Article
Straylight in monofocal and multifocal IOLs
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Published: | February 22, 2018 |
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Glare is an impairment of visual function caused by optical inhomogeneity of the eye media, which appears with the presence of bright light sources in the visual scene. Although it is most often described as blinding by intense light (e.g. cars’ headlights while driving at night), increased glare primarily reduces the contrast of the retinal image resulting in hazy vision, decreased color perception and difficulties with face recognition. As glare originates from light scattering in the eye (straylight), it can be quantified by the straylight parameter as standardized by the International Commission on Illumination. Increased straylight is often associated with pathological eye conditions, such as cataract. However, a recent literature review on straylight after crystalline lens exchange has shown that straylight elevation can also be found in pseudophakic patients that were considered free of pathology. Although the cause of the straylight increase in pseudophakia appears to be multifactorial, a series of studies have demonstrated that straylight from the implanted intraocular lens (IOL) can (partially) explain this problem. Straylight effects of the lens optical design have been investigated in vivo and in vitro in comparative studies (between monofocal and multifocal IOLs) showing rather inconclusive results. Small but statistically significant differences have been found between IOLs made of hydrophobic and hydrophilic material indicating that the composing material may be an important factor. IOL pathology, such as glistenings, surface deposits, and snowflake degeneration, has proven to be associated with significant straylight elevation. Given that seriously increased straylight can reduce the visual function of affected patients, the straylight parameter appears as an important (additional) indicator of the quality of vision.