| lens vesicle | In the embryo, the ectodermal invagination that forms opposite the optic cup; it is the primordium of the lens of the eye. Synonym: lenticular vesicle. (05 Mar 2000) |
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| lighthouse lens | <physics> A lens built up, progressively, in zones or steps, each zone with its own individual radius. Considerable spherical correction is attained, and the weight of the lens is greatly reduced. Fresnel lenses were originally designed for lighthouses but they are now attainable for small spotlights, automobile headlights, and similar uses. (05 Aug 1998) |