Home vision therapy and prism prescription in presbyopic persons with convergence insufficiency: study protocol for a randomized controlled trial.

BACKGROUND: Convergence insufficiency is a common issue in the field of binocular vision. Various treatment options have been suggested for managing this condition, but their efficacy in individuals with presbyopia remains unclear. The objective of this study is to compare the effectiveness of home-based vision therapy and prism prescription, in presbyopic patients with convergence insufficiency. METHODS/DESIGN: It is a randomized, prospective, double-blind clinical trial, with total of 150 participants randomly assigned to the three groups. The Control Group will receive a new near glasses as a conventional prescription, along with aimless and random eye movement exercises that do not have any convergence or accommodation effects. The Home Vision Therapy Group will receive new near glasses with accommodative and convergence eye exercises. The Prism Group will receive a near prismatic glasses prescribed using the Sheard's criterion. All treatments will be administered for a period of 2 months, and measurements of the modified convergence insufficiency symptoms survey (CISS), near point convergence, near phoria, and positive fusional vergence will be taken at baseline, one month later, and at the end of the treatment. DISCUSSION: We aim to identify which component - either the prism prescription or the home vision therapy - is more effective in improving binocular abilities and reducing patients' symptom scores. TRIAL REGISTRATION: ClinicalTrials.gov NCT05311917 with last update on 04/22/2023.

Intrathecal Vector Delivery in Juvenile Rats via Lumbar Cistern Injection.

Gene therapy is a powerful technology to deliver new genes to a patient for the treatment of disease, be it to introduce a functional gene, inactivate a toxic gene, or provide a gene whose product can modulate the biology of the disease. The delivery method for the therapeutic vector can take many forms, ranging from intravenous infusion for systemic delivery to direct injection into the target tissue. For neurodegenerative disorders, it is often desirable to skew transduction towards the brain and/or spinal cord. The least invasive approach to target the entire central nervous system involves injection into the cerebrospinal fluid (CSF), allowing the therapeutic to reach a large fraction of the central nervous system. The safest approach to deliver a vector into the CSF is the lumbar intrathecal injection, where a needle is introduced into the lumbar cistern of the spinal cord. This technique, also known as a lumbar puncture, has been widely used in neonatal and adult rodents and in large animal models. While the technique is similar across species and developmental stages, subtle differences in size, structure, and elasticity of tissues surrounding the intrathecal space require accommodations in the approach. This article describes a method for performing lumbar puncture in juvenile rats to deliver an adeno-associated serotype 9 vector. Here, 25-35 µL of vector were injected into the lumbar cistern, and a green fluorescent protein (GFP) reporter was used to evaluate the transduction profile resulting from each injection. The benefits and challenges of this approach are discussed.

Sex as a risk factor regarding presbyopia in the rhesus monkey.

PURPOSE: To determine the effect of sex as a risk factor regarding presbyopia. METHODS: Maximum accommodation was pharmacologically induced (40% cabachol corneal iontophoresis) in 97 rhesus monkeys (49 males and 48 females) ranging in age from 8 to 36 years old. Accommodation was measured by Hartinger coincidence refractometry. RESULTS: Accommodative amplitude measured refractometrically decreased with age, and the rate of change was not different between males and females (p = 0.827). CONCLUSIONS: Presbyopia is essentially sex neutral, and no one is spared. There may be modest variations between different populations for various reasons, but essentially it is monotonously predictable. At present there is no biological therapeutic.

Vergence-Accommodation Conflict: Increased Presbyopia in Virtual Reality.

BACKGROUND: Performance and symptoms in completing a visual search task on a PC monitor and using a head-mounted display (HMD) were compared for different viewing conditions and between users of different ages. PATIENTS AND METHODS: Twenty-three young (M = 30 y, SD = 7 y) and 23 older (M = 52 y, SD = 5 y) participants performed a visual search task presented on a PC monitor. The task was repeated using an HMD for a near and a far virtual viewing distance. Reaction times (RT), detection sensitivity (d'), and symptoms were recorded for the three different viewing conditions. RESULTS: RT and d' were not affected by the viewing condition (p > 0.05). In contrast, symptoms significantly depended on the viewing condition but were, in part, not significantly affected by age. It is interesting to note that although not significant, young participants reported more ocular symptoms than older participants in the near vision task carried out using the HMD. DISCUSSION: HMD increases visual symptoms. However, HMD could be, in part, a remedy to problems when using visual aids for near work, in particular for presbyopes.

Understanding accommodative control in the clinic: Modeling latency and amplitude for uncorrected refractive error, presbyopia and cycloplegia.

