Ocular Accommodation Research Articles (Page 1)

Common surgical approaches to the dorsal midbrain include: the occipital transtentorial, supracerebellar infratentorial, posterior subtemporal, and the tonsilloveal transaqueductal approaches. Case report. A 38-year-old man presented with mild right-sided weakness and diplopia following an episode of headache and vomiting two weeks prior to admission. A neurological examination revealed mild right-sided weakness, a downward and outward strabismus, a mild left ocular mydriasis and accommodation paralysis alongside alternating syndrome. Magnetic resonance imaging revealed a 20×30×25 mm rupture of the cavernous malformation of the left midbrain peduncle as well as hematomas within the cavernoma. Using the supracerebellar infratentorial approach in a sitting position with minimal incision of dorsal midbrain, the cavernoma was completely resected together with surrounding subacute hematoma. In the early postoperative period, a regression of neurological symptoms was observed. Discussion. The choice of median suboccipital craniotomy and contralateral supracerebellar infratentorial approach is the preferred route for complete resection of cavernoma of dorsal midbrain surface in order to avoid any postoperative neurological deficit.

To assess the relationship between accommodative lag (defocus) and accommodative response to determine which drives emmetropisation in highly farsighted 3-month-old infants who successfully reached emmetropia in a 15-month period. 35 highly hyperopic (≥+5.00 D most hyperopic meridian) 3-month-old infants (57% female) were enrolled in a clinical trial (NCT03669146) to determine the effect on emmetropisation (reaching <+3.0 D) of partial refractive correction (full correction reduced by 3.0 D) and visual exercises to stimulate accommodation. Refractive error was obtained by cycloplegic (1% cyclopentolate) retinoscopy and accommodation was assessed with the monocular estimation method (MEM) at near (33 cm) and with the PlusOptix PowerRefractor (Plusoptix, Nuremberg, Germany) at distance (6 m) and near (33 cm). The effect of accommodative response and lag on emmetropisation was analysed using a repeated measures regression model of change in spherical equivalent refractive error as a function of accommodative lag and accommodative response. Greater loss of hyperopia was associated with more robust accommodative response at both distance (measured with the PowerRefractor) and near (measured with MEM). These relationships increased in strength with increasing age, reaching B=-0.32 and B=-0.47 diopters of loss of hyperopia per diopter of accommodative response at 18 months (interaction between response and age p=0.004 and p<0.001 for distance and near, respectively). Linear regression analyses showed no significant associations between change in refractive error and defocus at distance or near. Contrary to defocus-based models of emmetropisation, greater accommodative response and not hyperopic defocus had the stronger influence on the rate of emmetropisation in hyperopic infants.

Can brightness illusions modulate ocular accommodation? Previous studies have shown that brightness illusions can influence pupil size as if caused by actual luminance increases. However, their effects on other ocular responses—such as accommodative or focusing dynamics—remain largely unexplored. This study investigates the influence of brightness illusions, under two ambient lighting conditions, on accommodative and pupillary dynamics (physiological responses), and on perceived brightness and visual comfort (subjective responses). Thirty-two young adults with healthy vision viewed four stimulus types (blue bright and non-bright, yellow bright and non-bright) under low- and high-contrast ambient lighting while ocular responses were recorded using a WAM-5500 open-field autorefractor. Brightness and comfort were rated after each session. The results showed that high ambient contrast (mesopic) and brightness illusions increased accommodative variability, while yellow stimuli elicited a greater lag under photopic condition. Pupil size decreased only under mesopic lighting. Perceived brightness was enhanced by brightness illusions and blue color, whereas visual comfort decreased for bright illusions, especially under low light. These findings suggest that ambient lighting and visual stimulus properties modulate both physiological and subjective responses, highlighting the need for dynamic accommodative assessment and visually ergonomic display design to reduce visual fatigue during digital device use.

