Evaluation of re-depositing hydropower trapped sediments at large rivers to improve flood protection and aquatic habitats - Case study Danube/Austria.

Sedimentation in impoundments of run-of-river hydropower plants is an ongoing and progressing management issue for hydropower operators because of its consequences for e.g., the maintenance of flood protection and waterway parameters. Current practices in sediment management are often unsustainable, associated with high costs, and can pose risks for downstream biota (e.g. during flushing). The present study elaborated a conceptual model of a novel sediment management strategy for impounded river sections consisting of a current-state and deficit analysis, and the application of a novel sediment management practice, which was practically implemented at the study site at the Austrian Danube River. This novel practice consists of (i) local dredging of gravel at locations in the impoundment, which are problematic in terms of flood protection and waterway maintenance, and (ii) the re-deposition of dredged sediments by artificial placement of gravel structures. The present study included morphological analyses of the impounded section at the study site by applying the channel profile budget technique. The knowledge of the long-term morphological development served as a basis for the evaluation of the sediment management measures and for the elaboration of the conceptual model. The combination of the morphodynamic characteristics in the impoundment with the implementation of the novel sediment management practice helped to derive generalized statements for the potential implementation of the presented conceptual model in large rivers with similar impoundment characteristics. We further defined several aspects, which are related to sediment dynamics in impounded river sections, flood protection, waterway demands, and ecological criteria that require consideration for an efficient realization of the proposed conceptual model.

Endophthalmitis after radial keratotomy enhancement.

A 45-year-old man developed endophthalmitis after a radial keratotomy (RK) enhancement. He developed severe intraocular inflammation, hypopyon, and dense vitreous membranes 4 days after the enhancement surgery. Cultures of the corneal wound yielded a heavy growth of Streptococcus viridans. The inflammation subsided after treatment with intraocular, intravenous, and topical antibiotics. The patient subsequently developed a cataract and retinal detachment. This case demonstrates the risk of endophthalmitis after RK enhancement.

Choroidal neovascularization after laser photocoagulation for diabetic macular edema.

Choroidal neovascular membranes (CNVMs) developed in eight patients after photocoagulation for clinically significant diabetic macular edema (DME). The CNVMs developed in areas where Bruch's membrane was ruptured and were diagnosed 2 weeks to 5 months after treatment. Only six patients had symptoms. The CNVMs were treated in four patients; final visual acuity was poor in all eight patients. This serious complication that follows laser treatment for DME may be related to the use of repeated small-size, short-duration laser or intense laser burns, or both.

Prevention of lens opacification during diabetic vitrectomy.

Lensectomy at the time of vitrectomy on diabetic patients markedly increases the risk of postoperative neovascular glaucoma, and is to be avoided when possible. We conducted a randomized prospective double-blind trial to determine if the addition of supplemental glucose to BSS Plus intraocular irrigating solution would lessen or prevent intraoperative lens opacification. Ten subjects received BSS Plus (glucose = 100 mg/dl); five (50%) developed intraoperative lens changes which interfered with the surgeon's view (three to an extent necessitating lensectomy). Ten subjects received glucose fortified BSS Plus (glucose = 400 mg/dl); none developed intraoperative lens changes (P less than 0.03, Mann-Whitney Rank). There was no statistically significant difference between the two study groups with respect to preoperative lens changes, infusion fluid volume, operative time, patient age, duration of diabetes, fasting blood glucose level, hemoglobin A1 level or lens clarity 5 months after surgery. We conclude that glucose fortification of BSS Plus significantly reduces intraoperative lens opacification during diabetic vitrectomy.

Predicting age of onset for individuals at risk for phakic retinal detachment.

Three hundred sixty-five cases of nontraumatic phakic retinal detachment were examined by analysis of covariance to determine the degree of association among type of detachment, refractive error, and age of onset. The combination of type of detachment and refractive error explained 57% of the variation in age of onset. Discrimination among types of detachment by variation in mean age was limited. Discrimination among types of detachment by variation in mean refractive error could not be established. Detachments due to vitreoretinal adhesion, lattice degeneration, and retinal dialysis differed significantly in mean age of onset and regression of age on refractive error. A regression model was created to predict from refractive error the age of onset with 95% confidence limits for individuals who appear to be at risk for these types of detachment.

The effect of intraocular irrigating solutions on lens clarity in normal and diabetic rabbits.

