Teaching modification to the Bausch and Lomb Autoplot.
Explore the source record for details and available documents.
Electronics↗
Biomedical subjects
D B Henson
Publications and source records attributed to D B Henson.
Evaluation of the Friedmann Visual Field Analyser Mark II. Part 1. Results from a normal population.
Normal subjects when examined with the Friedmann Mark II Analyser often miss stimuli in the extreme (greater than 20 degrees) superior field and in the arcuate regions. The majority of misses in the superior field are believed to result from the subjects' eyelashes acting as partial occluders. The misses in the arcuate region are believed to be the result of the retinal blood vessels. Isolated missed points at 0.8 or more log unit above threshold were found in 9% of the subjects, which means that it is 13 times more likely that an isolated missed point comes from a normal subject than a glaucomatous one (the incidence of glaucoma is taken as 0.7% of the total population). Clusters of two missed stimuli in the arcuate region at 0.4 and 0.6 log unit above threshold were found in 8% and 0% of the population. Clusters of three missed stimuli in the arcuate region were found in 0.7% of the population. It is suggested that isolated missed stimuli should be retested with the eccentric fixation point.
Evaluation Studies as Topic↗
Evaluation of the Friedmann Visual Field Analyser Mark II. Part 2. Results from a population with induced visual field defects.
The Friedmann Visual Field Analyser Mark II is evaluated with a group of 301 normal eyes, 155 of which had an induced visual field defect. Measures of sensitivity and specificity are calculated from these data by criteria similar to those used by other researchers. The inadequacies of using pass/fail criteria in the clinical situation are discussed, and a solution is proposed in which each field response is scored and the score compared with those from normal and defective populations. An example is given of how this form of analysis could be incorporated into the clinical situation.
Evaluation Studies as Topic↗
Effect of orthoptics upon the ability of patients to adapt to prism-induced heterophoria.
In a previous study we showed that subjects with abnormal binocular vision either lacked or had a deficient ability to adapt their oculomotor systems to a prism-induced heterophoria. In this study we report on the results of an experiment designed to establish whether the adaptation ability improves in patients who are successfully treated, by means of orthoptics, for convergence insufficiency. In all seven patients examined, we found an improved ability to adapt. Whereas at the beginning of the experiment only two patients fell within the 95% confidence limits of the norm, at the end five patients fell within these limits. These results demonstrate that the success of orthoptics in relieving symptoms is associated with an improved ability to adapt to prism-induced heterophoria.
Adaptation, Ocular↗
Oculomotor adaptation to induced heterophoria and anisometropia.
In the first part of the paper we demonstrate that the oculomotor system adapts to prism-induced heterophoria over limited motor fields. In the second part we demonstrate that it can also adapt to an induced anisometropia. When normal subjects are made 3 diopters anisometropic, they initially exhibit a phoria whose magnitude is dependent on eye position. After 21/2 hr of binocular visual experience, this incomitant phoria has largely disappeared.
Adaptation, Physiological↗
Adaptation to prism-induced heterophoria in subjects with abnormal binocular vision or asthenopia.
In a previous study we investigated how normal subjects adapted to prism-induced heterophoria. In this study we have continued this work by investigating this phenomena in 15 patients with abnormal binocular vision and/or asthenopia. It was found that the majority of subjects lacked or had a deficient adaptation system to base-in and/or base-out prisms, but all except two subjects examined adapted normally to vertical prism. These results suggest that it may be possible to treat the horizontal adaptation system independently from the vertical one. Prism vergences, heterophoria measurements, and the presence of fixation disparity gave little indication of the adaptation ability of the subjects. Symptoms correlated well with adaptation ability.
Accommodation, Ocular↗
The effect of anoxia on the human corneal epithelium.
After 6 hr of oxygen deprivation, the human corneal epithelium had not swollen. Over the first hour of recovery from anoxia, the epithelium shrank by up to 20% before returning toward its predeprivation thickness. No fluorescein staining of the epithelium was seen during these experiments, but some subjects were able to discern halos immediately after deprivation. We conclude that homeostasis is maintained in the corneal epithelium for up to 6 hr of anoxia, but the intercellular spaces may be altered.
Adult↗
Adaptation to prism-induced heterophoria.
Measurements of the way the oculomotor system adapts to prism-induced heterophorias have been made in eight normal subjects. Adaptation to 2 delta vertically and, on separate occasions, to 6 delta horizontally was found to be substantially completed after only 2-3 minutes of binocular visual experience. The form of the adaptive process for distant targets was asymmetrical in the horizontal meridian, being faster after the insertion of 6 delta base-out than for 6 delta base-in. This asymmetry largely disappeared for near vision.
Adaptation, Physiological↗
Depth perception in strabismus.
The monocular and binocular depth thresholds of strabismic subjects have been measured with a modified Howard-Dolman apparatus. Seven out of the 14 strabismic subjects tested were found to have binocular thresholds significantly higher than their monocular ones. These strabismic subjects all had small angles of deviation less than 8 prism dioptres and high acuities in both eyes.
Adolescent↗
Investigation into corrective saccadic eye movements for refixation amplitudes of 10 degrees and below.
Explore the source record for details and available documents.
Eye Movements↗
Normative and clinical data with a new type of dark adaptometer.
Dark adaptation has been measured with a new type of dark adaptometer in a group of 25 normal subjects, and in a group of 10 patients suffering from a variety of retinal pathologies. The results indicate that this instrument is capable of distinguishing between normal and pathological dark adaptation on the basis of data obtained in two clinical samples.
Adult↗
Measurement of corneal sensitivity and thickness with PMMA and gas-permeable contact lenses.
Corneal sensitivity and thickness were measured in nine subjects. Two different types of hard contact lenses were fitted to each subject; a traditional polymethylmethacrylate (PMMA) lens on one eye and a gas-permeable cellulose acetate butyrate (CAB) lens on the other eye. Corneal sensitivity did not differ significantly between the two eyes after 6 and 10 hr of wear, but PMMA lenses tended to induce slightly more corneal edema than CAB lenses. As oxygen tension behind such contact lenses is different, whereas mechanical stimulation is nearly the same, this would appear to support the view that corneal sensitivity changes are related to mechanical stimulation. However, careful scrutiny of the data does not support this view unequivocally, and other suggestions are made.
Acetates↗
Dark adaptation in diabetes mellitus.
The effect of diabetes mellitus on the normal dark adaptation curve is investigated. It has been found that diabetic patients take longer to adapt and that their absolute thresholds are raised. The degree of elevation in the final threshold correlates with the duration of diabetes.
Adolescent↗
Corrective saccades: effects of altering visual feedback.
Explore the source record for details and available documents.
Eye Movements↗
A new dark adaptometer.
A dark adaptometer that was designed for student-laboratory use is described and advocated for use in optometric practice because of its simplicity, accuracy, and low cost. Representative dark-adaptation results obtained from 2 naive and 2 sophisticated subjects are presented.
Dark Adaptation↗