Optical coherence tomography (OCT) image stability often suffers during in vivo imaging of the retina due to axial motion of the subject’s head and changes in their visual focus. Ocular accommodation can actively adjust the focus, affecting the axial intensity distribution across the retinal cross-section and the lateral resolution of the target layers. Axial motion shifts the retinal image and affects en face visualization of retinal layers. We present an automated procedure for stabilization of axial motion and focus during OCT retinal image acquisition using deep reinforcement learning (DRL) for defocus correction. The correction process requires only B-scan images as inputs, making it suitable for real-time correction. In silico training and in vivo fine-tuning experiments have been conducted and presented to validate the performance of the correction procedure for retinal imaging.

This study describes a new technique that integrates an electrically tunable lens with a dynamic infrared photorefractor for real-time manipulation of blur feedback for human ocular accommodation. This technique is straightforward to implement, and it also overcomes the limitations of present paradigms used for opening the blur-feedback loop (e.g., pinholes and low spatial frequency difference of Gaussian targets). To describe and validate a technique for real-time manipulation of blur feedback for ocular accommodation by integrating an electrically tunable lens with a dynamic eccentric infrared photorefractor. The EL-16-40-TC-VIS electrically tunable lens (Optotune, Dietikon, Switzerland AG) and the PowerRef 3 eccentric infrared photorefractor (PlusOptix, Nuremberg, Germany) were independently calibrated and integrated via a Secure Shell network protocol. The electrically tunable lens was positioned before the right eye, which accommodated multiple times to 2D step changes in optical vergence. The photorefractor captured consensual accommodative changes through the infrared filter occluded left eye at 50 fps. Blur feedback to the right eye was canceled by feeding in the sign-reversed refraction data into the electrically tunable lens in real-time at 25 fps. The feasibility of this setup to minimize robust blur-driven accommodative step responses was tested on five pre-presbyopic adults. All subjects showed robust monocular, blur-driven accommodative responses at baseline, with a median response magnitude of 1.54 D (1.47 D to 1.54 D). The responses were reduced to only baseline fluctuations following blur-feedback manipulation. The median response magnitude following blur-feedback manipulation (-0.34 D [-0.35 D to 0.09 D]) was significantly different from baseline values (Wilcoxon Sign rank test; p=0.043). The integration of an electrically tunable lens with the photorefractor provides a real-time method for manipulating blur feedback during ocular accommodation. This technique may be a promising tool for investigating sensorimotor properties of accommodation and refractive error development. Alternate schematics for manipulating the blur feedback, expanded operating range of the electrically tunable lens, and reduced signal transmission delays may be considered in the future to enhance the efficacy of this technique.

Oculomotor deficits in vergence and accommodation can arise in paediatric patients with persistent concussion symptoms, although the profile is not well established. This study aimed to describe the frequency of these deficits in persistently symptomatic concussed paediatric patients and identify effective screening tools. This was a prospective cohort study conducted at three clinical sites across the United States. Participants aged 8-18 years with diagnosed concussion were recruited within 9 months of injury through concussion clinics or referral to a vision provider. Participants without concussion were recruited through the local community and eye clinics. Clinical measures of ocular alignment, vergence and accommodation were collected. Group comparisons were assessed using Welch's t-test, Mann-Whitney U test and Fisher's exact test with Bonferroni correction. The diagnostic value of near point of convergence (NPC) and accommodative amplitude (AA) for identifying persistently symptomatic concussed participants was evaluated using logistic regression and receiver operating characteristic curve analysis. Seventy-one participants were recruited, including 34 concussed participants (mean age 14.3 [SD 2.4] years; 74% female, 26% male; median time since concussion 107 [IQR 80-118] days) and 32 controls (mean age, 12.7 [SD 2.1] years; 56% female, 44% male). Concussed participants scored significantly worse or had higher failure rates than controls on all vergence and accommodative tests (p < 0.05) except ocular alignment and monocular accommodative facility. Concussed participants had a higher frequency of diagnoses (vergence: 62% vs. 3%; accommodation: 76% vs. 3%; p < 0.001). NPC and AA were significant predictors for concussion in individual models (NPC: OR = 2.16 [95% CI: 1.52-3.61], p < 0.001, mean AUC [SD] = 0.88 [0.13]; AA: OR = 0.46 [95% CI: 0.29-0.64], p < 0.001, mean AUC [SD] = 0.88 [0.15]). The oculomotor profile of persistently symptomatic concussed paediatric participants shows a high frequency of vergence and accommodative deficits, for which NPC and AA are effective screening tools. Further investigation should examine oculomotor deficits in acutely concussed paediatric patients.

