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Proceedings Paper

Measurement of bifocal intraocular lens modulation transfer function using a charge-coupled device
Author(s): William J. Neubert; Jim L. McGarvey; George F. Green
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Paper Abstract

The special equipment requirements and limitations for bifocal intraocular lens MTF measurement using a CCD detector are discussed. Proper MTF measurement requires that at least 90% of the energy passing through the lens aperture be imaged within the sampled area of the sensor. Spectral filtering of optical density greater than 2.5 sufficiently eliminates out-of-band radiance. Well-corrected relay optics of numerical aperture at least twice that of the lens under test and a calibrated image scale are important for accurate results. Significant modulation losses at spatial frequencies well below the Nyquist sampling occur due to pixel geometry, blooming, and charge transfer inefficiency. for a bifocal intraocular lens, where the overall blur pattern may be as large as 0.5 mm, these factors can limit the ability to accurately compute modulation at spatial frequencies greater than 100 cycles/mm. Correction of equipment-induced modulation losses can be realized through improved data processing. Use of MTF measurement for quality control of the Storz TRUE VISTA TM bifocal intraocular lens is discussed. Results agree with theoretical expectations to within 10% modulation. Sensitivity to defects such as astigmatism and zone defects are demonstrated at low spatial frequencies.

Paper Details

Date Published: 26 May 1994
PDF: 12 pages
Proc. SPIE 2127, Ophthalmic Lens Design and Fabrication II, (26 May 1994); doi: 10.1117/12.176830
Show Author Affiliations
William J. Neubert, Storz Instrument Co. (United States)
Jim L. McGarvey, Storz Instrument Co. (United States)
George F. Green, Storz Instrument Co. (United States)

Published in SPIE Proceedings Vol. 2127:
Ophthalmic Lens Design and Fabrication II
Donn Michael Silberman, Editor(s)

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