Biomedical subjects

S J Dain

Publications and source records attributed to S J Dain.

At least 19 recordsLinked to original sources

PubMed2004

Ultraviolet properties of Australian mammal urine.

The exploitation of predator signals by potential prey is well researched, but relatively little is known about how predators exploit chemical cues (either deliberate signals or waste by-products) produced by their prey. In Finland, the urine of some small rodents ( Microtus spp. and Clethrionomys spp.) is reflective in the ultraviolet range of wavelengths, and diurnal raptors with ultraviolet vision use these urine marks to track their rodent prey. This study examines the potential for such a phenomenon in Australian systems by studying the ultraviolet properties of urine from 13 native and introduced mammal species that are variously preyed upon by raptors. Urine from all 13 species displayed various levels of ultraviolet absorbance in their urine and fluorescence in the ultraviolet range. However, no signs of ultraviolet hyper-reflectance were detected, suggesting that the urine of European voles have unique ultraviolet properties. Ultraviolet-sensitive predators in Australia may be able to distinguish between species based on variation in the ultraviolet absorbance of their urine, but ultraviolet properties did not differ between prey and non-prey species, nor marsupial and placental groups. Moreover, because many natural surfaces are ultraviolet absorbing, it is unlikely that raptors could rely upon the ultraviolet properties of urine to target key prey species.

Animal Communication↗

PubMed2004

Is the perception of brightness different in poor readers?

The transient system deficit hypothesis (TSDH) of specific reading disability [Percept. Psychophys. 40 (1986) 440] remains contentious. As part of a study examining multiple measures of transient and sustained system function, heterochromatic flicker matching (HFM) and brightness matching (HBM) were assessed in 30 poor readers (9.11+/-0.68 years) and 30 age, grade and sex matched controls (9.24+/-0.73 years). HBM and HFM are known to reflect the processing of brightness and luminance information and have been related to the function of magnocellular and parvocellular visual sub-systems. Flicker and brightness matches were determined for blue, green, yellow and red stimuli on Macintosh colour displays using 2AFC and double interleaved random staircases. A ratio of the luminances for brightness and flicker matches represented performance. A significant difference between controls and poor readers in performance for red and blue stimuli was found indicating different visual function in poor readers. While not providing direct support for the transient system deficit hypothesis, this effect implies a mismatch between those achromatic systems that subserve HFM and those more complex mechanisms involved in HBM. The most important aspect of this finding is that poor readers and normal controls could be differentiated on the basis of a paradigm known to be contingent upon magnocellular and parvocellular functioning.

Analysis of Variance↗

PubMed2004

Spatial load factor in prediction of reading performance.

Abstract This study investigated whether there is a relationship between reading age and clinical optometric tests that have varying degrees of spatial loading in their design. Spatial loading in this context is the demand on the visual system to process information about the relative position and orientation of stimuli. A total of 112 children aged 8-11 years were assessed using saccadic eye movement and rapid naming tasks with varying spatial loads. All were subtests of Garzia's Developmental Eye Movement test and Liubinas' SeeRite Reading Diagnostic Programme. Variability in load was achieved by comparing rapid naming of numerals vs the spatially loaded letters p, d, b, q; and by comparing the speed of reading numerals presented in increasingly complex arrays. Reading Age was assessed independently and results were analysed by multiple logistic regression. Spatially loaded naming tasks performed at speed exposed a Spatial Loading Factor which clearly differentiates children at risk with reading.

Age Factors↗

PubMed1999

Assessment of fogging resistance of anti-fog personal eye protection.

The propensity for occupational eye protectors to fog in warm and moist conditions is often offered as a reason by workers not to wear occupational eye protection even where mandatory eye protection areas have been specified. A study of eye protection practices in the New South Wales coal mining industry identified the number one issue in underground coal mine conditions as being fogging of eye safety wear. Conventional anti-fog treatments and cleaners were considered by the miners as completely inadequate in these conditions. At the time of the study claims were being made for a new generation of lens treatments. These merited evaluation. Spectacles and goggles claimed to be fog resistant were obtained from manufacturers and suppliers and subjected to the test set out in BS EN 168 and the compliance criterion of BS EN 166. Some lenses claimed to be fog resistant failed the requirement, some new technology lenses showed arguably superior performance but failed the criterion of the standard. Modifications to the test procedure of BS EN 168 and acceptance criteria of BS EN 166 are proposed.