The impact of break schedules on digital eye strain symptoms and ocular accommodation during prolonged near work.

ABSTRACTBackground and AimsGlycated Hemoglobin (HbA1c) is crucial for diagnosing and monitoring diabetes. However, current tests are complex, invasive, costly, and often met with low compliance. This study aimed to find whether simple clinical, noninvasive measures of the ocular accommodation function may predict the glycated hemoglobin results in type‐1 diabetes mellitus.MethodsIn a single‐examiner‐blind study, Near Point of Accommodation (NPA) and Lag of Accommodation (LoA) were compared between type‐1 diabetes patients and controls. NPA was measured by the push‐up‐to‐blur method, LoA by the Monocular Estimation Method (MEM) retinoscopy, and glycated hemoglobin was recorded with a Point‐of‐Care (POC) HbA1c analyzer. The independent t‐test was employed to assess the difference in means between groups. Correlational analysis was conducted to examine the relationship between HbA1c levels and accommodative measures. Additionally, Structural Equation Modeling (SEM) was utilized to evaluate the interrelationships among variables and to determine the extent to which the model could explain the variance in HbA1c.ResultsDiabetic patients had a receded mean NPA (15.16 ± 4.53 cm) compared to controls (9.48 ± 1.43 cm; p < 0.001). When converted to the Amplitude of Accommodation (AoA) in diopters (D), the mean AoA was lower in diabetics (6.6 ± 2.28D) than in controls (10.55 ± 1.52D; p < 0.001). Diabetics had a higher mean LoA (0.983 ± 0.74D) than controls (0.156 ± 0.44D; p < 0.001). After controlling for age (β = −0.167, p = 0.017) and the duration of diabetes mellitus (DM) (β = 0.665, p = 0.051), the SEM analysis indicated that the NPA was a significant predictor of HbA1c levels, with a path coefficient estimate (β) of 0.345 (p < 0.001). In contrast, the LoA did not significantly predict HbA1c levels (β = 0.005, p = 0.993). The model explained 38.7% of the variance in HbA1c, indicating a satisfactory fit to the experimental data.ConclusionsThe study found eye accommodation was significantly affected in recent type‐1 diabetes patients, indicating its sensitivity to diabetes. SEM using these ocular measures accounts for one‐third of HbA1c variance. Thus, accommodative function assessments could be a simple, noninvasive, and cost‐effective method for evaluating HbA1c levels. LoA is not a good predictor of HbA1c.

We review the current state of our knowledge of the neural control of vergence and ocular accommodation in primates including humans. We first describe the critical need for these behaviors for viewing in a three-dimensional world. We then consider the sensory stimuli that drive vergence eye movements and lens accommodation and describe models of the sensorimotor transformations required to drive these motor systems. We discuss the interaction of vergence with saccades to produce high-speed shifts in gaze between objects at different distances and eccentricities. We also cover the normal development of these eye movements as well as the sequelae associated with their maldevelopment. In particular, we examine the neural substrates that produce vergence and lens accommodation, including motoneurons, immediate premotor circuitry, cerebellar and precerebellar regions, and cerebral cortical areas.

