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PubMedDate not supplied

Telemedicine-friendly, portable tonometers: an evaluation for intraocular pressure screening.

PURPOSE: To evaluate the intraocular pressure (IOP) readings from two portable, telemedicine-friendly tonometers for suitability in glaucoma screening. METHODS: 213 eyes of 107 consenting patients attending an eye clinic were tested with an I-care tonometer and a Pulsair-Easy Eye puff-air tonometer. Gold standard IOP was measured with a Goldmann applanation tonometer (GAT). Effect of central corneal thickness, anterior chamber depth and refractive errors on IOP measurements were also analysed. RESULTS: The mean difference of IOP by GAT and both the portable tonometers was +/- 2.2 mmHg. The analysis indicates minimal difference between IOP readings of both the portable tonometers. The mean difference between two consecutive readings by I-care was 0.01 mmHg. Using 21 mmHg as a threshold for suspected glaucoma, both the portable digital tonometers reported a sensitivity of 38% and specificity of >95%. In the subjects studied, central corneal thickness had statistically significant influence on IOP measurements while refractive errors and anterior chamber depth had no significant influence on IOP measurements with any tonometry. CONCLUSION: The IOP readings by both portable tonometers are comparable and were within clinically acceptable range from GAT. These portable tonometers are useful tools for IOP screening.

Adult↗

PubMed2000

DNA cloning using in vitro site-specific recombination.

As a result of numerous genome sequencing projects, large numbers of candidate open reading frames are being identified, many of which have no known function. Analysis of these genes typically involves the transfer of DNA segments into a variety of vector backgrounds for protein expression and functional analysis. We describe a method called recombinational cloning that uses in vitro site-specific recombination to accomplish the directional cloning of PCR products and the subsequent automatic subcloning of the DNA segment into new vector backbones at high efficiency. Numerous DNA segments can be transferred in parallel into many different vector backgrounds, providing an approach to high-throughput, in-depth functional analysis of genes and rapid optimization of protein expression. The resulting subclones maintain orientation and reading frame register, allowing amino- and carboxy-terminal translation fusions to be generated. In this paper, we outline the concepts of this approach and provide several examples that highlight some of its potential.

Animals↗

PubMedDate not supplied

A simple model accounts for the response of disparity-tuned V1 neurons to anticorrelated images.

Disparity-tuned cells in primary visual cortex (VI) are thought to play a significant role in the processing of stereoscopic depth. The disparity-specific responses of these neurons have been previously described by an energy model based on local, feedforward interactions. This model fails to predict the response to binocularly anticorrelated stimuli, in which images presented to left and right eyes have opposite contrasts. The original energy model predicts that anticorrelation should invert the disparity tuning curve (phase difference pi), with no change in the amplitude of the response. Experimentally, the amplitude tends to be reduced with anticorrelated stimuli and a spread of phase differences is observed, although phase differences near pi are the most common. These experimental observations could potentially reflect a modulation of the V1 signals by feedback from higher visual areas (because anticorrelated stimuli create a weaker or nonexistent stereoscopic depth sensation). This hypothesis could explain the effects on amplitude, but the spread of phase differences is harder to understand. Here, we demonstrate that changes in both amplitude and phase can be explained by a straightforward modification of the energy model that involves only local processing. Input from each eye is passed through a monocular simple cell, incorporating a threshold, before being combined at a binocular simple cell that feeds into the energy computation. Since this local feedforward model can explain the responses of complex cells to both correlated and anticorrelated stimuli, there is no need to invoke any influence of global stereoscopic matching.

Animals↗

PubMed2005

Dual-wavelength phosphorimetry for determination of cortical and subcortical microvascular oxygenation in rat kidney.

