scholarly journals THE RELATION BETWEEN FOVEAL VISUAL ACUITY AND ILLUMINATION UNDER REDUCED OXYGEN TENSION

1940 ◽  
Vol 23 (5) ◽  
pp. 613-630 ◽  
Author(s):  
R. A. McFarland ◽  
M. H. Halperin
Keyword(s):  
Visual Acuity ◽  
Oxygen Tension ◽  
Cent Oxygen ◽  
Large Decrease ◽  
Atmospheric Conditions ◽  
Normal Value ◽  
Oxygen Tensions ◽  
The Right ◽  
Very High ◽  
Intensity Axis

1. The foveal visual acuity of eleven subjects was studied in relation to illumination under normal atmospheric conditions and at simulated altitudes of 10,000 feet (14.3 per cent O2) and 18,000 feet (10.3 per cent O2). A mask was used to administer the desired mixtures of oxygen and nitrogen. At the end of each experiment, measurements were made while inhaling 100 per cent oxygen from a cylinder. A red filter (No. 70 Wratten) was used so as to study only the behavior of the cones of the retina. 2. The logarithm of illumination was plotted horizontally (abscissa) and the logarithm of visual acuity vertically (ordinate). The reduced oxygen tensions resulted in a shift of the curve to the right, along the intensity axis, the extent of the change being 0.24 of a log unit at 14.3 per cent O2 and 0.47 of a log unit at 10.3 per cent O2. These effects were completely counteracted within a few minutes by inhaling oxygen. 3. As a consequence of the shape of the curve, such a shift to the right resulted in a relatively large decrease of visual acuity at low illuminations. At increasing light intensities anoxia produced less and less change, until at very high illuminations the decrease was negligible. Thus with 10.34 per cent O2 the visual acuity at 0.144 photons decreased an average of 0.344 of a log unit, to 45 per cent of its normal value. At 1320 photons, however, it decreased only 0.026 of a log unit, to 94 per cent of its normal value for that intensity.

POLYHYDRIC ALCOHOL PRODUCTION BY OSMOPHILIC YEASTS: EFFECT OF OXYGEN TENSION AND INORGANIC PHOSPHATE CONCENTRATION

1957 ◽  
Vol 3 (4) ◽  
pp. 559-567 ◽  
Author(s):  
J. F. T. Spencer ◽  
Ping Shu
Keyword(s):  
Oxygen Tension ◽  
Inorganic Phosphate ◽  
Opposite Effect ◽  
Ethanol Yield ◽  
Phosphate Concentration ◽  
Alcohol Production ◽  
Lower Oxygen ◽  
Oxygen Tensions ◽  
Effect Of Oxygen ◽  
Very High

A study was made of the effects of oxygen tension and inorganic phosphate concentration on the production of glycerol, arabitol, and ethanol by a strain of osmophilic yeast. Increasing the oxygen tension increased the yields of glycerol and arabitol and decreased the yield of ethanol, while increasing the concentration of inorganic phosphate had the opposite effect.The changes in yields of products with increasing phosphate concentration were most pronounced at a partial pressure of oxygen of 280 mm. of mercury. At lower oxygen tensions the yields of polyols were low and the yield of ethanol was high at all concentrations of phosphate, while at very high oxygen tensions the opposite effect was observed. When the ethanol yield was high, the respiratory quotient was also high. These results are discussed in relation to the oxidative phosphate-lack theory of the Pasteur effect.

In Vitro Studies of Erythropoiesis

Blood ◽  
1955 ◽  
Vol 10 (6) ◽  
pp. 612-615 ◽  
Author(s):  
E. D. THOMAS
Keyword(s):  
Bone Marrow ◽  
Oxygen Tension ◽  
In Vitro Studies ◽  
Cent Oxygen ◽  
In Vitro Synthesis ◽  
Heme Synthesis ◽  
Rabbit Bone ◽  
Oxygen Tensions ◽  
Effect Of Oxygen

Abstract The effect of various oxygen tensions on the in vitro synthesis of heme by rabbit bone marrow was measured. At levels above 4 per cent oxygen there was no effect of oxygen tension on heme synthesis. Total anoxia stopped heme synthesis completely. No level of oxygen tension was found to stimulate heme synthesis.

scholarly journals OXYGEN TENSION AND THE RATES OF MITOSIS AND INTERPHASE IN ROOTS

