Phakic pattern of exfoliation material on a posterior chamber intraocular lens

Abstract

Editor, Deposits of exfoliation material (XFM) on the anterior lens surface are the most consistent and important diagnostic feature of exfoliation syndrome (XFS). In phakic eyes, the characteristic pattern of XFM on the lens surface consists of three zones: (i) a central translucent disc; (ii) a clear intermediate zone; and (iii) a peripheral granular zone (Ritch & Schlötzer-Schrehardt 2001). The XFM is produced by several tissues of the anterior segment, including the iris pigment epithelium, non-pigmented ciliary epithelium and pre-equatorial lens epithelium. That the lens is unnecessary for the production of XFM is illustrated by its appearance years after cataract on intraocular lens (IOL) implants in pseudophakic eyes (Krause 1989; Ringvold & Bore 1990; Chen & Blumenthal 1992; Ritch 1994; Stewart & Jay 1995; FitzSimon & Johnson 1996). Most of these reports have portrayed scattered flecks of XFM on the surface of the IOL. Recently, two reports have been presented showing a pattern of mature deposition on the surfaces of IOLs years after implantation, suggestive of long-standing production, in patients who had no recorded findings of XFS prior to cataract surgery (Bahadur & Masket 2007; Park & Kee 2007). We would like to add another case of deposition of XFM on an IOL seen 10 years after lens implantation and in which the pattern of deposition reflected long-standing production of XFM with a granular appearance to the material extending over the surface of the IOL. An 82-year-old woman, with no history of glaucoma, presented with blurred vision in the left eye (OS) 10 years after extracapsular cataract extraction and implantation of a sulcus-fixated posterior chamber polymethylmethacrylate IOL. Her best-corrected visual acuity was 0.5 OS. Intraocular pressures were within normal limits. Slit-lamp biomicroscopy revealed XFM deposition on both the anterior and posterior surface of the IOL. The pattern of XFM accumulation on the anterior IOL surface showed a granular peripheral zone and radial striations in the intermediate zone without a clear central zone (Fig. 1A,B). The IOL was well centred and the pupil was round, reactive to light, and free of synechia and XFM deposits. Gonioscopy showed a hyperpigmented trabecular meshwork. The exfoliation material on the anterior surface of the intraocular lens has taken on a configuration similar to that of pregranular exfoliation syndrome, but is also deposited as densely as in phakic eyes with exfoliation syndrome. We feel that the appearance of the XFM on the lens surface in our case, and the others reported recently, can be explained by long-standing production in the absence of lens–pseudophakos friction. In the phakic eye, the central disc of XFM usually equals the pupillary diameter in size, and the intermediate clear zone is caused by friction of the iris on the lens anterior surface, rubbing the XFM off the mid-portion of the anterior lens surface and producing the classic three-ring appearance. When XFM is allowed to build up undisturbed in this region, it develops a granular appearance, similar to that found in the peripheral zone. However, in the presence of an IOL, space between the iris and the IOL prevents this rubbing, allowing the deposition of the material to progress undisturbed. Finally, one wonders why this phenomenon is rare, while XFS is extremely common, as is cataract extraction in these eyes. We conjecture that the distance from the posterior iris pigment epithelium, which produces the XFM, to the IOL is usually too large to allow deposition on the IOL surface and that any XFM secreted by these cells passes into the posterior chamber. Most of the eyes in the two other recent papers and our patient had IOL implantation in the sulcus, which would bring the IOL surface into closer contact with the iris. If the IOL is in the capsular bag but the zonules are loose, allowing the IOL and the bag to come forward, the same situation may apply.