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Results for “refractive error”

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At least 577 records · Page 32Linked to original sources
PubMed1987

Uncorrected refractive error among a hospital population.

Patients admitted for general medical care to a North London Hospital were screened using a pinhole disc in conjunction with their usual visual aid. One third of the group showed significant improvement in visual acuity, suggesting a change in refractive correction was necessary. These people were not more likely to have had less recent eye examinations or to complain of poor vision. They were more likely to be over 50 years old, have poor mobility, to have no idea of cost of change in refractive correction and to subjectively note improvement in vision with pinhole disc.

Adolescent↗
PubMedDate not supplied

[The incidence of refractive errors in strabismus with an early onset].

The paper represents one study effected at a number of two hundred and fifty children under three years old, examinated in Ophthalmological Clinic between 1992 and 1995. It was examinated strabismic deviation, visual acuity, state of binocular-eyesight refraction. Most of children (59%) present to hypermetropia under three dioptry; 23.3% medium hypermetropia (3-6 dioptries). Little percentage under 10% present others refraction vices: big hypermetropia, astigmatism, anisometropia, myopia. After optic correction and occlusion, most of deviations remained unaltered requiring surgical subsequent correction. This fact certifys the preponderence of neurogenic pathogenesis and not adjustment in strabismus with precocious debut.

Age Distribution↗
PubMed2005

Paired observations of refractive error after cataract surgery.

PURPOSE: To quantify the design effect if pairing between eyes is ignored when reporting refractive outcome following cataract surgery. METHODS: A retrospective review was conducted of biometry prediction error in 612 patients who had bilateral phacoemulsification with intraocular lens (IOL) implantation. The levels of uncertainty (confidence interval and variance) of the estimates for the biometry prediction error were compared when intra-cluster correlation between ocular measurements of paired eyes within each patient was either taken into account or ignored. The design effect (the ratio of the two variances) was calculated. RESULTS: The correlation between the two eyes was weak, as indicated by the intra-cluster correlation coefficient of 0.22 (confidence limits 0.15-0.30). The mean biometry prediction error was 0.73 dioptres (D) and the 95% confidence limits for the mean in the two situations were similar at 0.69-0.76D and 0.69-0.77D, respectively. The variance of the biometry prediction error if pairing of eyes was ignored (0.00033D) was slightly less than if pairing was taken into account (0.00041D). This yielded a design effect of 1.2. CONCLUSIONS: A high correlation between data collected from pairs of eyes is not inevitable. If data on both eyes are used to estimate biometry prediction error, the usual statistical procedures will underestimate the standard errors and the variance, but the effect will be trivial and the confidence intervals only negligibly smaller. The maximum variance is expected to be 1.2 times higher than that given by simple statistical methods that ignore the pairing of eyes.

Biometry↗
PubMed1977

Maturation of evoked potentials and visual preference in 6-45-day-old infants: effects of check size, visual acuity, and refractive error.

Visual evoked potentials (VEPs) and the percentage time fixated (PTF) were investigated in response to checkerboard light flashes in 10 human infaed as a function of the size of check in the evoking stimulus (diffuse light, 11, 22, 45, 90 and 180 min of arc), the refractive lens strength the checkerboards were viewed through (-6 to +6 diopters), and the age of the infants (6-26 or 27-45 days). Check size significantly influenced VEP amplitude in infants as young as 6 days. The 11' checks evoked greater responses that diffuse light suggesting a visual acuity of better than 20/220. Only the 27--45-day-olds behaviorally discriminated the checks, PTF indicating an acuity of 20/120. Evoked potential refraction with spherical lention between VEP amplitude and check size measured from different VEP components at different ages indicated the function contained two modes or components. The first mode was inverted "U-shaped" and was obtained in response to check sizes less than 45'. It was primarily due to changes in amplitude of the early VEP components (less than 210 msec after the evoking stimulus) and was poorly correlated with the behavioral PTF measure. It was proposed that this mode reflected subcortical activity. The second mode was a linear increase in amplitude as check size was increased from 45' to 180'. It was primarily due to changes in the amplitude of late VEP components (240--400 msec after the evoking stimulus) and was highly correlated with the percentage time the infants fixated the various check sizes. It was proposed that this mode reflected cortical activity. Age selectively influenced the late VEP components and the PTF behavioral measure, these measures being influenced by check size only in the 27--45-day-old infants. This change in responsivity of late VEP components and the transition from passive to more active and discriminating visual preference, suggest the onset of increased cortical function between 28 and 45 days of age.

Age Factors↗