1962 ◽  
Vol 13 (3) ◽  
pp. 365-371 ◽  
Author(s):  
J. E. Amoore
Keyword(s):  
Oxygen Tension ◽  
Cent Oxygen ◽  
Low Oxygen ◽  
Root Tips ◽  
Pea Root ◽  
Wide Range ◽  
Oxygen Tensions ◽  
Mitotic Figures

The object of this work was to determine the influence of a wide range of oxygen tensions upon the relative rates of respiration, mitosis, and interphase in pea root tips, compared with the normal rates of these processes in air. From the rates of disappearance of mitotic figures in excised tips kept in various oxygen tensions, the relative rates of mitosis were found to decrease gradually from 122 per cent in 100 per cent oxygen to 24 per cent in 0.0007 per cent oxygen. From the mitotic indices of intact seedlings, the relative rates of interphase were found to decrease sharply from 82 per cent in 10 per cent oxygen to 6 per cent in 5 per cent oxygen. The data on relative rates of respiration, mitosis, and interphase in root tips were compared, and it was shown that the three processes are perfectly distinct in their quantitative relationships to low oxygen tensions.

scholarly journals STUDIES ON BONE MARROW IN VITRO

Blood ◽  
1948 ◽  
Vol 3 (2) ◽  
pp. 165-174 ◽  
Author(s):  
A. ROSIN ◽  
M. RACHMILEWITZ
Keyword(s):  
Bone Marrow ◽  
Oxygen Tension ◽  
Gas Mixtures ◽  
Cent Oxygen ◽  
Low Oxygen ◽  
Bone Marrow Cultures ◽  
Oxygen Tensions ◽  
Marrow Cultures

Abstract The effect of various oxygen tensions on explanted bone marrow fragments was studied. It was found that gas mixtures containing 1, 3, 5, 10 and 12 per cent oxygen have an injurious effect on hemic cells. Bone marrow maintained in these gas mixtures showed various degrees of degeneration, which was the more pronounced the lower the oxygen tension. Mitotic activity was also found to be reduced under the influence of low oxygen tension. Bone marrow cultures maintained in a gas mixture containing 15 per cent oxygen did not show appreciable changes and were similar to the controls. Increased rate of maturation and multiplication occurred in bone marrow cultures maintained in an excess of oxygen, i.e. 50 per cent. The significance of these findings in the light of observations on the effect of anoxia in vivo has been discussed, and reported findings on the effect of low oxygen tensions on other tissues in vitro have been briefly reviewed.

Islamic hedging for pilgrimage funds: case of Indonesia

2019 ◽  
Vol 11 (3) ◽  
pp. 328-341
Author(s):  
Rifki Ismal ◽  
Nurul Izzati Septiana
Keyword(s):  
Exchange Rate ◽  
The Other ◽  
Exchange Rate Risk ◽  
Content Type ◽  
Other Hand ◽  
Rate Risk ◽  
Risk Identify ◽  
Hajj Season ◽  
The Right ◽  
Very High

Purpose The demand for Saudi Arabian real (SAR) is very high in the pilgrimage (hajj) season while the authority, unfortunately, does not hedge the hajj funds. As such, the hajj funds are potentially exposed to exchange rate risk, which can impact the value of hajj funds and generate extra cost to the pilgrims. The purpose of this paper is to conduct simulations of Islamic hedging for pilgrimage funds to: mitigate and minimize exchange rate risk, identify and recommend the ideal time, amount and tenors of Islamic hedging for hajj funds, estimate cost saving by pursuing Islamic hedging and propose technical and general recommendations for the authority. Design/methodology/approach Forward transaction mechanism is adopted to compute Islamic forward between SAR and Rupiah (Indonesian currency) or IDR. Findings – based on simulations, the paper finds that: the longer the Islamic hedging tenors, the better is the result of Islamic hedging, the decreasing of IDR/USD is the right time to hedge the hajj funds and, on the other hand, the IDR/SAR appreciation is not the right time to hedge the hajj funds. Findings Based on simulations, the paper finds that: the longer the Islamic hedging tenors, the better is the result of Islamic hedging, the decreasing of IDR/USD is the right time to hedge the hajj funds and, on the other hand, the IDR/SAR appreciation is not the right time to hedge the hajj funds. Research limitations/implications The research suggests the authority to (and not to) hedge the hajj fund, depending on economic conditions and market indicators. Even though the assessment is for the Indonesian case, other countries maintaining hajj funds might also learn from this paper. Originality/value To the best of author’s knowledge, this is the first paper in Indonesia that attempts to simulate the optimal hedging of hajj funds.

