Trends and connections across the Antarctic cryosphere

Satellite observations have transformed our understanding of the Antarctic cryosphere. The continent holds the vast majority of Earth’s fresh water, and blankets swathes of the Southern Hemisphere in ice. Reductions in the thickness and extent of floating ice shelves have disturbed inland ice, triggering retreat, acceleration and drawdown of marine-terminating glaciers. The waxing and waning of Antarctic sea ice is one of Earth’s greatest seasonal habitat changes, and although the maximum extent of the sea ice has increased modestly since the 1970s, inter-annual variability is high, and there is evidence of longer-term decline in its extent

A simple clinical test for perception of progressive addition lens peripheral image blue: a pilot study

Purpose: To introduce a simple method for subjective perception of progressive addition lens (PAL) peripheral image blur (PIB). The amounts of PIB induced by traditional PAL trial lenses (plano distant PAL, TPAL) and prescription PAL (FPAL) were also evaluated. Methods: Subjects wearing the PALs adjusted their heads laterally to view the fi xation target for PIB perception. 38 subjects were randomized and recruited from the Eye’ni optical shop. Outcomes were assessed by the high-contrast visual acuity chart (LogMAR scale), and by subjectively indicating the magnitude of PIB on a scale of 0 to 10 (10 is extremely blur) using astigmatism-sensitive optotype (Polatest® , Carl Zeiss Vision, Germany). Results: Visual acuities (mean ± SD) at the central and temporal fixations were measured at 0 ± 0.03 and 0.2 ± 0.04 with FPAL, and 0 ± 0.03 and 0.1 ± 0.03 with TPAL respectively. Signifi cantly lower visual acuities were found with the temporal fi xation than with the central fi xation in both PALs (p < 0.001). And signifi cant even reduction at the temporal fi xation with FPAL than with TPAL was observed (p < 0.001). For subjective measures of PIB using astigmatism-sensitive optotype, the average score of FPAL (7.4 ± 0.8, ranged 5-9) was found statistically higher than that of TPAL (6.7 ± 0.8, ranged 4-8) (p < 0.01). Conclusions: Our proposed simple clinical method appears to facilitate PAL peripheral image blur demonstration, which may help potential PAL wearers to effectively experience the peripheral PAL image blur. Opticians may caution the potential PAL wearers that prescription PAL may induce more peripheral image blur than that with the traditional distant plano PAL trial lenses. © 2010 Spanish General Council of Optometry. Published by Elsevier España, S.L. All rights reserved.link_to_OA_fulltex