scholarly journals The effect of uncorrected ametropia on ocular torsion induced by changes in fixation

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11932
Author(s):  
Kwang-Keun Oh ◽  
Byeong-Yeon Moon ◽  
Hyun Gug Cho ◽  
Sang-Yeob Kim ◽  
Dong-Sik Yu
Keyword(s):  
Eye Movements ◽  
Refractive Error ◽  
Line Of Sight ◽  
Refractive Errors ◽  
Slit Lamp ◽  
Ocular Torsion ◽  
Fixation Distance

Background and Objective Ocular torsion, the eye movements to rotating around the line of sight, has not been well investigated regarding the influence of refractive errors. The purpose of this study was to investigate the effect of uncorrected ametropia on ocular torsion induced by fixation distances. Methods Seventy-two subjects were classified according to the type of their refractive error, and ocular torsion of the uncorrected eye was compared based on changes induced by different fixation distances. Ocular torsion was measured using a slit-lamp biomicroscope equipped with an ophthalmic camera and a half-silvered mirror. Results In all groups, excyclotorsion values increased as the fixation distance decreased, but the myopia and astigmatism groups had larger amounts of ocular torsion than the emmetropia group. In addition, as the amount of uncorrected myopia and astigmatism increased, the amount of ocular torsion increased. Conclusion Since the amount of ocular torsion caused by a change to a shorter fixation distance was larger when the refractive error was uncorrected, we suggest that ametropia should be fully corrected in patients frequently exposed to ocular torsion due to changes in fixation distance.

scholarly journals Epidemiological Findings of Refractive Errors and Amblyopia among the Schoolchildren in Hatta Region of the United Arab Emirates

2021 ◽  
pp. 1-7
Author(s):  
Salam Chettian Kandi ◽  
Hayat Ahmad Khan
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
United Arab Emirates ◽  
Refractive Error ◽  
Screening Program ◽  
Low Vision ◽  
Refractive Errors ◽  
Vision Screening ◽  
Screening Programs ◽  
School Based

<b><i>Introduction:</i></b> Uncorrected refractive errors and amblyopia pose a major problem affecting schoolchildren. We had previously observed that many schoolchildren in the Hatta region presented to the ophthalmology clinic with uncorrected refractive errors and amblyopia, which led us to undertake this research. As per the WHO, the term “visual impairment” can be “low vision” or “blindness.” Based on the presenting vision, “low vision” is defined for children who have vision of &#x3c;6/18 to 3/60 or having visual field loss to &#x3c;20° in the better-seeing eye. Children defined to have “blindness” have presenting vision of &#x3c;3/60 or corresponding visual field of &#x3c;10°. <b><i>Purpose:</i></b> To estimate the magnitude of uncorrected refractive errors and amblyopia among the schoolchildren aged 6–19 years and to assess the efficacy of school-based refractive error screening programs in the Hatta region of the United Arab Emirates. <b><i>Methods:</i></b> An epidemiological, cross-sectional, descriptive study was conducted on the entire student population studying in the government schools of the region. Those who failed the Snellen visual acuity chart test and those who were wearing spectacles were evaluated comprehensively by the researcher in the Department of Ophthalmology of the Hatta Hospital. Data were entered in the Refractive Error Study in School Children (RESC) eye examination form recommended by the WHO, and were later transferred to Excel sheets and analyzed by SPSS. <b><i>Results:</i></b> 1,591 students were screened and evaluated from the end of 2016 to mid-2017. About 21.37% (<i>n</i> = 340) had impaired vision with 20.9% (<i>n</i> = 333) refractive errors, of which 58% were uncorrected. Among the refractive error group, 19% (64 subjects) had amblyopia (4% of total students). The incidence of low vision was 9.5% and blindness was 0.38%. Low vision was found to be 9.5% and blindness 0.38%, taking in to account presenting visual acuity rather than best-corrected visual acuity for defining low vision and blindness. <b><i>Conclusion:</i></b> A significant number of students were detected to have uncorrected refractive errors among the vision impaired group (59%, <i>n</i> = 197) despite a school-based vision screening program in place. Seventy-eight percent of the amblyopia cases (<i>n</i> = 50) were found to be in the 11–19 years age group. Noncompliance with optical corrections was the reason for the high number of cases. A rigorous vision screening program and refractive services, complimented with awareness among parents and teachers, are recommended.