scholarly journals Clinical Phenotype of PDE6B-Associated Retinitis Pigmentosa

2021 ◽  
Vol 22 (5) ◽  
pp. 2374
Author(s):  
Laura Kuehlewein ◽  
Ditta Zobor ◽  
Katarina Stingl ◽  
Melanie Kempf ◽  
Fadi Nasser ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Genetic Testing ◽  
Retinitis Pigmentosa ◽  
Fundus Autofluorescence ◽  
Retinal Disease ◽  
New Drugs ◽  
Autofluorescence Imaging ◽  
Full Field ◽  
Tertiary Referral Center ◽  
The Right

In this retrospective, longitudinal, observational cohort study, we investigated the phenotypic and genotypic features of retinitis pigmentosa associated with variants in the PDE6B gene. Patients underwent clinical examination and genetic testing at a single tertiary referral center, including best-corrected visual acuity (BCVA), kinetic visual field (VF), full-field electroretinography, full-field stimulus threshold, spectral domain optical coherence tomography, and fundus autofluorescence imaging. The genetic testing comprised candidate gene sequencing, inherited retinal disease gene panel sequencing, whole-genome sequencing, and testing for familial variants by Sanger sequencing. Twenty-four patients with mutations in PDE6B from 21 families were included in the study (mean age at the first visit: 32.1 ± 13.5 years). The majority of variants were putative splicing defects (8/23) and missense (7/23) mutations. Seventy-nine percent (38/48) of eyes had no visual acuity impairment at the first visit. Visual acuity impairment was mild in 4% (2/48), moderate in 13% (6/48), and severe in 4% (2/48). BCVA was symmetrical in the right and left eyes. The kinetic VF measurements were highly symmetrical in the right and left eyes, as was the horizontal ellipsoid zone (EZ) width. Regarding the genetic findings, 43% of the PDE6B variants found in our patients were novel. Thus, this study contributed substantially to the PDE6B mutation spectrum. The visual acuity impairment was mild in 83% of eyes, providing a window of opportunity for investigational new drugs. The EZ width was reduced in all patients and was highly symmetric between the eyes, making it a promising outcome measure. We expect these findings to have implications on the design of future PDE6B-related retinitis pigmentosa (RP) clinical trials.

Choroidal metastases: case report and review

2020 ◽  
pp. 1-7
Author(s):  
Victor Duque ◽  
Carolina de la Pinta ◽  
Ciriaco Corral ◽  
Carmen Vallejo ◽  
Margarita Martin ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Side Effects ◽  
External Beam Radiotherapy ◽  
Choroidal Metastasis ◽  
Good Visual Acuity ◽  
Good Local Control ◽  
Radiological Response ◽  
The Right ◽  
The Brain

Abstract Introduction: Choroidal metastases are the most frequent intraocular secondary tumours, with a prevalence of 2–7% according to the literature. Our aim was to review a clinical case of choroidal metastasis. We present a case of a 63-year-old male patient diagnosed in 2018 with lung adenocarcinoma cT4N0M1. The patient had three metastases in the brain, which were successfully treated with radiosurgery (RS). The patient was treated with chemotherapy with pemetrexed–cisplatin schedule. Five months after diagnosis, the patient presented with decreased vision in the right eye. After ophthalmologic evaluation, he was diagnosed with a right choroidal metastasis, which was treated with external beam radiotherapy with 20 Gy in five fractions, resulting in improved visual acuity and a complete clinical and radiological response. The patient took part in a clinical trial that continued with systemic chemotherapy. Twenty-two months after radiotherapy to the eye, the patient has good visual acuity without any side effects. Conclusions: Choroidal metastasis treated with radiotherapy achieves good local control, with limited side effects, allowing an improvement in visual acuity and consequently, an improvement in the patient´s quality of life.

scholarly journals Development of Stage 4 Macular Hole after Spontaneous Closure in a Patient with Stage 2 Macular Hole and a Lamellar Macular Hole-Associated Epiretinal Proliferation

2021 ◽  
pp. 481-484
Author(s):  
Masahisa Watanabe ◽  
Harumasa Yokota ◽  
Hiroshi Aso ◽  
Hirotsugu Hanazaki ◽  
Junya Hanaguri ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Macular Hole ◽  
Spontaneous Closure ◽  
Surgical Removal ◽  
Lamellar Macular Hole ◽  
Full Thickness ◽  
Stage 4 ◽  
Full Thickness Macular Hole ◽  
The Right ◽  
Hole Closure

