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S.D. Wadhwa, D.A. Belyea, V. Gregg, S. Thadani, B. Katz, H. Savage; Natural History of Capsular Block Syndrome: Implications for Accommodating Intraocular Lenses . Invest. Ophthalmol. Vis. Sci. 2003;44(13):220.
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Purpose: Capsular block syndrome (CBS) is a complication of cataract surgery in which viscoelastic material left in the capsular bag displaces an intraocular lens anteriorly, toward the iris plane. We studied the natural history and optical impact of capsular block syndrome. Methods: Records of 458 patients undergoing cataract surgery were reviewed retrospectively during a 1-year period. Of these, CBS occurred in five. We analyzed the clinical signs and symptoms and natural history of CBS. We also determined amount of refractive shift due CBS by subtracting the post-operative spherical equivalent refractive error (SE) during CBS, from SE after resolution of CBS. Regression analysis was performed on refractive shift and IOL power. Results: The incidence of CBS was 1.1%. Symptoms included blurred vision and monocular diplopia. Clinical signs of CBS included intraoperative iris prolapse after IOL insertion, pigment accumulation upon the IOL, and narrow anterior chamber angle. Anterior displacement of the IOL and distended capsular bag was seen in all. Two patients experienced spontaneous resolution of CBS. One patient required YAG capsulotomy for anisometropia and one required YAG capsulotomy for narrow angle closure and relative pupillary block. One patient persists in CBS yet with stable and good vision. The mean refractive shift due to CBS was 2.36 diopters of myopia. Regression analysis demonstrated a direct linear relationship between implant power and myopic shift. Analysis suggests that, in CBS, each additional 6.6 diopters of IOL power induce one diopter of myopia. Conclusions: CBS should be suspected in post-cataract patients with myopic surprise, angle closure, or monocular diplopia. Spontaneous resolution can occur early, or late. Posterior capsulotomy restores normal anatomy and reduces myopia. Refractive shift induced by CBS is proportional to the power of the IOL implanted. The correlation of myopic surprise and IOL power has implications for new IOL designs that achieve accommodation by moving within the eye. Our results demonstrate that, for a given amount of anterior displacement, significantly more "accommodation" would be produced by a high-powered implant. Therefore, this relationship may be useful in predicting the accommodative amplitudes possible when employing accommodating IOLs that achieve accommodation by movement within the capsular bag.
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