Coal Mining↗

PubMed1999

Performance of red-green color deficient subjects on the Farnsworth Lantern (FALANT).

BACKGROUND: The Farnsworth Lantern (Falant) is an occupational color vision test intended to identify people with significant red-green color deficiency who are unable to name aviation, marine or railway signal lights correctly. The colors shown are white, green and red selected to be within protan and deutan isochromatic zones. HYPOTHESIS: The Falant grades the severity of color deficiency and identifies subjects with different types of deficiency. METHOD: 270 color deficiency subjects (diagnosed with the Neitz anomaloscope) were examined. A subset of 108 subjects also completed the Farnsworth D15 and the Farnsworth-Munsell 100 hue test. RESULTS: All dichromats and 75% of anomalous trichromats failed the Falant. The mean error score of dichromats was greater than that anomalous trichromats, but errors were made in a similar number of qualitative color naming categories. The range of Falant error scores was continuous with no demarkation between the criteria for pass and fail. It was not possible to identify anomalous trichromats likely to pass the Falant from the size of the anomaloscope matching range or from the results of Farnsworth-Munsell tests. CONCLUSIONS: People with severe red-green color deficiency fail the Falant, but neither the type nor the severity of color deficiency can be determined either from the qualitative results or from the error score.

Aviation↗

PubMed1998

Skewness and transformations of Farnsworth-Munsell 100-hue test scores.

In the past, suggested transformations of Farnsworth-Munsell 100-Hue Test (FM 100-Hue) test scores distributions have been limited to a square root transformation. In this study, the choice of transformations of total error scores (TES) are considered by identifying a possible source of skewness. Several distributions of FM100-Hue Test TES were assessed for skewness (third moment). The error score (ES) distributions for the 85 individual caps in each of the populations were also analysed for skewness (Figs. 3 and 4). There is no single transformation which will normalise all TES distributions. The single cap ES distributions with low mean ES (such as those achieved normals and, for some regions of the test, by anomalous trichromats and dichromats) are symmetrical because most subjects can organise the cap perfectly (and could do even better given smaller colour differences). The distributions of ESs where the mean ES is in the moderate range (such as those achieved by diabetics) are skewed because some ESs at the lower end of the range represent performance which could also be better than the test allows. ES distributions with a high mean (such as random distributions and some regions of the test by congenital dichromats) are symmetrical being unaffected by the limitations of the test. TES distributions of diabetics are asymmetrical and comprise skewed cap ES distributions. A suggestion for a transformation is made.

Color Perception Tests↗

PubMed1998

Daylight simulators and colour vision tests.

Our previous studies have shown that the influence of the illuminating source used for colour vision examination on the intended function of the test is very test dependent, some being relatively unaffected by source characteristics while others can be significantly affected. The effects can even differ between the plates of one pseudo-isochromatic plate test set. In addition, in previous studies we have considered a large range of sources on one test at a time. For this study the emphasis is on four fluorescent tube sources, all of which meet the requirements of the CIE method for assessing the quality of daylight simulators. The colour vision tests include sorting tests (the D-15 tests [Standard, Lanthony Desat and Adams Desat]), the Lanthony New Colour Test and the FM100 Hue Test, pseudo-isochromatic plate tests (Ishihara, Standard Pseudo-isochromatic Plates Volume 1, Hahn New Colour Test and Lanthony Tritan Album) and a matching test (TCU Test). Two examples are quoted here. The tests were assessed on the basis of alignment of the colours of the tests to protanopic and deuteranopic confusion axes and, where appropriate, to the tritanopic confusion axis. The data and analysis indicate that the four fluorescent tubes are essentially equivalent.