The prevalence and causes of visual impairment in Dariyah, a rural community in Saudi Arabia

2021 ◽  
Vol 80 (1) ◽  
Author(s):  
Waleed Alghamdi ◽  
Godwin O. Ovenseri-Ogbomo
Keyword(s):  
Saudi Arabia ◽  
Visual Impairment ◽  
Rural Community ◽  
Refractive Error ◽  
Population Based ◽  
Vision Impairment ◽  
Health Examination ◽  
Refractive Errors ◽  
Cross Sectional ◽  
Eye Examination

Background: Visual impairment is disproportionately distributed between rural and urban dwellers. Rural dwellers have limited access to the eye care services that are available in urban cities.Aim: The aim of this study was to determine the prevalence and causes of visual impairment in Dariyah, a rural community in the Qassim region, Saudi Arabia.Setting: This research comprised a population-based assessment of the vision and visual status of the inhabitants of Dariyah community.Methods: A cross-sectional descriptive study was conducted amongst the inhabitants of the community of Dariyah. A comprehensive eye examination consisting of visual acuity, ocular health examination, objective and subjective refraction was performed. The examinations were conducted by registered ophthalmologists and optometrists from the Qassim University. Vision impairments were categorised according to the International Classification of Diseases (ICD), Section 9D90, ‘Vision impairment including blindness’ (2018).Results: In all, 68 (24.5%) participants had vision impairment (using the better-seeing eye), with refractive errors being the main cause of vision impairment. Other causes of vision impairment included cataract (20, 7.2%), trichiasis (5, 1.8%) and glaucoma (2, 0.7%). Refractive errors were present in 193 (69.7%), with astigmatism being the commonest refractive error. About 60% of those with refractive errors presented without spectacles for correction, and 20% reported that they had never had an eye examination. Refractive errors could not be determined in 19 (6.9%) of the subjects because of conditions such as matured cataract and other ocular abnormalities.Conclusion: Uncorrected refractive error was found to be the leading cause of vision impairment in this rural community in Saudi Arabia.

Evidence for a retinal velocity memory underlying the direction of anticipatory smooth pursuit eye movements

2013 ◽  
Vol 110 (3) ◽  
pp. 732-747 ◽  
Author(s):  
T. Scott Murdison ◽  
Chanel A. Paré-Bingley ◽  
Gunnar Blohm
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Target Velocity ◽  
Smooth Pursuit Eye Movements ◽  
Ocular Torsion ◽  
Pursuit Eye Movements ◽  
Ocular Counterroll ◽  
In Series ◽  
Head Roll ◽  
Directional Component

To compute spatially correct smooth pursuit eye movements, the brain uses both retinal motion and extraretinal signals about the eyes and head in space ( Blohm and Lefèvre 2010 ). However, when smooth eye movements rely solely on memorized target velocity, such as during anticipatory pursuit, it is unknown if this velocity memory also accounts for extraretinal information, such as head roll and ocular torsion. To answer this question, we used a novel behavioral updating paradigm in which participants pursued a repetitive, spatially constant fixation-gap-ramp stimulus in series of five trials. During the first four trials, participants' heads were rolled toward one shoulder, inducing ocular counterroll (OCR). With each repetition, participants increased their anticipatory pursuit gain, indicating a robust encoding of velocity memory. On the fifth trial, they rolled their heads to the opposite shoulder before pursuit, also inducing changes in ocular torsion. Consequently, for spatially accurate anticipatory pursuit, the velocity memory had to be updated across changes in head roll and ocular torsion. We tested how the velocity memory accounted for head roll and OCR by observing the effects of changes to these signals on anticipatory trajectories of the memory decoding (fifth) trials. We found that anticipatory pursuit was updated for changes in head roll; however, we observed no evidence of compensation for OCR, representing the absence of ocular torsion signals within the velocity memory. This indicated that the directional component of the memory must be coded retinally and updated to account for changes in head roll, but not OCR.

