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Purpose: To determine the distribution of the near point of convergence (NPC) and near point of accommodation (NPA) in a young student population in Iran.
Methods: The subjects were selected using a cluster sampling method. All students underwent optometry tests, including visual acuity measurement, refraction, and cover test, as well as ophthalmi...
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Many studies have established a relationship between visual function and motor development in toddlers. This is the first report to study two-year-olds via an assessment of their visual and motor skills. The purpose of this study is to describe the possible changes that can occur between visual and motor systems in typical developing toddlers. A to...
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... The spatial accuracy of the human eye can resolve measurement to 0.26 mm (Bould et al., 1999), which is based on the human eye's near-point of convergence, that is, the closest point at which the eye can focus without diplopia. This has been observed to be at a focal length of ~72 mm in a young population (Hashemi et al., 2019). Unlike the original specimen, a 3D photogrammetric model can be viewed as if millimetres from the specimen surface and topographical detail remains clear and in sharp focus. ...
Three-dimensional (3D) representations of anatomical specimens are increasingly used as learning resources. Photogrammetry is a well-established technique that can be used to generate 3D models and has only been recently applied to produce visualisations of cadaveric specimens. This study has developed a semi-standardised photogrammetry workflow to produce photorealistic models of human specimens. Eight specimens, each with unique anatomical characteristics, were successfully digitised into interactive 3D models using the described workflow and the strengths and limitations of the technique are described. Various tissue types were reconstructed with apparent preservation of geometry and texture which visually resembled the original specimen. Using this workflow, an institution could digitise their existing cadaveric resources, facilitating the delivery of novel educational experiences.
... The classroom environment acts as a predisposing factor for these conditions [3]. Besides, students experience these symptoms more often than any other group because of the high demand for near work [5]. Accommodation anomalies mainly occur as an inappropriate response to visual demand leading to poorly sustained bi-foveal fixation [3]. ...
... In contrast, studies in Nigeria found that the measured AA did not differ from Hofstetter's expectation [10,19]. Nevertheless, In Iran Hashemi and others [5] found that the equation generated a lower value among a young age group but it overestimated AA among older subjects beyond 30 years. Hofstetter's equation has been discovered that correctly identifies accommodation measured using pushup methods [7]. ...
Aim: The study aimed to examine the distribution of Accommodative Facility (AF) and Amplitude of Accommodation (AA) and compare the findings with established guidelines. Place and Duration of Study: Mzuzu University, Malawi. Between May and July 2022. Methods: This cross-sectional study was conducted among students at Mzuzu university in Malawi. We recruited 77 students using a stratified random sampling technique. The participants' age ranged from 16 to 35 years of age. We measured AA using the push-up method while AF was measured using +/-1.50 Diopters (D) flippers. Both techniques utilized black reading material on white background held at 40 centimeters (cm). Next, we measured the accommodation facility by counting the number of Cycles per Minute (c/m). We utilized the Pearson correlation test and the One-way ANOVA where appropriate. The value of p< 0.05 was considered statistically significant. Results: The participants comprised 44 (57.1%) males and 33 (42.9%) females. Monocular AA was 10.04D (SD=2.71) and Binocular AA was 10.51 (3.641). The difference was statistically significant (p=0.04). While Monocular AF and Binocular AF were 9 c/m (SD= SD=1.84) and 8.96 (SD=1.539) respectively but the difference was non-significant (p=0.868). AF and AA were not significantly different between males and females. All the parameters decreased with age. The measured AA was significantly higher than using Hofstetter's formula. Original Research Article Chikuse et al.; OR, 17(4): 51-56, 2022; Article no.OR.94134 52 Conclusion: The study provides a cutoff value for practitioners diagnosing Accommodation anomalies. However, indices in the study differ from the well-established guidelines hence practitioners should endeavor to perform the clinical assessment instead of relying on equations.
