Blue Light Defocus Induces A Positive Effect on Refractive Status and Ocular Health: A Randomized Crossover Trial

BACKGROUNDMyopia, as one of the common ocular diseases, often occurs in adolescence. In addition to the harm from itself, it may also lead to serious complications. Thus, prevention and control of myopia are attracting more and more attention. Previous research revealed that single-focal glasses and orthokeratology lenses (OK lenses) played an important part in slowing down myopia and preventing high myopia.AIMTo compare the clinical effects of OK lenses and frame glasses against the increase of diopter in adolescent myopia and further explore the mechanism of the OK lens. METHODSChanges in diopter and axial length were collected among 70 adolescent myopia patients (124 eyes) wearing OK lenses for 1 year (group A) and 59 adolescent myopia patients (113 eyes) wearing frame glasses (group B). Refractive states of their retina were inspected through multispectral refraction topography. The obtained hyperopic defocus was analyzed for the mechanism of OK lenses on slowing down the increase of myopic diopter by delaying the increase of ocular axis length and reducing the near hyperopia defocus.RESULTSTeenagers in groups A and B were divided into low myopia (0D - -3.00 D) and moderate myopia (-3.25D - -6.00 D), without statistical differences among gender and age. After 1-year treatment, the increase of diopter and axis length and changes of retinal hyperopic defocus amount of group A were significantly less than those of group B. According to the multiple linear analysis, the retinal defocus in the upper, lower, nasal, and temporal directions had almost the same effect on the total defocus. The amount of peripheral retinal defocus (15°-53°) in group A was significantly lower than that in group B.CONCLUSIONMultispectral refraction topography is progressive and instructive in clinical prevention and control of myopia.

BackgroundTo perform a three-dimensional assessment of the choroid, including choroidal volume and choroidal vascularity index (CVI), during the transition from intermediate to neovascular age-related macular degeneration (AMD), and following anti-VEGF therapy.MethodsA total of 42 participants (42 eyes) with intermediate AMD at baseline who developed neovascular AMD within 3 months were included in the analysis. Optical coherence tomography (OCT) scans at follow-up visits (after transition to neovascular AMD and 12 months after the initiation of anti-VEGF therapy) were compared with values at the latest visit with evidence of intermediate AMD to quantify longitudinal choroidal changes. Enhanced depth imaging (EDI) OCT scans were analyzed to obtain the following metrics: (i) choroidal volume, (ii) choroidal stromal volume, (iii) choroidal vascular volume, and (iv) CVI.ResultsAt baseline, the mean (median; IQR) choroidal volume (i.e., including both the stromal and vascular components) was 0.156 mm³ (0.149; 0.065), increasing to 0.163 mm³ (0.148; 0.068) at the follow-up when treatment-naïve exudative MNV was first detected (p = 0.013). After 12 months of anti-VEGF therapy, it returned to near-baseline levels at 0.156 mm³ (0.146; 0.065; p = 0.457). Similarly, the choroidal stromal and choroidal volumes increased at MNV detection but returned to baseline after treatment. Conversely, no alterations in CVI were observed between the baseline and follow-up visits.ConclusionThe transition from intermediate to exudative neovascular AMD is associated with a significant increase in choroidal volume, affecting both stromal and luminal components. After anti-VEGF treatment, these changes regress, returning to baseline levels.

Influence of the time of day on axial length and choroidal thickness changes to hyperopic and myopic defocus in human eyes

To investigate the serial choroidal volume change following orbital blow-out fracture (BOF) repair. The choroidal volume was measured by optical coherence tomography in patients who underwent BOF repair, preoperatively and postoperatively at 1, 4, 12 and 24weeks. The orbital volume ratio (OVR) was obtained by dividing the orbital volume of the traumatized orbit by that of the contralateral side using three-dimensional computed tomography imaging. The choroidal volume change was compared between both eyes using a linear mixed model. We analyzed the choroidal volume of 11 patients. Choroidal volume showed a trend of slight increase during the immediate postoperative period, and then, choroidal volume decreased abruptly between postoperative 1 to 4weeks (β-coefficient - 0.22, P < 0.001). Choroidal volume also showed gradual decrease between postoperative 4 to 24weeks (β-coefficient - 0.02, P < 0.001). During the study period, there were no significant differences in choroidal volume change between BOF and contralateral unaffected eyes (β-coefficient - 0.20, P = 0.711). The hyperopic refractive errors (β-coefficient 0.27, P = 0.028) and the larger preoperative OVR (β-coefficient 10.37, P = 0.013) were associated with larger choroidal volume. Choroidal volume showed a similar decreasing change following BOF repair between the BOF and the contralateral unaffected eyes. Moreover, choroidal volume of both eyes was associated with the degree of orbital volume expansion due to BOF, suggesting that choroidal volume change after BOF repair was affected not only by trauma-associated local hemodynamic changes but also by systemic influences such as inflammatory response.