Accommodation is the process of adjusting the eye's optical power so as to focus at different distances. Uncorrected refractive error and/or functional presbyopia mean that sharp focus may not be achievable for some distances, so observers experience sustained defocus. Here, we identify a problem with current models of accommodative control: They predict excessive internal responses to stimuli outside accommodative range, leading to unrealistic adaptation effects. Specifically, after prolonged exposure to stimuli outside range, current models predict long latencies in the accommodative response to stimuli within range, as well as unrealistic dynamics and amplitudes of accommodative vergence innervation driven by the accommodative neural controller. These behaviors are not observed empirically. To solve this issue, we propose that the input to blur-driven accommodation is not retinal defocus, but correctable defocus. Predictive models of accommodative control already estimate demand from sensed defocus, using a realistic "virtual plant" to estimate accommodation. Correctable defocus can be obtained by restricting this demand to values physically attainable by the eye. If we further postulate that correctable defocus is computed using an idealized virtual plant that retains a young accommodative range, we can explain why accommodative-convergence responses are observed for stimuli that are too near-but not too far-to focus on. We model cycloplegia as a change in gain, and postulate a form of neural myopia to explain the additional relaxation of accommodation often seen with cycloplegia. This model produces plausible predictions for the accommodative response and accommodative convergence signal in a wide range of clinically relevant situations.

Perceptual Thresholds for Radial Optic Flow Distortion in Near-Eye Stereoscopic Displays.

We provide the first perceptual quantification of user's sensitivity to radial optic flow artifacts and demonstrate a promising approach for masking this optic flow artifact via blink suppression. Near-eye HMOs allow users to feel immersed in virtual environments by providing visual cues, like motion parallax and stereoscopy, that mimic how we view the physical world. However, these systems exhibit a variety of perceptual artifacts that can limit their usability and the user's sense of presence in VR. One well-known artifact is the vergence-accommodation conflict (VAC). Varifocal displays can mitigate VAC, but bring with them other artifacts such as a change in virtual image size (radial optic flow) when the focal plane changes. We conducted a set of psychophysical studies to measure users' ability to perceive this radial flow artifact before, during, and after self-initiated blinks. Our results showed that visual sensitivity was reduced by a factor of 10 at the start and for ~70 ms after a blink was detected. Pre- and post-blink sensitivity was, on average, ~O.15% image size change during normal viewing and increased to ~1.5- 2.0% during blinks. Our results imply that a rapid (under 70 ms) radial optic flow distortion can go unnoticed during a blink. Furthermore, our results provide empirical data that can be used to inform engineering requirements for both hardware design and software-based graphical correction algorithms for future varifocal near-eye displays. Our project website is available at https://gamma.umd.edu/ROF/.

Model of zonular forces on the lens capsule during accommodation.

How the human eye focuses for near; i.e. accommodates, is still being evaluated after more than 165 years. The mechanism of accommodation is essential for understanding the etiology and potential treatments for myopia, glaucoma and presbyopia. Presbyopia affects 100% of the population in the fifth decade of life. The lens is encased in a semi-elastic capsule with attached ligaments called zonules that mediate ciliary muscle forces to alter lens shape. The zonules are attached at the lens capsule equator. The fundamental issue is whether during accommodation all the zonules relax causing the central and peripheral lens surfaces to steepen, or the equatorial zonules are under increased tension while the anterior and posterior zonules relax causing the lens surface to peripherally flatten and centrally steepen while maintaining lens stability. Here we show with a balloon capsule zonular force model that increased equatorial zonular tension with relaxation of the anterior and posterior zonules replicates the topographical changes observed during in vivo rhesus and human accommodation of the lens capsule without lens stroma. The zonular forces required to simulate lens capsule configuration during in vivo accommodation are inconsistent with the general belief that all the zonules relax during accommodation.

Anterior Segment Biometry During Accommodation After Posterior Chamber Phakic Implantable Collamer Lens Implantation.