We conducted a series of experiments on normal and diabetic rabbits to evaluate the effect of intraocular irrigating solutions on the lens. Lenticular clarity was studied in vivo in eyes undergoing vitreous cavity perfusions with various irrigating solutions. The clarity of isolated lenses incubated in these same solutions was also evaluated. In order to quantitate the cataractous changes observed, we measured the uptake of inulin (tagged with radioactive carbon) by isolated lenses. We found that balanced salt solution (BSS) and BSS Plus maintain excellent lens clarity in normal rabbits; that diabetic lenses are more likely to develop opacification than normal lenses, becoming cataractous when exposed to BSS Plus; and that adding supplemental glucose to BSS Plus allows this solution to maintain excellent lens clarity in diabetic rabbits.

Epidemiology of retinal detachment.

A survey of rhegmatogenous retinal detachment during 1976 was conducted on the population of Iowa. The annual incidences (per 100,000 populations) of four types of detachment were determined: nontraumatic phakic (6.1), traumatic phakic (1.0), nontraumatic aphakic (4.9), and traumatic aphakic (0.4). The incidences of nontraumatic phakic detachment for men and women were similar, although there was a preponderance of women that reflected their greater representation in the general population. The proportions of men were significantly higher in traumatic detachments compared with nontraumatic detachments. Men tended to be younger than women for all types of detachment; however, only in nontraumatic aphakic detachment was there a significant difference between mean ages. There was an insignificant preponderance of right eye involvement in all four detachment groups.

Fatty acid and lipid composition of the monkey retina in diet-induced hypercholesterolemia.

We determined the fatty acid composition of the lipids of cynomolgus monkey retina in animals fed commercial chow or a saturated fat, cholesterol-enriched atherogenic diet for 100 days. Doxosahexaenoic acid (22 : 6) accounted for 25.8% of the ethanolamine phosphoglyceride fatty acids, 17.6% of the serine plus inositol phosphoglyceride fatty acids, 8.4% of the choline phosphoglyceride fatty acids and 5.8% of the neutral lipid fatty acids in the retinas of the chow-fed animals. Therefore, monkey retinas, like those of other mammalian species, ordinarily contain large amounts of 22 : 6. Retinas from the monkeys fed the atherogenic diet contained less 22 : 6 as well as other polyunsaturates in each of the phospholipid classes. The decrease in polyunsaturates was compensated for by increases in palmitic, stearic, and oleic acids. There was no difference in the amount of phospholipid, the distribution of phospholipid classes, or the amount of cholesterol in the retinas of the monkeys fed the atherogenic diet. These results indicate that the single type of lipid alteration produced in the retina by a diet enriched in saturated fat and cholesterol is a decrease in the polyunsaturation of the retinal phospholipids. The reduction in retinal 22 : 6 content might have significance for photoreceptor function.

Prophylactic timolol for the prevention of high intraocular pressure after cataract extraction. A randomized, prospective, double-blind trial.

Eyes undergoing routine intracapsular cataract extraction (without alpha-chymotrypsin) often experience marked ocular hypertension in the first six hours after surgery. We conducted a randomized, prospective, double-blind study to determine if timolol maleate would prevent this increase in pressure. Thirty-five eyes undergoing routine cataract extraction were given a drop of either timolol 0.5% or placebo twice before and twice after surgery. Nine (56.3%) of 16 control eyes and 2 (10.5%) of 19 timolol-treated eyes had pressures above 30 mm Hg at six hours after surgery (P less than 0.025). Thus, prophylactic timolol 0.5% can substantially reduce the incidence of severe early postoperative ocular hypertension.

Plasma cortisol and elective cataract surgery.

Plasma cortisol was measured before and after elective cataract surgery in 19 patients given local anesthesia and in 11 patients given general anesthesia. In eight patients control plasma cortisols were measured at times corresponding to the surgical determinations. These eight patients demonstrated the circadian pattern of a fall in plasma cortisol. Only seven (37%) of 19 patients given local anesthesia failed to demonstrate the four-hour decrease in plasma cortisol (4-hr. p.o./8 A.M.0 greater than or equal to 0.80) following surgery, but this occurred in ten (91%) of 11 patients under general anesthesia (P less than .005). The 8:00 A.M. value was increased on the first postoperative day (8 A.M.1/8 A.M.0 greater than or equal to 1.37) in five (26%) of 19 patients given local anesthesia, but this occurred in 8 (73%) of 11 patients undergoing general anesthesia (P less than .025). The cortisol response to cataract surgery was significantly both more frequent and of greater magnitude in those patients undergoing general anesthesia.