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Journal of Ophthalmology 2018To measure the prevalence of amblyopia and amblyogenic factors among primary school children and to evaluate distance visual acuity (VA) as a screening test to detect...
OBJECTIVE
To measure the prevalence of amblyopia and amblyogenic factors among primary school children and to evaluate distance visual acuity (VA) as a screening test to detect amblyopia and define its cutoff value.
SUBJECTS AND METHODS
A cross-sectional study was conducted on primary school children in two schools in Central Cairo. Children underwent assessment of visual acuity using Landolt broken ring. Comprehensive ophthalmologic examination was performed for amblyopia suspects at the Ophthalmology Department of Ain Shams University Hospitals, including reassessment of best-corrected visual acuity (BCVA) using the same chart.
RESULTS
A total of 352 children were examined. Reduced screening VA (amblyopia suspect) was detected in 47 subjects (13.35%) proved amblyopia after comprehensive examination was 1.98% (7 cases). Refractive errors (REs) were present in all suspected and proved amblyopia cases (100%) but was only present in 11.6% of nonamblyopic students ( < 0.05). The prevalence of hyperopia in the whole sample was 3.6%, and was 27.6% in subjects with RE. Thirty percent of hyperopic eyes were amblyopic. The prevalence of myopia was 9.3% of the whole sample and 70% of students with RE. Only 9% of myopic eyes were amblyopic. Mild to moderate amblyopia (VA better than 0.2log MAR) was 42.9%, while severe amblyopia represented 57.1%.
CONCLUSION
This study emphasizes the importance of school-based eye care system targeting the detection of amblyopia by application of a fast screening distance VA test with a cutoff value of high sensitivity at log MAR 0.539 (Snellen's VA equivalent 6/18).
PubMed: 29850217
DOI: 10.1155/2018/8425319 -
Eastern Mediterranean Health Journal =... 2007A preliminary survey was conducted to detect the prevalence of refractive error (RE) and low vision among 5839 schoolchildren aged 7-14 years in Cairo, Egypt. Screening...
A preliminary survey was conducted to detect the prevalence of refractive error (RE) and low vision among 5839 schoolchildren aged 7-14 years in Cairo, Egypt. Screening was done using Landolt broken ring chart and pinhole test. The prevalence of RE (visual acuity < or = 6/12) among the schoolchildren was 22.1% and low vision (visual acuity < or = 6/18) was 12.5%. The prevalence of low vision was greatest among the preparatory schoolchildren aged 12+ years. RE was higher among the female students than males (21.4% and 13.6% respectively). Development of a national survey for detection of visual problems for both preschool and school-aged children is recommended.
Topics: Adolescent; Age Distribution; Chi-Square Distribution; Child; Child Welfare; Cross-Sectional Studies; Egypt; Eyeglasses; Female; Health Services Needs and Demand; Humans; Male; Population Surveillance; Prevalence; Refractive Errors; Sex Distribution; Urban Health; Vision Screening; Vision, Low; Visual Acuity
PubMed: 17687830
DOI: No ID Found -
Clinical Ophthalmology (Auckland, N.Z.) 2014To examine the effect of misalignment (decentration and tilt) of intraocular lenses (IOLs) on retinal image quality using a water-immersed model eye with corneal...
PURPOSE
To examine the effect of misalignment (decentration and tilt) of intraocular lenses (IOLs) on retinal image quality using a water-immersed model eye with corneal spherical aberration adjusted to the values found in normal human eyes (spherical aberration 0.25 μm; pupil diameter 6 mm).
METHODS
Three types of IOL holders were prepared. The first was without decentration or tilt, the second had a decentration of 0.5 mm, and the third had a tilt of 5.0°. One spherical IOL and three aspherical IOLs, each with a power of +20 D, were set in the holders and their optical properties (wave front aberration, defocused modulation transfer function, defocused point spread function, and Landolt ring simulations) were compared.
RESULTS
Coma aberrations generated by misaligned IOLs were related to the spherical aberration corrective power of the IOLs. Landolt ring simulations show that the depth of focus increased as spherical aberration increased and that the retinal image quality was degraded by increases in coma aberration.
CONCLUSION
Coma aberration was generated by IOLs with a large degree of spherical aberration correction, leading to reduced retinal image quality when the IOL was misaligned. This suggests that, in a clinical setting, the quality of vision might be improved by reducing the degree of coma aberration using IOLs that retain, or minimally correct, spherical aberration.
PubMed: 25506203
DOI: 10.2147/OPTH.S72053 -
The British Journal of Ophthalmology May 2000To investigate pattern of visual recovery of nine patients with Leber's hereditary optic neuropathy (LHON) and a mitochondrial DNA mutation at 11778.
AIMS
To investigate pattern of visual recovery of nine patients with Leber's hereditary optic neuropathy (LHON) and a mitochondrial DNA mutation at 11778.
