Vision screening devices have been successfully used for many years in the detection of amblyogenic risk factors, including refractive errors, media opacities, and strabismus. The purpose of this study was to demonstrate the ability of a digital vision screening device to detect strabismus accurately and effectively.

Patients with vertical strabismus due to 4th nerve palsy require surgical correction for diplopia and abnormal head postures. This study evaluates our long-term outcome in surgical treatment of this condition.

There are many different recommendations to guide ophthalmologists and optometrists when prescribing hyperopic correction in children. This study examines the difference in healthcare costs between the recommendations from the American Optometric Association (AOA) and the recommendations from the American Association for Pediatric Ophthalmology and Strabismus (AAPOS).

Prescribing glasses for children creates a unique challenge. Preschool vision screening identifies children in need of glasses but also creates false positive referrals that may lead to the over prescribing of glasses.

OBJECTIVE: Recent US Preventive Services Task Force recommendations on vision screening reported insufficient data to recommend vision screening in children <3 years of age. The Iowa photoscreening program, KidSight, has screened children from 6 months of age and older since 2000. We report our experience with vision screening in these children and compare the results of the photoscreens in children younger than 3 years with those of children of preschool age and older. METHODS: A retrospective review of results from the Iowa KidSight database using the MTI PhotoScreener containing results of children screened between May 1, 2000, and April 30, 2011. RESULTS: During the 11 years of the study, 210 695 photoscreens on children were performed at 13 750 sites. In the <3-year age group, the unreadable rate was 13.0%, the referral rate was 3.3%, and the overall positive-predictive value was 86.6%. In the 3- to 6-year-old children, the unreadable rate was 4.1%, the referral rate was 4.7%, and the overall positive-predictive value was 89.4%. CONCLUSIONS: No statistically significant difference was found in screening children from 1 to 3 years old compared with screening children >3 years old. These results confirm that early screening, before amblyopia is more pronounced, can reliably detect amblyogenic risk factors in children younger than 3 years of age, and we recommend initiation of photoscreening in children aged 1 year and older.

PURPOSE To investigate the incidence and characteristics of occlusion amblyopia with prescribed full-time patching and determine its effect on long-term visual acuity outcomes. METHODS The records of patients younger than 10 years diagnosed as having amblyopia between 1970 and 2000 were retrospectively reviewed. Patients were prescribed full-time occlusion and observed until completion of therapy. RESULTS Of 597 patients treated for amblyopia by full-time patching, 115 were diagnosed as having occlusion amblyopia (19.3%). Seventy-five percent (86 of 115) developed occlusion amblyopia during the first episode of full-time patching. Occlusion amblyopia occurred more frequently in children prescribed full-time patching at an earlier age (P = .0002), with an odds ratio of 8.56 (95% confidence interval: 2.73, 26.84) in children younger than 36 months and 2.66 (95% confidence interval: 0.96, 7.37) in children between 36 and 59 months old. Seven of the patients with occlusion amblyopia did not reverse fixation and continued to fixate with the initially amblyopic eye after treatment. Final visual acuity in these eyes with occlusion amblyopia was 20/30 or better. After cessation of treatment, the final interocular difference in visual acuity was less in patients with a history of occlusion amblyopia (P = .003). CONCLUSION Occlusion amblyopia occurred at all ages, but the incidence decreased with increasing age. Patients who developed occlusion amblyopia with prescribed full-time occlusion had less interocular visual acuity difference than patients who did not, suggesting that development of occlusion amblyopia can indicate the potential for the development of better vision in the originally amblyopic eye.

