PubMed Health⌕ Search

Biomedical subjects

M J Moseley

Publications and source records attributed to M J Moseley.

At least 37 records · Page 2Linked to original sources
PubMed1997

Graphical representation of visual acuity data.

Accurate graphical depiction of data requires that distances between points map precisely to the quantitative differences they represent. In the case of Snellen visual acuity, consecutive line sizes do not generally correspond to equal increments in visual angle, hence scores plotted against axes marked off in equal intervals provide a false representation of the relation between plotted values. A worked example illustrates the nature of this problem and its solution.

Humans↗
PubMed1996

Does stereopsis matter in humans?

Stereopsis has been one of the most popular fields of vision research for well over a century and is routinely measured in clinical practice, yet its functional significance has been largely neglected. Stereopsis is disrupted by blur, amblyopia and strabismus and is of potential value as a means of indirect screening for visual disorders in childhood. However, evidence for the functional effects of stereoscopic deficits is sparse. Recent investigations indicate that binocularity is an advantage in certain tasks, especially in the comprehension of complex visual presentations and those requiring good hand-eye coordination. The assumption derived from the evolutionary theory that stereopsis represents an adaptation by primates to arboreal life needs to be questioned. While the functional aspects of stereopsis are still not fully understood the direction that future research should take to unravel this important issue is apparent.

Adult↗
PubMed1996

Development of pupillary responses to grating stimuli.

Pupillary responses to stationary, achromatic sine wave gratings were measured in adults and in 1- and 3-month-old infants. Measurements of behaviourally determined contrast sensitivity were also obtained from the infant subjects. Contrast sensitivity functions were typical of those previously described: band-pass in nature with sensitivity increasing markedly with age. The pupil grating response amplitudes also exhibited a spatial frequency and age dependence similar to that observed for contrast sensitivity. These findings provide further evidence that the neural mechanisms which underlie visual sensitivity to contrast also mediate pupillary responses to spatial structure.

Adult↗
PubMed1996

Reliability of visual acuity in children with reduced vision.

We examined the test-retest reliability of visual acuity in 18 children referred to the Hospital Eye Service with reduced vision. Unaided distance acuities were recorded, using logarithmically scaled letter charts, on two occasions separated by an interval of one week during which no clinical intervention took place. Coefficients of repeatability were found to be +/- 0.25 and +/- 0.21 log units in left and right eyes, respectively. A further analysis of 14 subjects' data each of whom had one eye with consistently poorer acuity in both test sessions yielded coefficients of repeatability of +/- 0.15 and +/- 0.22 log units in, respectively, the better and poorer eyes. The reliability of visual acuity recorded in the better eye closely approximates to that previously found in normal adults, whilst that of the poorer eye appears more comparable to that of adult clinical populations.

Child↗
PubMed1995

Compliance in amblyopia therapy: objective monitoring of occlusion.

AIM/BACKGROUND: This study aimed to determine the feasibility of objective compliance monitoring of amblyopia therapy in clinical research. Occlusion has been the mainstay of amblyopia therapy for over 250 years, yet it has never been subjected to rigorous evaluation. Treatment regimens range arbitrarily from a few minutes to most of the waking hours of the day. Compliance is problematic and as, hitherto, accurate objective monitoring has been impossible it is not known how much occlusion is required to effect an improvement in vision. METHODS: An occlusion dose monitor (ODM) has been developed. The ODM consists of a modified occlusion patch and a miniature battery driven datalogger which periodically monitors patch skin contact. The patch is a standard disposable item with two miniature electrocardiogram electrodes attached to its undersurface. The datalogger comprises a high speed static RAM and a clock driven address counter. Data are retrieved using an IBM PC/AT computer. Fifteen child amblyopes were randomly allocated unilateral occlusion of 1, 4, or 8 hours per day for 4 weeks. Owing to data loss, presumed because of accumulation and discharge of static electricity, an additional child was included in the 8 hour group. Outcome measures were objective (ODM) and subjective (diary) compliance with treatment, logMAR visual acuity, and contrast sensitivity. RESULTS: Objective monitoring of occlusion is technically feasible and clinically informative. CONCLUSION: Objective monitoring of occlusion has opened up new research opportunities which, it is hoped, will enable the dose-effect relation of occlusion therapy in the various types of amblyopia to be investigated objectively, and facilitate the design of effective therapeutic regimens.