Associations between axial length (AL) to corneal radius of curvature (CR) ratio and refractive status in a healthy Nigerian adult population were studied. Healthy students and members of staff of Obafemi Awolowo Teaching Hospitals Complex, Ile-Ife, South West Nigeria, free of obvious ocular diseases except possible refractive errors were recruited. Consecutive consenting volunteers were recruited by simple random sampling and a proportionate sample of each population based on its representative fraction in the hospital community was recruited. The study was conducted between June and August 2011. Noncycloplegic objective refraction was done and spherical equivalent refraction (SER) of the right eyes was used for calculation. The AL, CR, and keratometric readings were measured with the IOL Master. The AL/CR ratio was calculated. The data were analyzed with statistical software package STATA 13. Three hundred and fifty volunteers aged 18-60 years were studied. The mean ± standard deviation of AL/CR and SER were 3.04 ± 0.10 and -0.38 ± 1.42D, respectively. AL in myopia was significantly higher than in emmetropia and hypermetropia. There were no significant differences between CR in the refraction groups. Myopes had significantly higher AL/CR than nonmyopes. On controlling for age and gender, 1 mm increase in AL increased SER by -0.77D (95% confidence interval [CI] -0.91--0.64D) while a unit increase in AL/CR increased SER by -8.89D (95% CI -10.00--7.78D). Whereas AL accounts for 39% of variability in SER (P < 0.001), AL/CR accounts for 51% of the variability observed in SER (P < 0.001). This study has further confirmed that the AL remains a strong determinant of refraction, but a derived factor AL/CR accounts for more variation in final refractive status than AL in isolation.

BackgroundThe anatomic structure of the anterior chamber (AC) helps to explain differences in refractive status in school-aged children and is closely associated with primary angle closure (PAC). The aim of this study was to quantify and analyze the anterior chamber and angle (ACA) characteristics in Chinese children with different refractive status by swept-source optical coherence tomography (SS-OCT).MethodsIn a cross-sectional observational study, 383 children from two primary schools in Shandong Province, China, underwent a complete ophthalmic examination. First, the anterior chamber depth (ACD), anterior chamber width (ACW), angle-opening distance (AOD), and trabecular-iris space area (TISA) were evaluated automatically using a CASIA2 imaging device. AOD and TISA were measured at 500, 750 μm nasal (N1 and N2, respectively), and temporal (T1 and T2, respectively) to the scleral spur (SS). Cycloplegic refraction and axial length (AL) were then measured. According to spherical equivalent refraction (SER), the children were assigned to hyperopic (SER > 0.50D), emmetropic (-0.50D < SER ≤ 0.50D), and myopic groups (SER ≤ -0.50D).ResultsOut of the 383 children, 349 healthy children (160 girls) with a mean age of 8.23 ± 1.06 years (range: 6–11 years) were included. The mean SER and AL were − 0.10 ± 1.57D and 23.44 ± 0.95 mm, respectively. The mean ACD and ACW were 3.17 ± 0.24 mm and 11.69 ± 0.43 mm. The mean AOD were 0.72 ± 0.25, 0.63 ± 0.22 mm at N1, T1, and 0.98 ± 0.30, 0.84 ± 0.27 mm at N2, T2. The mean TISA were 0.24 ± 0.09, 0.22 ± 0.09mm2 at N1, T1, and 0.46 ± 0.16, 0.40 ± 0.14mm2 at N2, T2. The myopic group had the deepest AC and the widest angle. Compared with boys, girls had shorter AL, shallower ACD, narrower ACW, and ACA (all p < 0.05). By Pearson’s correlation analysis, SER was negatively associated with ACD, AOD, and TISA. AL was positively associated with ACD, ACW, AOD, and TISA. In the multiple regression analysis, AOD and TISA were associated with deeper ACD, narrower ACW, and longer AL.ConclusionIn primary school students, the myopic eyes have deeper AC and wider angle. ACD, ACW, AOD, and TISA all increase with axial elongation. ACA is highly correlated with deeper ACD.

