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At least 163 records · Page 9Linked to original sources

PubMed2004

Performance of a write-once multilayer optical disk that uses transparent recording material with an optical switching layer.

A volumetric optical disk that has multiple transparent films with optical switching layers is used as a recording medium to increase the number of recording layers. In the disk the optical switching layer is adapted to reduce decay of laser energy and increase reading and recording sensitivity. Well-defined marks of approximately 100-nm depth can be placed precisely on the transparent films by a focused laser beam. Writing and reading of a four-layer recordable disk, fabricated by molding and spin bonding, have been demonstrated experimentally. The volumetric disk can achieve a high recording capacity with conventional optical pickups.

Journal Article↗

PubMed1988

Vision anomalies and reading skill: a meta-analysis of the literature.

We report a meta-analysis of studies of the relation of vision anomalies to reading skill. Meta-analysis is a quantitative technique for combining the results of multiple studies that reduces the subjectivity of literature reviews. The results of the analysis of 34 studies of vision anomalies and reading skill that met the criteria for inclusion in the meta-analysis showed that hyperopia, exophoria at near, vertical phoria, anisometropia, and aniseikonia are associated with below average reading performance. Myopia and esophoria and esophoria at far are associated with average and above average reading performance. Reduced visual acuity, astigmatism, esophoria at near, fusional convergence and divergence, strabismus, nearpoint of convergence, and stereopsis were not found to be associated with reading performance.

Depth Perception↗

PubMed2002

Component dependent risk factors for ocular parameters in Singapore Chinese children.

OBJECTIVE: To examine the risk factors for variations in ocular biometry parameters in Singapore Chinese children, a population with a known high prevalence rate of myopia at an early age. DESIGN: Cross-sectional study. PARTICIPANTS: Children aged 7 to 9 years (n = 1453) from three schools in Singapore. METHODS: The children underwent A scan biometry and cycloplegic autorefraction measurements. Questions were asked regarding number of books read per week, night lighting, and parental myopia. MAIN OUTCOME MEASURES: Axial length, vitreous chamber depth, lens thickness, anterior chamber depth, refraction, and corneal curvature radius measurements were made. RESULTS: After controlling for several factors, the axial lengths were found to be longer and vitreous chambers deeper in children who were older, male, read more than two books per week, or taller, and those who had at least one parent who was myopic. In these models, children who read more than two books per week had axial lengths that were 0.17 mm longer and vitreous chambers that were 0.15 mm deeper compared with children who read two or fewer books per week. Anterior chambers were deeper in males and taller children, whereas corneal curvature was steeper in female, older, and shorter children. CONCLUSIONS: Increases of axial length and vitreous cavity depth were associated with older age, being male, reading more than two books per week, increased height, and parental history of myopia. Of these risk factors, however, neither reading nor parental myopia history were associated with values for anterior chamber depth, corneal curvature, or lens thickness. These findings confirm that conventional risk factors for myopia associated with the vitreous cavity, but suggest that anterior segment parameters such as corneal curvature and lens thickness may be subject to unrelated postnatal growth control mechanisms.

Age Distribution↗

PubMed1999

[Microperimetry and reading saccades in retinopathia solaris. Follow-up with the scanning laser ophthalmoscope].

UNLABELLED: Patients with solar retinopathy often complain of minute central scotomas and are handicapped when reading. The purpose of this study was to verify scotomas that are too small to be detected by standard perimeters and to analyze patients' reading patterns. METHODS: Nineteen patients (12 female, 7 male, aged 5-46 years) with acute solar retinopathy after watching a solar eclipse on 12 October 1996 underwent scanning laser ophthalmoscope (SLO) microperimetry within 10 days after exposure using stimulus size Goldmann I (0.11 degree) with the 20 degrees field. Size and depth of scotomas were measured. Eye movements during reading were recorded on videotape. Follow-up was at 1 and 6 months. RESULTS: Thirty-one eyes (7 patients unilateral, 12 bilateral) showed scotomas. Four eyes showed anatomic changes in the retinal pigment epithelium but no functional loss. VA was 0.16 to 0.5 in 5 eyes, 26 had VA of 0.8-1.2. Scotomas could be detected in all eyes with subjective impairment. Scotoma size varied from 0.3 to 1.7 degrees (1 patient 6 degrees). Forty-four percent were deep scotomas (0 dB). All defects improved at 1 and at 6 months; 25% were no longer detectable. Reading speed was reduced in 75% of eyes (42% at 6 months): 200-560 signs/min, median: 510, normal > or = 660 (at 6 months: 350-920 signs/min, median 670). This was especially due to increased number of regressions (in 81% of eyes, 21% at 6 months). The frequency and width of saccades were no different from normal subjects. CONCLUSION: Minute scotomas (diameter = 0.3 degree) can be detected with the SLO. All patients showed objective improvement of their field defect up to 6 months, even when this was not noted by the patient or thought to be due to habituation. Small scotomas can dramatically reduce reading performance.