scholarly journals Case Report: Serial Topography Analysis After Acute Unilateral Diffuse Lamellar Keratitis

2020 ◽  
Vol 82 (3) ◽  
pp. 19-24
Author(s):  
Jonathan Jay Lytle
Keyword(s):  
Case Report ◽  
Refractive Error ◽  
Clinical Signs ◽  
Corneal Topography ◽  
Laser In Situ Keratomileusis ◽  
Refractive Errors ◽  
Fort Worth ◽  
Topical Corticosteroids ◽  
Gross Examination

Abstract Significance: Diffuse lamellar keratitis (DLK) is a widely reported complication of laser in-situ keratomileusis (LASIK); however, serial topography tracking the resolution of the condition is sparse. This case illustrates the healing profile which may be expected following an episode of DLK, and the patient reassurances which may be appropriate. Purpose: To report the topography changes and refractive resolution associated with a case of acute unilateral diffuse lamellar keratitis following bilateral femtosecond-assisted hyperopic LASIK. Case Report: A healthy 53-year old male presented with grade two-plus diffuse lamellar keratitis (DLK) 11 days after undergoing successful bilateral wavefront optimized (Alcon, Fort Worth, USA), femtosecond-assisted hyperopic LASIK. Resolution of the DLK was achieved in three weeks with topical corticosteroids. Stabilization of the patient’s topography and refractive error was observed two months after the resolution of the DLK. Conclusions: This case suggests that improvements in corneal topography and refractive error can be expected long after the clinical signs of DLK have subsided. Corneal irregularities and residual refractive errors (usually hyperopia and astigmatism) which exist at the time of resolution on gross examination should be monitored regularly and patients may be reassured that improvements appear likely even after topical regimens have been completed.

Prevalence and Determining Factors Of Refractive Errors Among Medical Students In FMU, Faisalabad

2021 ◽  
Vol 15 (11) ◽  
pp. 2934-2935
Author(s):  
Nadia Tufail ◽  
Huda Abbas ◽  
Ali Sarfraz ◽  
Sumaira Ashraf ◽  
M. Ashraf Majrooh
Keyword(s):  
Medical Students ◽  
Mobile Phone ◽  
Mobile Phones ◽  
Refractive Error ◽  
Contact Lenses ◽  
Electronic Devices ◽  
Quantitative Information ◽  
Refractive Errors ◽  
Cross Sectional ◽  
Determining Factors

Aim: Prevalence and determining factors of refractive errors among the medical students in FMU, Faisalabad. Methodology: Cross-sectional quantitative study conducted in Faisalabad Medical University from 01-03-2020 to 15-12-2020 after approval from institutional review committee. All students of MBBS in FMU were included in this study. A structured questionnaire was used to collect the required quantitative information. SPSS version 26 was used for analysis. Results: Prevalence of refractive error is 49%. Females were 59% and males were 41%. More students i.e. 85.2% were suffering from myopia. In our study, usage of electronic devices i.e. mobile phones especially was one of the risk factors in developing refractive errors. 20.6% students having refractive error said that they use mobile phone for 4 hours, 30.2% having refractive error said that they watch TV for one hour, 23.3% having refractive error said that they play video games for one hour. For the correction of the refractive error, 184 students i.e. 97.4% used spectacles whereas only 5 (2.6%) students used contact lenses. It is observed in this study that contact lenses were only used by those students having refractive error <1.5. Conclusion: Refractive errors were a significant cause of visual impairment among medical students. The prolonged use of electronic devices especially mobile phones should be discouraged. Keywords: Refractive errors, myopia, electronic devices, mobile phone

scholarly journals Refractive Errors and its Associated Factors among Undergraduate Medical Students in Kathmandu

2019 ◽  
Vol 21 (1) ◽  
pp. 26-30
Author(s):  
Aparna Rizyal ◽  
JS Sunrait ◽  
A Mishal
Keyword(s):  
Medical Students ◽  
Visual Impairment ◽  
Refractive Error ◽  
Single Point ◽  
Cross Sectional Study ◽  
Refractive Errors ◽  
Undergraduate Medical Students ◽  
Cross Sectional ◽  
Parental History ◽  
Medical College