Background: The rapid increase in smartphone screens led to eye problems. The study measured transient axial length variations during mobile screen exposure before and after hyperopic defocus. Methods: A quasi-experimental study on students utilizing non-probability sampling was conducted at Al-Shifa Trust Eye Hospital. LogMAR measured visual acuity, and retinoscopy measured refractive status of right eye only. Samsung Galaxy A7 provided full-blue screen exposure. -3.00 DS lens in trial frame caused hyperopic defocus. IOL Master Zeiss 700 measured axial length and ocular biometrics. The online web program Data tab was entered, and data was analyzed. Results: A total of 30 subjects, which includes 6 (20%) males and 24 (80%) females, with a mean age of 20.67 (±0.96) years. Mean visual acuity and Spherical Equivalent Refraction were 0.00 (±0.00) and 0.10 (±0.01). Comparing the median interquartile range (Median-IQR) pre-defocus axial length (PDAXL) and after defocus axial length (ADAXL), pre-defocus lens thickness (PDLT) and after defocus lens thickness (ADLT) following 1 h exposure to mobile screen a statistically significant difference were observed respectively – 23.2 (±0.93), 23.14 (±0.92), p value = 0.003 and 3.61 (±0.28), 3.61 (±0.22), p value = 0.001. Other ocular parameter like pre-defocus anterior chamber depth (PDACD) and after-defocus anterior chamber depth (ADACD), pre-defocus central corneal thickness (PDCCT) and after-defocus central corneal thickness (ADCCT) no statistically significant were observed respectively – 3.45 (±0.29), 3.44 (±0.26), p value = 0.861 and 528 (±31.50), 525.17 (±24.75), p value = 0.139. Conclusion: Exposure to mobile screens in blue mode, along with hyperopic defocus, was found to cause axial length shortening, offering potential implications for managing myopia progression.

Objective: To investigate the differences in reading efficiency and visual fatigue between the use of augmented reality (AR) glasses and laptops. Methods: A prospective self-controlled study was conducted. Healthy students from Capital Medical University who frequently engaged in long-term near work and used laptops and other digital display devices were recruited as subjects at Beijing Tongren Hospital, Capital Medical University between November 1 and November 15, 2023. LogMAR visual acuity, visual functions (accommodation, convergence, and fusion), and visual fatigue scores (Likert visual fatigue scale) of the participants were assessed. The order of using the laptop and AR glasses for each participant was determined by a coin toss. Reading efficiency (reading speed and error rate multiplied by the detection rate of incorrect numbers) with different devices for 10 minutes at the same time on different dates and visual fatigue scores after watching a 20-minute video were measured. Statistical analyses were performed using paired t-tests and Wilcoxon signed-rank tests. Results: A total of 20 eligible subjects were included, comprising 7 males and 13 females, with a mean age of (25.45±2.27) years. There was no significant change in binocular visual acuity before and after using AR glasses and laptops (both P>0.05). The reading speed and reading efficiency of using AR glasses [(34.03±9.25) and (29.19±7.62) digits/min, respectively] were significantly lower than those of using laptops [(39.43±10.36) and (35.67±9.87) digits/min, respectively] (t=4.36, P<0.001), while the difference in error detection rate was not statistically significant (t=1.29, P=0.213). There was no statistically significant difference in visual fatigue scores before watching videos with the two devices (Z=-0.71, P=0.480). However, the visual fatigue score after watching videos with AR glasses [(20.55±5.04) points] was significantly higher than that with laptops [16.50 (13.00, 19.75) points] (Z=-2.85, P=0.004). The visual fatigue scores after watching videos with both devices were significantly higher than before (P<0.05), with a more significant increase observed with AR glasses [(6.05±3.50) points] (Z=-3.41, P<0.001). Conclusion: Compared with using laptops, the reading speed and efficiency were lower, and the visual fatigue was more pronounced with the use of AR glasses at the current technical level. Further optimization and improvement of AR glasses are warranted.