Adolescent↗

PubMed2002

A Bayesian model of stereopsis depth and motion direction discrimination.

The extraction of stereoscopic depth from retinal disparity, and motion direction from two-frame kinematograms, requires the solution of a correspondence problem. In previous psychophysical work [Read and Eagle (2000) Vision Res 40: 3345-3358], we compared the performance of the human stereopsis and motion systems with correlated and anti-correlated stimuli. We found that, although the two systems performed similarly for narrow-band stimuli, broadband anti-correlated kinematograms produced a strong perception of reversed motion, whereas the stereograms appeared merely rivalrous. I now model these psychophysical data with a computational model of the correspondence problem based on the known properties of visual cortical cells. Noisy retinal images are filtered through a set of Fourier channels tuned to different spatial frequencies and orientations. Within each channel, a Bayesian analysis incorporating a prior preference for small disparities is used to assess the probability of each possible match. Finally, information from the different channels is combined to arrive at a judgement of stimulus disparity. Each model system--stereopsis and motion--has two free parameters: the amount of noise they are subject to, and the strength of their preference for small disparities. By adjusting these parameters independently for each system, qualitative matches are produced to psychophysical data, for both correlated and anti-correlated stimuli, across a range of spatial frequency and orientation bandwidths. The motion model is found to require much higher noise levels and a weaker preference for small disparities. This makes the motion model more tolerant of poor-quality reverse-direction false matches encountered with anti-correlated stimuli, matching the strong perception of reversed motion that humans experience with these stimuli. In contrast, the lower noise level and tighter prior preference used with the stereopsis model means that it performs close to chance with anti-correlated stimuli, in accordance with human psychophysics. Thus, the key features of the experimental data can be reproduced assuming that the motion system experiences more effective noise than the stereoscopy system and imposes a less stringent preference for small disparities.

Animals↗

PubMed1999

[Analysis of intraocular pressure and corneal thickness after laser in situ keratomileusis].

OBJECTIVE: To analyze the changes and relationship of the intraocular pressure (IOP) and the corneal thickness (CT) after laser in situ keratomileusis (LASIK). METHODS: This prospective study comprised two groups: noncontact tonometer group 221 eyes (156 patients) 1 month after LASIK and 72 eyes (50 patients) 3 months after LASIK; Goldmann applanation tonometer group 60 eyes (36 patients) 1 month after LASIK. The spherical equivalent, the corneal thickness and the IOP readings were measured pre- and post-LASIK. RESULTS: The CT was thicker than the predicted value and it was much more prominent in the higher myopic group with more regression degree of refraction. The CT at postoperative 3 month was thicker than that at 1 month. There was a statistical decrease in mean tonometer readings, both with non-contact tonometer and Goldmann applanation tonometer; and there was statistically significant correlation between the changes of central corneal thickness and the changes of non-contact tonometer readings (r = 0.2, P < 0.002). The IOP decrease with Goldmann applanation tonometer was less than that with noncontact tonometer. CONCLUSIONS: The actual ablation depth of cornea is lower than the predicted. The IOP readings of the patients after LASIK are lower than the real IOP values. Further efforts should be made to improve the accuracy. Goldmann applanation tonometer is a better choice measuring IOP after excimer photoablative corneal refractive surgery.

Adolescent↗

PubMed2000

Genetically determined male infertility and assisted reproduction techniques.

This is a review of the common chromosome and genetic disorders associated with male infertility that need to be considered by the clinician and the couple in the context of treatment. Until recently the most relevant disorders have been those inherited from parents, however, with the advent of technologies enabling recovery of sperm from the testicle in men with severely damaged spermatogenesis there is increased interest in those genetic abnormalities that may occur in mitosis and meioses. It is likely that over the next ten years there will be increasing focus on this aspect of male fertility genetic disorders. This article needs to be read in conjunction with the specific in depth reviews in this journal edition.

Aging↗

PubMed2005

Effect of clonidine pre-medication on propofol requirements during lower extremity vascular surgery: a randomized controlled trial.

