| 摘要 |
<p>1484382 Ophthalmic lenses AMERICAN OPTICAL CORP 14 Aug 1974 [16 Aug 1973] 35846/74 Heading G2J A progressive power ophthalmic lens having an umbilical principal meridian 52 extending in a generally vertical direction includes a viewing zone 58 between an upper distance vision zone 54 and a lower close vision zone 56, the zone 58 having a progressively increasing dioptric power from its upper boundary to its lower boundary and having vertical and horizontal axes of astigmatism to provide astigmatic correction in the laterally outer portions CEF, C'E'F'. The centre portion BFF'B' of the reading zone is of constant dioptric power while the laterally outer portions are contoured to connect smoothly with adjoining portions of the lens. The boundaries between vertically juxtaposed viewing zones may be smooth, the dioptric power changing continuously, or they may be formed by ledges which are shaped to render them substantially invisible.</p> |