Ocular accommodation, the autofocus mechanism of the human eye, is fundamental for the achievement and maintenance of clear vision across viewing distances. Together with its close ally, vergence eye movements, this mechanism also ensures that binocular single vision is achieved at all these distances. Several dimensions of this mechanism have been investigated for well over a century. The present article summarizes this large volume of work under three themes: (a) biomechanics and neural control of the accommodative apparatus, (b) its behavioral properties, and (c) control-engineering modeling endeavors that offer a theoretical framework for gaining insights into the functioning of this mechanism. Built into these themes is a discussion on the development of accommodation, its loss with aging (presbyopia), sensory cues that aid the generation of these responses, and the technologies available for the measurement of these responses. The article also raises several unresolved questions for future research.

Encircling scleral buckling is a surgical intervention employed for the purpose of visual restoration in individuals diagnosed with rhegmatogenous retinal detachment (RRD). While this particular approach is not commonly used for the purpose of enhancing accommodation, it has garnered attention in various studies. This research aimed to objectively measure accommodation changes using the iTrace device in patients with RRD who have undergone encircling scleral buckling surgery. This pilot prospective cohort study included 40 eyes from 20 patients with RRD who underwent encircling scleralbuckling surgery in one eye. The surgical group included 20 RRD eyes and the non-exposure group included 20 healthy eyes. The objective aberrometry was performed by directing a light beam at a 6-m and 20-cm distant using the iTrace. We assessed post-surgical accommodation changes within two groups using the Wilcoxon signed-rank test, quantified clinically relevant changes with the mean difference (MD), and evaluated change magnitude with thestandardized mean difference (Hedges' g). The average age of the patients was 33.9 ± 8 years, with 12 males and 8 females. Baseline accommodation for the non-operated eye measured 2.76 diopters at 20cm and 1.37 diopters at 50cm. At 20cm, the non-operated and operated eyes showed mean accommodation changes of 0.2 diopters (p = 0.123) and 0.01 diopters (p = 0.949), respectively. At 50cm, the non-operated eye changed by 0.12 diopters (p = 0.292) while the operated eye decreased by - 0.01 diopters (p = 0.930). Overall, minor postoperative accommodation changes were observed, with no significant differences detected. Encircling scleral buckling in RRD patients shows no significant changes observed postoperatively in either operated or non-operated eyes and the 98.75% CI suggests any potential benefit is likely too small to be clinically meaningful.

PurposeTo investigate the relationship between crystalline lens thickness (LT) and subtypes of intermittent exotropia (IXT) in children, focusing on ocular biometry and accommodation characteristics.MethodsThis cross-sectional study included 501 children aged from 8 to 12 years: 122 with orthophoria (Group A) and 379 with IXT, which were further categorized into basic type (Group B, n = 254), convergence insufficiency (CI) type (Group C, n = 92), and divergence excess (DE) type (Group D, n = 33). Evaluation of strabismus was measured after diagnostic occlusion. Cycloplegic refraction and assessments of accommodation and convergence functions were performed. All children were examined with Lenstar LS-900 with fixation at non-accommodative target monocularly and ocular biometric parameters including axial length (AL), mean keratometry (Km), central corneal thickness (CCT), LT and aqueous depth (AD) were recorded. Regression analyses were performed to evaluate associations among groups.ResultsThe basic type was the most prevalent IXT subtype (67.0%), followed by CI (24.3%) and DE (8.7%). The CI group exhibited greater binocular LT (P = .002) and lower accommodative convergence-to-accommodation (AC/A) ratio compared to the basic type (P = 0.016). Compared to orthophoric controls, the basic IXT group showed greater accommodative amplitude (AMP) (P = 0.004), reduced accommodation lag (P = 0.006), and more distant near point of convergence (NPC) (P < 0.001). Both univariate and multivariate logistic regression analyses indicated that the CI IXT was associated with greater LT (P = 0.006) and lower AC/A ratio (P = 0.007) compared to basic IXT. Basic IXT was correlated with greater AMP (P < 0.001), reduced lag of accommodation (P = 0.002) and more distant NPC (P = 0.003) compared to controls.ConclusionsIncreased LT and lower AC/A ratio were significantly associated with the CI subtype of IXT in children. The basic type is characterized by greater AMP, reduced accommodation lag, and more distant NPC compared to orthophoric controls. These findings could serve as valuable clinical markers for managing IXT, and contribute to a deeper understanding of the pathophysiology of types of IXT.

