Older observers' tolerance of optical blur: age differences in the identification of defocused text signs.

To determine if visual aging affects the ability to identify blurred text signs in daytime or nighttime viewing conditions, the photopic and mesopic legibility thresholds of young and old adult observers were compared at three levels of optically induced acuity (Experiment 1). For both age groups, legibility was reduced by nighttime luminance and degraded acuity. Surprisingly, older observers were better than younger ones in identifying defocused (optically blurred) text in both daytime and nighttime conditions. In Experiment 2, older observers were also superior to younger ones in identifying defocused standard and spatially matched novel text signs. These findings indicate that older observers' tolerance of optical blur is a generic ability, rather than one explained by familiarity with the low-pass optical profile of specific signs. Consistent with the notion that factors beyond acuity contribute more importantly to text legibility for older than for younger observers, acuity was a stronger predictor of legibility thresholds in the younger group. Actual or potential applications of this research include the need to consider functional acuity in visual screening protocols and the design of text displays, as well as the utilization of compensatory letter-recognition training for older observers or others with diminished acuity.

Contact allergy to Manilla resin. Nomenclature and physico-chemistry of Manilla, kauri, damar and copal resins.

16 cases of allergic eczema from a resin used in a surgical adhesive (Alphacopal) are described. Because of the extreme confusion regarding the nomenclature and origin of the resins called copals and damars, this report attempts to give a terminological, botanical, physico-chemical and allergological restatement of this problem. Copals and damars are produced by trees belonging to the Araucariaceae, Caesalpiniaceae, Dipterocarpaceae and Burseraceae families. We suggest that the word "copal" be reserved for the resins of the Caesalpiniaceae and that of "damar" for the resins of the Dipterocarpaceae. The resins of the Araucariaceae are special products that may be called Manilla resin and kauri resin, which are relatively different from each other. As far as the soft resins of the Burseraceae are concerned, it would be appropriate to use the word "elemi". The component resin of the surgical adhesive implicated (Alphacopal) is a Manilla resin, produced by a variety of Agathis dammara (Lamb.) Rich., native to the Philippines. We suggest 3 allergen screening series. Finally 2 pseudo-cross-sensitivities are mentioned.

Mini-epidemic of contact dermatitis from ginkgo tree fruit (Ginkgo biloba L.).

3 cases of contact dermatitis from ginkgo fruit are reported. Swelling of the prepuce can be the only clinical sign of intolerance, as was observed in 1 case. Diagnosis of contact dermatitis to ginkgo fruit should be made in cities where female ginkgo trees grow, in Chinese, Japanese and South-East Asian subjects, who are aware of the ginkgo nut's culinary qualities within the fruit, as well as in children who play with the fallen fruits as "marbles".