Redoubt Volcano in south-central Alaska began erupting on March 15, 2009, and by April 4, 2009, had produced at least 20 explosive events that generated multiple plumes of ash and numerous lahars. The 3108-m-high, snow- and ice-clad stratovolcano has an ice-filled summit crater that is breached to the north. The volcano supports about 4 km3 of ice and snow and about 1 km3 of this makes up the Drift glacier on the north side of the volcano. Explosive eruptions between March 23 and April 4, which included the destruction of at least two lava domes, triggered significant lahars in the Drift River valley on March 23 and April 4, and several smaller lahars between March 24 and March 31. Mud-line high-water marks, character of deposits, areas of inundation, and estimates of flow velocity revealed that the lahars on March 23 and April 4 were the largest of the eruption. In the 2-km-wide upper Drift River valley, average flow depths were at least 2–5 m. Average peak-flow velocities were likely between 10 and 15 ms− 1, and peak discharges were on the order of 104–105 m3 s− 1. The area inundated by lahars on March 23 was at least 100 km2 and on April 4 about 125 km2. Two substantial lahars emplaced on March 23 and one on April 4 had volumes on the order of 107–108 m3 and were similar in size to the largest lahar of the 1989–90 eruption. The two principal March 23 lahars were primarily flowing slurries of snow and ice derived from Drift glacier and the Drift River valley where seasonal snow and tabular blocks of river ice were entrained and incorporated into the lahars. Despite morphologic evidence of two lahars, only a single deposit up to 5 m thick was found in most places and it contained about 80–95% of poorly sorted, massive to imbricate assemblages of snow and ice clasts. The deposit was frozen soon after it was emplaced and later eroded and buried by the April 4 lahar. The lahar of April 4, in contrast, was primarily a hyperconcentrated flow, as interpreted from 1- to 6-m-thick deposits of massive to horizontally stratified sand to fine gravel. Rock material in the April 4 lahar deposit is predominantly juvenile andesite, whereas rock material in the March 23 deposit is rare and not obviously juvenile. We infer that the lahars generated on March 23 were initiated by a rapid succession of vent-clearing explosions that blasted through about 50–100 m of crater-filling glacier ice and snow, producing a voluminous release of meltwater from Drift glacier. The resulting surge of water entrained snow, fragments of glacier and river ice, and river water along its flow path. Small-volume pyroclastic flows, possibly associated with destruction of a small dome or minor eruption-column collapses, may have contributed additional meltwater to the March 23 lahars. Meltwater generated by subglacial hydrothermal activity and stored beneath Drift glacier may have been ejected or released rapidly as well. The April 4 lahar was initiated when hot dome-collapse pyroclastic flows entrained and swiftly melted snow and ice on Drift glacier. The resulting meltwater incorporated pyroclastic debris and rock material from Drift glacier to form the largest lahar of the 2009 eruption. The peak discharge of the April 4 lahar was in the range of 60,000–160,000 m3 s− 1. For comparison, the largest lahar of the 1989–90 eruption had a peak discharge of about 80,000 m3 s− 1. Lahars generated by the 2009 eruption led to significant channel aggradation in the lower Drift River valley and caused extensive inundation at an oil storage and transfer facility located there. The April 4, 2009, lahar was 6–30 times larger than the largest meteorological floods known or estimated in the Drift River drainage.

The factors that control the explosivity of silicic volcanoes are critical for hazard assessment, but are often poorly constrained for specific volcanic systems. Mount Hood, Oregon, is a somewhat atypical arc volcano in that it is characterized by a lack of large explosive eruptions over the entire lifetime of the current edifice (similar to 500,000 years). Erupted Mount Hood lavas are also compositionally homogeneous, with similar to 95% having SiO2 contents between 58 and 66 wt.%. The last three eruptive periods in particular have produced compositionally homogeneous andesite-dacite lava domes and flows.In this paper we report major element and volatile (H2O, CO2, Cl, S. F) contents of melt inclusions and selected phenocrysts from these three most recent eruptive phases, and use these and other data to consider possible origins for the low explosivity of Mount Hood. Measured volatile concentrations of melt inclusions in plagioclase, pyroxene, and amphibole from pumice indicate that the volatile contents of Mount Hood magmas are comparable to those in more explosive silicic arc volcanoes, including Mount St. Helens, Mount Mazama, and others, suggesting that the lack of explosive activity is unlikely to result solely from low intrinsic volatile concentrations or from substantial degassing prior to magma ascent and eruption. We instead argue that an important control over explosivity is the increased temperature and decreased magma viscosity that results from mafic recharge and magma mixing prior to eruption, similar to a model recently proposed by Ruprecht and Bachmann (2010). Erupted Mount Hood magmas show extensive evidence for mixing between magmas of broadly basaltic and dacitic-rhyolitic compositions, and mineral zoning studies show that mixing occurred immediately prior to eruption. Amphibole chemistry and thermobarometry also reveal the presence of multiple amphibole populations and indicate that the mixed andesites and dacites are at least 100 degrees C hotter than the high-SiO2 resident magma prior to mixing. Viscosity models suggest that recharge by hot, mafic magma prior to eruption can lower magmatic viscosity by at least a factor of four. Lower viscosity during ascent delays fragmentation and allows volatile escape through degassing, thus lowering the potential for explosive eruptions. These results suggest that low explosivity should be more common in volcanoes where intermediate magmas are produced through mixing of mafic and silicic magmas shortly before eruption. (C) 2012 Elsevier B.V. All rights reserved.