... Por otra parte, estas necesidades variarán en dependencia del defecto refractivo residual. (30) Cuando se analizó la amplitud de convergencia en estos pacientes, pudo observarse, que los valores de la media de la amplitud de convergencia reporta una caída significativa de lejos, no hubo una diferencia significativa de cerca, tanto en los pacientes tratados con PRK-MMC, como con LASEK-MMC, y la media de la amplitud de divergencia de lejos también reporta una caída significativa, pero la amplitud de divergencia de cerca sigue igual cae en los pacientes tratados con PRK-MMC, pero se presentó ligero aumento en el grupo tratado con LASEK-MMC, la variación observada no fue estadísticamente significativa. ...
Objetivo:
Evaluar los resultados sensoriales y motores poscirugía refractiva con técnicas de superficie (LASEK-MMC o PRK-MMC) en pacientes miopes con o sin astigmatismo asociado.
Método:
Se realizó estudio experimental controlado aleatorizado abierto, en el cual fueron incluidos 160 pacientes (320 ojos), de ellos tratados con LASEK-MMC (80 pacientes) y con PRK-MMC (80 pacientes), seguidos por 3 meses. Las principales variables evaluadas fueron: edad, tipo de error refractivo, equivalente esférico, ángulo Kappa, anisometropía, estereopsis, punto próximo de convergencia y su anomalía, amplitud de convergencia y de divergencia (cerca y lejos) y magnitud de la desviación del alineamiento ocular.
Resultados:
El grupo tratado con PRK-MMC tenía edad media de 26,48 años ± 4,47 y equivalente esférico preoperatorio de -3,27 ±1,54 que disminuyó significativamente (p <0,05) a -0,04 ± 0,23 dioptrías (D) a los tres meses de la cirugía. El grupo tratado con LASEK-MMC tenía edad media de 26,31 años ± 4,86 y equivalente esférico preoperatorio de -3,34 ± 1,66 dioptrías (D) que disminuyó significativamente (p <0,05) a -0,06 ± 0,26 D a los tres meses de la cirugía. Además, disminuyó la anisometropía, mejoró la estereopsis y disminuyó la amplitud la amplitud de convergencia y divergencia para lejos. El alineamiento ocular también mejoró.
Conclusiones:
Las técnicas de superficies para tratar pacientes con miopía o astigmatismo miópico compuesto disminuyen la anisometropía, mejoran la estereopsis y disminuyen la amplitud de convergencia y divergencia para lejos, con mayor proporción de pacientes con ortoforia después de la operación.
... Both monocular and binocular near point of accommodation and accommodative facility using ± 2.00 D flipper lenses were measured. The monocular estimate method was used to determine accommodative response [23][24][25]. ...
Background: Focusing the gaze for prolonged periods on a fixed distance demands high visual efficiency in handloom silk weavers and might result in various accommodative and vergence dysfunctions. The aim of the present study was to assess accommodative and vergence parameters and determine the frequency of non-strabismic binocular vision anomalies (NSBVAs) among handloom silk weavers. Methods: In this cross-sectional study, we recruited voluntary handloom silk weavers from the Government-aided Society of Arignar Anna Silk Co-op Society K.H.-1, Kanchipuram, aged 20–39 years. All participants underwent preliminary visual examinations and comprehensive binocular vision testing of accommodative and vergence parameters. Sensory evaluation was performed using stereopsis testing and the Worth 4 Dot test. Motor evaluation included the ocular motility assessment, heterophoria checks for distance and near, near point of convergence, negative and positive fusional vergences for distance and near, vergence facility, negative and positive relative accommodations, both monocular and binocular near points of accommodation, and accommodative facility. The monocular estimate method was used to determine the accommodative response. Quantitative data are expressed as mean (standard deviation [SD]), and qualitative data are expressed as frequency (percentage). Results: We recruited a total of 72 weavers, including 41 (56.9%) men and, 31 (43.1%) women with mean (SD) age, working hours, and work experience of 34.15 (4.12) years, 9 (2.5) h/day, and 17.5 (6.9) years, respectively. Of the 29 (40.3%) weavers with a refractive error, 18 (25%) had astigmatism; seven (9.7%) had myopia; and four (5.6%) had hyperopia. Of the 72 weavers, 38 (52.8%) presented with NSBVAs, including 13 (18.1%) with accommodative dysfunctions, 11 (15.3%) with vergence dysfunctions, and 14 (19.4%) with combined accommodative and vergence dysfunctions. Accommodative insufficiency was the most prevalent dysfunction among all NSBVAs. Overall, 57 (79.2%) patients reported vision-related symptoms during their weaving hours, all with NSBVAs (n = 38), 19 with normal parameters in the binocular vision test, and 15 with no symptoms. Conclusions: The frequency of NSBVAs was high among handloom silk weavers compared to the literature. This implies a need for comprehensive binocular vision examination for people in this occupation to rule out NSBVAs for improving their quality of life and occupational productivity. Future large-scale studies are required to determine the exact NSBVAs prevalence among workers of this near vision-related occupation.