To evaluate the impact of gaming on ocular accommodative parameters. A comparative and experimental study was conducted among non-orthoptic university students for a duration of six months from September 2023 to March 2024. After a half-hour of gaming, the subjects' accommodative parameters were examined and compared. The accommodative parameters before and after iPad gaming were compared. The study included 80 participants (mean age 22.96 ± 2.23 years; 50 males, 30 females). Post gaming near-point of accommodation decreased (right eye: 10.75D to 7.15D, p < 0.001), Negative Relative Accommodation (NRA) increased from 2.64 ± 0.23 DS to 2.92 ± 0.37 DS, whereas Positive Relative Accommodation (PRA) decreased from -2.46 ± 0.41 DS to -1.78 ± 0.31 DS. The Monocular Estimation Method (MEM) values showed accommodative lag (right eye: +0.46 ± 0.15 DS to +1.24 ± 0.26 DS, p < 0.001). Monocular Accommodative Facility (MAF) and Binocular Accommodative Facility (BAF) exhibited decrease in facility (MAF; right eye: 10.34 to 4.54 cpm, BAF: 10.65 to 4.90 cpm, p < 0.001). This study shows 30 minutes of gaming using digital devices leads to decrease in accommodative parameters, potentially causing ocular fatigue and binocular vision anomalies in young individuals.

The purpose of this study was to investigate the in vivo biomechanical properties of crystalline lens nucleus and cortex in adults with myopia, their potential influences, and the correlation between these properties and ocular accommodation. The study included 195 right eyes of 195 participants, divided into 4 groups based on spherical equivalent: emmetropia (37 eyes), low myopia (41 eyes), moderate myopia (59 eyes), and high myopia (58 eyes). Participants underwent comprehensive ophthalmological examinations, including intraocular pressure, axial length, cycloplegic refraction, lens morphology, accommodation measurements, and Brillouin optical scanning of the lens. Additionally, demographic information, such as age and sex, was recorded. Normality tests were performed on the data using the Kolmogorov-Smirnov test. Between-group differences were examined using the Kruskal-Wallis test. Correlation and multiple regression analyses were conducted to analyze the factors associated with lens biomechanical properties and accommodation. The mean longitudinal modulus of the crystalline lens nucleus (LMN), anterior cortex (LMAC), and posterior cortex (LMPC) was 3.395 ± 0.027 GPa, 3.030 ± 0.066 GPa, and 2.990 ± 0.066 GPa, respectively, in adult myopia and 3.342 ± 0.024 GPa, 3.015 ± 0.0488 GPa, and 2.978 ± 0.049 GPa, respectively, in emmetropia. LMN was significantly higher in myopia (difference = 0.047, 95% confidence interval [CI] = 0.037 to 0.057, P < 0.001) and increased significantly with higher degrees of myopia (standardized β = -0.712, P < 0.001). No statistical differences in the LMAC or LMPC were observed between myopia and emmetropia. Lens densitometry on the centerline was the only lens parameter independently correlated with LMN (standardized β = -0.282, P < 0.01). Increased LMN in myopia was independently correlated with increased amplitude of accommodation (AMP) and decreased accommodative facility (AF; standardized β = 0.198, -0.237, all P < 0.05). LMN was significantly higher in adult patients with myopia than in emmetropia and increased with increasing myopia. Increased LMN in myopia significantly correlated with decreased AF and increased AMP. High LMN may be an important biological alteration during the development of adult myopia, especially high myopia, providing new insights into myopia pathogenesis.