Kasatochi volcano in the central Aleutian Islands erupted unexpectedly on 7–8 August 2008. Kasatochi has received little study by volcanologists and has had no confirmed historical eruptions. The island is an important nesting area for seabirds and a long‐term biological study site of the U.S. Fish and Wildlife Service. After a notably energetic preeruptive earthquake swarm, the volcano erupted violently in a series of explosive events beginning in the early afternoon of 7 August. Each event produced ash‐gas plumes that reached 14–18 km above sea level. The volcanic plume contained large amounts of SO2 and was tracked around the globe by satellite observations. The cumulative volcanic cloud interfered with air travel across the North Pacific, causing many flight cancelations that affected thousands of travelers. Visits to the volcano in 2008–2009 indicated that the eruption generated pyroclastic flows and surges that swept all flanks of the island, accumulated several tens of meters of pyroclastic debris, and increased the diameter of the island by about 800 m. Pyroclastic flow deposits contain abundant accidental lithic debris derived from the inner walls of the Kasatochi crater. Juvenile material is crystal‐rich silicic andesite that ranges from slightly pumiceous to frothy pumice. Fine‐grained pyroclastic surge and fall deposits with accretionary lapilli cover the lithic‐rich pyroclastic flow deposits and mark a change in eruptive style from episodic explosive activity to more continuous ash emission with smaller intermittent explosions. Pyroclastic deposits completely cover the island, but wave erosion and gully development on the flanks have begun to modify the surface mantle of volcanic deposits.

Analysis of satellite images of Kasatochi volcano and field studies in 2008 and 2009 have shown that within about one year of the 7-8 August 2008 eruption, significant geomorphic changes associated with surface and coastal erosion have occurred. Gully erosion has removed 300,000 to 600,000 m(3) of mostly fine-grained volcanic sediment from the flanks of the volcano and much of this has reached the ocean. Sediment yield estimates from two representative drainage basins on the south and west flanks of the volcano, with drainage areas of 0.7 and 0.5 km(2), are about 10(4) m(3) km(-2) yr(-1) and are comparable to sediment yields documented at other volcanoes affected by recent eruptive activity. Estimates of the retreat of coastal cliffs also made from analysis of satellite images indicate average annual erosion rates of 80 to 140 m yr(-1). If such rates persist it could take 3-5 years for wave erosion to reach the pre-eruption coastline, which was extended seaward about 400 m by the accumulation of erupted volcanic material. As of 13 September 2009, the date of the most recent satellite image of the island, the total volume of material eroded by wave action was about 10(6) m(3). We did not investigate the distribution of volcanic sediment in the near shore ocean around Kasatochi Island, but it appears that erosion and sediment dispersal in the nearshore environment will be greatest during large storms when the combination of high waves and rainfall runoff are most likely to coincide.

