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Marrie Van der Mooren, Patricia Piers, Jacolien Graver, Henk A Weeber; Halo measurement method for intraocular lenses. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3117.
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© ARVO (1962-2015); The Authors (2016-present)
Occurrences of halos after cataract surgery have been reported for pseudophakic subjects with monofocal and multifocal intraocular lenses (IOLs). The purpose of this study is to introduce an objective and subjective in vitro halo measurement method for IOLs.
To investigate the characteristics of halos, an in-vitro setup was developed. Based on a literature review of pseudophakic halos, the measurements should be capable of: 1) recording a light intensity profile in the focal plane with more than four decades of dynamic range; 2) providing an image of the halo; 3) providing intensity profiles and images that can discriminate monofocal from multifocal IOLs and, 4) measuring a field of view of at least 1 degree. The chosen setup consists of a model eye and an extended light source representing the headlight of a car. The model eye has dimensions and optical properties of a real eye, and is composed of a convex-concave cornea, an anterior chamber, a pupil, a holder for an IOL and a vitreous chamber. A CCD detector serves as the retina with a field flattener placed directly in front of the CCD chip.
Images with a total field of view of 1.2 degrees were recorded with a dynamic range of more than 4 decades and intensity profiles were determined up to seven decades using different shutter time. The halos were faint in comparison to the light intensity of the central focus. For displaying the halo without saturation of the central focus a gamma correction between 0.1 and 0.2 was needed. Images recorded for monofocal and multifocal IOLs showed clear differences, which were confirmed by the significant difference between the intensity profiles of both lens types. The difference was approximately one decade for the angular range from 0.25 to 0.6 degrees. The measured radial halo size of a multifocal lens with an add power of 4 diopters was found similar to the theoretical calculated halo size of 0.33 degrees.
The described in-vitro halo measurement method is capable of providing halo images and intensity profiles. The obtained intensity profiles may provide information about halo sizes and intensities and corresponds well with the reported range of clinical data for monofocal and multifocal IOLs.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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