This study presents a dual-wavelength phosphorimeter developed to measure microvascular PO2 (microPO2) in different depths in tissue and demonstrates its use in rat kidney. The used phosphorescent dye is Oxyphor G2 with excitation bands at 440 and 632 nm. The broad spectral gap between the excitation bands combined with a relatively low light absorption of 632 nm light by tissue results in a marked difference in penetration depths of both excitation wavelengths. In rat kidney, we determine the catchments depth of the 440-nm excitation to be 700 microm, whereas the catchments depth of 632 nm is as much as 4 mm. Therefore, the measurements differentiate between cortex and outer medulla, respectively. In vitro, no difference in PO2 readings between both channels was found. On the rat kidney in vivo, the measured cortical microPO2 was on average 20 Torr higher than the medullary microPO2 over a wide PO2 range induced by variations in inspired oxygen fraction. Examples provided from endotoxemia and resuscitation show differences in responses of mean cortical and medullary PO2 readings as well as in the shape of the PO2 histograms. It can be concluded that oxygen-dependent quenching of phosphorescence of Oxyphor G2 allows quantitative measurement of microPO2 noninvasively in two different depths in vivo. Oxygen levels measured by this technique in the rat renal cortex and outer medulla are consistent with previously published values detected by Clark-type oxygen electrodes. Dual-wavelength phosphorimetry is excellently suited for monitoring microPO2 changes in two different anatomical layers under pathophysiological conditions with the characteristics of providing oxygen histograms from two depths and having a penetration depth of several millimeters.

Animals↗

PubMed1991

Stereopsis, accommodative and vergence facility: do they relate to dyslexia?

The relation between visual functions and reading performance has been the subject of conflicting opinion over the years. The purpose of this study is 2-fold: first, to examine factors other than visual acuity, i.e., stereopsis, accommodative facility and vergence facility, which might show a greater impact on reading achievement; and second, to utilize well defined dyslexic and normal controls to ensure that the reading deficits were not caused by overt neurological, psychological, educational, or environmental factors. Thirteen normal readers and 13 dyslexics were carefully matched by rigorous quantitative criteria. The performance of both groups on tests of visual acuity and stereopsis was similar. The dyslexic readers tended to show better accommodative facility. Dyslexics performed significantly worse than the matched normal readers on a test of vergence facility. These results, in agreement with those reported by other studies, indicate that less efficient dynamic vergence facility may contribute to reading impairment, unlike other static functions such as visual acuity and stereopsis. It may be that the vergence problems of the dyslexics are related to sequential oculo-motor abnormalities. The dyslexics' vergence problems may also be partly responsible for their large number of small eye movements.

Accommodation, Ocular↗

PubMed2003

Winter operation of an on-stream stormwater management pond.

The winter operation of an on-stream stormwater management pond in Kingston, Canada is characterised. The pond froze over in late November. Ice thickness varied from 0.2 to 0.5 m, and initially, was well described by Stefan's formula. The measured and modelled velocity field indicated a fast flow region, a small dead zone and a large recirculating zone. During a snowmelt event, near-bottom velocities reached 0.05 m x s(-1), but were not sufficient to scour the bottom sediment. Pond water temperature increased with depth, from 0.5 degrees C to 3.5 degrees C. The dissolved oxygen (DO) levels observed in the pond (6-13 mg x L(-1)) indicated stable aerobic conditions at the sediment-water interface. In one brief episode, DO fell to zero after a long cold spell. Reduction in DO readings from inlet to outlet indicated an oxygen consumption of about 1.7 kg x day(-1). pH ranged from 7.1 to 8.9. Conductivity readings indicated large quantities of total dissolved solids, representing mostly chloride from de-icing agents. During baseflow, conductivity increased with depth (total dissolved solids concentrations up to 1,200 mg x L(-1) near the bottom), indicating density stratification. Average trace metal concentrations were mostly below detection limits.

Geologic Sediments↗

PubMed2025

A chromosome-level reference genome assembly of the Small snakehead (Channa asiatica).

