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PubMed2002

The future of medical computing.

The practice of medicine is inherently dependent upon health technology. Clinicians use a wide variety of technologies in diagnosing, treating, and assessing the care of their patients. In this book, The Future of Health Technology, many different aspects of health technology are discussed in detail. Considering this breadth of coverage, it is challenging to ascertain what remains to be discussed in this chapter on "the future of medical computing". Given this considerable coverage, this chapter will open with a brief vision of the future of medical computing from three perspectives--the Patient, the Ambulatory Provider, and the Hospitalist. Discussion follows on the current and future driving forces for change in healthcare technology, and an overview of the unresolved issues that must be addressed. Necessarily, this chapter will not provide more than an overview of these topics and issues. Rather, it is the author's intent to present several visions of the future of medical computing and outline the issues, which must be overcome to achieve the vision.

Ambulatory Care↗
PubMed2000

Coats' syndrome: long term follow up.

AIM: To increase the understanding of the long term results in pseudo-retinoblastoma eyes with infantile Coats' syndrome. METHODS: This study design was a retrospective case review. 10 patients were analysed who were initially referred with a diagnosis of retinoblastoma but had Coats' syndrome on the basis of ocular oncological evaluation. Vision, fundus photography, ultrasonography, and computed tomography scans were obtained and evaluated. Changes in vision and retinal status were measured. RESULTS: The initial age at presentation was 2.4 years (range 0.25-4 years). All patients had retinal detachment at diagnosis. Nine of 10 retinas were reattached after various treatments. Reattached retinas had closure of peripheral telangiectasia and visible intraretinal crystals. Vision was dismal. At last follow up (mean 8.8 years), only two patients had 20/400 or better visual acuities. Five eyes had no light perception despite early treatment to reattach the retina. Nine of 10 eyes remain cosmetically acceptable. One patient wore a cosmetic shell. CONCLUSIONS: Long term results indicate that these eyes can be salvaged and the retina reattached but the visual outcome is poor.

Child, Preschool↗
PubMed1995

Characteristics of visual display units that may cause visual difficulties.

The physical characteristics of a visual display unit (VDU) are compared to those of paperwork, through a review of the literature. Certain display characteristics are shown to enhance visual performance using a VDU whilst others significantly decrease it when compared to using hard copy. Overall, display characteristics do not necessarily render VDU use more difficult than if doing similar visual tasks without using a VDU.

Accommodation, Ocular↗
PubMed2002

Multi-modal estimation of collinearity and parallelism in natural image sequences.

In this paper we address the statistics of second-order relations of feature vectors derived from image sequences. We compute the individual vector components corresponding to the visual modalities orientation, contrast transition, optic flow, and colour by conventional low-level early vision algorithms. As a main result, we observe that collinear (or parallel) line pairs are, with very great likelihood, also associated with other identical features, for example sharing the same flow pattern, or colour or even sharing multiple feature combinations. It is known that low level processes, such as edge detection, optic flow estimation and stereo are ambiguous. Our results provide support for the assumption that the ambiguity of low level processes can be substantially reduced by integrating information across visual modalities. Furthermore, the attempt to model the application of Gestalt laws in computer vision systems based on statistical measurements, as suggested recently by some researchers (Krüger N 1998 Neural Process. Lett. 8 117-29; Elder H and Goldberg R M 1998 Perception Suppl. 27 11; Sigman M, Cecchi G A, Gilbert C D and Magnasco M O 200.1 Proc. Natl Acad. Sci. USA 98 1935-49; Geisler W S, Perry J S, Super B J and Gallogly D P 2002 Vis. Res. 41 711-24), gets further support and the results in this paper suggest formulation of Gestalt principles in artificial vision systems in a multi-modal way.

Artificial Intelligence↗
PubMed2005

Ophthalmic complications of dental anesthesia: three new cases.

Two patients had ipsilateral optic neuropathy and one patient had an ipsilateral abduction deficit and a dilated, poorly reactive pupil immediately after anesthesia of upper alveolar teeth. In one patient with optic neuropathy, the optic disc was not swollen, brain and orbit computed tomography (CT) was negative, and vision recovered completely within 2 weeks. In the other patient with optic neuropathy, the optic disc was swollen, brain and orbit CT were negative, and vision did not recover. In the patient with ductional and pupil deficits, recovery was complete within 24 hours. Since 1960, 39 cases of ophthalmic complications have been reported in the English literature. A majority have followed anesthesia of upper alveolar teeth. In all but three cases, the deficits were temporary. Diffusion, inadvertent needle penetration into the orbit, venous injection, or retrograde arterial injection is postulated as the mechanism by which the anesthetic agent reaches the cavernous sinus or orbit to cause the deficits.

Adult↗
PubMed1994

Luminance noise and the rapid determination of discrimination ellipses in colour deficiency.