To assess the retinal peripheral defocus changes following femtosecond laser in situ-keratomileusis (FS-LASIK) in myopic adults and analyse influencing factors. This study recruited 202 patients who underwent FS-LASIK with myopia at Beijing Ming Vision Eye Hospital. Participants were divided into low myopia (LM, -0.50D to -3.00D), moderate myopia (MM, -3.00D to -6.00D), and high myopia (HM, ≥-6.00D) groups according to spherical equivalent (SE). We measured axial length (AL), total retinal defocus (TRDV), and defocus values at eccentricities ranging from 0° to 53° from the fovea, and defocus values at the superior, inferior, temporal, and nasal quadrants. With a 3-month follow-up, changes in peripheral defocus (ΔRDV) were recorded and analysed. No significant differences were observed in TRDV, RDV20°-53°, and RDV-S among the three groups after surgery (all P > 0.05). RDV at 10°-53° increased with eccentricity, while all groups showed significant reductions in hyperopic defocus at 20°-53° compared to preoperative measurements (all P < 0.05). This reduction was more pronounced with severe myopia and greater eccentricity. Correlation analysis revealed that ΔRDV20°-30° and ΔRDV30°-40° positively correlated with SE and negatively correlated with AL and cutting thickness. ΔRDV40°-53° negatively correlated with AL. ΔRDV-T negatively correlated with SE, ΔRDV-N positively correlated with SE and negatively correlated with AL and cutting thickness (all P < 0.05). FS-LASIK does not change the asymmetric distribution of RDV after surgery. It effectively reduces hyperopic defocus within the 20°-53° range around the fovea, with greater reductions noted peripherally. Higher myopia and greater cutting thickness are associated with larger defocus reductions.

Quantitative analysis of peripheral retinal defocus checked by multispectral refraction topography in myopia among youth.

BackgroundTo investigate the factors related to the change in axial length after repeated low-level red-light(RLRL) therapy.MethodsA retrospective case study. A total of 323 children and adolescents who underwent RLRL therapy concurrently with their eye examinations at Wuhan Children’s Hospital from 2022 to 2023 were included. The biological eye parameters, including the axial length (AL), spherical equivalent refractive (SER), the subfoveal choroidal thickness (SFCT), intraocular pressure (IOP), corneal curvature and corneal thickness, were recorded at baseline, 3-month, 6-month, 12-month, 12-month, 18-month and 24-month. The factors related to the degree of change in axial length were analyzed.ResultsThere was a statistical difference in the amount of AL changes during the follow-up (F = 16.12, P < 0.001), and the amount of AL changes was significant at the 6-month follow-up (△AL=-0.16 ± 0.18), and then gradually decreased with the extension of follow-up time. There was a statistically positive correlation between baseline AL and baseline SER and changes in AL (P < 0.05). The axial regression in high myopia group was significantly greater than that in mild and moderate myopia group (P < 0.05). There was also a statistically positive correlation between age and changes in AL (P < 0.05). At the follow-up of 6 months, 12 months, 18 months, combined with other myopia prevention and control was correlated with the change of AL (P < 0.05). Baseline corneal thickness, baseline corneal curvature and baseline IOP were not correlated with changes in AL (all P > 0.05).ConclusionThe longer the baseline AL, the higher SER, the thinner SFCT, the older the age and the combination of other myopia prevention and control measures, the more obvious the change of AL. However, the changes of AL were not affected by IOP, corneal curvature and corneal thickness.

The purpose of this study was to evaluate the diurnal variation in choroidal parameters in a wide field area among healthy subjects and to identify correlations between choroidal luminal area and stromal area and various systemic factors. In this cross-sectional study, 42 eyes from 21 healthy participants (mean age = 32.4 ± 8.8 years) were examined using wide-field swept-source optical coherence tomography angiography (WF SS-OCTA, 24 mm × 20 mm). Measurements of choroidal parameters, including choroidal volume (CV), choroidal thickness (CT), choroidal vessel volume (CVV), and choroidal stromal volume (CSV), were taken at 8:00, 12:00, 18:00, and 22:00. Systemic factors, such as blood pressure and heart rate, were concurrently monitored. Our study observed significant diurnal variations in the mean total CV, CT, CVV, and CSV, with minimum measurements around 12:00 (P < 0.001) and peak values at 22:00 (P < 0.001). Furthermore, changes in CV in specific regions were more closely associated with fluctuations in CVV than CSV in the same regions. No significant diurnal variations were found in systolic (P = 0.137) or diastolic blood pressure (P = 0.236), whereas significant variations were observed in the heart rate (P = 0.001). Our study reveals diurnal variations in choroidal parameters and their associations, emphasizing that changes in choroidal volume relate more to the luminal than the stromal area in vessel-rich regions. This enhances our understanding of choroidal-related ocular diseases. Regions with higher choroidal vasculature observed greater choroidal volume changes.