PURPOSE: To evaluate the dynamic changes in anterior segment parameters during accommodation following Implantable Collamer Lens (ICL) implantation with swept-source optical coherence tomography (SS-OCT). METHODS: Under the accommodation of 0.00 diopters (D), 3.00 D, and maximum amplitude, SS-OCT was used to examine the anterior segment parameters, including ICL vault, ICL depth (the distance between the corneal endothelium and the posterior surface of ICL), crystalline lens thickness, anterior chamber depth, and various parameters of the anterior chamber angle, comprising angle opening distance, angle recess area, trabecular iris space area, and trabecular iris angle. RESULTS: During accommodation, the ICL vault showed a significant decrease from baseline (536 ± 278 µm) to 3.00 D (522 ± 281 µm), followed by an increase from 3.00 D to maximum amplitude (548 ± 306 µm) (analysis of variance [ANOVA], P < .001). Four eyes (2.61%) exhibited a decrease in ICL vault to less than 100 µm (47 ± 32 µm) at maximum accommodation. The ICL depth decreased significantly as accommodation increased (ANOVA, P < .001). Crystalline lens thickness increased, whereas anterior chamber depth decreased during accommodation (ANOVA, P < .001). The anterior chamber angle widened during 3.00 D of accommodation but narrowed at maximum accommodation, leading to significant changes in the angle opening distance, angle recess area, trabecular iris space area, and trabecular iris angle during accommodation (ANOVA, P < .001 for all). CONCLUSIONS: The anterior segment, including ICL vault and anterior chamber angle, undergo significant dynamic changes during accommodation. These accommodative changes may require careful monitoring for the surgery design of ICL implantation. [J Refract Surg. 2024;40(3):e164-e172.].

A method for generating zonular tension in the murine eye by embedding and compressing the globe in a hydrogel.

The ocular lens is the primary organ within the eye responsible for accommodation. During accommodation, the lens is subject to biomechanical forces. We previously demonstrated that stretching the porcine lens can increase lens epithelial cell proliferation. Although murine lenses are commonly employed in lens research, murine lens stretching has remained unexplored. Murine lens stretching thus represents a novel source of potential discovery in lens research. In the present study, we describe a method for stretching the murine lens by compressing the murine globe embedded in a hydrogel. We hypothesized that, as the eye is compressed along the optic axis, the lens would stretch through zonular tension due to the equatorial region of the eye bulging outward. Our results showed that this led to a compression-dependent increase in murine lens epithelial cell proliferation, suggesting that compression of the embedded murine globe is a viable technique for studying the mechanobiology of the lens epithelium.

Ciliary muscle and anterior segment characteristics in pre-presbyopic adults with Down syndrome.

PURPOSE: Previous research has shown that accommodation deficits are common in individuals with Down syndrome (DS), but the origin and mechanisms behind these deficits are still unknown. The aim of this study was to investigate the characteristics of different ocular structures involved in accommodation, in particular the ciliary muscle (CM), in a population of individuals with DS to further understand this deficit and its mechanisms. METHODS: Thirty-two volunteer participants of pre-presbyopic age with (n = 16) and without DS (n = 16) were recruited. Temporal and nasal images of the CM were acquired using anterior segment optical coherence tomography (AS-OCT) while participants fixated an eccentrically located target. Analysis of CM parameters was undertaken using validated semi-automated software. Axial length, anterior chamber depth, lens thickness and corneal curvature were obtained with the Topcon Aladdin Optical Biometer and Corneal Topographer. Non-cycloplegic refractive error and accommodative ability were obtained with an open-field autorefractor and dynamic retinoscopy, respectively. Independent t-tests were conducted to determine differences in CM and other anterior segment parameters between participants with and without DS. RESULTS: No significant differences were found in the CM parameters studied between participants with and without DS (p > 0.05). In contrast, significant differences were found in visual acuity (p < 0.001), accommodative response (p < 0.001) and corneal curvature (K1 p = 0.003 and K2 p < 0.001) between participants with and without DS. CONCLUSIONS: Despite having poorer accommodation, pre-presbyopic adults with DS do not have a different CM morphology to that found in typically developing adults. These findings suggest that the accommodative deficit found in this population is not due to a mechanical deficit of the CM.

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.

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.

Intracapsular accommodation mechanism in terms of lens curvature gradient.

The intracapsular accommodation mechanism (IAM) may be understood as an increase in the lens equivalent refractive index as the eye accommodates. Our goal was to evaluate the existence of an IAM by analysing observed changes in the inner curvature gradient of the lens. To this end, we fitted a gradient index and curvature lens model to published experimental data on external and nucleus geometry changes during accommodation. For each case analysed, we computed the refractive power and equivalent index for each accommodative state using a ray transfer matrix. All data sets showed an increase in the effective refractive index, indicating a positive IAM, which was stronger for older lenses. These results suggest a strong dependence of the lens equivalent refractive index on the inner curvature gradient.

The effect of multifocal contact lenses on the dynamic accommodation step response.