IntroductionMultisegment (MS) spectacles are intended to slow myopia progression by modifying images falling on the peripheral retina. Some published optical treatments of these lenses assume normal incidence of light at the surfaces, but images falling on the peripheral retina are usually associated with oblique ray pencils. Here, we model representative images of point objects produced by the Hoya MiyoSmart MS spectacle lens when oblique ray pencils are used.MethodsVarious imaging aspects of the MS lens alone and in combination with a suitable accommodating eye model for a 4D myope were evaluated using the Optical Design program Ansys Zemax OpticStudio. Configurations studied included object points at vergences of zero and –4 D, with the objects being either on the lens axis or at a field angle of about 30°. The effect on foveal vision of rotating the axis of the eye with respect to that of the lens was also considered. Images of point objects were described in terms of spot diagrams and fast Fourier transform point‐spread functions.ResultsSymmetry and overall optical quality of images decreased with the obliquity of the ray pencils, due to the increased off‐axis aberrations of the lens and the eye. Images of near object points were strongly affected by the level of accommodation: optimal retinal image quality occurred when accommodation brought the carrier lens focus close to the retina, rather than that of the lenslets.ConclusionsAttempts to understand why MS lenses slow myopia progression need to consider the way in which through‐focus retinal image quality changes with obliquity of the ray pencils across the visual field and the possible effects of ocular accommodation.

ABSTRACT Clinical relevance Accommodation is crucial for clear near vision and is predominantly affected by presbyopia. The ability to modulate accommodative function with eye drops could offer a pharmacological approach to manage presbyopia. Background To investigate the effects of different concentrations of pilocarpine eye drops on ocular accommodation in young volunteers. Methods In this prospective study, healthy volunteers with mild or moderate myopia with corrected visual acuity of no less than 20/20 were recruited. Participants underwent four visits for baselining and administration of low (0.75%), medium (1.00%), and high (1.25%) concentrations of pilocarpine eye drops respectively. One eye of each participant was chosen and analysed. Ophthalmologic examinations included objective and subjective refraction, corrected distance visual acuity, intraocular pressure, and pupil size. Accommodation was assessed using the WAM-5500 binocular autorefractor. Accommodation facility and the defocus curve were measured. Results Volunteers (n = 24, mean age 23.7 ± 1.5 years) with a mean spherical equivalent of −2.91 ± 1.54 dioptres (D) were recruited. No serious adverse events occurred. All pilocarpine concentrations showed similar pupil constriction without significant intraocular pressure changes (p > 0.05). Pilocarpine induced greater objective refraction changes with higher concentrations (−1.12 ± 1.07D, −1.56 ± 1.38D, −1.68 ± 1.60D for low, medium, and high concentrations, respectively; p < 0.01). Subjective refraction showed a similar dose-response. Accommodative response decreased significantly at the 20 cm stimulus for medium and high concentrations (p < 0.05). Corrected distance visual acuity improved beyond −1.00D to + 0.50D defocus after all three pilocarpines. Accommodative facility improved more by 1.25% than 0.75% (p = 0.04). Conclusions Pilocarpine eye drops are effective in improving ocular accommodation, with higher concentrations leading to greater accommodative changes. Pilocarpine has potential for managing presbyopia.

Evidence from human studies of ocular accommodation and studies of animals reared in monochromatic conditions suggest that chromatic signals can guide ocular growth. We hypothesized that ocular biometric response in humans can be manipulated by simulating the chromatic contrast differences associated with imposition of optical defocus. The red, green, and blue (RGB) channels of an RGB movie of the natural world were individually incorporated with computational defocus to create two different movie stimuli. The magnitude of defocus incorporated in the red and blue layers was chosen such that, in one case, it simulated +3 D defocus, referred to as color-signed myopic (CSM) defocus, and in another case it simulated -3 D defocus, referred to as color-signed hyperopic (CSH) defocus. Seventeen subjects viewed the reference stimulus (unaltered movie) and at least one of the two color-signed defocus stimuli for ∼1 hour. Axial length (AL) and choroidal thickness (ChT) were measured immediately before and after each session. AL and subfoveal ChT showed no significant change under any of the three conditions. A significant increase in vitreous chamber depth (VCD) was observed following viewing of the CSH stimulus compared with the reference stimulus (0.034 ± 0.03 mm and 0 ± 0.02 mm, respectively; p = 0.018). A significant thinning of the crystalline lens was observed following viewing of the CSH stimulus relative to the CSM stimulus (-0.033 ± 0.03 mm and 0.001 ± 0.03 mm, respectively; p = 0.015). Differences in the effects of CSM and CSH conditions on VCD and lens thickness suggest a directional, modulatory influence of chromatic defocus. On the other hand, ChT responses showed large variability, rendering it an unreliable biomarker for chromatic defocus-driven responses, at least for the conditions of this study.