Kasatochi Island, the subaerial portion of a small volcano in the western Aleutian volcanic arc, erupted on 7-8 August 2008. Pyroclastic flows and surges swept the island repeatedly and buried most of it and the near-shore zone in decimeters to tens of meters of deposits. Several key seabird rookeries in taluses were rendered useless. The eruption lasted for about 24 hours and included two initial explosive pulses and pauses over a 6-hr period that produced ash-poor eruption clouds, a 10-hr period of continuous ash-rich emissions initiated by an explosive pulse and punctuated by two others, and a final 8-hr period of waning ash emissions. The deposits of the eruption include a basal muddy tephra that probably reflects initial eruptions through the shallow crater lake, a sequence of pumiceous and lithic-rich pyroclastic deposits produced by flow, surge, and fall processes during a period of energetic explosive eruption, and a fine-grained upper mantle of pyroclastic-fall and -surge deposits that probably reflects the waning eruptive stage as lake and ground water again gained access to the erupting magma. An eruption with similar impact on the island's environment had not occurred for at least several centuries. Since the 2008 eruption, the volcano has remained quiet other than emission of volcanic gases. Erosion and deposition are rapidly altering slopes and beaches.

PURPOSE:To present the largest cohort of preschool children screened by the MTI PhotoScreener over a 9-year period from a single, statewide vision screening effort.DESIGN:Cross-sectional study.PARTICIPANTS:We included 147,809 children screened between May 1, 2000, and April 30, 2009 by a photoscreening program.METHODS:Retrospective review of results from the Iowa photoscreening program using the MTI PhotoScreener. The photographs were taken by volunteers from local Lions clubs and sent to the University of Iowa for interpretation. Children who failed the photoscreening were referred to local eye care professionals, who preformed a comprehensive eye evaluation and forwarded the results to the Iowa KidSight program.MAIN OUTCOME MEASURES:Number of screenings, referral rate, positive predictive value (PPV), follow-up rate, and associated costs per year are described.RESULTS:Over the 9 years of the continuously operating program, 147,809 children underwent photoscreens to detect amblyopic risk factors at 9746 sites. Because of abnormal photoscreen results, 6247 children (4.2%) were referred. Of the children, 24.3% were evaluated by local ophthalmologists and 76.7% were seen by local optometrists. Between 2000 and 2009, the follow-up rate ranged from a low of 36.1% to a high of 89.5%, with an overall program follow-up rate after the addition of the follow-up coordinator of 81.3%. The overall PPV of the MTI PhotoScreener was 94.2%. Taking into account overall operating budget including salaries and associated costs, the cost of screening 1 child has been reduced to $US9 per child.CONCLUSIONS:The addition of a part-time follow-up coordinator to the photoscreening program produced 89.5% follow-up rate when screening 147,809 children for amblyopia risk factors over a 9-year period.

A mass of snow and ice 400‐m‐wide and 105‐m‐thick began melting in the summit crater of Mount Chiginagak volcano sometime between November 2004 and early May 2005, presumably owing to increased heat flux from the hydrothermal system, or possibly from magma intrusion and degassing. In early May 2005, an estimated 3.8 × 106 m3 of sulfurous, clay‐rich debris and acidic water, with an accompanying acidic aerosol component, exited the crater through a tunnel at the base of a glacier that breaches the south crater rim. Over 27 km downstream, the acidic waters of the flood inundated an important salmon spawning drainage, acidifying Mother Goose Lake from surface to depth (approximately 0.5 km3 in volume at a pH of 2.9 to 3.1), killing all aquatic life, and preventing the annual salmon run. Over 2 months later, crater lake water sampled 8 km downstream of the outlet after considerable dilution from glacial meltwater was a weak sulfuric acid solution (pH = 3.2, SO4 = 504 mg/L, Cl = 53.6 mg/L, and F = 7.92 mg/L). The acid flood waters caused severe vegetation damage, including plant death and leaf kill along the flood path. The crater lake drainage was accompanied by an ambioructic flow of acidic aerosols that followed the flood path, contributing to defoliation and necrotic leaf damage to vegetation in a 29 km2 area along and above affected streams, in areas to heights of over 150 m above stream level. Moss species killed in the event contained high levels of sulfur, indicating extremely elevated atmospheric sulfur content. The most abundant airborne phytotoxic constituent was likely sulfuric acid aerosols that were generated during the catastrophic partial crater lake drainage event. Two mechanisms of acidic aerosol formation are proposed: (1) generation of aerosol mist through turbulent flow of acidic water and (2) catastrophic gas exsolution. This previously undocumented phenomenon of simultaneous vegetation‐damaging acidic aerosols accompanying drainage of an acidic crater lake has important implications for the study of hazards associated with active volcanic crater lakes.