BACKGROUND: Pre-medication with clonidine reduces the requirement for volatile agents during general anaesthesia. This may also be true for anaesthesia with propofol, but the amount of dose reduction has not been measured. Because clonidine also affects cardiac output and thus regional blood flow it could alter the pharmacokinetics of propofol. This randomized, double-blind placebo-controlled trial aimed to study the effect of clonidine pre-medication on dose requirement for propofol during lower extremity vascular surgery using the bispectral index (BIS) as a measure of anaesthetic depth. METHODS: After oral pre-medication with either clonidine 3 microg kg(-1) or placebo, 39 subjects had lower limb vascular surgery using propofol infusion for anaesthesia. Anaesthetic depth was adjusted to a BIS of 45. Predicted plasma propofol concentrations were noted every 30 min from a target-controlled propofol infusion pump and arterial samples were taken at the same time for propofol measurements. RESULTS: Patients in both groups were anaesthetized to similar depths of anaesthesia as indicated by BIS readings (P=0.44). The groups had comparable mean (95% CI) arterial concentrations of propofol, 4.8 (3.5-6.1) microg ml(-1) in the patients given clonidine, and 4.6 (3.4-5.7) microg ml(-1) in the patients given placebo (P=0.81). However, the average plasma concentration predicted by the target-controlled infusion was less in the clonidine group [3.2 (2.9-3.5)] than in the group given placebo [3.6 (3.3-3.9)] microg ml(-1) (P<0.05). CONCLUSIONS: Pre-medication with clonidine reduces the requirement for propofol, which is a pharmacokinetic effect and not a pharmacodynamic central sedative effect.

Aged↗

PubMedDate not supplied

Productivity in clinical engineering.

There are various methods of computing productivity in Clinical Engineering. A simple algorithm based on time standards is presented in this paper. Duties required to support the inspection and repair functions and the time needed to perform them, as well as other functions provided by the Clinical Engineering Department, are discussed. The final "standards" presented in this paper may be applied to other facilities and other situations only with great caution. This study was performed on a certain complement of equipment and with a certain depth of testing. This paper should be read in its entirety to place the results reported in proper context. This is preliminary information, and an expanded data base of studies would be required before a universal standard, if indeed possible, could be adopted. This paper does, however, provide results comparable to other studies performed in recent years, and some consensus on typical inspection and repair time is emerging. Radiographic units, laboratory equipment, and various specialty items are not included.

Biomedical Engineering↗

PubMedDate not supplied

Evaluation of increased aqueous outflow after radial keratotomy in enucleated bovine eyes.

PURPOSE: We studied the efficacy of using radial keratotomy incisions as a surgical method of increasing outflow facility in enucleated bovine eyes. METHODS: Each freshly enucleated bovine eye (n = 23) was cannulated to a system measuring the rate of flow into the eyes. Preoperatively, corneal thickness measurements were determined for all treated eyes. Radial keratotomy was performed in 13 eyes and a control set of eyes (n = 10) had no surgical manipulation. The intraocular pressure was set at 16.9 mm Hg. A clear zone of 10 mm was used for each eye with the incision depth set at 100% of the pachymetric reading. One set of experimental eyes had incisions that remained in the clear cornea, and the other set had incisions that reached 2 mm beyond the limbus into sclera. Preoperative outflow measurements were performed on each eye. Postoperative measurements were made after 10 incisions and 20 incisions. All eyes were checked for perforation after surgery and discarded if a perforation was found. RESULTS: No eye included in the analysis was perforated. The preoperative (baseline) total flow rate was 27.90 +/- 3.72 mu 1/min at 16.9 mmHg. The flow rate increased by 23.5% (over baseline) with 20 radial keratotomy incisions. A paired t-test was used to statistically compare the outflow measurements before radial keratotomy and after the first and second set of radial incisions. The increases in flow were found to be statistically significant (P < .005) for both 10 and 20 radial incisions. CONCLUSION: Assuming the flow measurements (flow rate) in these experiments parallel outflow facility, radial keratotomy increases the outflow facility in enucleated bovine eyes.

Animals↗

PubMed1990

[Anamnesis of brain-originated vision disorders].

A questionnaire for the subjective assessment of cerebral visual disorders was administered to 269 brain damaged patients. The patients' subjective complaints were correlated with the outcome of objective diagnostic procedures (visual perimetry, visual search, spatial contrast sensitivity, visual evoked potentials, depth perception, light- and dark-adaptation, reading, colour vision). A significant correlation was found between subjective complaints and objective diagnostic results for all fields. The prediction of visual impairments on the basis of subjective complaints and verified by objective tests was correct in 80 to 98% of the brain damaged patients tested. Interrater reliability was about 0.84. Thus, the questionnaire is suitable for the assessment of cerebral visual disorders because of its simplicity, short administration time (10-15 min) and high predictive value.

