Search Results (108)

Clinical Relevance and Background: Motion sickness is a common manifestation of autonomic dysfunction. Increasingly induced by modern technology, such as virtual reality (VR), it presents a pressing challenge that warrants investigation. However, the relationship between binocular function, visual perception, and motion sickness remains largely unexplored. Therefore, this study investigated the correlations between binocular visual functions, visual perception, and motion sickness susceptibility in adults. Methods: Adults aged 20 to 25 years were recruited. Based on a background and motion sickness susceptibility questionnaire, participants were divided into two groups: the Sick Tendency (ST) group (n = 21) and the Normal group (n = 33). Clinical assessments included habitual distance prescription and visual acuity (VA), phoria, fixation disparity (FD), positive/negative fusional vergence (PFV/NFV), vertical fusional vergence (VFV), positive/negative relative accommodation (PRA/NRA), accommodative facility (AF), vergence facility (VF), stereopsis, contrast sensitivity (CS), near point of convergence (NPC), and near point of accommodation (NPA). Additionally, motor-free visual perception test (MVPT), peripheral awareness (PA), and body balance (center of pressure) were assessed. Results: The ST group exhibited significantly higher distance NFV, distance VFV, and near PFV. Conversely, their NPA, stereopsis, and body balance (center of pressure) were significantly poorer than those of the Normal group. These deficits may be attributed to the accommodation–convergence conflict. Conclusions: Motion sickness susceptibility is closely associated with specific binocular functions. Individuals susceptible to motion sickness exhibit poorer postural stability, likely due to diminished stereopsis and accommodative amplitude (NPA). Future research should further investigate the underlying mechanisms and their clinical implications. Full article

Background/Objectives: Visual dysfunction is a common non-motor symptom in Parkinson’s Disease (PD), as evidenced by deficits in color vision (CV) and binocular vision (BV). Computerized CV tests, such as the Cambridge Color Test (CCT), are underutilized in this patient population despite the known limitations of common CV tests. Methods: In total, 19 PD and 12 control participants underwent a comprehensive eye exam, including ocular motility testing and the CCT, utilizing thresholds obtained along 12 contrast vectors to fit a discrimination ellipse. Findings were compared across groups, and the association with disease severity was analyzed. Results: PD participants showed increases in ellipse area (p = 0.012) and short-axis length (p = 0.009). PD participants demonstrated convergence insufficiency type exotropia (p < 0.001) and impaired stereopsis (p = 0.006). No significant correlation with UPDRS scores was seen for either BV or CV. Conclusions: PD participants exhibited binocular vision dysfunction with selective changes in color vision. CV changes are more variable in PD, likely due to mixed parvocellular and cortical dysfunction. Convergence insufficiency type exotropia is more common in PD, likely due to combined cortical and subcortical neurodegeneration. Both BV and CV changes occur independently of motor severity, emphasizing the need for routine visual testing regardless of symptom progression. Full article

The purpose of the study was to analyze, characterize, and compare the measurements of saccades that occurred during the positive and negative fusional vergence test (PFV and NFV, respectively) as a function of the disparity vergence demand. Thirty-four participants’ PFV and NFV amplitudes were measured in a haploscopic setup, recording eye movements with an Eyelink 1000 Plus (SR Research). The visual stimulus was a column of letters. Break and recovery points were determined objectively offline, and saccades were detected with a velocity-threshold-based method. A total of 13,103 and 14,381 saccades were detected during the measurement of the PFV and NFV ranges, respectively. Saccades followed the main sequence (ρ = 0.97, p < 0.001). The distributions of saccadic amplitudes during PFV and NFV differed significantly (U = 4.28, p < 0.001). The amplitude of saccades that occurred while fusion was maintained (median (IQR) 0.73 (0.92) deg) was significantly smaller than that of saccades during diplopia (2.10 (3.90) deg) (U = −75.63, p < 0.001). The distributions of saccade direction during the measurement of PFV and NFV amplitudes were statistically significantly different (p < 0.01). These findings contribute to a better understanding of how the visual system adjusts saccades in response to different disparity vergence demand during fusional vergence amplitudes evaluation. Full article

