To assess corneal refractive changes after 15-minute visual tasks and their association with eyelid morphology.
Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University ...of Technology, Brisbane, Queensland, Australia.
Eighteen young subjects with normal ocular health were recruited. Corneal topography was measured with a videokeratoscope before and after 4 conditions consisting of 2 downward gaze angles (20 degrees and 40 degrees) and 2 types of visual tasks (reading and steady fixation). Anterior eye photography in downward gaze was used to determine the eyelid angle, tilt, and position with respect to the cornea.
Corneal refractive power changed significantly after the 15-minute downward gaze tasks. The largest mean corneal spherocylindrical change was +0.33 -0.30 x 84 after reading in the 40-degree downward gaze (4.0 mm corneal diameter). The refractive changes were significantly larger after the 40-degree tasks than after the 20-degree tasks (P<.001). The changes in refractive root-mean-square error were significant for all conditions, except the 20-degree steady fixation task, with 4.0 and 6.0 mm analysis diameters (P<.05). Significant correlations were found between some aspects of eyelid morphometry and corneal refractive change.
The pressure of the eyelids on the cornea in short-term downward gaze resulted in optically and clinically relevant corneal changes. Correlation between the refractive corneal changes and eyelid parameters suggests that the angle, shape, and position of the eyelids influence the nature of the corneal changes. When high accuracy is required, refraction should be qualified by the visual tasks undertaken before assessment.
The SIU Consensus Group on Genitourinary Trauma continue their report with the statement on trauma to the external genitalia. This will be the last such report, completing the series. These have been ...extremely important, and an excellent reference point for people interested in this subject.
In this paper, novel procedures were developed using a thin (0.17 mm) tactile piezoresistive pressure sensor mounted on a rigid contact lens to measure upper eyelid pressure. A hydrostatic ...calibration system was constructed, and the influence of conditioning (prestressing), drift (continued increasing response with a static load), and temperature variations on the response of the sensor were examined. To optimally position the sensor-contact lens combination under the upper eyelid margin, an in vivo measurement apparatus was constructed. Calibration gave a linear relationship between raw sensor output and actual pressure units for loads between 1 and 10 mmHg ( R 2 = 0.96 ). Conditioning the sensor prior to use regulated the measurement response, and sensor output stabilized about 10 s after loading. While sensor output drifts slightly over several hours, it was not significant beyond the measurement time of 1 min used for eyelid pressure. The error associated with calibrating at room temperature but measuring at ocular surface temperature led to a very small overestimation of pressure. Eyelid pressure readings were observed when the upper eyelid was placed on the sensor, and removed during a recording. When the eyelid pressure was increased by pulling the lids tighter against the eye, the readings from the sensor significantly increased.
BACKGROUNDRanitidine was the most prescribed histamine-2 receptor antagonist (H2RA) in Canada when recalled in 2019 because of potential carcinogenicity. We sought to compare geographic and temporal ...patterns in use of prescription ranitidine and 3 other HRAs and estimated population exposure to ranitidine in 6 provinces between 1996 and 2019.METHODSThis population-based serial cross-sectional study used prescription claims for H2RAs dispensed from community pharmacies in Nova Scotia, Ontario, Manitoba, Saskatchewan, Alberta and British Columbia. We estimated the period prevalence of ranitidine use per 100 population by province, age category and sex. We estimated exposure to ranitidine between 2015 and 2019 using defined daily doses (DDDs).RESULTSOverall, 2.4 million ranitidine prescriptions were dispensed to patients aged 65 years and older, and 1.7 million were dispensed to younger adults. Among older adults, the median period prevalence of ranitidine use among females was 16% (interquartile range IQR 13%-27%) higher than among males. Among younger adults, the median prevalence was 50% (IQR 37%-70%) higher among females. Among older adults, between 1996 and 1999, use was highest in Nova Scotia (33%) and Ontario (30%), lower in the prairies (Manitoba 18%, Saskatchewan 26%, Alberta 17%) and lowest in BC (11%). By 2015-2019, use of ranitidine among older adults dropped by at least 50% in all provinces except BC. We estimate that at least 142 million DDDs of prescribed ranitidine were consumed annually in 6 provinces (2015-2019).INTERPRETATIONOver the 24-year period in 6 provinces, patients aged 65 years and older were dispensed 2.4 million prescriptions of ranitidine and younger adults were dispensed 1.7 million prescriptions of ranitidine. These estimates of ranitidine exposure can be used for planning studies of cancer risk and identifying target populations for cancer surveillance.