Accommodation, Ocular↗

PubMed1996

Visual predictors of reading performance in kindergarten and first grade children.

PURPOSE: A masked investigation of the relation between performance on various vision tests and reading was conducted with 90 kindergartners (mean age 5.73 years) and 91 first graders (mean age 6.76 years) from a middle class, suburban, elementary school near Cleveland, Ohio. METHODS: Vision testing included the Modified Clinical Technique (MCT), +/- 2.00 D flipper lenses with red/green suppression check for accommodative facility, and Randot for stereoacuity. Reading performance was independently evaluated with the Metropolitan Achievement Test 6 Reading Test and teachers' assessments. RESULTS: The results revealed that accommodative facility was predictive of successful reading performance in 7-year-olds (p = 0.0431), first graders (p = 0.0125), and in the entire subject group when age (p = 0.0254) or grade (p = 0.0224) was controlled. Failure on the MCT was significantly associated with decreased reading skill in 5-year-olds (p = 0.0431). In addition, stereoacuity worse than 100 sec arc (p = 0.0316), MCT failure plus stereoacuity worse than 50 sec arc (p = 0.0316), and accommodative facility (p 0.0155) were predictive of whether children of average intelligence would show successful or unsuccessful reading ability. CONCLUSIONS: Thus, visual performance was significantly related to reading performance even in children of average intelligence when IQ was partially controlled. Also, the predictive value of the MCT for reading achievement could be improved by the addition of a referral criterion for stereoacuity. This would make the results of MCT screening more readily applicable to educators.

Accommodation, Ocular↗

PubMed1992

Genotype and treatment biases in estimation of carcass lean of swine.

Carcasses of 181 barrows, representing five genotypes, 1) H x HD, 2) SYN, 3) HD x L[YD], 4) L x YD, and 5) Y x L (H = Hampshire, D = Duroc, SYN = synthetic terminal sire line, L = Landrace, and Y = Yorkshire), and two levels of ractopamine (RAC) treatment (0 and 20 ppm) were completely dissected and the data were used to examine genotype and treatment (RAC) biases in estimation of fat-standardized lean weight and to evaluate accuracies and precisions realized by use of equations based on variables derived from different technologies. Independent variables used to establish regression equations represented technologies of direct carcass measurements, optical probe data, TOBEC (total body electrical conductivity) readings, and dissected (DHMLN) and fat-standardized (FSHMLN) ham lean. Genotype bias existed when any equation from a single technology was used and was minimized by combining FSHMLN with one TOBEC reading, carcass length, and the probe measurement of 10th rib fat depth. Large RAC biases appeared when equations from direct carcass measurements or optical probe data were used and were minimized by an equation using either DHMLN or FSHMLN. A practical equation with relatively high R2 value and small genotype and RAC biases were developed by combining TOBEC readings with direct carcass measurements of 10th rib fat depth and warm carcass weight.

Adipose Tissue↗

PubMed2026

Long-read proteogenomic atlas of human neuronal differentiation reveals isoform diversity informing neurodevelopmental risk mechanisms.

RNA splicing shapes neuronal identity and disease risk, yet current maps lack the developmental resolution and depth to resolve this complexity. Here, we integrate deep long-read RNA sequencing and proteomics in induced pluripotent stem cell-derived cortical neurons to generate a high-resolution proteogenomic atlas of human neuron development. We identify 182,371 mRNA isoforms (over half previously unknown) and provide direct peptide evidence for the translation of hundreds of novel protein-coding sequences. Population genetics demonstrates that variants affecting novel exons and splice sites are under negative selection, underscoring the potential significance of these isoforms. During neuronal maturation, we observe that autism risk genes undergo dynamic isoform switching, including microexon inclusion and intron retention, that remodel key protein domains and regulatory regions. Furthermore, we uncover widespread, long-range coordination between alternative transcript processing events, including transcription start sites, exon splicing, and polyadenylation. Finally, our atlas enables variant reinterpretation in autism, highlighting the value of an isoform-centric view for interpreting pathogenic variation in neurodevelopment.

Humans↗

PubMed1995

Clinical use of carbon-loaded thermoluminescent dosimeters for skin dose determination.