The Small snakehead (Channa asiatica) is an economically important species in both aquaculture and ornamental trade, mainly distributed in South China and Southeast Asia. Despite its significance, limited genomic resources have impeded in-depth genetic studies and breeding programs. In this study, we used PacBio HiFi long-read sequencing, Illumina short-read sequencing, and Hi-C technologies to generate a high-quality chromosome-level genome of the C. asiatica. The final genome spans 659.44 Mb, with an impressive 98.18% anchored to 23 chromosomes. Notably, the contig N50 and scaffold N50 are 23.92 Mb and 29.61 Mb, validated by a BUSCO completeness score of 98.93%. Genome annotation identified 26,603 protein-coding genes, 99.29% of which were confirmed by BUSCO analysis, and 93.68% were functionally annotated. Approximately 27.72% of the genome sequences were classified as repeat elements. This high-fidelity genome assembly provides a robust foundation for advancing molecular breeding, comparative genomics, and evolutionary studies of C. asiatica and related species.

Animals↗

PubMed2005

Monovision slows juvenile myopia progression unilaterally.

AIM: To evaluate the acceptability, effectivity, and side effects of a monovision spectacle correction designed to reduce accommodation and myopia progression in schoolchildren. METHODS: Dominant eyes of 11 year old children with myopia (-1.00 to -3.00 D mean spherical equivalent) were corrected for distance; fellow eyes were uncorrected or corrected to keep the refractive imbalance <or=2.00 D. Myopia progression was followed with cycloplegic autorefraction and A-scan ultrasonography measures of vitreous chamber depth (VCD) for up to 30 months. Dynamic retinoscopy was used to assess accommodation while reading. RESULTS: All children accommodated to read with the distance corrected (dominant) eye. Thus, the near corrected eye experienced myopic defocus at all levels of accommodation. Myopia progression in the near corrected eyes was significantly slower than in the distance corrected eyes (inter-eye difference=0.36 D/year (95% CI: 0.54 to 0.19, p=0.0015, n=13); difference in VCD elongation=0.13 mm/year (95% CI: 0.18 to 0.08, p=0.0003, n=13)). After refitting with conventional spectacles, the resultant anisometropia returned to baseline levels after 9-18 months. CONCLUSIONS: Monovision is not effective in reducing accommodation in juvenile myopia. However, myopia progression was significantly reduced in the near corrected eye, suggesting that sustained myopic defocus slows axial elongation of the human eye.

Accommodation, Ocular↗

PubMed1993

Associative priming in perceptual identification: effects of prime-processing requirements.

Three experiments assessed the effects of prime-processing instructions on associative priming in word identification and episodic memory for primes. In Experiment 1, groups instructed to read the prime silently or generate silently an associate of the prime showed a larger accuracy benefit for related over unrelated targets than did a group that decided whether an asterisk was to the right or left of the prime. The asterisk-search group showed a weaker repetition effect on a subsequent identification test of primes, indicating that the weaker priming in this group was a result of poorer perceptual processing. On a cued-recall test for primes, the generate group was superior to the other groups. In Experiment 2, we found that with weak prime-target associations, priming was comparable for read and generate groups and stronger than estimated for a guessing strategy, on the basis of single predictions made from each prime by an additional group. In Experiment 3, we demonstrated that the read and generate instructions produced similar mispriming and inhibitory effects. The results suggest that the depths of prime-processing manipulations do not have parallel effects on priming and episodic memory, and that associative priming in word identification, as in other tasks, may involve an expectancy process.

Adult↗

PubMedDate not supplied

Correlation of bottom-to-top surface microhardness and conversion ratios for a variety of resin composite compositions.