Background/Objectives: Premium intraocular lenses (IOLs) are increasingly being selected for cataract and refractive lens surgery, but their functional performance depends critically on pupil size and corneal spherical aberration (SA). This study evaluates how these factors modulate the optical behavior of the RayOne EMV and Tecnis Synergy using a profilometry-based Through Object modulation transfer function (TO MTF) analysis. Methods: The surface profiles of the RayOne EMV and Tecnis Synergy were measured with a confocal optical profilometer and implemented in pseudophakic eye models via ray tracing. TO MTF at 50 cycles/mm was computed for object vergences from −4.0 D to +2.0 D over entrance pupil diameters from 2.0 to 5.5 mm in three corneal configurations derived from the Liou–Brennan model and ISO recommendations: mean population SA, aberration-free, and a myopic LASIK-like oblate cornea. Simulated optotype images were generated to relate TO MTF values to the expected distant, intermediate, and near visual performances. Results: RayOne EMV delivered high-quality distant image performance in all models. Its depth of focus increased only modestly and showed a strong dependence on pupil size. Intermediate and near vision rarely reached clinically acceptable levels. The Tecnis Synergy produced a broad depth-of-field plateau in distant to near visual performance for mean population spherical aberration at a 3.5 mm pupil. However, image quality at 90 cm remained limited. Optical performance worsened with increasing pupil size and positive spherical aberration, particularly under post-myopic LASIK conditions. Conclusions: The RayOne EMV behaves predominantly as a distance-oriented design with minimal true presbyopic benefit; the Tecnis Synergy provides a wider range of vision but is highly sensitive to corneal spherical aberration and pupil size, so thorough preoperative evaluation of corneal asphericity and functional pupil diameter is essential for IOL selection and power targeting. Full article

Purpose: To evaluate short-term motor and sensory–motor outcomes following postoperative OT in children with IXT after strabismus surgery. Methods: This prospective before–after observational study included children with IXT who underwent bilateral lateral rectus recession and were referred for postoperative OT based on predefined clinical criteria. A structured 12-week OTplan was initiated approximately six months after surgery. Outcome measures included angle of deviation (prism diopters, PD), near point of convergence (cm), positive fusional vergence amplitudes (PD), and convergence amplitudes at distance and near (PD). Pre- and post-therapy changes were analysed using paired-samples t-tests with effect sizes calculated using Cohen’s d. Final postoperative alignment was additionally compared cross-sectionally between children who underwent OT and those managed without OT. Results: Eighty-eight children had complete paired motor and sensory–motor data and were included in the analyses. Changes in static ocular alignment were small, with mean residual deviation improving from −7.02 ± 6.91 PD to −5.22 ± 6.60 PD after OT (mean change +1.80 PD; p < 0.01; d ≈ 0.30). No significant difference in final postoperative alignment was observed between the OT and non-OT groups (p = 0.827). In contrast, marked improvements were observed in sensory–motor outcomes. Positive fusional vergence amplitude increased from 7.30 ± 8.33 PD to 22.19 ± 9.26 PD (p < 0.001; d ≈ 1.5). Distance convergence amplitude improved from 7.30 ± 8.33 PD to 22.19 ± 9.26 PD, and near convergence amplitude from 10.95 ± 12.50 PD to 33.29 ± 13.89 PD (both p < 0.001; d ≈ 1.5). Near point of convergence showed a modest but significant improvement. Conclusions: Postoperative OT was associated with substantial short-term improvements in sensory–motor function, particularly fusional and convergence capacities, while changes in static ocular alignment were small and of limited clinical relevance. These findings support the role of OT as a functional adjunct to surgery, aimed at enhancing binocular control and postoperative sensory–motor stability in children with IXT. Full article

