Biomedical subjects

Jonathan S Pointer

Publications and source records attributed to Jonathan S Pointer.

6 recordsLinked to original sources

PubMed2005

An enhancement to the Maddox Wing test for the reliable measurement of horizontal heterophoria.

PURPOSE: To attempt to improve the reliability of the Maddox Wing (MW) test for the measurement of horizontal heterophoria at near. METHODS: Horizontal heterophoria measurements at 30 cm using the MW instrument were made on a group of 58 normally-sighted binocular young adult subjects. The procedures were repeated at each of five weekly visits. The standard tangent scale card provided by the instrument's manufacturer was used as the control condition vs four alternative cards designed to enhance accommodative stimulation and improve operational reliability. RESULTS: A statistically-similar mean near phoria value was recorded using each of the five cards. However one of the alternative card designs produced a small but statistically significantly less variable result than the others: this design featured a much smaller typeface (4pt) than that used for the digits on the standard card, and the horizontal row of numbers was flanked by two periods of a low spatial frequency (< 2 c deg(-1)) square wave grating. CONCLUSIONS: It is suggested that for improved reliability of near phoria measurement when using the MW instrument a more appropriately detailed design of tangent card would promote enhanced accommodation, an operational consideration likely to be especially relevant when examining children.

Accommodation, Ocular↗

PubMed2004

A novel visual analogue scale (VAS) device: an instrument based on the VAS designed to quantify the subjective visual experience.

PURPOSE: To evaluate a novel device intended to facilitate the direct quantification of the subjective visual experience. The design principle is based on that of the visual analogue scale (VAS) technique but obviates the need for subsequent measurement unlike the administration of the conventional paper VAS. METHODS: The visual experience of 134 normally sighted 17-40-year-olds was quantified using (in randomised sequence) a paper VAS and the novel VAS device. A notional 100-point scale was utilised in either case, and the extreme descriptive anchors for both instruments were 'dreadful' and 'perfect'. RESULTS: The degree of clinical agreement between the two alternative VAS techniques was very high. A small bias (mean = +0.7 VAS units: 95% confidence interval 0.3-1.2 units) towards the paper VAS was evident in these data, an outcome of no clinical significance or impediment as regards the substitution of the novel device for the conventional paper-based approach. CONCLUSIONS: The moving of a bead along a wire is shown to be a clinically and statistically reliable alternative procedure to the pen-marking of a conventional paper VAS for the evaluation of the recent subjective visual experience, provided that the same minimum/maximum descriptive anchors are used for either instrument. The instant quantification of the VAS score afforded by the novel technique introduced here broadens the potential clinical application of this technique.

Adolescent↗

PubMed2004

Clinical characteristics of unilateral myopic anisometropia in a juvenile optometric practice population.

PURPOSE: A retrospective study of longitudinal case histories, undertaken to establish the clinical and statistical characteristics of unilateral myopic anisometropia (UMA) amongst the juvenile and adolescent population at an optometric practice, is reported. UMA was defined as that specific refractive state where an unequivocally myopic eye is paired with a 'plano' [spherical equivalent refraction, (SER) = +/-0.25 Dioptres (D)] companion eye. METHODS: The clinical records of all patients aged <19 years on file at an established independent optometric practice were categorised as 'myopic' (SER < or =-0.50 D), 'hypermetropic' (> or =+0.75 D) or 'emmetropic' (> or =-0.37< or =+0.62 D). Subsequently all juvenile patients matching the UMA criterion, together with a case-matched group of bilaterally myopic individuals, were selected as the comparative study populations. RESULTS: A total of 14.4% (n = 21 of 146) of the juvenile myopic case histories were identified as cases of UMA. More than half of these UMA cases emerged between the ages of 11.5 and 13.5 years. There was a marked female gender bias. The linear gradient of the age-related mean refractive trend in the myopic eye of the UMA population was not statistically significantly different (p > 0.1) to that fitted to the ametropic progression recorded in either eye of the case-matched population of young bilateral myopes; uniquely the slope associated with the companion eye of UMA cases was statistically significantly (p < 0.025) less steep. Compared with bilateral myopes fewer cases of UMA required a refractive correction to relieve visual or asthenopic symptoms, and this initial correction was dispensed on average 1 year later (at age 12.7 years) in UMA patients. CONCLUSIONS: Individuals identified as demonstrating clinically-defined UMA can be considered as distinct but functionally normal cases on the continuum of human refractive error. However, any unilaterally-acting determining factor(s) underlying the genesis of the condition remain obscure.

Adolescent↗

PubMed2003

Border distinctness in amblyopia.

On the basis of the contrast sensitivity loss in amblyopia which mainly affects higher spatial frequencies, one would expect amblyopes to perceive sharp edges as blurred. We show that they perceive sharp edges as sharp and have veridical edge blur perception. Contrary to the currently accepted view, this suggests that the amblyopic visual system is not characterized by a blurred visual representation.

Amblyopia↗

PubMed2003

Evaluating the visual experience: visual acuity and the visual analogue scale.

PURPOSE: To attempt a comparison of the visual experience [assessed using a visual analogue scale (VAS)] with visual acuity in a group of normally-sighted adult optometric patients. METHODS: A single-item 100 mm paper VAS was administered to a sequence of 142 normally-sighted pre-presbyopic patients. Each individual was invited to indicate their recent subjective distance visual experience between the extremes of 'dreadful' (0 mm) and 'perfect' (100 mm). Each patient's binocular visual acuity was then determined at 6 m using a high-contrast logMAR chart under usual consulting room conditions. RESULTS: A weak association was revealed between the subjective indication of recent visual experience and the actual level of binocular acuity recorded in this normally-sighted group of subjects. On the basis of group responses a statistically significant discontinuity in the scores recorded with the VAS was demonstrated between patients who attained a clinical acuity better or worse than 0.10 logMAR units (6/7.5). Patient gender, age, and whether spectacles were habitually worn for distance viewing, were each revealed to be not statistically significant features. CONCLUSIONS: For normally-sighted optometric patients the subjective criterion of visual satisfaction would appear to be only loosely associated with the contemporaneous record of clinical acuity.

Adult↗

PubMed2002

Gender-related optical aspects of the onset of presbyopia.

Evidence is presented which substantiates the frequent clinical impression that female optometric patients require their first reading prescription at a slightly earlier age than males. Furthermore newly presbyopic females require an initial add of slightly greater magnitude than age-matched males. A high (>+1.50 D) first add requirement is revealed as a predominantly male characteristic, an outcome attributable essentially to their often relatively later age of presentation for an initial presbyopic refractive examination.

Age of Onset↗