Color Perception Tests↗

PubMed1995

Reading-related wavelength and spatial frequency effects in visual spatial location.

Specific deficits in the processing of transient visual stimuli have been identified in reading-disabled children, and it has been shown that the filtering out of some medium to high spatial frequencies and some visible wavelengths impacts on their performance in a number of visual tasks. To assess further how these light diffusing and colour filtering manipulations might mediate visual processing, this study compared the letter-naming accuracy and visual spatial location judgements of eighteen poor readers with those made by eighteen good readers of the same age. Naming and spatial discrepancy measures were recorded for briefly displayed target letters at varying eccentricities, for each child, under a normal (NI) condition and wearing blue (Be), yellow (Yw), diffusion (Dn), blue with diffusion (BeDn), and yellow with diffusion (YwDn) optical framed lenses. A preliminary analysis of the data detected larger spatial discrepancies for the poor readers, and this finding was consistent with the presence of a deficit in transient (or magnocellular) activity in these children. Both the naming accuracy data and the spatial location data showed filter-dependent differences in reading ability. The letter-naming data showed that the addition of the blue filter to the diffusion lens significantly depressed performance only for the good readers, and that the addition of the yellow filter to the diffusion lens significantly improved performance only for the poor readers. Comparison of the spatial discrepancies showed that the rate at which location accuracy declined with increasing target eccentricity was smaller for the blue and yellow lenses than for normal viewing in the case of the good readers but not in the case of the poor readers.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗

PubMed1993

Comparison of the transmittance and coloration requirements of the four national sunglass standards.

There are four national standards on nonprescription sunglasses and two international draft standards at different levels of development and activity. The variation in test specifications and pass/fail criteria among the national standards makes comparisons difficult and agreement on international standards slow. Arguments about the relative stringency of standards may be, as a consequence, ill-informed and self-defeating. In this study I compared the requirements of the four national sunglass standards and then the compliance of 253 sunglass and fashion spectacle lenses with the standards in the erythemal ultraviolet (UV), near UV, luminous transmittance, and coloration. The methods and criteria of the four standards vary quite substantially but the lenses failing to comply are frequently the same. The differences and similarities among the standards are clearly demonstrated. In the erythemal UV, the standards form two pairs in their stringency (Australian and British Standards as against German and U.S. Standards). In the near UV, the British Standard stands out as being more stringent. In the luminous transmittance region there is a basic agreement. In coloration requirements, even though there is extreme variation of methods, these too provide very similar results. The U.S. requirements on signal transmittance do not serve a useful function. Some comments on the differences in labeling requirements are made.

Color↗

PubMed1993

Identification of rigid gas permeable contact lens materials by means of ultraviolet-visible spectrophotometry.

Identification of the material used in an unknown rigid gas permeable (RGP) contact lens is not easily achieved by either manufacturer or contact lens practitioner. It is proposed that the spectral transmittance characteristics in the ultraviolet and visible regions can characterize a material sufficiently to identify it. The characteristics of some materials are discussed and a short double blind trial of the identification system reported. Ultraviolet-visible spectrophotometers are widely available and can be relatively inexpensive. The method is proposed as being a practical reality.

Contact Lenses↗

PubMed1991

Color-mediated contrast sensitivity in disabled readers.

Specific deficits in the processing of transient visual stimuli have been identified in reading-disabled children. It has been suggested that suitably chosen colored filters can assist reading-disabled children but this is controversial. In order to assess how colored lenses might assist a reading-disabled child, we compared contrast sensitivity judgments of 20 disabled readers with those made by 20 good readers of the same age. Contrast sensitivity thresholds were measured over a spatial frequency range of 0.4 to 12.8 cpd. Contrast sensitivity functions were recorded for each child under four different conditions. For each condition the child wore a spectacle frame with a colored filter which had been selected on the basis of the child's best and worst performances on a spatial location task (BEST and WORST), a neutral density optical filter (GRAY), and an untinted filter (CLEAR). The results showed that the best colored filter selected for each of the disabled readers dramatically reduced sensitivity as the spatial frequency moved into the range of printed material (i.e., sensitivity declined sharply from 0.4 to 12.8 cpd). In contrast, there was very little change in sensitivity for the good readers using their best filters. These provocative findings suggest that colored optical filters might improve transient-on-sustained inhibition in disabled readers. It is possible that individually designed filters will provide a way of mitigating the effects of weak transient processing in reading-disabled children. However, our results should not be interpreted as supporting the efficacy of prescribed, colored optical filters as a remediation technique for reading disability.

