In routine cataract surgery, the natural cloudy lens (cataract) is removed, and an artificial intraocular lens is implanted. The implanted intraocular lens should improve vision and remain clear. There is growing evidence that the most commonly implanted lens in Canada, the Alcon Acrysof Intraocular lens, has inclusions, called glistenings (see Appendix 1, photograph of glistenings) which degrade vision.
Patients who have an Acrysof lens in one eye, and a lens of another material in the other eye will demonstrate glistenings only in the eye with the Acrysof lens. Thus, this phenomenom is related to the material that the Acrysof lens is made from and is not due to a patient factor.
These inclusions are due to the manufacturing process of this lens. The Acrysof lens is molded, and the process results in gaps forming within the Acrysof material. Temperature changes when the lens is implanted (going from room temperature to body temperature) allows water to collect in the gaps. (Miyata A, Yaguchi S. Equilibrium water content and glistenings in acrylic intraocular lenses. J Cataract Refract Surg. 2004 Aug;30(8):1768-72 ).
Glistenings are present in the majority of patients with Acrysof lenses. (Christiansen G, Durcan FJ, Olson RJ, Christiansen K. Glistenings in the AcrySof intraocular lens: pilot study. J Cataract Refract Surg. 2001 May;27(5):728-33.) In a review of 254 eyes with Acrysof lenses, it was found that 62 % had mild glistening inclusion, 16% had moderate, 11% had marked and 1% had severe glistenings (Dr. Richard Smith, Australia).
In order to improve vision in patients with cataracts, the cloudy lenses are removed and replaced with clear artificial intraocular lenses. Studies have demonstrated that intraocular lenses can restore the vision to that of a 20 year old young adult. Glistenings, however, cause light to be scattered and can result in vision comparable to that of a 70 year old individual with cataracts. Thus, instead of achieving a sharp, clear Snellen acuity of 20/20, the patient has vision degraded by glare and poor contrast. (Van der Mooren M, Coppens J, Bandhauer M, Van den Berg T. Presented at ARVO 2007.) Appendix 2 shows a simulation of night time vision in a patient with glistenings.
A study on visual function has shown that glistenings in AcrySof lenses were related to a statistically significant loss in contrast sensitivity at high spatial frequencies (Gunenc U, Oner FH, Tongal S, Ferliel M. Effects on visual function of glistenings and folding marks in AcrySof intraocular lenses. J Cataract Refract Surg. 2001 Oct;27(10):1611-4. Another study has shown that eyes with higher grades of glistenings had a small but significantly greater decrease in visual acuity than those with lesser grades (Christiansen G, Durcan FJ, Olson RJ, Christiansen K. Glistenings in the AcrySof intraocular lens: pilot study. J Cataract Refract Surg. 2001 May;27(5):728-33.)
Probably the most important recent finding is that the density of glistenings increases with the duration of follow-up, and that the density does not level out. This was found in a study that subjectively and objectively evaluated patients with Acrysof lenses with 150 months of follow-up. Thus, the severity of impact on vision will increase over the lifetime of a patient implanted with these lenses. (Behndig A, Monestam E. Quantification of Glistenings in Intraocular Lenses using Scheimpflug Phtography. J Cat Refract Surg 2009; 35: 7-14.) (See Appendix 3).
Surgeons are becoming increasingly aware of the adverse effects of these glsitenings; a search of the FDA website for reporting adverse effects has 106 records between July 3, 1997 and June 4, 2009; 96 were regarding Acrysof lenses in cases with decreased visual acuity or other symptoms leading to a decrease in visual quality and fourteen reports were related to IOL explantation of Acrysof lenses (Werner L. Glistenings and surface light scattering in intraocular lenses. J Cat Refract Surg. 2010 36: 1398-1420). Public health officials are also becoming aware of the effect sof glistenings. In a recent review of the Alcon Acrysof lens by the US Department of Health and Human Services, (DEPARTMENT OF HEALTH AND HUMAN SERVICES, Centers for Medicare & Medicaid Services, 42 CFR Parts 410, 411, 412, 413, 416, 419, and 489 [CMS-1504-FC and CMS-1498-IFC2], RIN 0938-AP82 and RIN 0938-AP80, published Nov 2010; available at default http://www.ofr.gov/OFRUpload/OFRData/2010-27926_PI.pdf , pages 994 and following:
- "We conclude that the Acrysof Natural IOLs do not demonstrate substantial clinical benefit in comparison with currently available IOLs" (p. 1010)
- "Moreover, in our review......regarding the blue light filtering optic, we found evidence suggesting that the blue-filtering lenses could decrease best possible vision." (p. 1006)
- "Finally, this commentor stated that the glistenings associated with Acrysof Natural lenses that develops overtime causes disability glare rather than reduces it." (p. 1009)