Hiroyuki Matsushima, MD, PhD on Whitening
Whitening (sub-surface nano glistening)
Whitening is a phenomenon that increases Surface Light Scattering（SLS, Figure 1）and is found in long term follow-up after implantation of Alcon AcrySof. Nishihara et al 1) first reported this phenomenon. Initially, deposition of substances such as protein was regarded as the cause of whitening. Nevertheless, SLS disappeared when drying the removed lens with whiting but reappeared when it was soaked into water. Thus, this fact concluded similarly for glistening, that the cause of whitening was a water phase separation in the optic material of intraocular lens (IOL) 2). We made an observation of removed IOL with whitening using cryo FIB-SEM and found that water in the optic material turned into about 100nm spherical configuration3). This is substantially smaller compared to the size of water phase separation in glistening; 1-20μm. This size difference is thought to cause distinctive views between glistening as bright spotting and whitening as dense cloudiness like fog. While glistening spreads all over the optic part of IOL, whitening occurs within near-surface of IOL optic. Thus, Alcon refers this phenomenon as sub-surface nano glistening.
Although whitening and glistening are observed often on AcrySof, influence on visual function is considered as not significant4, 5). Despite the circumstances, there are reported cases of deterioration of visual function where impacts from high level of whitening and glistening are suspected6-8). We have engaged in the recovery of visual function of such cases by removing the IOL and replacing with a new one. Not all implanted AcrySofs impose a disturbing level of whitening and glistening that may affect on visual function. Reportedly, a level of whitening increases over time. Therefore, condition may deteriorate over time and result in severe visual impairment. As IOL retrieval requires advanced surgical skill, it is crucial to develop and disseminate criteria for indication of IOL replacement and less-invasive operation procedures.
For fundamental solution, it is critical to understand the risk of whitening and glistening in various IOL products that are currently in market. We made implants of 3 kinds of IOLs using white domestic rabbits for 6 months as an experimental evaluation on change in IOL transparency. These lenses are AcrySof (Alcon), AF-1 (Hoya) and Avansee (Kowa). The removed IOLs were stored in 33°C saline to prevent post-surgical separation of water phase and examined at constant temperature (Figure 2). The study showed whitening and glistening on Acrysof, only glistening but not whitening on AF-1 and neither whitening nor glistening on Avansee. As shown in these lenses, latest IOL materials may have addressed problems in older products. It is important to develop an experiment system that expedites evaluations of long-term transparency while continuously engaging in development of IOL optic material for lasting transparency.
- Nishihara H, Yaguchi S, Onishi T, Chida M, Ayaki M. Surface scattering in implanted hydrophobic intraocular lenses. J Cataract Refract Surg 2003; 29: 1385-1388
- Matsushima H, Mukai k, Nagata M. Analysis of surface “whitening” of extracted AcrySof intraocular lenses. J Cataract Refract Surg 2009; 35: 1927-1934
- Matsushima H, Katsuki Y, Mukai K, Nagata M, Senoo T. Observation of whitening by cryo-focused ion beam scanning electron microscope. J Cataract Refract Surg 2011; 37: 788-789
- Miyata K, Otani S, Nejima R, Miyai T, Samejima T, Honbo M, Minami K, Amano S. Comparison of postoperative surface light scattering of different intraocular lenses. Br J Ophthalmol 2009; 93: 684-687
- Mönestam E, Behndig A. Impact on visual function from light scattering and glistenings in intraocular lenses, a long-term study. Acta Ophthalmol. 2010; 88: 1-5
- Werner L, Storsberg J, Mauger O, Brasse K, Gerl R, Muller M, Tetz M. Unusual pattern of glistening formation on a 3-piece hydrophobic acrylic intraocular lens. J Cataract Refract Surg. 2008; 34: 1604-1609
- Mitooka K, Shiba T, Tsuneoka H, Kitahara K. [A case of IOL eye with decrease of visual function by glistening]. [Japanese] Ganka 1998; 40: 1501-1504
- Yoshida S, Matsushima H, Nagata M, Senoo T, Ota I, Miyake K. Decreased visual function due to high-level light scattering in a hydrophobic acrylic intraocular lens. Jpn J Ophthalmol. 2011; 55: 62-66
Hiroyuki Matsushima, MD, PhD
Department of Ophthalmology,
Dokkyo Medical University,
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