Child↗

PubMed1991

Colour-mediated grouping effects in good and disabled readers.

Specific deficits in the processing of transient visual stimuli have been identified in reading disabled children. It has, separately, been suggested that suitably chosen coloured lenses can be used to assist reading disabled children but this is controversial. To assess an hypothesis as to how coloured lenses might remediate visual processing, this study compared the visual perceptual grouping effects of eighteen disabled readers with those made by eighteen good readers of the same age. Perceptual grouping effects were obtained for each child under a normal condition and wearing blue, yellow, grey, red and green optical framed lenses. The results replicated previous work in demonstrating a larger grouping effect for the disabled readers, and it was suggested that this finding was consistent with the presence of a transient deficit in these children. Comparison of the grouping effects obtained using the coloured lenses showed that although there was no significant impact on the performances of the disabled readers, the blue lens significantly increased the size of the grouping effect for the good readers. The presence of the blue lens decreased the activity initiated by stimulation of the red and green cones relative to the level of activity initiated by blue cone stimulation. As blue cone initiated activity appears to play little part in the transfer of acuity information, the presence of the blue lens could depress performance in a normal visual system by decreasing the level of acuity information transfer (i.e., the information required for efficient selective attention sorting and minimizing the grouping effect).(ABSTRACT TRUNCATED AT 250 WORDS)

Color↗

PubMed1990

Chromatic, spatial, and temporal losses of sensitivity in multiple sclerosis.

Chromatic, spatial, and temporal losses of sensitivity were measured in 15 eyes of 10 patients with recovered optic neuritis. Chromatic sensitivities (for both red-green and blue-yellow) were measured using color-mixture thresholds; the chromatic sensitivity loss was classified as "selective" if it was significantly greater than the achromatic loss. Spatial and temporal sensitivities were measured with contrast sensitivity functions and flicker modulation sensitivity, respectively; these losses were classified as selective if the losses at high (spatial or temporal) frequencies were significantly greater (or significantly less) than losses at low frequencies. All patients had central fixation and were optically corrected carefully. In 1 eye, selective losses of sensitivity for red-green and blue-yellow were combined with a selective loss of sensitivity at high spatial (but not temporal) frequencies. This type of loss may indicate a selective loss of small axons in the optic nerve. The 8 other eyes that showed significant losses were generally nonselective in their chromatic, spatial, and temporal losses; this may indicate a nonselective loss of small and large axons.

Adult↗

PubMed1990

Comparison of the standard and Adams desaturated D-15 tests with congenital colour vision deficiencies.

The Adams desaturated D-15 was designed to be administered to patients with acquired colour vision defects by simply reducing the chroma of the Munsell colours by 2 for each cap in the test. In this study, the performance of the Adams desat D-15 in the assessment of congenital colour vision deficiencies is evaluated. The standard D-15 and Adams desat D-15 tests were administered to 75 congenital red-green colour deficient subjects who had been diagnosed on the basis of their performance on the Nagel anomaloscope Mark 1. The results were analysed in terms of the directions, extent and specificity of errors and compared with the diagnosis on the Nagel anomaloscope. Of the 13 colour-deficient subjects who made no errors on the standard D-15, 1 failed the Adams desat D-15 and 2 made single crossings. No colour-deficient subject who failed the standard D-15 made anything less than a simple inversion of adjacent caps on the Adams desat D-15. The Adams desat D-15 did not perform as well as the standard D-15 in identification of the type of defect in dichromats. On the basis of these data, it is predicted that about 5% of dichromats will be mis-classified by the Adams desat D-15 whilst under 0.1% will be mis-classified by the standard D-15. However, with the anomalous trichomats, more crossings were made on the Adams desat D-15, particularly by the milder anomals, and a diagnosis was possible in more cases. Where a diagnosis was possible, it was also correct more often with the Adams desat D-15.(ABSTRACT TRUNCATED AT 250 WORDS)