Amblyopia↗
PubMed1994

Reliability of the Cambridge Low Contrast Gratings.

We examined the reliability of the Cambridge Low Contrast Gratings over four sessions at intervals of 1 hour, 1 day and 1 week. The 95% ranges of difference scores were found to be +/- 10.3 and +/- 10.5 test units for left and right eyes respectively. These reliability estimates span almost one-quarter of the test's dynamic range and one-third of the subjects' performance range. Practice effects were not found to be significant. Though previous reports have emphasized the usefulness of the Cambridge Gratings in screening for eye disease, caution is advised when interpreting changes that occur over time.

Adolescent↗
PubMed1994

Analysis of method-comparison data.

Method-comparison studies, in which new 'candidate' techniques are compared with an established 'gold standard', feature commonly in optometric research. Investigators often analyse their findings using least squares regression, Pearson's product-moment correlation coefficient and the paired t-test. We describe more appropriate methods which include: the 'limits of agreement', the intraclass correlation coefficient, and Deming's method for estimating a straight line fit. Comparisons between methods are made with the aid of a computer simulation. Computer program listings are provided to assist in implementing the analyses.

Computer Simulation↗
PubMed1994

Binocular inhibition of visual performance in patients with cataract. The influence of test reliability.

Patients with cataract may show binocular inhibition: their sight improves on closing the eye in which vision is poorer. Of 36 patients questioned, one-third reported this to be the case. To quantify this phenomenon, all patients undertook a battery of tests of spatial visual performance and, in an attempt to define the reliability of their scores, were tested on two separate occasions. Patients generally performed inconsistently: at best, of 8 patients who demonstrated inhibition on a single test, only 5 did so again when re-tested after a short interval. In general, the magnitude of inhibition was less than that which could be reliably detected using the test battery. In addition, self-reported inhibition was not predictive of inhibition measured psychophysically. It is concluded that clinical tests of form vision lack either the necessary reliability or sensitivity to identify patients with cataract who report inhibition of binocular visual function.

Aged↗
PubMed1994

Visual acuity and pupillary responses to spatial structure in infants.

PURPOSE: To determine the age of onset of the pupil grating response (PGR). To compare estimates of resolution acuity obtained by pupillometric and behavioral methods in early infancy. METHODS: Dynamic infrared pupillometry was undertaken on 19 newborn infants while they fixated a uniform background upon which a 0.1 c/deg sine wave grating was briefly presented. Pupillary responses were also recorded to an increment in luminance of a spatially homogeneous target. Longitudinal measurements of PGRs were obtained from a subset of eight infants between 3.5 and 38 weeks of age. In this group, behavioral estimates of visual resolution obtained using the acuity card procedure were compared with the highest spatial frequency grating to elicit a PGR. RESULTS: When presented with the pattern stimulus, newborn infants did not show any pupil reaction indicative of a PGR. This finding could not be attributed to immaturity of pupillomotor function: All infants showed marked pupillary construction to diffuse light stimulation. By 1 month of age, pupillary responses to pattern stimuli were reliably present. For these and older infants, the spatial frequency of the finest grating to elicit a PGR was comparable to the behaviorally determined resolution threshold: mean difference (+/- 95% confidence interval) = 0.28 +/- 0.23 octaves. CONCLUSIONS: A PGR could not be detected in newborn infants. From 1 month of age, responses to spatial structure can provide objective estimates of visual acuity comparable to those determined by established methods.

Age of Onset↗