Knoop microhardness (KHN) and degree of conversion (DC) values were obtained from the bottom and top surfaces of 1-, 2- and 3-mm thick samples of three types of resin composite: an anterior microfill, an anterior hybrid and a posterior hybrid, all having differing filler size and loading but similar shade (A2) and basic monomeric content. Sample infrared spectra were obtained using attenuated total reflectance (ATR) in a Fourier transform infrared (FTIR) spectrometer. The samples were exposed using a 40-second exposure to a quartz-tungsten-halogen light source with an irradiance of approximately 560 mW/cm2. They were stored for 24 hours in complete darkness at 37 degrees C and 100% humidity prior to obtaining cured spectra and KHN readings. KHN andDC values were obtained from the same sample specimen made at similar surface depths, but separate groups were made for obtaining top and bottom values. Cure and hardness data were analyzed with one- and two-way ANOVAs followed by the Tukey-Kramer post-hoc test. Linear regression was also applied. Statistical testing was per. formed at a pre-set 0.05 level of significance. KHN and DC were significantly different according to composite type and depth (p=0.0001), with an interaction effect (p=0.0022). KHN, DC and corresponding bottom/top surface (B/T) ratios decreased with depth. Regression revealed a linear relationship between DC and KHN for each composite type, with no r2 less than 0.96. When B/T ratios were correlated, a B/T-KHN ratio of 0.80 corresponded to a narrow range of B/T-DC ratios (between 88 to 91%) for the three composites tested. When combining results from composite types, linear regression of B/T-DC and B/T-KHN produced a very predictable relationship (r2=0.959), for which a B/T-KHN ratio of 0.80 corresponded to a B/T-DC ratio of 0.90. As a measure of completeness of conversion, B/T-KHN was approximately 2.5 times more sensitive than the B/T-DC ratio. In summary, while KHN cannot be used to directly compare conversion of the different composites tested, the use of B/T ratios for both hardness and conversion resulted in a linear relationship independent of filler size or loading.

Barium↗

PubMed1984

Diamond knife corneal incisions.

In the following study, eight linear corneal incisions were made in two human cadaver eyes with three diamond-bladed knives: the KOI, Cooper, and Micra micrometer knives. Prior to the incisions, ultrasonic pachymetry readings of the corneas were recorded, and all knives were calibrated to a guarded cutting depth of 0.55 mm (550 microns). Following the incisions, the corneas were fixed, sectioned, and incision depth carefully measured histologically. In all but two incisions made with the Cooper knife, the incision depth was significantly or highly significantly greater than the calibrated diamond length. There was a significant or highly significant difference in depth among incisions made with the same knife, as well as among incisions made with different knives. Depth variability was noted for all knives except for two comparisons between incisions made with a Micra and KOI knife, and one comparison between two incisions, both made with the Cooper knife. Difference in knife design which may account for the variation of incision depth and contribute to the unpredictability of radial keratotomy is discussed.

Cadaver↗

PubMed2005

Excimer laser phototherapeutic keratectomy in eyes with anterior corneal dystrophies: short-term clinical outcomes with and without an antihyperopia treatment and poor effectiveness of ultrasound biomicroscopic evaluation.

PURPOSE: To evaluate the use of high-frequency ultrasound biomicroscopy (UBM) in determining the depth of corneal pathology in eyes undergoing excimer laser phototherapeutic keratectomy (PTK) for primary or recurrent anterior stromal corneal dystrophies. Corneal clarity, visual acuity, and refractive changes in eyes with and without an antihyperopia treatment were also analyzed. METHODS: Twenty eyes of 14 patients with anterior stromal corneal dystrophies were treated with PTK. Eyes were evaluated pre- and 6-8 weeks postoperatively with slit-lamp biomicroscopy, manifest refraction, keratometry, computerized corneal topography, ultrasound pachymetry, and UBM. RESULTS: Nineteen of 20 corneas (95%) had greatly improved corneal clarity after PTK. Mean uncorrected Snellen vision improved from 20/102 to 20/69, and best corrected vision improved from 20/62 to 20/38. Nine eyes (45%) improved two or more lines of uncorrected vision, and 13 eyes (65%) improved two or more lines of best corrected vision. Mean change in spherical equivalent was just -0.92 diopters (SD 4.3 diopters); however, the range was large (-13 to +3.88 diopters). UBM measurement of central corneal pathology did not correlate significantly with the actual PTK ablation depth (P = 0.07). The amount of antihyperopia treatment did not correlate with changes in manifest refraction spherical equivalent, keratometry, or computerized corneal topography readings but did correlate with length of time until corneal reepithelialization after PTK (P = 0.003). CONCLUSIONS: PTK resulted in improvements in corneal clarity and visual acuity in most patients with superficial corneal stromal dystrophies. UBM was not an effective tool to accurately measure the depth of corneal pathology preoperatively. The combined approach of minimizing ablation depth and selective use of an antihyperopia treatment resulted in minimal mean change in spherical equivalent; however, the range was large. PTK is a very good minimally invasive technique to improve vision in eyes with anterior stromal corneal dystrophies.

