Glistenings in hydrophobic acrylic intraocular lenses do affect visual function

We recently read the paper "Evaluation of in vitro glistening formation in hydrophobic acrylic intraocular lenses" by Thomes and Callaghan. 1 The paper is extremely interesting in that the authors, employees of Alcon Research Ltd (Forth Worth, TX, USA), report not only that Alcon lenses have glistenings, but also that "continuous improvements on glistening formation" 1 have been made by Alcon over the years from 2003 to 2012.We congratulate the authors and Alcon on their efforts, and on making this admission.The paper raises a number of concerns and questions.Firstly, the statement in the introduction, "Glistenings are typically observed within a few months of surgery and plateau approximately 1 year after surgical implantation of the [intraocular lens] IOL" 1 is not referenced.The reported literature is in contradiction to this statement, in that the glistenings formation, as well as the severity of glistenings, has been reported to increase with longer follow-up times.[2][3][4][5][6][7][8] Very few studies that evaluate the progression beyond one year find glistening formation to be stable.[9][10] In addition, this statement is contradicted by the authors themselves in the introduction section of this paper where they state that a study by Colin et al 4 found that 73.8% of the IOLs had glistenings when follow-up was less than 2 years, and 94.2% of the IOLs had glistenings when the follow-up was longer than 2 years.Even after10 years of follow-up, no plateau was seen. 2 In the Introduction, the authors state that "These results are consistent with most studies regarding glistening formation in AcrySof ® IOLs that found no impact on visual function." 1 This statement is incorrect.Although Snellen visual acuity is only affected by severe grades of glistenings, visual function is affected earlier.Six published papers examined the effect of glistenings on contrast sensitivity (CS).Four of these studies reported that glistenings had a significant negative effect on the high spatial frequency of CS, 3,[11][12][13] and two studies were inconclusive.9,10 While some studies do show a decrease in visual acuity with increased severity of glistenings, 4,13 the general consensus in the literature tends to be that visual acuity is unaffected by glistening.In vitro studies report a positively correlated relationship between the total integrated light scatter and the severity of glistenings.14,15 Also, several in vivo studies found increased levels of intraocular stray light.[16][17][18] This analysis is published in van der Mooren et al. 19 The authors state that continuous improvements "... include the implementation of advanced manufacturing equipment, improved environmental controls, and tightened process controls/specifications. Specific details of these improvements cannot be fully disclosed due to the proprietary nature of the IOL manufacturing process." 1 This is Clinical Ophthalmology downloaded from https://www.dovepress.

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