Objectives: To evaluate the feasibility and efficacy of a brief, scaffolded virtual reality (VR)-based perceptual-learning protocol to improve stereovision in adults without measurable baseline global stereopsis. Methods: Prospective interventional pilot study with a normal-vision reference group. Fourteen adults were enrolled; nine with nil global stereoacuity formed the intervention group and five with normal binocular vision served as controls. Intervention participants completed 8–10 VR sessions (~30 min each over two weeks) using a disparity-driven depth-matching task with individualized thresholds, virtual prism compensation, and interocular contrast balancing. Primary outcomes were changes in clinical stereoacuity (local and global) and Binocular Function (BF). Secondary outcomes included positive fusional vergence (PFV), binocular imbalance (inter-ocular contrast ratio), and in-game depth discrimination error (arcseconds). Results: Global stereoacuity improved with four of nine participants who initially showed no measurable global stereopsis achieving measurable thresholds after training (post: 861.11 ± 537.08 arcsec, IQR = 800.00; p = 0.06). Local stereoacuity improved near (pre: 616.67 ± 532.68 arcsec, IQR = 1100.00; post: 361.67 ± 537.11, IQR = 200.00; p = 0.03) and at a distance (pre: 715.11 ± 573.54 arcsec, IQR = 1114.00; post: 437.11 ± 510.41, IQR = 405.00; p = 0.03). BF score improved from 4.33 ± 0.50 (IQR = 1.00) to 3.51 ± 1.14 (IQR = 1.30) (p = 0.03). PFV break at distance increased (pre: 17.83 ± 17.53Δ, IQR = 23.50; post: 24.50 ± 17.12Δ, IQR = 28.50; p = 0.04), and the binocular imbalance showed a nonsignificant trend towards improvement (p = 0.09). In-game depth error decreased from 752.11 ± 384.50 arcsec (IQR = 553.00) to 221.78 ± 79.12 (IQR = 105.00) (p < 0.01). Control participants achieved a mean depth error of 43.00 ± 10.30 arcsec after three sessions. Conclusions: A short-dose, individualized VR protocol yielded gains in stereoacuity and binocular function in adults with severe stereodeficiency, with transfer from in-game learning to standard clinical measures. While the sample size was limited, the approach proved feasible and was well tolerated, showing encouraging efficiency versus prior high-dose regimens. Full article

Background/Objectives: Accurate intraocular lens (IOL) power calculation is vital for achieving the desired postoperative spherical equivalent (SE) in cataract surgery. Generative Artificial-Intelligence (AI) systems are increasingly being used in ophthalmology to refine diagnostic and surgical planning. However, it is still unknown whether a low-cost, easily accessible generative AI model like DeepSeek can match the accuracy of conventional biometric formulas. To evaluate the accuracy of DeepSeek, an open-source generative artificial intelligence (AI), in predicting postoperative refractive spherical equivalent compared to the Barrett Universal II formula in uncomplicated cataract surgeries. Methods: This study analyzed biometric data from 50 eyes of 50 patients who underwent cataract surgery between July 2024 and January 2025 at Humanitas Research Hospital in Milan, Italy. Only uncomplicated cases of emmetropia with Alcon AcrySof^® SA60WF IOL implantation were included. 30–40 days postoperative subjective refraction was measured with a calibrated trial-frame and 6 m logMAR chart by an experienced optometrist. Prediction error (PE), median absolute error (MedAE), standard deviation (SD), and cumulative frequency of PE diopters range were calculated. A Wilcoxon signed-rank test was performed to assess statistical significance. Results: Barrett showed MedAE 0.36 D [0.16–0.64] and MAE 0.43 D (95% CI, 0.34–0.52) while DeepSeek-R1 showed MedAE 0.76 D [0.52–1.01] and MAE 0.77 D (95% CI, 0.67–0.87). Cumulative accuracy (AE threshold) at ±0.25/±0.50/±0.75/±1.00/±1.25/±1.50/±1.75 D was 37.7/71.7/81.1/92.5/100.0/100.0/100.0% for Barrett Universal II and 11.1/25.9/50.0/74.1/88.9/96.3/100.0% for DeepSeek-R1 (McNemar p < 0.01 at each threshold). The paired comparison of per-eye absolute errors favored Barrett (Wilcoxon signed-rank test, p < 0.0001). Conclusions: In this cohort, Barrett Universal II outperformed DeepSeek-R1 across MedAE/MAE and cumulative accuracy thresholds, with a significant paired difference. A general-purpose generative model used off-the-shelf (fixed A-constant, no ophthalmology-specific tuning) did not match the accuracy of a validated vergence-based formula; established formulas remain the reference standard for clinical IOL power calculation. Full article