Adult↗

PubMed2003

Excimer laser phototherapeutic keratectomy in eyes with anterior corneal dystrophies: preoperative and postoperative ultrasound biomicroscopic examination and short-term clinical outcomes with and without an antihyperopia treatment.

PURPOSE: To evaluate the use of high-frequency ultrasound biomicroscopy (UBM) in determining the depth of corneal pathology in eyes undergoing excimer laser phototherapeutic keratectomy (PTK) for primary or recurrent anterior stromal corneal dystrophies. Corneal clarity, visual acuity and refractive changes in eyes with and without an antihyperopia treatment were also analyzed. METHODS: Twenty eyes of 14 patients with anterior stromal corneal dystrophies were treated with PTK. Eyes were evaluated preoperatively and 6 to 8 weeks postoperatively with slit-lamp biomicroscopy, manifest refraction, keratometry, computerized corneal topography, ultrasound pachymetry, and UBM. RESULTS: Nineteen of 20 corneas (95%) had greatly improved corneal clarity after PTK. Mean uncorrected Snellen vision improved from 20/102 to 20/69 and best corrected vision improved from 20/62 to 20/38. Nine eyes (45%) improved 2 or more lines of uncorrected vision, and 13 eyes (65%) improved 2 or more lines of best corrected vision. Mean change in spherical equivalent was just -0.92 diopters (D); however, the range was large (-13 to +3.88 D). UBM measurement of central corneal pathology did not correlate with the actual PTK ablation depth (P = .07). The amount of antihyperopia treatment did not correlate with changes in manifest refraction spherical equivalent, keratometry, or computerized corneal topography readings, but did correlate with length of time until corneal reepithelialization after PTK (P = .003). CONCLUSIONS: PTK resulted in improvements in corneal clarity and visual acuity in most patients with superficial corneal stromal dystrophies. UBM was not an effective tool to accurately measure the depth of corneal pathology preoperatively. The combined approach of minimizing ablation depth and selective use of an antihyperopia treatment resulted in minimal mean change in spherical equivalent; however, the range was large. PTK is a very good minimally invasive technique to improve vision in eyes with anterior stromal corneal dystrophies.

Adult↗

PubMed1998

Large discrepancies between calculated Dmax and diode readings for small field sizes and small SSDs of 15 MV photon beams.

Clinical observations have revealed that diode readings from 15 MV photon beams with small field sizes and small SSD values were consistently 5%-10% higher than doses calculated at the maximum depth. Dose at depth depends on the collimator scattering factor and the phantom scattering factor--both field size dependent. Diodes are placed on the skin surface, and therefore the phantom scatter factor is different than at depth. In addition, inverse square corrections should be calculated with respect to the location of the diode itself rather than the location of Dmax within the tissue. This may account for about 8% difference between calculated Dmax and diode readings for very small radiation fields and small SSDs, e.g., a prostate boost.

Biophysical Phenomena↗

PubMed1984

[Determination of the field size for a telegamma therapy apparatus].