 Refractive error is a defect in the optical system of the eye which prevents light from being brought to a single point focus on the retina, thus reducing normal vision. This optical defect is the second most common cause of visual impairment globally as well in Nepal. At present, there are 285 million visually impaired people in the world. An estimated 4 out of 5 visual impairment (80%) can be prevented or cured, uncorrected refractive errors are the leading cause (42%) followed by cataract (33%). A descriptive cross sectional study was conducted to determine the proportion of undergraduate medical students with refractive errors in Nepal Medical College, and to identify factors associated with it. A total of 210 medical students volunteered for this study, with 100 males (47.6%) and 110 females (52.4%). The age of these students were between 18 to 26 years, with an average of 20.5 years. The proportion of medical students with refractive error was slightly more than half (51.4%), with simple myopia being the leading type (42.9%), followed by astigmatism (7.1%) and simple hypermetropia (1.4%). Parental history of refractive error was observed to be significantly associated with that of the medical students. There was also a significant association between refractive error and the daily use of mobile phones and laptops. However, years spent in medical education were not observed to be significant.

scholarly journals PREVALENCE OF REFRACTIVE ERRORS IN ADOLESCENTS IN OUT- PATIENT ATTENDEES OF THE PREVENTIVE OPHTHALMOLOGY CLINIC OF COMMUNITY MEDICINE, S K I M S, KASHMIR, INDIA

2013 ◽  
Vol 03 (01) ◽  
pp. 17-20
Author(s):  
Jabeen Rohul ◽  
Aakifa Maqbool ◽  
Syed Arshad Hussain ◽  
Hamid Shamila ◽  
Fazli Anjum ◽  
...  
Keyword(s):  
Early Detection ◽  
Refractive Error ◽  
Social Problems ◽  
Low Vision ◽  
Community Medicine ◽  
Refractive Errors ◽  
High Prevalence ◽  
Males And Females ◽  
The Mean ◽  
Eye Clinic

AbstractBlindness is one of the most significant social problems in India with uncorrected refractive errors as the second major cause accounting for 19.7% of blindness and low vision.All adolescents (12-18 years) attending the eye clinic from Jan 2007-Jan 2009 for any eye ailment were examined and screened for refractive error using Snellen's chart.Out of total 930 adolescents, 508(54.62%) of adolescents had refractive errors. Of the total males and females examined 57.43% and 52.12% respectively had refractive errors. The mean age of presentation was 14.3 years. Most of the adolescents presented with myopia 257(50.59%) followed by astigmatism (35.23%) and hypermetropia (14.17%).High prevalence of refractive errors warrants early detection and treatment.

Dynamics of Squirrel Monkey Linear Vestibuloocular Reflex and Interactions with Fixation Distance

1997 ◽  
Vol 78 (4) ◽  
pp. 1775-1790 ◽  
Author(s):  
Laura Telford ◽  
Scott H. Seidman ◽  
Gary D. Paige
Keyword(s):  
Eye Movements ◽  
Squirrel Monkey ◽  
Head Tilt ◽  
Linear Acceleration ◽  
Head Orientation ◽  
Vestibuloocular Reflex ◽  
Response Characteristics ◽  
Fixation Distance ◽  
Eye Rotation ◽  
Low Pass