It is known that eyelid pressure can influence the corneal surface. However, the distribution of eyelid pressure and the eyelid contact area and the biomechanics of the changes are unknown. Although ...these factors are difficult to directly measure, analysis of eyelid-induced corneal topographic changes and eyelid morphometry enables some inferences to be drawn.
Eighteen subjects, aged between 19 and 29 years, with normal ocular health were recruited. Corneal topographic changes were measured after 4 conditions consisting of 2 downward gaze angles (20 and 40 degrees) and 2 types of visual tasks (reading and steady fixation). Digital photography recorded the width of Marx line, the assumed region of primary eyelid contact with the cornea.
Significantly larger corneal changes were found after the 40-degree downward gaze conditions compared with 20-degree conditions because of the upper eyelid contact (P < 0.001). For the 40-degree downward gaze tasks, the lower eyelid changes were greater than those because of the upper eyelid (P < 0.01). The upper eyelid Marx line width was associated with the amplitude of corneal change (R = 0.32, P < 0.05).
Analysis of the corneal topographic changes gives insight into the pressure applied by the upper and lower eyelids in different situations. These include greater upper eyelid pressure with increasing downward gaze and greater lower eyelid pressure compared with the upper eyelid in 40-degree downward gaze. There was some evidence that supports Marx line as the primary site of contact between the eyelid margins and the cornea.
The naturally occurring compound 3β,16β,17α-trihydroxycholest-5-en-22-one 16-O-(2-O-4-methoxybenzoyl-β-D-xylopyranosyl)-(1→3)-(2-O-acetyl-α-L-arabinopyranoside) (OSW-1) is found in the bulbs of ...Ornithogalum saudersiae and is highly cytotoxic against tumor cell lines. Using various human cancer and nonmalignant cell lines, we investigated the anticancer activity and selectivity of OSW-1 and its underlying mechanisms of action. OSW-1 exhibited extremely potent cytotoxic activity against cancer cells in vitro. Nonmalignant cells were statistically significantly less sensitive to OSW-1 than cancer cells, with concentrations that cause a 50% loss of cell viability 40–150-fold greater than those observed in malignant cells. Electron microscopy and biochemical analyses revealed that OSW-1 damaged the mitochondrial membrane and cristae in both human leukemia and pancreatic cancer cells, leading to the loss of transmembrane potential, increase of cytosolic calcium, and activation of calcium-dependent apoptosis. Clones of leukemia cells with mitochondrial DNA defects and respiration deficiency that had adapted the ability to survive in culture without mitochondrial respiration also were resistant to OSW-1. In vitro analysis revealed that OSW-1 effectively killed primary leukemia cells from chronic lymphocytic leukemia patients with disease refractory to fludarabine. The promising anticancer activity of OSW-1 and its unique mechanism of action make this compound worthy of further investigation for its potential to overcome drug resistance.
This report describes the synthesis, structural characterization, and polymerization behavior of a series of chromium(II) and chromium(III) complexes ligated by tris(2-pyridylmethyl)amine (TPA), ...including chromium(III) organometallic derivatives. For instance, the combination of TPA with CrCl2 yields monomeric (TPA)CrCl2 (1). A similar reaction of CrCl2 with TPA, followed by chloride abstraction with NaBPh4 or NaBArF 4 (ArF = 3,5-(CF3)2C6H3), provides the weakly associated cationic dimers (TPA)CrCl2BPh42 (2A) and (TPA)CrCl2BArF 42 (2B), respectively. X-ray crystallographic analysis reveals that each chromium(II) center in 1, 2A, and 2B is a tetragonally elongated octahedron; such Jahn−Teller distortions are consistent with the observed high spin (S = 2) electronic configurations for these chromium(II) complexes. Likewise, reaction of CrCl3(THF)3 with TPA, followed by anion metathesis with NaBPh4 or NaBArF 4, yields the monomeric, cationic chromium(III) complexes (TPA)CrCl2BPh4 (4A) and (TPA)CrCl2BArF 4 (4B), respectively. Treatment of 4A with methyl and phenyl Grignard reagents produces the cationic chromium(III) organometallic derivatives (TPA)Cr(CH3)2BPh4 (5) and (TPA)CrPh2BPh4 (6), respectively. Similar reactions of 4A with organolithium reagents leads to intractable solids, presumably due to overreduction of the chromium(III) center. X-ray crystallographic analysis of 4A, 5, and 6 confirms that each possesses a largely undistorted octahedral chromium center, consistent with the observed S = 3/2 electronic ground states. Compounds 1, 2A, 2B, 4A, 4B, 5, and 6 are all active polymerization catalysts in the presence of methylalumoxane, producing low to moderate molecular weight high-density polyethylene.
To investigate if diurnal variation occurs in corneal topography.