Proceeding from an analysis of radiation field sizes (by a 50% dose) measured on gamma-beam units under various conditions of irradiation by means of the LSC-2 precision linear dosimetric scanner (Terados production, Sweden), the author recommends verifying the conformity of the sizes of these fields at a preset distance from a source with the readings of digital indication on the unit but not with the sizes of light fields. The divergence of the sizes of radiation fields measured at a preset distance from a source has been shown in the air, in the water at the depth of maximum ionization and in the water at 15 cm depth. In calibration of the diaphragm scale by the geometric field, i.e. by opening up its fringes , unavoidable non-correspondence of the actual sizes of radiation fields to the readings of digital indication is marked; the bigger the field and a source-surface distance the greater this non-correspondence. When measuring in the water at 15 cm depth, this divergence is greater than that in the water at the depth of maximum ionization, and the latter is greater than that measured in the air. It is found more appropriate to calibrate the diaphragm scale by the sizes of radiation fields measured in the air. The author assesses a maximum error in the determination of a field size by the manual shifting of a detector and an error of a dose meter. Basing on the above assessment it is found appropriate to use the precision automatic shifting of a detector in measuring a dose distribution pattern in the beam cross-section.

Gamma Rays↗

PubMed1999

Tracing therapeutic discourse in material culture.

Approaches to language and subjectivity from post-structuralist theory outside psychology and from deconstructive perspectives within counselling and psychotherapy have questioned the way therapeutic relationships are formed in Western culture. Discourse analysis has been developed as a methodological framework to take this questioning further, and to provide detailed readings of therapeutic patterns of meaning. Foucauldian discourse analytic approaches help us to address how we are made into selves that speak, how we experience the self therapeutically. I will elaborate this methodological framework through an analysis of a piece of text--an item of consumer packaging--tracing the contours of therapeutic discourse through a series of 20 methodological steps. Therapeutic discourse draws the reader in as the kind of subject who must feel a relationship at some depth with the (imagined) authors for the text to work. This paper thus illustrates the value of discourse analytic readings of texts, and helps us to reflect upon our commitment to discourses of counselling and psychotherapy as empowering stories and as culturally-specific patterns of subjectivity.

Counseling↗

PubMed1998

Single-use, disposable, presterilized light-activation probe: the future?

OBJECTIVE: The purpose of this study was to compare a single-use, disposable, presterilized light activation probe with an equivalent autoclavable probe. Light output, heat generation, and depth of cure were investigated. METHOD AND MATERIALS: Ten disposable and two reusable probe tips were tested. Three maximum light output readings for each tip were recorded with a radiometer. Heat generation at the probe tip was recorded, at 30-second intervals over a five-minute period, with a thermocouple probe placed under a 3-mm-thick glass slide. After light-activated "compomer" was placed in a sectional two-piece stainless steel mold and cured, depth of cure was evaluated using the scrape technique. RESULTS: With respect to light output and depth of cure, there were no statistically significant differences between probe types, but the disposable probe generated significantly less heat. CONCLUSION: The disposable probe performed clinically as well as an autoclavable counterpart with respect to light output, heat generation, and depth of cure.

Dental Instruments↗

PubMed1998

Anomalies of genetic development as predictors of oculo-visual abnormalities in velo-cardio-facial syndrome.

BACKGROUND: Subjects with velo-cardio-facial syndrome (VCFS) were assessed to determine whether the learning disabilities (LDs) characterizing the syndrome are compounded by visual function deficits, which would be predicted on the basis of the proposed embryonic derivation of the genetic anomaly. METHODS: Twelve subjects diagnosed with VCFS underwent a vision screening with emphasis on binocular function. RESULTS: Subjects exhibited deficits in accommodation (N = 5), convergence (N = 7), fusional reserves (N = 9), and stereopsis (N = 10). Three patients were strabismic at near. No patient was in the clinically normal range for all tests of binocular function. CONCLUSIONS: Individuals with VCFS have a chromosome 22 deficit thought to alter the migration of neural crest (NC) cells, which are the embryonic precursors of the autonomic innervation of the smooth muscle components of the eye and of cranial nerves III, IV, and VI. It was predicted that VCFS patients would demonstrate reduced accommodation and convergence flexibility, which would reduce visual comfort for near work. The pathological etiology of the visual anomalies suggests that if visual training is not successful, these patients should be provided with a suitable optical reading correction from an early age.

Accommodation, Ocular↗