摘要:

ABSTRACTA concentric variation in sagittal power, Fs, with zonal radius, y, has been used in some designs of varifocal and aphakic spectacle lenses. It is shown theoretically, using a paraxial approximation, that a gradient dFs/dy in sagittal power leads to the introduction of an amount ydFs/dy of unwanted astigmatism. The validity of this result is illustrated experimentally.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTOf the 800 presbyopes studied, 286 (35.75%) entered presbyopia at or before the age of 38 years. About 63% of these patients lived in rural areas and 37% in urban areas. Environmental conditions including high average temperature, much ultraviolet radiation, chronic deficiency of essential amino acids, and exposure to toxic factors, particularly hair dye, may play a significant role in precipitating the early onset of presbyopia.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTOxygen availability under hydrogel lenses was followed for 19 subjects over the first 6 months of wear. Each subject was assigned to a specific cleaning group, through which the method and intensity of cleaning was varied. The mean oxygen availability did not change significantly over the first six months of wear, regardless of the cleaning system used. However, the stability of the oxygen supply was dependent on the intensity of the cleaning system.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID