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Optical clarity of the intraocular lens (IOL) is paramount in maintaining visual improvement after cataract extraction. While the advent of newer foldable IOLs have revolutionised cataract surgery by the smaller incisions required, their long term safety will be established only with time. There have been recent reports of two separate groups of hydrophilic IOLs that have shown various degrees of opacification, 6 months to 2 years after implantation.1 These include the Hydroview lens (Bausch & Lomb Surgical, Claremont, CA, USA) and the model SC60B-OUV (Medical Developmental Research, Clearwater, FL, USA).1, 2 We report our experiences with two patients who had permanent reduction in visual acuity 1–2 years after implantation of the SC60B-OUV IOL.
An 82 year old man with visual acuities of 6/60 in both eyes because of a right macular hole and left posterior subcapsular cataract underwent routine left phacoemulsification and intraocular lens implantation in March 1998. A foldable hydrophilic acrylic IOL (Model SC60B-OUV, MDR, Inc) was implanted in the capsular bag. Postoperative recovery was uneventful, with left visual acuity improving to 6/4 with correction, 6 weeks after the surgery.
He was referred back to the clinic in March 2000 with symptoms of intermittent binocular diplopia, which was relieved with fresnel prisms. His left visual acuity was 6/6, but the intraocular lens was found to be uniformly cloudy (Fig 1A). As the patient was not experiencing any symptoms from his cloudy IOL, no intervention was advised. Over the next 6 months the brownish discoloration of the IOL increased in intensity and the patient complained of “foggy vision.” His visual acuity dropped to 6/12 and he was disturbed by the distorted, but clear images from his right eye and hazy images from his left eye. Fundus examination of the left eye has also become progressively difficult. IOL exchange is being considered, bearing in mind the presence of the macular hole in the fellow eye and the risks of removing a posterior chamber IOL 3 years after implantation.
A 78 year old woman with bilateral Fuchs' corneal endothelial dystrophy and long standing central retinal vein occlusion in the left eye, underwent uneventful right phacoemulsification with intraocular lens implantation (Model SC60B-OUV, MDR, Inc) in August 1998. Her right visual acuity improved to 6/9, but approximately 1 year after the surgery there was gradual deterioration of vision to 6/24 in August 2000. At this stage the IOL was noted to be cloudy; there was also progression of her endothelial dystrophy. She underwent uneventful right penetrating keratoplasty with exchange of posterior chamber IOL in November 2000 and has a current right visual acuity of 6/12. The explanted opacified IOL is compared to a normal clear acrylic IOL in Figure 1B.
The safety and efficacy of AcrySof polyacrylic IOLs has been reported to be equal to or better than poly(methylmethacrylate) IOLs.3 The unexpected late opacification of the acrylic IOL (SC60B-OUV), implanted in the only “good” eye of both our patients, resulted in significant visual disability and clinical dilemma. This model of IOL was first produced in June 1997 by Medical Development Research (MDR, Inc). More than 60 000 of these lenses have been implanted worldwide, but only outside the United States.1 Reports of opacification of the IOL started coming through to the manufacturer in May 1999. (Summary of SC60B-OUV lens opacification investigation, personal communication from MDR, Inc, 20 July 2001.)
Several theories have been put forward to explain the late clouding of the IOL optic.2, 4, 5 Analysis of 23 explanted IOLs of the same model has shown that degeneration of the ultraviolet filtration material and calcium deposits within the optic biomaterial are responsible for the opacification of the IOL.1 Werner et al analysed nine explanted IOLs of the same model and demonstrated the presence of calcium phosphate salts in the deposits within the optics of the IOL.6 Investigations by the manufacturers identified four lots of polymer biomaterial formulated and prepared by Vista Optics (London) and used by MDR, Inc in the IOL manufacture, that correlated with opacification complaints (Summary of SC60B-OUV lens opacification investigation, personal communication from MDR, Inc, 20 July 2001).
Ninety two of the estimated 60 0000 SC60B-OUV IOLs implanted were explanted and returned to the company. MDR, Inc ceased exporting SC60B-OUV lenses in June 2000 and claims that the opacification represents only 0.15% of total SC60B-OUV IOLs implanted. (Summary of SC60B-OUV lens opacification investigation, personal communication from MDR, Inc, 20 July 2001). However, this does not account for those patients who have not yet had their opaque IOLs identified or explanted. The lateness of the onset of opacification and resulting visual disability may mean that we are seeing only the tip of the iceberg.