... A detailed history of each participant was documented. A comprehensive eye examination was performed, including near and distance visual acuity measurements [21], stereopsis testing [22], cover test [21], Hirschberg test [23], pupillary examination [24], measurements of near point of accommodation [25] and near point of convergence [25], confrontation visual field test [26], color vision test [27], subjective and objective refraction [28], intraocular pressure measurement [28], slit-lamp examination [28], and fundus examination [28]. Those who fulfilled the inclusion criteria were first administered a visual fatigue questionnaire. ...
... A detailed history of each participant was documented. A comprehensive eye examination was performed, including near and distance visual acuity measurements [21], stereopsis testing [22], cover test [21], Hirschberg test [23], pupillary examination [24], measurements of near point of accommodation [25] and near point of convergence [25], confrontation visual field test [26], color vision test [27], subjective and objective refraction [28], intraocular pressure measurement [28], slit-lamp examination [28], and fundus examination [28]. Those who fulfilled the inclusion criteria were first administered a visual fatigue questionnaire. ...
Background: Visual fatigue is categorized as a complex phenomenon that decreases visual performance. The aim of the present study was to assess changes in accommodation at different levels of visual fatigue among students of a Malaysian private university using digital devices. Methods: In this cross-sectional study, students regardless of sex and ethnicity were included. A comprehensive eye examination was performed. After estimating the level of visual fatigue, the amplitude of accommodation (AA), accommodation facility (AF), and monocular estimation method (MEM) were measured. The visual fatigue questionnaire was filled out by the participants. Participants were categorized based on the visual fatigue scores into low, moderate, and high visual fatigue groups. Moderate and severe visual fatigue groups were combined, as the distribution of participants was uneven across the groups. Accommodation parameters were measured for each group and compared between the two groups, i.e., the low visual fatigue group and the combined moderate to severe visual fatigue group. Results: We enrolled a total of 86 students, including 29 (33.72%) men and 57 (66.28%) women, with a mean (standard deviation [SD]) age of 22.02 (1.51) years and age ranging from 19 to 26 years. By ethnicity, there were 69 (80.23%) Chinese, five (5.81%) Indian, four (4.65%) Malay, and eight (9.30%) participants from other ethnicities. Most participants were in the low visual fatigue group (54.65%), followed by the severe (25.58%) and moderate (19.77%) visual fatigue groups. AA for both eyes and AF for the right eye differed significantly between the two groups (both P < 0.05). None of the accommodative parameters correlated with visual fatigue (P > 0.05). Conclusions: Binocular AA and monocular AF significantly differed between the visual fatigue groups, but MEM was comparable. However, none of the accommodative parameters correlated with visual fatigue. These perceived vision dysfunctions could affect the visual skills of students. Therefore, future studies on the relationship between the observed dysfunctions and students’ reading performance are necessary.