BackgroundAs a key element of ocular accommodation, the inherent mechanical stiffness gradient and the gradient refractive index (GRIN) of the crystalline lens determine its deformability and optical functionality. Quantifying the GRIN profile and deformation characteristics in the lens has the potential to improve the diagnosis and follow-up of lenticular disorders and guide refractive interventions in the future.MethodsHere, we present a type of optical coherence elastography able to examine the mechanical characteristics of the human crystalline lens and the GRIN distribution in vivo. The concept is demonstrated in a case series of 12 persons through lens displacement and strain measurements in an age-mixed group of human subjects in response to an external (ambient pressure modulation) and an intrinsic (micro-fluctuations of accommodation) mechanical deformation stimulus.ResultsHere we show an excellent agreement between the high-resolution strain map retrieved during steady-state micro-fluctuations and earlier reports on lens stiffness in the cortex and nucleus suggesting a 2.0 to 2.3 times stiffer cortex than the nucleus in young lenses and a 1.0 to 7.0 times stiffer nucleus than the cortex in the old lenses.ConclusionsOptical coherence tomography is suitable to quantify the internal stiffness and refractive index distribution of the crystalline lens in vivo and thus might contribute to reveal its inner working mechanism. Our methodology provides new routes for ophthalmic pre-surgical examinations and basic research.

BackgroundMyopia is a significant public health problem across the globe. This study aimed to examine the regional disparity in prevalence and correlated factors of myopia in children and adolescents in two typical regions, Gannan Tibetan Autonomous Prefecture (Gannan Prefecture for short, a Tibetan residential area) and Wuwei City (a Han residential area) in Gansu Province, China, and to provide a reference for the prevention and control of regional myopia.MethodsThe study was a cross-sectional study of children and adolescents in Gansu Province, China. A total of 6,187 (Wuwei City: 3,266, Gannan Tibetan Autonomous Prefecture: 2,921) students were selected by stratified cluster sampling. Eye examinations and questionnaires were administered to the participants. Myopia is defined as a condition in which the spherical equivalent refractive error of an eye is less than or equal to −0.50 D when ocular accommodation is relaxed. The χ2 test and multivariate logistic regression analysis were used to analyze the correlated factors of myopia.ResultsThe myopia rate of 6,187 students was 71.4%, and students had a higher rate of myopia (77.5%) in Wuwei City compared to Gannan Prefecture (64.6%) (p < 0.001). The results of multivariate analysis in Wuwei City showed that girls (odds ratio (OR) = 1.325), junior students (OR = 2.542), senior students(OR = 4.605), distance between eyes and book less than one foot (OR = 1.291), and parents with myopia (one, OR = 2.437; two, OR = 4.453) had higher risks of myopia (all, p < 0.05). For Gannan Prefecture, girls (OR = 1.477), senior students (OR = 1.537), daily time spent doing homework ≥2 h (OR = 1.420), the distance between eyes and book less than one foot (OR = 1.205), mean time continuous eye use (0.25–<0.5 h, OR = 1.345, 0.5–<1 h, OR = 1.317, ≥1 h, OR = 1.313), average daily sleep duration <8 h (OR = 1.399), and parents with myopia (one, OR = 1.852; two, OR = 2.913) had higher risks of myopia (all, p < 0.05).ConclusionThe prevalence of myopia is at a relatively high level in Gansu Province. The prevalence and risk factors for myopia vary by region.

BCLA CLEAR presbyopia: Mechanism and optics