PURPOSE: To measure the dynamic accommodation response (AR) to step stimuli with and without multifocal contact lenses (MFCLs), in emmetropes and myopes. METHODS: Twenty-two adult subjects viewed alternating distance (0.25D) and near (3D) Maltese crosses placed in free space, through two contact lens types: single vision (SVCL) or centre-distance multifocal (MFCL; +2.50D add). The AR level was measured along with near to far (N-F) and far to near (F-N) step response characteristics: percentage of correct responses, magnitude, latency, peak velocity and duration of step response. RESULTS: There was no difference between N-F and F-N responses, or between refractive groups in any aspect of the accommodation step response dynamics. The percentage of correct responses was unaffected by contact lens type. Through MFCLs, subjects demonstrated smaller magnitude, longer latency, shorter duration and slower peak velocity steps than through SVCLs. When viewing the near target, the AR through MFCLs was significantly lower than through SVCLs. When viewing the distance target with the MFCL, the focal points from rays travelling through the distance and near zones were approximately 0.004D behind and 2.50D in front of the retina, respectively. When viewing the near target, the respective values were approximately 1.89D behind and 0.61D in front of the retina. CONCLUSION: The defocus error required for accommodation control appears not to be solely derived from the distance zone of the MFCL. This results in reduced performance in response to abruptly changing vergence stimuli; however, these errors were small and unlikely to impact everyday visual tasks. There was a decrease in ocular accommodation during near tasks, which has previously been correlated with a reduced myopic treatment response through these lenses. With MFCLs, the estimated dioptric myopic defocus was the largest when viewing a distant stimulus, supporting the hypothesis that the outdoors provides a beneficial visual environment to reduce myopia progression.

Ocular accommodation and wavelength: The effect of longitudinal chromatic aberration on the stimulus-response curve.

The longitudinal chromatic aberration (LCA) of the eye creates a chromatic blur on the retina that is an important cue for accommodation. Although this mechanism can work optimally in broadband illuminants such as daylight, it is not clear how the system responds to the narrowband illuminants used by many modern displays. Here, we measured pupil and accommodative responses as well as visual acuity under narrowband light-emitting diode (LED) illuminants of different peak wavelengths. Observers were able to accommodate under narrowband light and compensate for the LCA of the eye, with no difference in the variability of the steady-state accommodation response between narrowband and broadband illuminants. Intriguingly, our subjects compensated more fully for LCA at nearer distances. That is, the difference in accommodation to different wavelengths became larger when the object was placed nearer the observer, causing the slope of the accommodation response curve to become shallower for shorter wavelengths and steeper for longer ones. Within the accommodative range of observers, accommodative errors were small and visual acuity normal. When comparing between illuminants, when accommodation was accurate, visual acuity was worst for blue narrowband light. This cannot be due to the sparser spacing for S-cones, as our stimuli had equal luminance and thus activated LM-cones roughly equally. It is likely because ocular LCA changes more rapidly at shorter wavelength and so the finite spectral bandwidth of LEDs corresponds to a greater dioptric range at shorter wavelengths. This effect disappears for larger accommodative errors, due to the increased depth of focus of the eye.

Impact of focus cue presentation on perceived realism of 3-D scene structure: Implications for scene perception and for display technology.

Stereoscopic imagery often aims to evoke three-dimensional (3-D) percepts that are accurate and realistic-looking. The "gap" between 3-D imagery and real scenes is small, but focus cues typically remain incorrect because images are displayed on a single focal plane. Research has concentrated on the resulting vergence-accommodation conflicts. Yet, incorrect focus cues may also affect the appearance of 3-D imagery. We investigated whether incorrect focus cues reduce perceived realism of 3-D structure ("depth realism"). Experiment 1 used a multiple-focal-planes display to compare depth realism with correct focus cues vs. conventional stereo presentation. The stimuli were random-dot stereograms, which isolated the role of focus cues. Depth realism was consistently lower with incorrect focus cues, providing proof-of-principle evidence that they contribute to perceptual realism. Experiments 2 and 3 examined whether focus cues play a similar role with realistic objects, presented with an almost complete set of visual cues using a high-resolution, high-dynamic-range multiple-focal-planes display. We also examined the efficacy of approximating correct focus cues via gaze-contingent depth-of-field rendering. Improvements in depth realism with correct focus cues were less clear in more realistic scenes, indicating that the role of focus cues in depth realism depends on scene content. Rendering-based approaches, if anything, reduced depth realism, which we attribute to their inability to present higher-order aspects of blur correctly. Our findings suggest future general 3-D display solutions may need to present focus cues correctly to maximise perceptual realism.

Bruch's membrane and Brücke's muscle in the pars plana region.