Color Vision Defects↗

PubMed1988

Postural modifications of VDU operators wearing bifocal spectacles.

This paper describes the postural changes experienced by presbyopic operators of VDU workstations while wearing a pair of bifocal spectacles. All operators reported in this paper had suffered neck and back aches, in addition to generalised problems of asthenopia, while using the VDU workstation. The ages of the operators ranged between 47 and 58 years. The operators' head movements, in looking from the keyboard to the screen, were two to three times greater when bifocal spectacles were worn compared with specially prescribed single-vision occupational spectacles. There were also greater movements in the flexion of the wrist and elbow while using bifocal spectacles and looking from the keyboard to the screen. There was no relationship between the amount of head movement and the position of the bifocal reading segment with respect to the operators' pupil. It was concluded that the symptoms reported by these presbyopic operators were due to static loading of the muscles in the neck and back, induced by the use of bifocal spectacles.

Journal Article↗

PubMed1988

Symptoms in VDU operators.

The investigation of the role of visual and ocular characteristics of visual display unit (VDU) operators in the causation of subjective visual fatigue has not been reported previously. A retrospective study in which the visual and ocular characteristics of symptomatic and asymptomatic VDU operators was carried out in order to determine whether such a relation could be demonstrated. Three groups totaling 1013 VDU operators from two semigovernment organizations were assessed using either a full eye examination or a modified clinical screening technique. Before examination, the operators completed a short questionnaire on the symptoms they experienced when using VDU's. Significant differences between the symptomatic and asymptomatic operators in some groups were found for over-refraction (spherical equivalent and cylindrical) and near horizontal heterophoria. Despite the existence of this relation, no basis for valid visual standards could be established. In particular, no basis was found for the automatic prescribing of low plus corrections and, in the absence of clearly definable visual standards, the involvement of clinical judgment in the assessment of operators was found to be necessary.

Adolescent↗

PubMed1988

Identification of polarity in FM 100-Hue plots: a comparison of methods.

Several methods which have been proposed to aid the identification of polarity in Farnsworth-Munsell (FM) 100-Hue test plots are described. The assumptions which underlie one type of method are discussed and problems identified. Two methods are taken as representative of the two types of analysis and their performance compared on plots from congenital and acquired color defectives. The key difference between the two methods and the types of method which they represent lies in the imposition of symmetry on the plot. From the performance of 200 diabetic subjects, the problems created by the presence of monopolar plots, plots with unequal magnitudes of errors in the two poles of bipolar plots, and plots in which the two poles are not diametrically opposite are highlighted. It is concluded that the simpler type of analysis is sufficient and retains more information.

Color Perception↗

PubMed1988

Performance of the standard pseudoisochromatic plate test.

The Standard pseudoisochromatic Plate (SPP) test was administered to 346 normals, 55 anomalous trichromats, and 46 dichromats. Its ability to detect and classify congenital color defectives was assessed. The performance of each plate was assessed separately and compared with its colorimetric properties. The test as a whole achieves a high level of accuracy in separating normals from color vision defectives [Youden's Index (YI) = 92.4%] and a high reliability (71.3%) in classification of the congenital color vision defectives. The performance of individual plates in separating color normals and color vision defectives of individual plates varies (YI ranges from 69.8 to 86.1%). A set of three plates can be chosen, which achieves a performance similar to that of the whole test. The test is found to be a reliable clinical screening method for congenital red-green color vision defectives.

Color Perception Tests↗