-legged support, accompanied by a decrease in the PGC in double-legged support, compared with normal vision (P < 0.05). (3) The myopic intervention leads to increased variability in JT of the hip and the knee during the single-leg support and swing, as compared to individuals with normal vision (P < 0.05). Severe myopic interventions result in more changes in JT of ankle.

Conclusion

Myopia has been found to have a negative impact on postural control during walking, leading to changes in balance, increased instability, and an elevated risk of injury.

Impact of text contrast polarity on the retinal activity in myopes and emmetropes using modified pattern ERG

Environmental factors favoring myopia development are still being studied and there is accumulating evidence for a significant role of nearwork. Recently, reading standard black-on-white text was found to activate the retinal OFF pathway and induce choroidal thinning, which is associated with myopia onset. Contrarily, reading white-on-black text led to thicker choroids, being protective against myopia. Respective effects on retinal processing are yet unknown. Here, we exploratively assessed the impact of contrast polarity on the retinal activity and possible interactions with eccentricity and refractive error. We recorded pattern electroretinograms in myopic and emmetropic adults while presenting a dead leaves stimulus (DLS), overlaid by masks of different size in ring or circle shape, either filled with uniform gray or text of inverted or standard contrast. In myopes, retinal responses for DLS with standard and inverted contrast were larger when the perifovea was stimulated (6-12 deg), however, including the fovea resulted in smaller amplitudes for inverted contrast than in emmetropes. The retina of emmetropes was more sensitive to inverted contrast than to standard and gray within 12 deg, but most sensitive for gray in the perifovea. This demonstrates that the refractive error influences the sensitivity to text contrast polarity, with a special role of the peripheral retina, which is in line with previous studies about blur sensitivity. Defining whether the differences derive from retinal processing or anatomical features of a myopic eye requires further investigation. Our approach might be a first step to explain how nearwork promotes the eye's elongation.

Size of living space as a moderator for central and peripheral refractions in children

Undesirable living environment may impose risk on myopia development. Furthermore, peripheral refractive error was suggested to contribute to juvenile eye growth modulation. This study aimed to investigate the interaction between peripheral refractive error and living environment in relation to central refractive status in Hong Kong schoolchildren. Central and peripheral refractive errors, axial length (AL), and corneal radius of curvature (CR) were measured in 573 schoolchildren (age 9.5 ± 0.9 years). The AL/CR ratio was used to represent the central refractive status, accounting for non-cycloplegic refraction. The relative peripheral refractive errors (RPRE) up to ± 20° eccentricities were converted into power vectors: spherical-equivalent error (SER) and J₀ astigmatic components and fitted with quadratic equations. The second-order coefficients of SER (a_SER) and J₀ astigmatism (a_J0) and home size reported by parental questionnaires were analyzed to indicate their relationships with AL/CR. Our results showed that children with higher AL/CR lived in smaller homes (p = 0.01) and had a more hyperopic (p < 0.001) but less astigmatic RPRE (p = 0.01). We further analyzed the relationship between AL/CR with RPRE for children living in small (< 300 ft²), moderate (300-600 ft²), and large home sizes (> 600 ft²). Regardless of the home size, a higher AL/CR remained moderately correlated with a more hyperopic a_SER (all p < 0.001). However, a higher AL/CR was associated with a more positive a_J0 only in children living in large homes, and the relationships were not significant for small and moderate home sizes. Linear regression models further indicated that home size was a significant moderator contributing to the relationship between AL/CR and a_J0. In conclusion, our results were consistent with previous studies, showing that children with axial myopia usually lived in smaller homes and had more hyperopic defocus and more positive J₀ astigmatism. However, the relationship between peripheral astigmatism and axial refraction was modulated by the home size of Hong Kong schoolchildren. While peripheral astigmatism is hypothesized as a visual cue for axial refractive development in children, extrinsic environmental factors, such as home size, might interfere with the relationship and dominate refractive development.

Extrinsic and Intrinsic Factors Regulating Juvenile Refractive Development and Eye Growth

Purpose

Peripheral refraction and accommodation are intrinsic factors that were once hypothesized to trigger myopia but are now controversial. Previously, home nearwork environment (i.e., extrinsic factor) was reported to be associated with myopia progression. In this study, we aimed to evaluate the potential interaction between extrinsic and intrinsic factors with juvenile refractive development.

Methods

Nearwork environmental parameters were measured for 50 children (aged 9.3 ± 1.2 years), including net amount and dispersion of defocus. Refraction was measured at near distances and in central field (±30° horizontal) at 3m. The relative peripheral refraction (RPRE) was obtained and presented in a vectoral approach. The linear regression coefficient was extracted (mAcc) from the accommodative stimulus-response curve. RPRE was quadratically regressed against field eccentricity, and the first coefficients (aM, aJ0, aP90, and aP180) were extracted. Relationships between RPRE, baseline accommodation, and 1-year myopia progression (∆M), controlled for the nearwork environment, were evaluated.

Results

Coefficients of RPRE were independent of ∆M. However, additional nearwork environmental parameters significantly improved the variance in ∆M explained by aM and aP180 (P < 0.03). The relationship between intrinsic factor and ∆M was stronger when the extrinsic risk was low (P ≤ 0.01), whereas the relationship was abolished when extrinsic risk was high. For mAcc, it also significantly improved the variance in ∆M explained by nearwork environmental parameters.

Conclusions

The interaction between extrinsic (environment) and intrinsic (RPRE and accommodation) factors is speculated to contribute to juvenile myopia progression. Our findings may also explain the inconsistencies of such intrinsic factors in the literature.