Risk factors for complications following traumatic hyphema

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Effect of melanin on traumatic hyphema in rabbits

Objective: To investigate the role of melanin in influencing the clearance of traumatic hyphema and in the incidence of rebleeds following the hyphemas. Methods: Hyphemas were induced in 30 eyes of New Zealand white albino rabbits using an Nd:YAG laser. A total of 3.75 mg of synthetic melanin suspended in 0.1 mL of balanced salt solution was introduced into the anterior chambers of 16 animals. A total of 0.1 mL of balanced salt solution was injected into 14 control eyes. Hyphema levels were measured by a masked observer (V.D.B.) daily for 15 days. Pairs of animals were sacrificed at 1, 3, 5, 10, and 15 days and the eyes studied histologically. Results: Hyphemas were consistently produced in all eyes with mean ± SD levels of 1.44 ± 0.22 mm and 1.57 ± 0.24 mm in the melanin-treated and control eyes, respectively. The clearance of hyphemas in the melanin-treated eyes was significantly prolonged throughout the study (P < .001). The rate of rebleed in the melanin-treated group was 18.8% and in the control group was 7.1% (P < .01). Histologically, both groups showed variable degrees of blood in the anterior chambers and trabecular meshwork. In addition, the melanin-treated eyes showed free melanin, melanin-laden macrophages, and an inflammatory response in the anterior chamber and trabecular meshwork that was greater than that in the control eyes. Melanin-treated eyes with rebleeds showed organized hemorrhage with neovascularization. Conclusions: The presence of melanin results in a significantly prolonged course of hyphemas and may influence the rate of rebleeds. Occlusion of the trabecular meshwork with melanin-laden macrophages and inflammation may be the mechanisms responsible for these effects. Clinical Relevance: The release of melanin into the anterior chamber during ocular trauma may be partly responsible for the susceptibility of darker-pigmented individuals to more serious complications following a traumatic hyphema.link_to_subscribed_fulltex

Corneal 'dellen' as a complication of strabismus surgery

PURPOSE: This paper presents results of an analysis on patients operated on for strabismus in order to evaluate frequency and clinical characteristics of corneal alterations. In our experience, this kind of complication occurs more frequently after reoperation and/or after surgery for esotropia in sixth nerve palsy using transposition procedures. METHODS: A retrospective analysis was made of 655 consecutive patients operated on for strabismus on the recti muscles with a limbal approach from January 2001 to July 2003 (30 months). RESULTS: We found 30 corneal dellen out of the 184 eyes (16.30%) reoperated on medial rectus muscles, 7 corneal dellen out of the 37 eyes (18.92%) operated on using transposition procedures, 4 corneal dellen out of the 101 eyes (3.96%) operated of lateral rectus muscle recession combined with medial rectus muscle resection and no corneal dellen in the other 976 eyes operated of using different surgical procedures on the recti muscles. All patients had been operated on using a conjunctival limbal approach. All corneal dellen disappeared in about 10-15 days, using topical antibiotics and a firm bandage applied to the eye at night, leaving permanent alterations in corneal homogeneity in 8 eyes (19.51%). CONCLUSION: This study showed that this kind of complication is relatively frequent after reoperations and/or transposition procedures, thus indicating that it is possible to identify surgical procedures which might play a role in the development of corneal dellen. Therefore, the post-operative monitoring of patients at risk should not be delayed for more than one week, in order to avoid possible corneal perforation

Co-evolution of wetland landscapes, flooding, and human settlement in the Mississippi River Delta Plain

© 2016, The Author(s). River deltas all over the world are sinking beneath sea-level rise, causing significant threats to natural and social systems. This is due to the combined effects of anthropogenic changes to sediment supply and river flow, subsidence, and sea-level rise, posing an immediate threat to the 500–1,000 million residents, many in megacities that live on deltaic coasts. The Mississippi River Deltaic Plain (MRDP) provides examples for many of the functions and feedbacks, regarding how human river management has impacted source-sink processes in coastal deltaic basins, resulting in human settlements more at risk to coastal storms. The survival of human settlement on the MRDP is arguably coupled to a shifting mass balance between a deltaic landscape occupied by either land built by the Mississippi River or water occupied by the Gulf of Mexico. We developed an approach to compare 50 % L:W isopleths (L:W is ratio of land to water) across the Atchafalaya and Terrebonne Basins to test landscape behavior over the last six decades to measure delta instability in coastal deltaic basins as a function of reduced sediment supply from river flooding. The Atchafalaya Basin, with continued sediment delivery, compared to Terrebonne Basin, with reduced river inputs, allow us to test assumptions of how coastal deltaic basins respond to river management over the last 75 years by analyzing landward migration rate of 50 % L:W isopleths between 1932 and 2010. The average landward migration for Terrebonne Basin was nearly 17,000 m (17 km) compared to only 22 m in Atchafalaya Basin over the last 78 years (p \u3c 0.001), resulting in migration rates of 218 m/year (0.22 km/year) and \u3c0.5 m/year, respectively. In addition, freshwater vegetation expanded in Atchafalaya Basin since 1949 compared to migration of intermediate and brackish marshes landward in the Terrebonne Basin. Changes in salt marsh vegetation patterns were very distinct in these two basins with gain of 25 % in the Terrebonne Basin compared to 90 % decrease in the Atchafalaya Basin since 1949. These shifts in vegetation types as L:W ratio decreases with reduced sediment input and increase in salinity also coincide with an increase in wind fetch in Terrebonne Bay. In the upper Terrebonne Bay, where the largest landward migration of the 50 % L:W ratio isopleth occurred, we estimate that the wave power has increased by 50–100 % from 1932 to 2010, as the bathymetric and topographic conditions changed, and increase in maximum storm-surge height also increased owing to the landward migration of the L:W ratio isopleth. We argue that this balance of land relative to water in this delta provides a much clearer understanding of increased flood risk from tropical cyclones rather than just estimates of areal land loss. We describe how coastal deltaic basins of the MRDP can be used as experimental landscapes to provide insights into how varying degrees of sediment delivery to coastal deltaic floodplains change flooding risks of a sinking delta using landward migrations of 50 % L:W isopleths. The nonlinear response of migrating L:W isopleths as wind fetch increases is a critical feedback effect that should influence human river-management decisions in deltaic coast. Changes in land area alone do not capture how corresponding landscape degradation and increased water area can lead to exponential increase in flood risk to human populations in low-lying coastal regions. Reduced land formation in coastal deltaic basins (measured by changes in the land:water ratio) can contribute significantly to increasing flood risks by removing the negative feedback of wetlands on wave and storm-surge that occur during extreme weather events. Increased flood risks will promote population migration as human risks associated with living in a deltaic landscape increase, as land is submerged and coastal inundation threats rise. These system linkages in dynamic deltaic coasts define a balance of river management and human settlement dependent on a certain level of land area within coastal deltaic basins (L)