METHODS
Recovery was judged significant when a gain of two lines or more in the Landolt ring chart, 10 dB or more improvement of the mean deviation of static perimetry, or improvement of critical flicker frequency (CFF) over 35 Hz was shown.
RESULTS
All three visual functions tested dramatically recovered in one patient. Two other patients exhibited isolated improvement of CFF or visual field, respectively.
CONCLUSION
Partial improvement of visual function may be more widespread than previously recognised in LHON patients with the 11778 mutation.
Topics: Adolescent; Adult; Female; Flicker Fusion; Follow-Up Studies; Humans; Male; Middle Aged; Optic Neuropathy, Ischemic; Prognosis; Vision Disorders; Vision, Ocular; Visual Acuity; Visual Field Tests; Visual Fields
PubMed: 10781521
DOI: 10.1136/bjo.84.5.534 -
Case Reports in Ophthalmology Jan 2014To report a case of choroidal neovascularization secondary to unilateral retinal pigment epithelium dysgenesis (URPED), which was resistant to posterior subtenon...
AIM
To report a case of choroidal neovascularization secondary to unilateral retinal pigment epithelium dysgenesis (URPED), which was resistant to posterior subtenon injection of triamcinolone acetonide (STTA) and intravitreal bevacizumab injection (IVB).
CASE REPORT
An 8-year-old boy was referred to us because of a unilateral unique clinical appearance on funduscopic examination in his left eye (OS). A geometric lesion at the retinal pigment epithelium level of the interpapillomacular area was disclosed OS. The optic nerve was slightly hyperemic OS. Findings from the right fundus examination were normal. Based on these characteristic findings, he was diagnosed as having URPED. Best corrected Landolt ring chart visual acuity (BCVA) was 1.0 in both eyes. Twenty-three months after the first visit, the patient presented with visual disturbance OS. Funduscopic examination showed an expansion of the geometric lesion and the development of a subfoveal choroidal neovascularization (CNV). BCVA was 0.4 OS. Two-time STTA (40 mg/1 ml) was performed at the onset of CNV and 6 months later, and additional IVB (1.25 mg/0.05 ml) was done 10 months later for the treatment of CNV, but the geometric lesion and CNV were resistant to the treatment and continued to expand. Seven years after the first visit, the geometric lesion and the CNV kept expanding steadily.
CONCLUSION
URPED is a rare clinical entity, and the prognosis of this disease is still unclear. The visual prognosis may depend on whether CNV fully develops.
PubMed: 24575036
DOI: 10.1159/000358426 -
The Journal of Physiology Jul 19731. The ability of rhesus monkeys to detect the gap in Landolt ring test-objects that were presented against background luminances between 5 x 10(-5) cd/m(2) and 5 x...
1. The ability of rhesus monkeys to detect the gap in Landolt ring test-objects that were presented against background luminances between 5 x 10(-5) cd/m(2) and 5 x 10(3) cd/m(2) was compared with similar human data.2. At high luminance-levels the acuity of human observers is slightly better than that of rhesus, but rhesus have better acuity at scotopic luminance-levels. Both species have distinct photopic and scotopic acuity functions that cross at 6 x 10(-3) cd/m(2).3. The threshold for light detection is estimated to be the same for both species when specified in quanta incident on the retina.4. It is concluded that the receptor and neural mechanisms that mediate visual-acuity function similarly in rhesus and man, and that the differences in acuity that were measured in the two species may be attributed to optical rather than to physiological factors.
Topics: Animals; Dark Adaptation; Haplorhini; Humans; Light; Macaca; Photometry; Psychometrics; Pupil; Retina; Sensory Receptor Cells; Visual Acuity
PubMed: 4199366
DOI: 10.1113/jphysiol.1973.sp010267 -
PloS One Mar 2011The present study examined the factors that determine the dwell times in a visual search task, that is, the duration the gaze remains fixated on an object. It has been...
The present study examined the factors that determine the dwell times in a visual search task, that is, the duration the gaze remains fixated on an object. It has been suggested that an item's similarity to the search target should be an important determiner of dwell times, because dwell times are taken to reflect the time needed to reject the item as a distractor, and such discriminations are supposed to be harder the more similar an item is to the search target. In line with this similarity view, a previous study shows that, in search for a target ring of thin line-width, dwell times on thin linewidth Landolt C's distractors were longer than dwell times on Landolt C's with thick or medium linewidth. However, dwell times may have been longer on thin Landolt C's because the thin line-width made it harder to detect whether the stimuli had a gap or not. Thus, it is an open question whether dwell times on thin line-width distractors were longer because they were similar to the target or because the perceptual decision was more difficult. The present study de-coupled similarity from perceptual difficulty, by measuring dwell times on thin, medium and thick line-width distractors when the target had thin, medium or thick line-width. The results showed that dwell times were longer on target-similar than target-dissimilar stimuli across all target conditions and regardless of the line-width. It is concluded that prior findings of longer dwell times on thin linewidth-distractors can clearly be attributed to target similarity. As will be discussed towards the end, the finding of similarity effects on dwell times has important implications for current theories of visual search and eye movement control.