Herein, we report the longitudinal observation of a case with reopening of the macular hole associated with a lamellar macular hole-associated epiretinal proliferation (LHEP) followed by spontaneous closure in patients with stage 2 idiopathic macular hole. A 64-year-old woman was referred for the decreased visual acuity (VA) and acute anorthopia in the right eye. Funduscopy and optical coherence tomography (OCT) showed stage 2 full-thickness macular hole without posterior vitreous detachment (PVD) and operculum formation. Her best-corrected visual acuity (BCVA) was 20/32. One month later, the diameter of the macular hole was getting small and VA improved. Six months later, the macular hole was treated spontaneously with the attached hyaloid membrane to the macula by OCT and the BCVA improved to 20/20. Fourteen months after the first visit, the BCVA decreased to 20/50 and the patient was diagnosed with stage 4 macular hole with complete PVD. OCT showed full-thickness macular hole with a LHEP in the right eye. After 25G-gauge vitrectomy with the peeling of internal limiting membrane (ILM) and LHEP, the macular hole was closed and BCVA finally improved to 20/25. Spontaneous macular hole closure without PVD may rarely occur in patients with LHEP. The surgical removal of ILM and LHEP may contribute to the successful macular hole closure after vitrectomy.

scholarly journals Valsalva Retinopathy Associated with Sexual Activity

2014 ◽  
Vol 2014 ◽  
pp. 1-3 ◽  
Author(s):  
Khalid Al Rubaie ◽  
J. Fernando Arevalo
Keyword(s):  
Visual Acuity ◽  
Sexual Activity ◽  
Vision Loss ◽  
Internal Limiting Membrane ◽  
Internal Limiting Membrane Peeling ◽  
Sudden Loss ◽  
Initial Visual Acuity ◽  
Pars Plana ◽  
23 Gauge ◽  
The Right

A 54-year-old healthy male presented complaining of sudden loss of vision in the right eye. Initial visual acuity was counting fingers. The patient’s acute vision loss developed after sexual activity. Color fundus photos and fluorescein angiography were performed showing a large subinternal limiting membrane hemorrhage in the macular area. A 23-gauge sutureless pars plana vitrectomy with brilliant blue assisted internal limiting membrane peeling was performed with best-corrected visual acuity recovery to 20/50 at 6 months of followup.

scholarly journals Spontaneous Thrombosis of an Orbital Arteriovenous Malformation Revealing Hereditary Haemorrhagic Telangiectasia (Rendu-Osler-Weber Disease)

2011 ◽  
Vol 17 (4) ◽  
pp. 466-471 ◽  
Author(s):  
C. Van Went ◽  
A. Ozanne ◽  
G. Saliou ◽  
G. Dethorey ◽  
I. De Monchy ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Intraocular Pressure ◽  
Arteriovenous Malformation ◽  
Genetic Disorder ◽  
Hereditary Haemorrhagic Telangiectasia ◽  
Spontaneous Thrombosis ◽  
Vein Thrombosis ◽  
Recurrent Epistaxis ◽  
The Right ◽  
Central Retinal Vein

Hereditary Haemorrhagic Telangiectasia (HHT) is a genetic disorder responsible for cutaneous or mucosal telangiectasia and arteriovenous malformations (AVMs). The most frequent locations are lung and brain. In contrast, orbital AVMs are very rare. We describe a case of symptomatic orbital arteriovenous malformation due to spontaneous thrombosis. A 65-year-old woman was referred for chronic right eye proptosis associated with dilation of conjunctival vessels with a jellyfish pattern. Right visual acuity was 20/40 and intraocular pressure was 40 mmHg. Personal and familial history of recurrent epistaxis, associated with multiple telangiectasia within lips and palate, led to the diagnosis of HHT. Magnetic resonance imaging (MRI) completed with cerebral angiography found a giant and occluded AVM within the right orbit. Other AVMs were also found in brain and chest, confirming the diagnosis. Antiglaucomatous eyedrops were added to reduce intraocular pressure and a steroid therapy was begun. Two months later, visual acuity decreased in the right eye, due to a central retinal vein thrombosis. In conclusion, Most brain or pulmonary AVM can be treated by embolization. By contrast, this treatment in case of orbital location can lead to central retinal artery and/or central retinal vein occlusion, which may also appear as a spontaneous complication of the orbital AVM. Therapeutic management of orbital AVM is thus not standardized, and the balance between spontaneous and iatrogenic risk of visual loss has to be taken into account.

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