An area of snow and ice 400 m wide and 105 m deep began melting at the summit crater of Mount Chiginagak volcano sometime between November 2004 and early May 2005, presumably due to increased heat flux from the hydrothermal system, or possible magma intrusion and degassing. In early May 2005, an estimated 3.8 x 106 m 3 of sulfurous, clay-rich debris and acidic water, with an accompanying acidic aerosol component, exited the crater through a tunnel at the base of a glacier that breaches the south crater rim. Over 27 km downstream, the acidic waters of the flood inundated an important salmon spawning drainage, acidifying Mother Goose Lake from surface to depth (approximately 0.5 km in volume with a pH of 2.9 to 3.1), killing all aquatic life, and preventing the annual salmon run. Crater lake water sampled 8 km downstream of the summit outflow after considerable dilution from glacial meltwater was a weak sulfuric acid solution (pH = 3.2, SO4 = 504 mg/L, CI = 53.6 mg/L, and F = 7.92 mg/L). The acid flood waters caused severe vegetation damage including plant death and leaf kill along the flood flow path. The flood was accompanied by an ambioructic flow of acidic aerosols that followed the flood flow-path, contributing to defoliation and necrotic leaf damage to vegetation in a 29 km 2 area along and above affected streams, in areas to heights of over 150 m in elevation above the drainage. Moss species killed in the event contained high levels of sulfur indicating an extremely elevated atmospheric sulfur content. The most abundant airborne phytotoxic constituents were likely wet sulfuric acid aerosols in possible combination with dry SO2 gas that were released during the catastrophic partial crater-lake drainage event. Two mechanisms of acidic aerosol formation are proposed: (1) generation of aerosol mist through turbulent flow of acidic water, and (2) catastrophic gas exsolution. This previously undocumented phenomenon of simultaneous vegetation-damaging acidic aerosols accompanying an acid crater lake drainage has important implications for the study of hazards associated with active volcanic crater lakes.

Purpose: To determine the stability of visual acuity (VA) after a standardized occlusion regimen in children with strabismic and/or anisometropic amblyopia.Design: Retrospective, population-based, consecutive observational case series.Participants: Four hundred forty-nine patients younger than 10 years who underwent an occlusion trial for amblyopia and were observed until there was a recurrence of amblyopia or for a maximum of 1 year after decrease or cessation of occlusion therapy.Methods: We performed a retrospective chart review of all patients treated by occlusion therapy for strabismic and/or anisometropic amblyopia at our institution over a 34-year period. Of the 1621 patients identified in our database, 449 met the eligibility criteria and were included in this study. Patients having at least a 2 logarithm of the minimum angle of resolution (logMAR)-level improvement in VA by optotypes or a change from unmaintained to maintained fixation preference during the course of occlusion therapy were included. A recurrence of amblyopia was defined as >= 2 logMAR levels of VA reduction or reversal of fixation preference within 1 year after a decrease or cessation of occlusion therapy.Main Outcome Measure: Recurrence of amblyopia after a decrease or cessation of occlusion therapy and its relationship with patient age and VA of the amblyopic eye at the time of decrease or cessation of occlusion therapy.Results: Of 653 occlusion trials, 179 (27%) resulted in recurrence of amblyopia. The recurrence was found to be inversely correlated with patient age. There was no statistically significant association between the recurrence of amblyopia and VA of the amblyopic eye at the end of maximal occlusion therapy.Conclusions: There is a clinically important risk of amblyopia recurrence when occlusion therapy is decreased before the age of 10 years. The risk of recurrence is inversely correlated with age (P < 0.0001). (c) 2006 by the American Academy of Ophthalmology.