PURPOSE: To examine Bruch's membrane (BM) in association with the longitudinal part of the ciliary muscle (LPCM) in the pars plana region. METHODS: Using light microscopy, we histomorphometrically assessed BM and the LPCM in the pars plana region. RESULTS: The histomorphometric study included 51 eyes (51 patients; mean age: 60.8 ± 15.0 years; axial length: 26.0 ± 3.3 mm; range: 21.0-36.0 mm). The LPCM (total length: 4.60 ± 1.10 mm) ended 1.15 ± 0.56 mm anterior to the ora serrata. Within the pars plana region, the LPCM (length: 2.58 ± 0.98 mm) had direct contact with BM for 1.95 ± 0.99 mm (71.1 ± 18.4% of the BM undersurface), while a capillary layer was interposed between the BM and the LPCM for 0.70 ± 0.40 mm (29.0 ± 18.4%). In the pars plana region free of LPCM close to the ora serrata, the percentage of BM covered by the capillary layer was higher than in the pars plana region containing the LPCM (63.0 ± 42.1% vs. 29.0 ± 18.4%; p < 0.001). At the LPCM end, BM was in direct contact with a collagenous tissue from the LPCM and was focally thickened as compared to BM with an underlying capillary layer (9.5 ± 5.3 µm vs. 4.3 ± 1.2 µm; p < 0.001). CONCLUSIONS: The direct contact of BM with the LPCM in the pars plana in association with focal BM thickening at the LPCM end suggests an insertion of LPCM on the BM. Taking into account the biomechanical strength of BM, it may imply a functional unit of the LPCM with BM in the process of accommodation with a secondary movement of the posterior BM and tertiary thickening of the subfoveal choroidal space.

The status of binocular visual functions among Taiwan high-tech industry engineers and its correlation with computer vision symptom.

To analyze the status of binocular visual functions, the relationship between binocular visual function and computer vision-related symptoms in the high-tech industry group. The study sample was comprised of 33 participants aged between 20 and 40 years of age. After completing basic information and the Computer Vision Symptom Scale (CVSS-17) questionnaire, the participants underwent a comprehensive examination of binocular visual function. All data were statistically analyzed with SPSS V26.0 software. The value of the binocular vision function of the Taiwan high-tech industry group was significantly different compared with the Scheiman and Morgan standard value. Study subjects were generally found to exhibit larger exophoric at distance, which in turn might lead to a lower ability to maintain binocular fusion to a single image, or recover from fusional disruption at distance. Subjects also experienced accommodation and convergence problems at near at the same time. Age, gender, and refractive errors had no significant impact on CVSS-17 scores, only the duration of computer usage showed a significant effect, particularly for internal symptom factor (ISF) dimensions. In addition, the interaction between the ISF and external symptom factor resulted in more severe visual symptoms. Long-term use of electronic devices may lead to an imbalance in binocular vision function, thereby increasing or exacerbating visual symptoms. If the use of electronic devices is an unchangeable trend, interventions in prescription, visual training or the visual design of electronic products become worthwhile topics for development.

The double whammy: Advanced medical training and parenting.

Clinicians may become parents during their clinical training and may be exposed to several challenges in career development, burnout and work-life balance. Previous research findings have reported that stressors facing trainees with children warrant greater attention from graduate medical institutions. Additionally, parenting-related information and considerations about the needs of trainees with children across clinical specialties are needed to inform institutional and national policies. A quantitative approach was used to examine clinical trainees' perceptions and experiences of parenting in relation to different specialties, sociodemographic traits, levels of support, and other potential factors influencing their residency and fellowship training and well-being. We used a survey that was distributed to all University of Toronto medical trainees (2214) via email correspondence and social media platforms. The trainees were asked to base their answers on their experience during the academic year of 2019 to 2020 (before the Coronavirus Disease 2019-related shutdown). Our study revealed that clearly, burnout is a concern for physicians who are raising children while in training. Notably, it was higher among younger aged trainees and those beginning their training journey including, first-year fellows and second-year residents, in addition to parents with toddlers. Moreover, female residents and male fellows showed higher burnout than their counterparts. Institutional support was associated with lower rates of burnout, evidenced by access to opportunities, allowing time to breastfeed/express milk and having access to medical care. We found multiple independent and significant factors affecting their rate of burnout including limited access to opportunities, lack of a self-care routine and absence of social community outside of work. The results show the importance of creating a positive learning experience for trainees juggling parenting and training needs, especially those starting their training both as residents and as fellows and those with younger children. Interventions can be categorized into those targeted at the individual and family levels, and institutional levels, with the overarching goal of balancing training and parenting. This can be achieved by fostering learning environments that prevent and decrease burnout and enhance the well-being of trainees and their families, which can start with ensuring trainees are aware of available resources and possible accommodations.