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Star testing: a novel evaluation of intraocular lens optical quality

¹ Ophthalmology Department, Dunedin Hospital, Dunedin, New Zealand
² Ophthalmology Section, Department of Medical and Surgical Sciences, University of Otago Dunedin School of Medicine, Dunedin, New Zealand

Correspondence to:
Correspondence to:
Dr Logan Mitchell
Ophthalmology Department, Dunedin Hospital, Private Bag 1921, Great King Street, Dunedin 9001, New Zealand; acb.molteno{at}stonebow.otago.ac.nz

Background: Despite the importance of optical quality of an intraocular lens (IOL) on visual outcomes following cataract surgery, objective data on their optical quality are not readily available, and manufacturing standards are industry regulated. The star test is a classic test of optical quality based on examination of the Airy disc and expanded diffraction rings of a point source of light, used mainly for telescope and microscope objectives.

Methods: A physical model eye cell allowed star testing of IOLs under conditions similar to the optical environment in which they operate. 18 IOLs were tested and results compared to actual images produced by these lenses in the model eye cell. Quantitative measures of star testing performance were developed.

Results: The optical performance of the IOLs varied, some performing very poorly. Most lenses (13/17) performed better in reverse orientation, while aberrations induced by the haptics of foldable IOLs were also detected. There was excellent correlation between actual images formed and star testing parameters.

Conclusion: Star testing IOLs was a novel biomedical application of a centuries old, inexpensive method. A concerning variation of optical quality was found, suggesting IOL optical performance data should be more readily available. Independent, authority mandated IOL optical quality standards should be developed, and results readily available to ophthalmologists.

Abbreviations: ANSI, American National Standards Institute; IOL, intraocular lens; ISO, International Standards Organisation; MTF, modulation transfer function; NA, numerical aperture

Keywords: intraocular lens; star test; optics