Use of the Humphrey Lens Analyzer for Off-Axis Measurements of Spectacle Lenses
Atchison, David A., Kris, Michy, Sheedy, James E., & Bailey, Ian L. (1991) Use of the Humphrey Lens Analyzer for Off-Axis Measurements of Spectacle Lenses. Optometry and Vision Science, 68(4), pp. 299-308.
Automated focimeters can be used to make quick, precise measurements of off-axis power and prismatic effects corresponding to an eye rotating behind a spectacle lens. An automated focimeter, the Humphrey Lens Analyzer, was assessed in this regard. The Humphrey Lens Analyzer can be used to give a valid measure of off-axis power of lenses low power, but not of lenses with moderate to higher power (>3 D). For 3 D spherical lenses discrepancies of the order of 0.1 D occur at 30 degree rotation, and 6 D spheres give discrepancies of 0.5 D at the same rotation. Small discrepancies were found for measurements of prism. The Humphrey Lens Analyzer was also used in a mode where the lens being tested is rotated about the center of curvature of its back surface. This is the mode often used to assess aberrations and prism of progressive-addition lenses. In this mode, the instrument provides reasonable accuracy in estimating off-axis power corresponding to eye rotation for lenses with low power, but not for lenses with moderate to higher power (>3 D). However, it provides accurate values of the variation in off-axis surface power for low powered lenses with aspheric front surfaces. There were considerable systematic errors associated with the measurement of prism. A simple raytracing method was developed to predict the results of measurements with the Humphrey Lens Analyzer. Predictions of off-axis power were good when lenses were rotated about a position corresponding to the center-of-rotation of an eye, but were poorer when lenses were rotated about the center of curvature of their back surfaces. Predictions of prismatic efforts were good in both situations. A method by which the Humphrey Lens Analyzer should provide an accurate measurement of off-axis powers corresponding to eye rotation behind a spectacle lens is described, but has not been tested.
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|Item Type:||Journal Article|
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|Keywords:||aberration, automated focimeter, Humphrey Lens Analyzer, off, axis power, spectacle lenses|
|Subjects:||Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300)|
|Divisions:||Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
|Copyright Owner:||Copyright 1991 Lippincott Williams & Wilkins|
|Deposited On:||15 Aug 2006 00:00|
|Last Modified:||15 Jan 2009 07:09|
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