EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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March 2013 A case continued from page 66 CAUTION: Federal (USA) law restricts this device to the sale by or on the order of a physician. INDICATIONS: The AcrySof® IQ posterior chamber intraocular lens is intended for the replacement of the human lens to achieve visual correction of aphakia in adult patients following cataract surgery. This lens is intended for placement in the capsular bag. WARNING/PRECAUTION: Careful preoperative evaluation and sound clinical judgment should be used by the surgeon to decide the risk/beneft ratio before implanting a lens in a patient with any of the conditions described in the Directions for Use labeling. Caution should be used prior to lens encapsulation to avoid lens decentrations or dislocations. Studies have shown that color vision discrimination is not adversely affected in individuals with the AcrySof® Natural IOL and normal color vision. The effect on vision of the AcrySof® Natural IOL in subjects with hereditary color vision defects and acquired color vision defects secondary to ocular disease (e.g., glaucoma, diabetic retinopathy, chronic uveitis, and other retinal or optic nerve diseases) has not been studied. Do not resterilize; do not store over 45° C; use only sterile irrigating solutions such as BSS® or BSS PLUS® Sterile Intraocular Irrigating Solutions. ATTENTION: Reference the Directions for Use labeling for a complete listing of indications, warnings and precautions. © 2013 Novartis 2/13 NIQ13007JAD Figure 2: Gross and light microscopic photographs of the explanted PMMA lens from the patient in this case Source: Mamalis/Werner laboratory, Moran Eye Center Figure 3: Gross photographs of a PMMA lens explanted because of optic opacification, in the dry and hydrated states Source: Mamalis/Werner laboratory, Moran Eye Center (case of Fernando Trindade, M.D., Brazil) degeneration is a result of long-term ultraviolet (UV) light exposure. The explanted lenses analyzed in our laboratory had spherical lesions with an aspect of "snowflakes" under high magnification light microscopy, which were interpreted as foci of degenerated PMMA material clustered in the central zone and mid-peripheral portion of the optic. This led to the hypothesis that the central optic was exposed to UV light over an extended period, whereas the peripheral optic may be protected by the iris. Therefore, snowflake lesions are generally not observed in the optic periphery, they generally involve the anterior third of the optic substance, and they do not disappear when the lens is in the dry state. Although the snowflake lesions are dry, it has been observed that an unusual amount of water is collected within the affected optic area upon hydration of explanted PMMA lenses with this condition, leading to more significant optic opacification. Consequently, the clinical significance of snowflake degeneration may depend on the amount of water collected within the IOL optic (Figure 3). It is important to point out that today industry has far greater control over the production of the PMMA material/ lenses. Modern PMMA lenses are mostly produced by lathing; therefore, we do not expect to see development of snowflake degeneration in association with them. Differential diagnosis Calcification is generally an issue with some hydrophilic acrylic IOLs. It can occur either on the surface/ subsurface of the optic and/or within the substance and can be confirmed with histochemical stains such as alizarin red or the von Kossa method. The degree of IOL opacification due to calcification is significant in the dry or hydrated states. Calcification may also occur in silicone lenses implanted in eyes with asteroid hyalosis (asteroid bodies are rich in calcium/phosphate). In these cases, the calcification occurs primarily on the posterior surface of the optic. Glistenings are fluid-filled vacuoles that are mostly described in relation to some hydrophobic acrylic IOLs. They are significantly smaller than snowflakes lesions and disappear in the dry state. EW References Apple DJ, et al. Ophthalmology 2002; 109:1666-1675. Werner L. J Cataract Refract Surg 2007; 33:713-726. Apple DJ, Werner L. Trans Am Ophthalmol Soc 2001; 99:95-109. Dahle N, Werner L, Fry L, Mamalis N. Arch Ophthalmol 2006; 124:1350-1353. Editors' note: Drs. Liu, Werner, and Mamalis are affiliated with the John A. Moran Eye Center, University of Utah, Salt Lake City. The physicians do not have any financial interests related to this article. Contact information Liu: Erica.Liu@hsc.utah.edu Mamalis: nick.mamalis@hsc.utah.edu Werner: Liliana.Werner@hsc.utah.edu