Telford, Laura, Scott H. Seidman, and Gary D. Paige. Dynamics of squirrel monkey linear vestibuloocular reflex and interactions with fixation distance. J. Neurophysiol. 78: 1775–1790, 1997. Horizontal, vertical, and torsional eye movements were recorded using the magnetic search-coil technique during linear accelerations along the interaural (IA) and dorsoventral (DV) head axes. Four squirrel monkeys were translated sinusoidally over a range of frequencies (0.5–4.0 Hz) and amplitudes (0.1–0.7 g peak acceleration). The linear vestibuloocular reflex (LVOR) was recorded in darkness after brief presentations of visual targets at various distances from the subject. With subjects positioned upright or nose-up relative to gravity, IA translations generated conjugate horizontal (IA horizontal) eye movements, whereas DV translations with the head nose-up or right-side down generated conjugate vertical (DV vertical) responses. Both were compensatory for linear head motion and are thus translational LVOR responses. In concert with geometric requirements, both IA-horizontal and DV-vertical response sensitivities (in deg eye rotation/cm head translation) were related linearly to reciprocal fixation distance as measured by vergence (in m−1, or meter-angles, MA). The relationship was characterized by linear regressions, yielding sensitivity slopes (in deg⋅cm−1⋅MA−1) and intercepts (sensitivity at 0 vergence). Sensitivity slopes were greatest at 4.0 Hz, but were only slightly more than half the ideal required to maintain fixation. Slopes declined with decreasing frequency, becoming negligible at 0.5 Hz. Small responses were observed when vergence was zero (intercept), although no response is required. Like sensitivity slope, the intercept was largest at 4.0 Hz and declined with decreasing frequency. Phase lead was near zero (compensatory) at 4.0 Hz, but increased as frequency declined. Changes in head orientation, motion axis (IA vs. DV), and acceleration amplitude produced slight and sporadic changes in LVOR parameters. Translational LVOR response characteristics are consistent with high-pass filtering within LVOR pathways. Along with horizontal eye movements, IA translation generated small torsional responses. In contrast to the translational LVORs, IA-torsional responses were not systematically modulated by vergence angle. The IA-torsional LVOR is not compensatory for translation because it cannot maintain image stability. Rather, it likely compensates for the effective head tilt simulated by translation. When analyzed in terms of effective head tilt, torsional responses were greatest at the lowest frequency and declined as frequency increased, consistent with low-pass filtering of otolith input. It is unlikely that IA-torsional responses compensate for actual head tilt, however, because they were similar for both upright and nose-up head orientations. The IA-torsional and -horizontal LVORs seem to respond only to linear acceleration along the IA head axis, and the DV-vertical LVOR to acceleration along the head's DV axis, regardless of gravity.

Effect of Eye Movement on Perception of Flicker

1979 ◽  
Vol 48 (3) ◽  
pp. 943-950 ◽  
Author(s):  
Tadahiko Fukuda
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Target Size ◽  
Line Of Sight ◽  
Moving Line

With 3 experienced subjects CFF during eye movements was higher than that obtained by fixing a line of sight. CFF increased with a moving line of sight. With additional subjects CFF during eye movements was related to various factors such as target size and conditions of eye movement. More thorough study is required.

scholarly journals Advancing Digital Workflows for Refractive Error Measurements

2020 ◽  
Vol 9 (7) ◽  
pp. 2205
Author(s):  
Arne Ohlendorf ◽  
Alexander Leube ◽  
Siegfried Wahl
Keyword(s):  
Refractive Error ◽  
T Test ◽  
Refractive Errors ◽  
Altman Analysis ◽  
Limits Of Agreement ◽  
Clinical Measurement ◽  
Different Types ◽  
Method Of Measurement ◽  
Mean Differences ◽  
The Right

Advancements in clinical measurement of refractive errors should lead to faster and more reliable measurements of such errors. The study investigated different aspects of advancements and the agreement of the spherocylindrical prescriptions obtained with an objective method of measurement (“Aberrometry” (AR)) and two methods of subjective refinements (“Wavefront Refraction” (WR) and “Standard Refraction” (StdR)). One hundred adults aged 20–78 years participated in the course of the study. Bland–Altman analysis of the right eye measurement of the spherocylindrical refractive error (M) identified mean differences (±95% limits of agreement) between the different types of measurements of +0.36 D (±0.76 D) for WR vs. AR (t-test: p < 0.001), +0.35 D (± 0.84 D) for StdR vs. AR (t-test: p < 0.001), and 0.0 D (± 0.65 D) for StdR vs. WR (t-test: p < 0.001). Monocular visual acuity was 0.0 logMAR in 96% of the tested eyes, when refractive errors were corrected with measurements from AR, indicating that only small differences between the different types of prescriptions are present.

Sign in / Sign up

Export Citation Format

Share Document