Retinal neurovascular coupling in patients with glaucoma and ocular hypertension and its association with the level of glaucomatous damage

Purpose: To analyze neurovascular coupling in the retina of untreated primary open-angle glaucoma (POAG) and ocular hypertension (OHT) patients. Patients and methods: Maximal vessel dilation in response to flicker light was analyzed with Retinal Vessel Analyzer (RVA) in temporal superior/inferior arterioles and veins in 51 POAG patients, 46 OHT and 59 control subjects. RVA parameters were compared between groups, between contralateral POAG eyes, and correlated to intraocular pressure, visual field mean defect and retinal nerve fiber layer thickness. Results: POAG eyes demonstrated generally smaller response of all vessels to flicker light than the other two groups (ANOVA p = 0.026; mean arterial flicker response in percent of baseline, averaged superior and inferior was 3.48 ± 2.22% for controls , 2.35 ± 2.06 % for POAG patients , and 2.97 ± 2.35 % for OHT patients; corresponding values for venules were 3.88 ± 1.98%, 2.89 ± 1.72%, 3.45 ± 2.77%). There was no difference in flicker response between the eye with more and less advanced damage in each patient of the POAG group (ANOVA p = 0.79). Correlation of flicker response to intraocular pressure (IOP) was borderline at best, correlations to the level of glaucomatous damage were not significant. Correlation of flicker response of superior and inferior vessels of the same eye was significant for the arteries (Pearson r = 0.23, p = 0.004), as well as venules (r = 0.52, p < 0.001). Conclusion: General vessel response to flicker light was decreased in POAG patients, compared to normal controls and OHT patients. In contrast to significant correlation between the two contralateral eyes of the flicker response itself, only its borderline correlation to IOP was seen. There was no correlation to the level of damage, altogether indicating a systemic dysregulation phenomenon. Grants: Swiss National Foundation Grant 3200B0-113685, Velux Stiftung Grant, Freie Akademische Gesellschaft (FAG) Grant, Pfizer Inc. Grant Clinical trial registration reference number: ClinicalTrials.gov NCT0043020

Dynamics of retinal vessel response to flicker light in glaucoma patients and ocular hypertensives

Purpose: To analyze dynamics of retinal vessel dilation response to flicker light in patients with glaucoma and ocular hypertension. Patients and methods: Response to flicker light was measured in retinal vessels by means of Retinal Vessel Analyzer. After the baseline 50seconds long diameter recording of inferior and superior temporal artery and vein, three flicker stimulations of 20seconds duration was applied, with a 80seconds break in between. Area under the curve of the vessel diameter (AUC) was compared during 3 flicker periods in the open angle glaucoma patients group (POAG, n = 47) and ocular hypertensives (OHT, n = 46) and age-matched healthy controls (n = 56) Results: POAG eyes demonstrated smaller response of all vessels to flicker light in general than the other two groups (p = 0.0008), but the response dynamics was significantly different between the groups (p = 0.038), showing in three flicker periods a delayed increasing response in the POAG and OHT groups, and remaining stable in healthy subjects. Conclusion: General vessel response to flicker light was decreased in POAG patients despite the slow improvement in repeated flicker stimulation, indicating an altered response patter

Reaction chemistry of gold leaching in thiourea solution for a Turkish gold ore

This study was carried out on a finely disseminated gold-bearing ore from Kaymaz, Turkey. The main objective was to determine the mechanism of reaction between thiourea and Fe 31 in the thiourea leaching of gold. Thiourea consumption levels were also examined during the leaching operations for different leaching parameters, i.e., molar ratio of ferric sulfate/thiourea, pH, and temperature. The leaching using the thiourea process was compared with cyanidation. In optimum leach conditions, 85.8% gold extraction was obtained with feed of -53 mum particle size in 6 h

The prospects for an alternative gold leach reagent: Thiourea

Gold has been traditionally extracted from ores by leaching with an alkaline cyanide solution. However, certain characteristics and drawbacks of cyanidation process have stimulated research into alternative processes. A number of non-cyanide reagents have been tried for the dissolution of gold. Among them, thiourea leaching seems to be a promising process. This study was carried out on a finely disseminated Kaymaz gold ore (4 g/t Au). The effect of various leaching parameters such as concentration of thiourea, concentration of ferric sulphate, molar ratio of ferric sulphate/ thiourea, leaching duration, temperature and pulp density are studied. The investigations indicated that at room temperature with 16.04 kg/ton consumption of thiourea at pH of 1.35, it was possible to obtain a gold extraction of 85.8 % for the particle size of 80 % passing 53 micron feed in 6 hours. Staged addition of chemical reagents, pretreatment of ore by acid washing and microwave heating were also tested in accordance with lowering the thiourea consumption

Awareness about glaucoma and related eye health attitudes in Switzerland: a survey of the general public

OBJECTIVE: To assess the level of awareness about glaucoma and its consequences and to evaluate associated eye health attitudes in a randomly selected general urban and rural population in Switzerland. METHODS: A cluster random sample of the Swiss population was interviewed. Five-hundred and two telephone interviews with subjects who were representative of the 35- to 70-year-old population of the German- and French-speaking parts of Switzerland were conducted. Data were collected about their gender, age, educational status and professional situation. Study Type: Cross-sectional survey. RESULTS: In total, 76% (n = 383) of respondents did not have any (or any correct) association with the term 'glaucoma'. Only 24.7% (n = 123) of the interviewees could describe glaucoma as an eye condition. Awareness of glaucoma was independent of age, gender, educational status, and household income. Associated therapeutic measures were surgery (75%) and medical treatment (57%). Seventy-one percent of all respondents wear eyeglasses, 74% of all females and 67% of males. CONCLUSION: Awareness and knowledge about glaucoma are relatively low in the average Swiss population across all segments of society. The lack of awareness on this insidious disease has important implications for the uptake of ophthalmic care and may result in avoidable blindness. These data also show that the ophthalmologist is considered by the majority of people to be the primary contact for eye health-related information and sight corrections