PURPOSE: Carbon-loaded thermoluminescent dosimeters (TLDs) are designed for surface/skin dose measurements. Following 4 years in clinical use at the Mater Hospital, the accuracy and clinical usefulness of the carbon-loaded TLDs was assessed. METHODS AND MATERIALS: Teflon-based carbon-loaded lithium fluoride (LiF) disks with a diameter of 13 mm were used in the present study. The TLDs were compared with ion chamber readings and TLD extrapolation to determine the effective depth of the TLD measurement. In vivo measurements were made on patients receiving open-field treatments to the chest, abdomen, and groin. Skin entry dose or entry and exit dose were assessed in comparison with doses estimated from phantom measurements. RESULTS: The effective depth of measurement in a 6 MV therapeutic x-ray beam was found to be about 0.10 mm using TLD extrapolation as a comparison. Entrance surface dose measurements made on a solid water phantom agreed well with ion chamber and TLD extrapolation measurements, and black TLDs provide a more accurate exit dose than the other methods. Under clinical conditions, the black TLDs have an accuracy of +/- 5% (+/- 2 SD). The dose predicted from black TLD readings correlate with observed skin reactions as assessed with reflectance spectroscopy. CONCLUSION: In vivo dosimetry with carbon-loaded TLDs proved to be a useful tool in assessing the dose delivered to the basal cell layer in the skin of patients undergoing radiotherapy.

Carbon↗

PubMed1988

Task performance with base-in and base-out prism.

The effects of base-in (BI) and base-out (BO) prism upon performance of four occupational-like tasks were measured on a group of 10 subjects who had normal binocular vision. Performance on tasks which required depth perception was significantly poorer when subjects wore prism glasses with 8 and 12 delta BI and BO, whereas 4 delta BI and BO did not significantly affect performance. The performance decrements with prism (3.0 to 6.7%) were considerably less than those induced by denial of binocularity (20 to 30%) as measured in a previous study. Thus, vergence-inducing prism does impair task performance but not as much as does the denial of binocularity. The reading and counting tasks did not require critical depth judgement and were much less affected by the prism than the needle-threading and pointers-and-straws tasks.

Adult↗

PubMed1999

Dissociative effects of alcohol on recollective experience.

This article reports a study comparing the effects of a single dose of alcohol with a matched placebo drink on recognition memory with and without conscious recollection. A double-blind, cross-over design was used with healthy volunteers who were all social drinkers. Processing depth at study was manipulated using generate versus read instructions. Conscious recollection at test was assessed using the remember-know-guess paradigm (Gardiner, 1988; Tulving, 1985). Alcohol significantly reduced conscious recollection (remember responses) but had no effect on recognition in the absence of conscious recollection (know responses). False alarms rates were low and unaffected by alcohol. Previous findings that generation effects are found only for remember responses were closely replicated. A further dissociation of the generation effect occurred between treatments in that deeper processing at study facilitated recognition on placebo but not on alcohol. That both alcohol and depth of processing produce dissociative effects on recollective experience provides further evidence that remembering and knowing reflect distinct memory systems.

Adult↗

PubMed2005

Evaluation of the safety and efficacy of periodontal applications of a living tissue-engineered human fibroblast-derived dermal substitute. II. Comparison to the subepithelial connective tissue graft: a randomized controlled feasibility study.

BACKGROUND: The subepithelial connective tissue graft, traditionally harvested from the patient's palate, is commonly used for root coverage in periodontal recession defects. This study evaluates the safety and effectiveness of a living human fibroblast-derived dermal substitute (HF-DDS) compared to a connective tissue graft (CTG) for root coverage in these situations. METHODS: Thirteen patients were selected for this study. Each patient had Miller Class I or II bilateral facial recession defects > or =3 mm on two non-adjacent teeth. The test tooth received an HF-DDS graft, while a CTG was placed on the control site. The 10 test surgeries were performed by one operator and three pilot surgeries were performed by another surgeon. Eight of the HF-DDS sites received a single thickness of material; five received a double thickness. Clinical measurements were taken at baseline; 1 week; and 1, 3, and 6 months following surgery. Parameters measured were plaque index, recession depth, clinical attachment levels, recession width, probing depth, and width of keratinized tissue. All clinical readings were taken by a masked, calibrated examiner. RESULTS: There were no statistically significant differences between the test and control groups. The amount of root coverage was slightly greater for the control group than for the test group, but statistically the difference was insignificant. The width of the recession defect measured at the cemento-enamel junction (CEJ) for the test group was slightly smaller than that of the control group at the conclusion of the study. The amount of keratinized tissue was the same in both groups at 6 months. The probing depth was slightly greater in the control group as was the gain in clinical attachment, but neither was statistically significant. The amount of root coverage obtained when one layer of HF-DDS was used compared to the amount of coverage obtained when two layers were used approached statistical significance, but the small sample size may have been responsible for the difference. CONCLUSION: Within the limits of this study, the human fibroblast-derived dermal substitute may offer potential as a substitute to the connective tissue graft for covering areas of facial Miller Class I or Class II gingival recession in humans.

Adult↗