... Hofstetter's equation has been commonly used to diagnose accommodation insufficiency; however, its clinical value has been questioned, especially in children (Sterner et al. 2004;Hashemi et al. 2018). In a study of university students in Iran, Hashemi et al. found that Hofstetter's equation overestimated the accommodation amplitude in younger age groups and underestimated it in older age groups (Hashemi, Pakbin, et al. 2019). According to this study, it was most accurate at the age of 30 years; thus, it should be applicable in the current study group, where the participants were all 25 to 29 years of age at the time of the study. ...
Purpose
The aim of the study was to evaluate strabismus, stereoacuity, accommodation and convergence in prematurely born young adults; screened for retinopathy of prematurity in the neonatal period and compare with term-born individuals of the same age.
Materials and methods
The study participants included 59 prematurely born individuals with a birthweight of ≤1,500 grams and 44 term-born controls, all born during 1988–1990 in Stockholm County, Sweden. Ocular alignment was assessed with a cover test, stereoacuity with the TNO stereo test and the amplitude of accommodation and the near point of convergence with the Royal Air Force Rule.
Results
Seven of 59 (12%) preterms had manifest strabismus, 4/59 (7%) had esotropia and 3/59 (5%) exotropia. One of 44 (2%) controls had esotropia; no other controls had manifest strabismus. Stereoacuity was within normal limits in 38/59 (64%) preterms and 43/44 (98%) controls, p < 0.01; the difference remained after excluding those with strabismus. A neurological complication at 2.5 years of age was the strongest risk factor for subnormal stereoacuity within the preterm group after excluding those with strabismus. The mean amplitude of accommodation was poorer in the preterms than the controls in better (p < 0.05) and worse eyes (p < 0.05). The preterms were more likely to have an amplitude of accommodation below the minimum, according to Hofstetter’s equation. There were no differences between the groups regarding the near point of convergence.
Conclusion
Prematurely born young adults had a higher prevalence of strabismus, reduced stereoacuity and worse amplitude of accommodation than term-born controls.
NPC is a vital factor in determination and diagnosis and treatment of various ocular
problems. To evaluate near point of convergence in refractive errors a descriptive crosssectional study on 140 patients ages 18 to 35 irrespective of sex visiting eye department was
carried out by measuring near point of convergence of the patients with refractive errors.
59(42.1%) were presented with headache and 55(39.3%) were presented with eye strain
while 26(18.6%) were presented with the problem of blurring of vision. 89(63.0%) were
having visual acuities in the range of 6/6 to 6/12 and 31(22.1%) were having visual acuities
ranges between 6/18 to 6/60 while 20(14.2%) were having their visual acuities >6/60.
Overall (106)75.7% patients were having NPC between 6-10 cm while (33)23.6% were
having NPC between 11-15cm. 55(37.9%) patients were myopic, 42(30.0%)were hyperopic
and 45(32.1%) patients were astigmatic. 38(71.1%) myopic had their NPC between 6-10cm
and 15(28.3%) were between 11-15cm. 32(76.2%) hyperopic patients had their NPC
between 6-10cm and 10(23.8%) had between 11-15cm. 36 (80.0%) astigmatic patients had
their NPC in between 6-10cm and 8(17.8%) had their NPC in between 11-15cm while only
1(0.7%) reported their NPC between 16-20cm. Near point of convergence values in
refractive error were found mostly in normal range. No significant difference of near point of
convergence was found in low to medium refractive errors. Moreover, higher myopes had
increased near point of convergence values than other refractive error.