Topics: Adult; Female; Fixation, Ocular; Humans; Male; Reaction Time; Visual Perception
PubMed: 21408139
DOI: 10.1371/journal.pone.0017740 -
Case Reports in Ophthalmological... 2017. To report a case of atypical dome-shaped choroidal osteoma, which was diagnosed by histopathological finding of surgically extracted tumor. . A 35-year-old woman...
. To report a case of atypical dome-shaped choroidal osteoma, which was diagnosed by histopathological finding of surgically extracted tumor. . A 35-year-old woman presented with visual field abnormality in the left eye (OS). Her best-corrected visual acuity with Landolt ring chart was 1.0 OS. The funduscopic examination revealed a yellowish dome-shaped choroidal tumor located in the temporal side of the macula with exudative retinal detachment. 25-gauge pars plana vitrectomy and the extraction of the tumor were performed for the definitive diagnosis. . As a result of histopathological finding from the extracted tumor, she was diagnosed with choroidal osteoma. 10 months after the last surgery, the BCVA is 0.7 OS. The tumor is not relapsed. . We must keep in mind that choroidal osteoma can be one of the differential diagnoses for the dome-shaped choroidal tumor.
PubMed: 28396814
DOI: 10.1155/2017/2874823 -
Improvement of visual acuity by spatial cueing: a comparative study in human and non-human primates.Vision Research 2004This study investigated the influence of spatial cueing (valid/invalid/no cue) on visual discrimination in human and non-human primates. We employed a spatial resolution... (Comparative Study)
Comparative Study
This study investigated the influence of spatial cueing (valid/invalid/no cue) on visual discrimination in human and non-human primates. We employed a spatial resolution task which required the accurate discrimination of the orientation of a Landolt "C" ring. The C appeared as single target in specific retinal locations while subjects maintained fixation of a central fixation point. The minimal discernable size of the "C" (=acuity threshold) was determined as a function of cue condition, retinal eccentricity (3 degrees -15 degrees ), and stimulus onset asynchrony (SOA) (200-1100 ms). For both species, we found consistent benefits from spatial cueing with differences in absolute thresholds ranging from 6% to 25%. These differences increased with retinal eccentricity and decreased with longer SOAs. Further experiments performed with humans only, showed that the effect of spatial cueing on visual discrimination is independent of spatial uncertainty, i.e. the number of possible target locations (2 versus 4), but fades with longer target presentation times. From our results we draw the following conclusions. (i) Since sensory noise and spatial uncertainty was small in our tasks, spatial shifts of attention involve signal enhancement in both, human and non-human primates. (ii) The similarity of the results obtained for humans and macaque monkeys indicates that the latter may serve as a suitable model system in studies trying to tackle the neural underpinnings of attentional control. (iii) In order to elicit robust effects on visual discrimination by spatial shifts of attention, a paradigm comprising short SOAs (approximately 200 ms) and target presentation times (approximately 150 ms), and retinal eccentricities larger than approximately 9 degrees seems most promising.
Topics: Adult; Animals; Cues; Female; Humans; Macaca mulatta; Male; Psychophysics; Visual Acuity
PubMed: 15126067
DOI: 10.1016/j.visres.2004.01.009 -
Acta Ophthalmologica Scandinavica Aug 2001To document the effect upon human foveal vision of changes in the level and polarity of figure-ground contrast under photopic controlled test conditions, with particular...
PURPOSE
To document the effect upon human foveal vision of changes in the level and polarity of figure-ground contrast under photopic controlled test conditions, with particular emphasis on performance at low contrast levels.
METHODS
Using a forced-choice psychophysical paradigm, threshold acuity estimates were derived at 9 discrete levels over a near-3 octave contrast range for Landolt ring-type stimuli of either positive or negative polarity. Data were obtained under binocular conditions from 10 young adults, each wearing their optimum low myopic spectacle correction.
RESULTS
Visual acuity declined linearly with reducing stimulus contrast, the deterioration increasing substantially at <10% figure-ground contrast regardless of stimulus polarity. Performance was slightly (but not statistically significantly) better for positive contrast stimuli.
CONCLUSION
Irrespective of contrast polarity, a reduction in stimulus figure-ground contrast <10% produces an accelerated decrement in photopic foveal vision compared to the performance at levels >10%. Some clinical and practical implications of this outcome are considered with regard to the examination of patients with normal and compromised visual function.
Topics: Adult; Choice Behavior; Contrast Sensitivity; Female; Humans; Male; Psychophysics; Vision Tests; Vision, Binocular; Visual Acuity
PubMed: 11453867
DOI: 10.1034/j.1600-0420.2001.079004422.x