Eyeworld

18 | EYEWORLD | JULY 2019 ASCRS NEWS power, as suggested previously. 10 Furthermore, while a majority of the IOLs with glistenings had a "typical" configuration with highest concentration centrally, some had a peak density of glistenings in an eccentric location. It is not known how this configuration could affect the metrices measured. Lastly, it is unclear how repeated heating of the IOL to reach a desired glistening grade could affect the integrity of the IOL and image quality. Straylight, or light scattering, can be induced by glistenings and is another factor that can affect image quality, causing glare symptoms. While not studied in this paper, straylight may be significantly higher in IOLs with increased glistenings causing visual disturbances even in the presence of a high MTF value or Strehl ratio. Weindler et al.'s results are consistent with previous in vivo studies assessing the impact of glistenings on visual function. The AcrySof SA60AT lens with a limited degree of glisten- ings has a comparable optical quality to a clear IOL. Even the development of severe glisten- ings may not translate to a meaningful reduction in visual acuity or contrast sensitivity. As clini- cians examining glistenings in our pseudophakic patients, we should recognize that this seeming- ly impressive examination finding plays only a marginal role in optical performance. The authors concluded that image quality is not compromised in IOLs with low–moderate glistenings (grade 1–3). In IOLs with severe glistenings (>500 MV/mm 2 ), the impact on the MTF and Strehl ratio is limited and likely not visually significant. Previous in vivo studies as- sessing the impact of glistenings on visual acu- ity and contrast sensitivity have reported mixed results, with some showing reduced contrast sensitivity at higher special frequencies. 6,7 This study showed a similar trend: MTF decline was greater in frequencies higher than 25 lp/mm. Interestingly, the investigators found that monochromatic high order aberrations have a greater impact than glistenings on imaging qual- ity. In assessing the Strehl ratio in the 3.0 and 4.5 mm aperture size for clear IOLs, the ratio was 0.386 lower in the larger aperture group. Because the SA60AT is a spherical lens, an increased aperture size may induce significant spherical aberrations affecting optical perfor- mance. By comparison, grade 4 glistening in the 3 mm and 4.5 mm aperture IOLs only caused a decreased Strehl ratio of 0.068 and 0.096, respectively. This in vitro analysis assessed the impact of glistenings on a single type of hydrophobic IOL of a single power. It is possible that the visual impact of glistenings could depend on IOL continued from page 17 The impact of glistenings on the optical quality of a hydrophobic acrylic intraocular lens Jan Weindler, MD, Grzegorz Labuz, PhD, Timur Yildirim, MD, Tamer Tandogan, MD, Ramin Khoramnia, MD, Gerd Auffarth, MD J Cataract Refract Surg. 2019;45(7):1020–1025. n Results: Glistenings were observed in all IOLs. The mean glistening number ± standard deviation [MV/mm²] in grade 14 was 74±12.7 (grade 1), 142±22.2 (grade 2), 297±76.2 (grade 3), and 1509±311.9 (grade 4). The mean glistening size was 13.28±3.85 µm in grade 1, 15.88±2.08 µm in grade 2, 16.85±3.23 µm in grade 3 and 15.27±2.25 µm in grade 4. Statistical analysis showed that grades 1–3 did not change the optical quality, however, in grade 4 the MTF and the Strehl ratio were significantly affected. n Conclusions: We demonstrated that a limited number of glistenings (<500 MV/mm 2 ) have no impact on the image quality. Although a statistically significant deterioration of the MTF and the Strehl ratio was observed in grade 4, the effects found were small and are unlikely to affect the visual quality. n Purpose: To study the impact of glistenings on the optical quality of a hydrophobic acrylic intraocular lens (IOL). n Setting: David J. Apple Laboratory, Heidelberg, Germany n Design: An in vitro laboratory study. n Methods: An accelerated-aging protocol was used to induce glistenings (microvacuoles) in 38 SA60AT (Alcon) IOLs. The IOLs were subjected to 45 degrees C and then cooled to 37 degrees C. Image analysis of light- microcopy photographs determined the number and size of microvacuoles. A classification was applied based on the glistening number per mm 2 : grade 0 (none), grade 1 (1–100), grade 2 (101–200), grade 3 (201–500) and grade 4 (more than 500). An optical bench was used to measure the IOL's modulation transfer function (MTF) and Strehl ratio, to evaluate the impact of glistenings on image quality. References 1. Werner L. Glistenings and sur- face light scattering in intraocular lenses. J Cataract Refract Surg. 2010;36:1398–420. 2. Waite A, et al. Glistenings in the single-piece, hydrophobic, acrylic intraocular lenses. Am J Ophthalmol. 2007;144:143–4. 3. Hayashi K, et al. Long-term effect of surface light scattering and glistenings of intraocular lenses on visual function. Am J Ophthalmol. 2012;154:240–251. 4. Dhaliwal DK, et al. Visual significance of glistenings seen in the AcrySof intraocular lens. J Cataract Refract Surg. 1996;22:452–7. 5. Christiansen G, et al. Glisten- ings in the AcrySof intraocular lens: pilot study. J Cataract Refract Surg. 2001;27:728–33. 6. Gunenc U, et al. Effects on visual function of glistenings and folding marks in AcrySof intra- ocular lenses. J Cataract Refract Surg. 2001;27:1611–4. 7. Xi L, et al. Analysis of glis- tenings in hydrophobic acrylic intraocular lenses on visual performance. Int J Ophthalmol. 2014;7:446–51. 8. Pieh S, et al. In vitro Strehl ratios with spherical, aberration-free, average, and customized spherical aber- ration-correcting intraocular lenses. Invest Ophthalmol Vis Sci. 2009;50:1264–70. 9. Henriksen BS, et al. Effect of intraocular lens glistening size on visual quality. J Cataract Refract Surg. 2015;41:1190–8. 10. Colin J, et al. Glistenings in a large series of hydrophobic acryl- ic intraocular lenses. J Cataract Refract Surg. 2009;35:2121–6.

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