Objective: To establish a correlation model between static refraction and the main refractive parameters of children aged 3-12 years. Methods: This cross sectional study was divided into two parts. In part one, in Changsha Aier Eye Hospital from July 2014 to June 2016, 245 children were randomly selected and measurements were taken of their axial length (AL), corneal curvature (Km) and anterior chamber depth, spherical equivalent refractive (SE) and calculated lens power (LP). The correlations between refraction and the refractive parameters were analyzed to establisha correlative mathematical model. In part two, in Changsha Aier Eye Hospital from July to December 2016, 43 children were randomly selected to measure the above refractive parameters and their cycloplegic refraction (SEmeasured). The lens power and static refraction (SEcalculated) were calculated. The consistency between SEmeasured and SEcalculated was compared by Bland-Altman analysis. Results: The correlation model was established as follows: The correlation coefficients between SE and AL, Km and LP were -0.95, -0.83 and -0.62, respectively (all P<0.001). SE=110.56-2.51×AL-0.97×Km-0.44×LP (R2=0.95, F=2534.52, P<0.001). There was a significant correlation between SEmeasured and SEcalculated (r=0.97, P<0.001), the 95% limit of agreement was -1.00-0.63 D, average error was -0.19 D (95% consistency limit: -0.28 to -0.10 D), and 81.40% of the data points were within the clinically acceptable range (-0.55 to 0.55 D). Conclusions: The axial length is the most important factor in refraction besides corneal curvature and lens power. The refraction correlation model can accurately estimate the static refraction of children from 3 to 12 years old. Key words: refraction; axial length; corneal power; lens power; correlation model

Change in body height, axial length and refractive status over a four-year period in caucasian children and young adults

Introduction: Prolonged smartphone usage has been linked to visual fatigue, primarily due to continuous exposure to blue light emitted from screens. Critical Flicker Fusion Frequency (CFFF) is a well-established physiological marker for assessing visual fatigue, where a decline in CFFF values indicates increased ocular strain and reduced visual efficiency. Medical students, who extensively use smartphones for both academic and personal activities, are particularly vulnerable to digital eye strain. Understanding the impact of sustained screen exposure on CFFF is essential for promoting visual health and implementing preventive strategies to mitigate screen-induced fatigue. Aim: To assess the effect of one hour of smartphone usage on CFFF as a marker of visual fatigue among MBBS students aged 18-25 years. Materials and Methods: This pre-post experimental study was conducted over a period of six months, from October 2023 to April 2024, at SRM Medical College and Hospital, Kattankulathur, Tamil Nadu, India involving 182 MBBS students aged 18-25 years with daily smartphone usage exceeding three hours. Baseline CFFF values were recorded using a flicker fusion apparatus, followed by one hour of smartphone usage that involved reading text and watching videos. Postexposure CFFF values were then measured under standardised conditions. Data were analysed using Statistical Package for the Social Sciences (SPSS) version 21.0 and a paired t-test was performed to assess statistical significance (p-value &lt;0.05). Results: A statistically significant reduction in CFFF was observed following one hour of continuous smartphone usage, indicating increased visual fatigue. The baseline CFFF values averaged 35.46±3.58 Hz, which declined to 25.91±3.50 Hz postexposure. The mean difference in CFFF values was 9.555±4.770 Hz, confirming a notable reduction in visual processing efficiency which was statistically significant (p-value of 0.001) highlighting the impact of prolonged smartphone exposure on visual strain and fatigue. Conclusion: This study demonstrated that one hour of continuous smartphone usage leads to a measurable decline in CFFF, indicating significant visual fatigue. Implementing preventive strategies, such as the 20-20-20 rule, blue light filters and controlled screen brightness, may help mitigate screeninduced eye strain among medical students. Further research is recommended to explore the long-term impact of smartphoneinduced ocular fatigue and its potential implications for digital eye health.