Seventeen young subjects had corneal topography measured 3 times a day (around 9 AM, 1 PM, and 5 PM) on 3 days of the week (Monday, ...Tuesday, and Friday). Corneal tangential and refractive power were analyzed. To investigate diurnal variation in corneal aberrations, the corneal height data were converted into corneal wavefront error and expressed as Zernike wavefront coefficients.
A significant diurnal change in corneal tangential power maps was found in 15 of the 17 subjects. This change typically consisted of a horizontal band of distortion in the superior and, to a lesser extent, inferior cornea, increasing throughout the day. Corneal refractive power showed small but significant diurnal changes occurring in the best fit sphere. Corneal wavefront error analysis revealed significant diurnal changes occurring in astigmatism 90/180 degrees and astigmatism 45/135 degrees. Two higher-order aberrations, primary vertical coma and trefoil along 30 degrees, also showed significant diurnal change. The combination of these 2 aberrations represents a "wavelike" distortion increasing throughout the day and returning to baseline the next morning.
We have shown that significant diurnal change occurs in certain corneal aberrations. The changes appear to be related to forces from the eyelids on the anterior cornea. These findings may have important implications for customized refractive corrections and refractive error development.
Purpose
To examine the symmetry of corneal changes following near work in the fellow eyes of non‐amblyopic myopic anisometropes.
Methods
Thirty‐four non‐amblyopic, myopic anisometropes (minimum 1 D ...spherical equivalent anisometropia) had corneal topography measured before and after a controlled near work task. Subjects were positioned in a headrest to minimise head movements and read continuous text on a computer monitor for 10 min at an angle of 25 degrees downward gaze and an accommodation demand of 2.5 D. Measures of the morphology of the palpebral aperture during primary and downward gaze were also obtained.
Results
The more and less myopic eyes exhibited a high degree of interocular symmetry for measures of palpebral aperture morphology during both primary and downward gaze. Following the near work task, fellow eyes also displayed a symmetrical change in superior corneal topography (hyperopic defocus) which correlated with the position of the upper eyelid during downward gaze. Greater changes in the spherical corneal power vector (M) following reading were associated with a narrower palpebral aperture during downward gaze (p = 0.07 for more myopic and p = 0.03 for less myopic eyes). A significantly greater change in J0 (an increase in against the rule astigmatism) was observed in the more myopic eyes (−0.04 ± 0.04 D) compared to the less myopic eyes (−0.02 ± 0.06 D) over a 6 mm corneal diameter (p = 0.01).
Conclusions
Changes in corneal topography following near work are highly symmetrical between the fellow eyes of myopic anisometropes due to the interocular symmetry of the palpebral aperture. However, the more myopic eye exhibits changes in corneal astigmatism of greater magnitude compared to the less myopic eye.
Purpose
To investigate the diagnostic performance of perfusion single-photon emission computed tomography/computed tomography (Q-SPECT/CT) in patients suspected to have pulmonary embolism (PE) but ...with indeterminate computed tomographic pulmonary angiography (CTPA) or planar ventilation/perfusion (V/Q) scans.
Methods
This retrospective study included two groups of patients. Group I consisted of 49 patients with nondiagnostic CTPA. These 49 patients underwent subsequent V/Q scans. Further Q-SPECTs were obtained in patients with indeterminate planar images and fused with existing CTPA. Group II consisted of 182 non-CTPA patients with indeterminate V/Q scans. These 182 patients underwent further Q-SPECT and separate noncontrast low-dose CT chest. Fusion Q-SPECT/CT scans were obtained through FDA-approved software and interpreted according to published criteria as positive, negative, or indeterminate for PE. Upon retrospective analyses, the final diagnosis was made using composite reference standards including all available clinical and imaging information for at least 6-month follow-up.
Results
In group I patients, 1 was positive, 24 were negative, and another 24 (49 %, 24/49) were indeterminate. In the subsequent 24 Q-SPECT/CTPAs, 4 were positive, 19 were negative, and 1 was indeterminate (4.2 %, 1/24). In group II patients, 9 (4.9 %, 9/182) were indeterminate, 33 were positive, and 140 were negative. The combined nondiagnostic rate for Q-SPECT/CT was only 4.9 % (10/206). There was six false-negative and one false-positive Q-SPECT/CT examinations. The sensitivity, specificity, and positive and negative predictive value of Q-SPECT/CT were 85.7 % (36/42), 99.4 % (153/154), 97.3 % (36/37) and 96.2 % (153/159), respectively.
Conclusions
Q-SPECT/CT improves the diagnostic rate with promising accuracy in diagnosing PE that yields a satisfactory clinical verdict, especially when the CTPA and planar V/Q scan are indeterminate.
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