Introduction: Accommodation is the ability of the eye to change its refractive power (by altering the curvature of the crystalline lens) with the aim of focusing on different distances. In modern times, close working distances require good accommodation to ensure quality work without vision problems. However, dysfunction in accommodation is not uncommon. Specifically, accommodation insufficiency is the most common dysfunction associated with accommodation that can be observed at any age. Accommodation insufficiency is characterized by the eye's inability to reach its maximum potential for accommodation (amplitude of accommodation) based on age, with many individuals experiencing deviations equal to or greater than 2 diopters (2D) from the theoretically normal range. Finally, measuring the amplitude of accommodation and near vision tests should be established in routine eye examinations, as life now involves a variety of different distances. Objective: To record the rates of accommodative insufficiency in young Caucasian adults. Methods: The method used was minus to blur, and the comparison charts were based on Donder's and Hofstetter's values. Depending on the result, they were categorized as "normal," which refers to deviations from zero to 1 diopter (1D) (due to the fact that minus lenses underestimate or are quite strict regarding the range of accommodation compared to other methods in free space (e.g., push-up); "borderline," which refers to deviations from 1.25D to 1.75D or 2D with at least one eye deviating by less than 1.75D; and "accommodation insufficiency," which refers to deviations greater than 2D from the expected values, as proposed in other studies. Results: The results show a significant percentage of accommodation insufficiency in these age groups, with the percentage exceeding 50%. Additionally, men had significantly lower rates of normal accommodation amplitude compared to women. Further research is needed to study the role of refractive errors in accommodation problems. Conclusions: In a broader context, accommodation insufficiency appears to be a significant issue in young age groups, and additional studies should be conducted to analyze the problem in depth and determine its prevalence. Furthermore, a universal system for measuring the range of accommodation should be established to obtain safer results. Additionally, it would be interesting to observe the role and contribution of the ciliary muscle in the accommodation process in young adults, as theoretically, the crystalline lens is almost transparent, the issue with adaptation primarily concerns the majority's inability of the ciliary muscle to function effectively.
Vergence dysfunctions and accommodation anomalies are the main causes of asthenopic symptoms. These may be related to differences in the anthropometric measurements.
The anthropometric measurements have a significance in understanding human physical and physiological variations. This study was carried out with the purpose of measuring the near point of convergence (NPC), near point of accommodation (NPA) and to determine their association with interpupillary distance (IPD) in a population of North-western India.
This was a cross sectional study carried out on young adults of 18-22 years age group. The NPC and NPA were measured with a Royal Air Force (RAF) scale. Distance IPD was measured with a ruler and autorefractometer. The results were analysed statistically to study the relation of the variables with each other.
The average IPD of the study population was 62.18 mm, IICD was 29.65, NPC was 6.55 cm, NPA was 9.42 cm. The correlation between IPD and IICD was 0.15 (weak). The correlation between IPD and NPC was found to be 0.18, correlation between IPD and NPA OD was 0.35 and the correlation between IPD and NPA OS was 0.30, which all were statistically weak.
The anthropometric measurements of the study population were similar to those reported by other studies on the Indian population. The correlation between NPA and IPD and that between NPC and IPD was found to be weak.
Recent years have seen the proliferation of VR-based dental simulators using a wide variety of different VR configurations with varying degrees of realism. Important aspects distinguishing VR hardware configurations are 3D stereoscopic rendering and visual alignment of the user’s hands with the virtual tools. New dental simulators are often evaluated without analysing the impact of these simulation aspects. In this paper, we seek to determine the impact of 3D stereoscopic rendering and of hand-tool alignment on the teaching effectiveness and skill assessment accuracy of a VR dental simulator. We developed a bimanual simulator using an HMD and two haptic devices that provides an immersive environment with both 3D stereoscopic rendering and hand-tool alignment. We then independently controlled for each of the two aspects of the simulation. We trained four groups of students in root canal access opening using the simulator and measured the virtual and real learning gains. We quantified the real learning gains by pre- and post-testing using realistic plastic teeth and the virtual learning gains by scoring the training outcomes inside the simulator. We developed a scoring metric to automatically score the training outcomes that strongly correlates with experts’ scoring of those outcomes. We found that hand-tool alignment has a positive impact on virtual and real learning gains, and improves the accuracy of skill assessment. We found that stereoscopic 3D had a negative impact on virtual and real learning gains, however it improves the accuracy of skill assessment. This finding is counter-intuitive, and we found eye-tooth distance to be a confounding variable of stereoscopic 3D, as it was significantly lower for the monoscopic 3D condition and negatively correlates with real learning gain. The results of our study provide valuable information for the future design of dental simulators, as well as simulators for other high-precision psycho-motor tasks.