The brainstem plays a pivotal role in the generation and control of eye movements—including saccades, smooth pursuit, the vestibulo-ocular reflex (VOR), vergence, and gaze holding. Beyond its vital physiological functions, it is also essential for the coordination of balance and movement. Consequently, eye movement disorders of brainstem origin are often accompanied by vertigo, imbalance, unsteady gait, and diplopia, particularly during changes in head or body position. A sound understanding of the neural structures involved in oculomotor and vestibular control is therefore crucial for accurately identifying and localizing a wide variety of brainstem syndromes. However, oculomotor abnormalities resulting from brainstem disease represent a major diagnostic challenge for the neurotologist, owing to the wide spectrum of possible etiologies (vascular, traumatic, degenerative, neoplastic), their variable severity and clinical course (acute, fluctuating, or progressive), and the frequent concomitant involvement of other central structures, particularly the cerebellum. This mini review summarizes the pathophysiological mechanisms and clinical features of oculomotor disorders and nystagmus associated with brainstem disease. Full article

Purpose: The accurate intraocular lens (IOL) power calculation is essential in phacoemulsification. The latest IOL power calculation formulas, and their new classification and method to assess their accuracy, were described and analyzed. Design: Narrative review. Methods: The manuscript includes articles on IOL power calculation published between 2019 and 2025. The following key words, such as “phacoemulsification”, “IOL power calculation formula”, “AI-based formulas”, “IOL power selection”, “IOL formulas classification”, IOL prediction” were used to identify papers by searching medical databases (Pubmed/MEDLINE, Google Scholar, Crossref). PRISMA methodology was used to select articles. Finally, 33 peer-reviewed English-language studies with a sample size of at least 120 eyes were included in the analysis. Results: Ten IOL power calculation formulas that have been introduced and published over the past 5 years were included in the study. Five of them are artificial intelligence based (Karmona, Hoffer QST, Nallasamy, Zhu-Lu and Zeiss-AI), four are vergence (Emmetropia Verifying Optical, Naeser 2, Voytsekhivskyy Regression Function-Gender and Castrop), and one is ray-tracing (the O formula). In this review, the formulas are introduced and analyzed, with a discussion of selected studies assessing the accuracy of these IOL power calculation methods. Conclusions: New IOL power calculation formulas are constantly being developed. They are mostly based on artificial intelligence. New methods are still being sought to assess the accuracy of formulas, and root mean square absolute error is one of them Full article

(1) Background: This study investigates the impact of digital device usage on the visual system, with a focus on binocular vision. It also highlights the importance of objective assessment in accurately diagnosing and guiding therapeutic approaches for Digital Eye Strain Syndrome (DESS). (2) Methods: A comprehensive narrative review was conducted to synthesize existing evidence. The methodological quality of observational and case–control studies was assessed using the Newcastle–Ottawa scale, while randomized controlled trials (RCTs) were evaluated using the Cochrane risk-of-bias (RoB 2) tool. (3) Results: Fifteen articles were included in this review, with a predominant focus on binocular vision anomalies, particularly accommodative and vergence dysfunctions, as well as ocular surface anomalies related to DESS. Clinical assessments relied primarily on symptom-based questionnaires, which represent a significant limitation. The included studies were largely observational, with a lack of longitudinal and RCTs. In contrast, research in dry eye disease has been more comprehensive, with multiple RCTs already conducted. (4) Therefore, it is essential to develop validated objective metrics that support accurate clinical diagnosis and guide evidence-based interventions. Conclusions: It remains unclear whether changes in binocular vision are a cause or consequence of DESS. However, prolonged screen time can exacerbate pre-existing binocular vision anomalies due to continuous strain on convergence and accommodation, leading to symptoms. Future research should prioritize prospective longitudinal studies and well-designed RCTs that integrate objective clinical measures to elucidate causal relationships and improve diagnostic and therapeutic frameworks. Full article

Herein, we report a USB-powered VR-HMD prototype integrated with our 33 mm aperture varifocal liquid lenses and electronic drive components, all assembled in a conventional VR-HMD form-factor. In this volumetric-display-based VR system, a sequence of virtual images are rapidly flash-projected at different plane depths in front of the observer and are synchronized with the correct accommodations provided by the varifocal lenses for depth-matched focusing at chosen sweep frequency. This projection mechanism aids in resolving the VAC that is present in conventional fixed-depth VR. Additionally, this system can address refractive error corrections like myopia and hyperopia for prescription users and do not require any eye-tracking systems. We experimentally demonstrate these lenses can vibrate up to frequencies approaching 100 Hz and report the frequency response of the varifocal lenses and their focal characteristics in real time as a function of the drive frequency. When integrated with the prototype’s 120 fps VR display system, these lenses produce a net diopter change of 2.3 D at a sweep frequency of 45 Hz while operating at ~70% of its maximum actuation voltage. The components add a total weight of around 50 g to the off-the-shelf VR set, making it a cost-effective but lightweight minimal solution. Full article

