LETTER TO THE EDITOR IOLs glistenings and quality of vision Andrzej Grzybowski 1,2 & Piotr Kanclerz 3 & George H. H. Beiko 4,5 Received: 16 August 2019 /Revised: 13 September 2019 /Accepted: 20 September 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Glistenings are small (1.0 to 20.0 μm) fluid-filled microvacuoles which appear within the intraocular lens (IOL) optic when it is placed in an aqueous environment [1]. It has been reported that the glistenings only occur when the IOL is immersed in liquid, suggesting that an influx of aqueous humour into existing spaces in the optic is the reason for this phenomena and not the degen- eration of IOL optic material [2]. Subsurface nanoglistenings (SSNGs) are much smaller fluid-filled gaps, measuring < 200 nm in size and < 120 microns from the surface of the optic of the IOL. SSNGs may give the IOL surface whitish coloration when the light is directed at the IOL at the angle of incidence of 30° or greater [3]. Primarily, glistenings and SSNGs were reported in Acrysof hydrophobic acrylic IOLs including clear and blue light filter- ing IOLs. In some IOL models glistenings were observed within a few months after cataract surgery, while up to 94.2% of patients had glistenings more than 2 years after IOL implantation [1]. Glistenings most frequently manifest in hydrophobic acrylic IOLs; however, hydrophobic IOLs dif- fer in their resistance to glistening [4]. Currently, glistenings have been reported in all types of IOL materials, including polymethylmethacrylate (PMMA), silicone, and hydrophilic acrylates. It has been suggested that only heparin-surface- modified PMMA lenses do not manifest glistenings. In a re- cent study by Łabuz et al., the glistening was induced in lenses made of different materials, with and without blue light filter, produced by different manufacturers (including Carl Zeiss Meditec, Hoya, Alcon, and Nidek) and manufacturing pro- cesses (lathe-cut and cast-molding) [4]. The number of glis- tenings differed among the studied IOLs and ranged from 0 to 3532 MW/mm 2 [4]. Recent studies have demonstrated that low water content, which in hydrophobic acrylic materials might typically be less than 0.5%, might partially be responsible for glistenings [5]. Its development is also associated with the breakdown of the blood-aqueous barrier, which is one of the hypotheses that explained why glistenings are more frequently seen and of greater severity in diabetic patients and glaucomatous eyes [1, 6]. Other factors such as temperature variations or issues related to the packaging have been suggested as independent risk factors. A potential association between the severity of glistenings and IOL power has been presented; a greater num- ber of glistenings would be expected in the higher power and thicker IOL matrix due to the greater amount of material [1]. Initially, the severity of glistenings was believed to stabilize after an initial increase [2]. More recent papers reported an increase in glistenings and SSNGs in hydrophobic IOLs even 15 years after IOL implantation, with no indication of levelling off of the phenomenon [7]. It has been argued that the optical quality of an IOL is not significantly affected by the level of glistenings. However, glistening was shown to degrade vision by inducing glare symptoms (straylight) rather than by lowering visual acuity [4]; straylight elevation demonstrates a proportional relation- ship with the number of glistenings [8]. Retinal straylight, even presenting in low levels, can cause increase in halo size, eleva- tion in luminance detection threshold, and reduction in contrast sensitivity, being a reason for persistent visual complaints [9]. The magnitude of retinal straylight might be clinically deter- mined by the level of disability glare. Another issue that should be considered, both in adult and pediatric cataract surgery, is that in the recent years, the antic- ipated duration of IOLs in the eye has significantly increased. The physico-chemical properties and IOL endurance should allow the lens to keep its optical properties for several decades. Glistenings are not unique to adults and have been reported in * Andrzej Grzybowski ae.grzybowski@gmail.com 1 Department of Ophthalmology, University of Warmia and Mazury, Olsztyn, Poland 2 Institute for Research in Ophthalmology, Foundation for Ophthalmology Development, 60-554 Gorczyczewskiego 2/3, Poznan, Poland 3 Private Practice, Gdańsk, Poland 4 Department of Surgery, McMaster University, Hamilton, Canada 5 Department of Ophthalmology and Visual Sciences, University of Toronto, Toronto, Canada Graefe's Archive for Clinical and Experimental Ophthalmology https://doi.org/10.1007/s00417-019-04496-8