A computer-controlled test of colour vision is described, in which luminance noise and masking contours are used to ensure that the subject's responses depend on chromatic signals. The test avoids the need--common to most computer-controlled tests--to define equiluminance for the individual subject before the colour test itself can be administered. The test achieves a good separation of protan and deutan subjects and reveals the large range of chromatic sensibilities among anomalous trichromats. As a population, dichromats had higher thresholds on the tritan axis of the test than did normals. In an extension of the test, full discrimination ellipses were measured for normal and colour-deficient observers. The nature of anomalous trichromacy is discussed and the possibility is raised that hybrid genes, resulting from genetic recombination, may code for incorrectly labelled or functionally impaired molecules.

Adolescent↗
PubMed1997

Partial reversal of protan and tritan colour defects with inhaled oxygen in insulin dependent diabetic subjects.

AIMS: Abnormalities in colour perception occur early in the development of diabetic retinopathy. Whether these changes can be influenced by increasing circulating oxygen saturation was studied in comparison with non-diabetic controls. METHODS: Protan and tritan colour thresholds were measured using a computer graphics system in 37 insulin dependent diabetic subjects, with no or minimal background retinopathy, and 27 matched controls. Colour thresholds were performed after subjects inhaled either gaseous air or 100% oxygen for a minimum of 5 minutes. RESULTS: Diabetic subjects had higher colour vision thresholds when inhaling air when compared with controls (protan (mean 3.93 (SEM 0.39), v 2.36 (0.16), p < 0.0002) and tritan (8.15 (0.62) v 5.42 (0.31), p < 0.002)). The colour vision thresholds observed in diabetic subjects inhaling air fell when they inhaled oxygen (protan (3.93 (0.39) v 3.57 (0.33), p < 0.025) and tritan (8.15 (0.62) v 7.35 (0.59), p < 0.005)). No fall in colour thresholds was seen in non-diabetic controls who inhaled oxygen. CONCLUSION: A small improvement in the colour vision thresholds was observed using computer graphics in diabetic subjects, with minimal or no retinopathy, who inhaled oxygen. This study supports a hypothesis that reduced retinal oxygenation contributes to the colour vision defects in diabetes.

Adult↗
PubMed1991

Cortical blindness and residual vision: is the "second" visual system in humans capable of more than rudimentary visual perception?

We studied 12 patients with static cortical blindness to evaluate residual vision after destruction of area 17 and to assess the visual capacity of the subcortical "second" visual system in humans. In each case, the cause was bilateral infarction of the occipital lobes. Five patients had total blindness, and four had residual rudimentary vision (RRV), characterized by homonymous areas of light perception in the peripheral field and ability to detect moving objects. Only three patients had the ability to read; two of these had spared macular vision, and the other had spared left homonymous hemimaculae and spared temporal crescent. Neuroimaging and visual evoked potentials (VEPs) correlated with the extent of the visual dysfunction. Total destruction of area 17 bilaterally was associated with total permanent visual loss. The larger the amount of spared visual cortex, the better the vision. Positron emission tomography (PET) or single photon emission computed tomography (SPECT) demonstrated retained metabolic activity in islands of preserved area 17 in patients with some residual vision. VEPs were present in totally blind individuals. We conclude that, in humans, useful visual function is preserved only when a critical amount of area 17 is spared. The subcortical second system may participate in the generation of VEPs, but is incapable of conscious visual perception.

Aged↗
PubMed1992

Factors influencing hand/eye synchronicity in the computer age.

In using a computer, the relation of vision to hand/finger actuated keyboard usage in performing fine motor-coordinated functions is influenced by the physical location, size, and collective placement of the keys. Traditional nonprehensile flat/rectangular keyboard applications usually require a high and nearly constant level of visual attention. Biometrically shaped keyboards would allow for prehensile hand-posturing, thus affording better tactile familiarity with the keys, requiring less intense and less constant level of visual attention to the task, and providing a greater measure of freedom from having to visualize the key(s). Workpace and related physiological changes, aging, onset of monocularization (intermittent lapsing of binocularity for near vision) that accompanies presbyopia, tool colors, and background contrast are factors affecting constancy of visual attention to task performance. Capitas extension, excessive excyclotorsion, and repetitive strain injuries (such as carpal tunnel syndrome) are common and debilitating concomitants to computer usage. These problems can be remedied by improved keyboard design. The salutary role of mnemonics in minimizing visual dependency is discussed.

Accommodation, Ocular↗
PubMed2002

Calculated impact of higher-order monochromatic aberrations on retinal image quality in a population of human eyes.