This prospective pilot study aimed to develop and evaluate a VR–based screening tool for assessing distance fusional vergence amplitude in healthy orthotropic young adults aged 18 to 30 years. A VR–based balloon-hitting game was used to measure hitting deviation angles and total vergence amplitudes under five conditions: control (0 prism diopter [PD]), inward image rotation for 10 and 20 PD (negative fusional vergence [NFV] 10/20 groups), and outward image rotation for 10 and 20 PD (positive fusional vergence [PFV] 10/20 groups). Of the 20 subjects recruited, one was excluded due to esotropia, leaving 19 participants (mean age: 22.2 ± 2.2 years; 13 wore glasses and 3 were female). In the control group, the mean hitting deviation was 0.65 ± 0.25 PD. The PFV 10 PD group showed similar deviation (0.67 ± 0.25 PD, p = 0.67), while the PFV 20 PD group had a significant increase (1.71 ± 2.0 PD, p = 0.04). NFV groups demonstrated greater deviations (NFV 10 PD: 3.40 ± 2.05 PD; NFV 20 PD: 9.9 ± 2.40 PD, both p < 0.01). Total vergence amplitudes were 8.65, 16.48, 6.60, and 10.05 PD for PFV 10, PFV 20, NFV 10, and NFV 20 PD, respectively. The VR–based tool enables standardized, efficient assessment of fusional vergence and shows promise for large-scale screening. Full article

Background/Objectives: Myopia is associated with peripapillary changes, namely, gamma peripapillary atrophy (γPPA) and optic disc ovalization, estimated by the ovality index (OI). These changes have been suggested to be promoted by adduction. Recent studies highlight that near reading significantly contributes to the development and progression of myopia and that the interpupillary distance (IPD) influences vergence amplitudes. While both adduction and convergence are involved during near reading, a potential link between IPD and myopic peripapillary changes has not yet been explored. We, therefore, sought to determine whether IPD is related to the OI or γPPA width. Methods: In this monocentric cross-sectional study, 100 eyes from 100 adults (mean age of 62.6 ± 13.7 years) were analyzed. Axial length (AL), refractive error, and IPD were recorded. The OI and γPPA width were assessed using spectral-domain Optical Coherence Tomography. Pearson correlations and multivariable linear regressions were performed, adjusting for age, gender, and myopia status. Results: IPD showed no significant correlation with the OI (r = 0.001; p = 0.989) or γPPA (r = −0.028; p = 0.789). A weak, non-significant correlation was found between IPD and AL (p = 0.059). In contrast, AL was strongly correlated with both a lower OI and wider γPPA (p < 0.001). Conclusions: These findings suggest that IPD-related biomechanical forces do not influence optic nerve head (ONH) shape or γPPA. Axial elongation remains the key driver of myopic ONH remodeling. Full article

This study investigates whether eye movement abnormalities can differentiate between distinct clinical annotations of dyslexia, attention deficit, or school learning difficulties in children. Utilizing a selection of saccade and vergence eye movement data from a large clinical dataset recorded across 20 European centers using the REMOBI and AIDEAL technologies, this research study focuses on individuals annotated with only one of the three annotations. The selected dataset includes 355 individuals for saccade tests and 454 for vergence tasks. Eye movement analysis was performed with AIDEAL software. Key parameters, such as amplitude, latency, duration, and velocity, are extracted and processed to remove outliers and standardize values. Machine learning models, including logistic regression, random forest, support vector machines, and neural networks, are trained using a GroupKFold strategy to ensure patient data are present in either the training or test set. Results from the machine learning models revealed that children annotated solely with dyslexia could be successfully identified based on their saccade and vergence eye movements, while identification of the other two categories was less distinct. Statistical evaluation using the Kruskal–Wallis test highlighted significant group mean differences in several saccade parameters, such as a velocity and latency, particularly for dyslexics relative to the other two groups. These findings suggest that specific terminology, such as “dyslexia”, may capture unique eye movement patterns, underscoring the importance of eye movement analysis as a diagnostic tool for understanding the complexity of these conditions. This study emphasizes the potential of eye movement analysis in refining diagnostic precision and capturing the nuanced differences between dyslexia, attention deficits, and general learning difficulties. Full article