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Straylight measurements in intraocular lenses with an optical integration method


Purpose : Different types of intraocular lenses (IOL’s) vary in their optical design (mono-, multi-focal), materials and manufacturing processes. All these factors may affect the wide-angle point spread function (PSF), and associated straylight, of the lenses affecting quality of vision. In this context, a new optical integration method was developed to measure straylight of different IOLs in vitro.

Methods : A new single-pass instrument based on the optical integration method (Ginis et al., JOV, 2012) has been developed and adapted to test IOLs. Multiple uniform bright disks with increasing size are projected on a screen using a pico-projector. The IOL under testing forms images of the disks onto a CMOS camera through a 2 millimetres aperture conjugated on the IOL immersed into purified water within a custom mount. The intensity in the center of imaged disk is recorded for 200 angular sizes from 0 to 9.7 degrees (radius). The wide-angle PSF is derived from the slope of the curve resulting from the normalised intensity of the centre of a disk as a function of its size. The values of the PSF at specific angles provided a straylight parameter (S) which was used a metric for comparison. Monofocal and two diffractive multifocal IOLs were tested with the instrument.

Results : The measured straylight parameter at 3 degrees (S3) was 3.28±0.01 for the monofocal IOL. For the multifocals, at their near focal plane, S3 was 9.27 ±0.01 and 6.16 ±0.01 whereas for their far focal plane were 9.07±0.03 and 5.86±0.06 respectively. At a larger angle (5 degrees), S5 was 3.13±0.03 for the monofocal IOL and 9.05±0.01; 9.72±0.01; 10.02±0.05 and 10.53±0.03 for the two multifocal at operating at near and far respectively.

Conclusions : A new single-pass instrument to measure the quantify the wide angle PSF associated to various IOLs has been developed. The use of the instrument in a few IOL samples showed a significant increase of straylight in multifocal diffractive IOLs compared to standard monofocal ones.

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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