We calculated the impact of higher-order aberrations on retinal image quality and the magnitude of the visual benefit expected from their correction in a large population of human eyes. Wave aberrations for both eyes of 109 normal subjects and 4 keratoconic patients were measured for 3-, 4-, and 5.7-mm pupils with a Shack-Hartmann sensor. Retinal image quality was estimated by means of the modulation transfer function (MTF) in white light. The visual benefit was calculated as the ratio of the MTF when the monochromatic higher-order aberrations are corrected to the MTF corresponding to the best correction of defocus and astigmatism. On average, the impact of the higher-order aberrations for a 5.7-mm pupil in normal eyes is similar to an equivalent defocus of approximately 0.3 D. The average visual benefit for normal eyes at 16 c/deg is approximately 2.5 for a 5.7-mm pupil and is negligible for small pupils (1.25 for a 3-mm pupil). The benefit varies greatly among eyes, with some normal eyes showing almost no benefit and others a benefit higher than 4 at 16 c/deg across a 5.7-mm pupil. The benefit for keratoconic eyes is much larger. The benefit at 16 c/deg is 12 and 3 for 5.7- and 3-mm pupils, respectively, averaged across four keratoconics. These theoretical benefits could be realized in normal viewing conditions but only under specific conditions.

Adult↗
PubMed1986

Evaluation of linear models of surface spectral reflectance with small numbers of parameters.

Recent computational models of color vision demonstrate that it is possible to achieve exact color constancy over a limited range of lights and surfaces described by linear models. The success of these computational models hinges on whether any sizable range of surface spectral reflectances can be described by a linear model with about three parameters. In the first part of this paper, I analyze two large sets of empirical surface spectral reflectances and examine three conjectures concerning constraints on surface reflectance: that empirical surface reflectances fall within a linear model with a small number of parameters, that empirical surface reflectances fall within a linear model composed of band-limited functions with a small number of parameters, and that the shape of the spectral-sensitivity curves of human vision enhance the fit between empirical surface reflectances and a linear model. I conclude that the first and second conjectures hold for the two sets of spectral reflectances analyzed but that the number of parameters required to model the spectral reflectances is five to seven, not three. A reanalysis of the empirical data that takes human visual sensitivity into account gives more promising results. The linear models derived provide excellent fits to the data with as few as three or four parameters, confirming the third conjecture. The results suggest that constraints on possible surface-reflectance functions and the "filtering" properties of the shapes of the spectral-sensitivity curves of photoreceptors can both contribute to color constancy. In the last part of the paper I derive the relation between the number of photoreceptor classes present in vision and the "filtering" properties of each class. The results of this analysis reverse a conclusion reached by Barlow: the "filtering" properties of human photoreceptors are consistent with a trichromatic visual system that is color constant.

Analysis of Variance↗
PubMed2006

Perceptual grouping induces non-retinotopic feature attribution in human vision.

The human visual system computes features of moving objects with high precision despite the fact that these features can change or blend into each other in the retinotopic image. Very little is known about how the human brain accomplishes this complex feat. Using a Ternus-Pikler display, introduced by Gestalt psychologists about a century ago, we show that human observers can perceive features of moving objects at locations these features are not present. More importantly, our results indicate that these non-retinotopic feature attributions are not errors caused by the limitations of the perceptual system but follow rules of perceptual grouping. From a computational perspective, our data imply sophisticated real-time transformations of retinotopic relations in the visual cortex. Our results suggest that the human motion and form systems interact with each other to remap the retinotopic projection of the physical space in order to maintain the identity of moving objects in the perceptual space.

Eye Movements↗
PubMed2002

Orbital teratoma: late presentation with normal vision.

Orbital teratoma is a rare, rapidly growing tumour that usually presents with congenital proptosis. Visual outcome is usually poor. A case is described of orbital teratoma presenting in an 18-month-old child as an inferior orbital mass with normal vision and intermittent hypertropia. Computed tomography demonstrated a cystic mass containing a tooth adjacent to the inferior orbital fissure. Histology revealed tissues derived from all three germ cell layers. The tumour was removed with preservation of vision and resolution of the strabismus. Late presentation of an orbital teratoma with a good visual outcome is exceptional.

Choristoma↗
PubMed1996

Cortical dynamics of lateral inhibition: visual persistence and ISI.

Psychophysical studies show that increasing the interstimulus interval (ISI) between two stimuli decreases persistence of the first stimulus. While some researchers account for these results with interactions of transient and sustained inhibition, this paper describes an alternative explanation. In a neural-network model of boundary detection called the boundary contour system, persistence is the result of feedback-generated reverberations. Mechanisms to control these reverberations include lateral inhibition, which computer simulations show allows persistence in the network to qualitatively match the psychophysical data. Additional simulations predict that increasing the duration of the second stimulus should cause persistence to increase with ISI. The model links psychophysical data on visual persistence with computational requirements of spatial vision and properties of cells in visual cortex.

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