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To the Editor: Cautiousness is an appropriate response to the letter by Fakhrudin Valibhai, Pharm.D., et al. (1). First, Mr. A’s lens changes were not representative of the most common forms of lens opacity, which are usually ascribed to lens toxins. Nor were they a type of lens opacity that is subject to reliable and consistent ascertainment. In fact, it has proven so difficult to evaluate minor lens opacities, such as the cortical vacuoles noted in Mr. A, that the most-accepted lens opacity classification system (Lens Opacities Classification System III) largely ignores them in favor of the more reliable ascertainment of cortical wedges and spokes (2).
Perhaps more important, the authors’ assertion that Mr. A did not have any other risk factors is mistaken. Although their MEDLINE search "of articles on the patient’s other medications revealed no association with cataracts" (1, p. 966), an abundant literature nevertheless exists on the association of agents used to treat schizophrenia and lens opacities. For instance, haloperidol, one of the agents used to treat Mr. A, has a recognized association with capsular cataracts after long-term therapy (3). Phenothiazines, also used to treat Mr. A, are recognized as causing deposits to form within the lens (4). Moreover, Isaac et al. (5) reported that the lens changes induced by phenothiazines are clearly deleterious. McCarty et al. (6) raised the suspicion that schizophrenia itself might be a risk factor for cataracts. Since poor nutrition is also a risk factor for cataracts (7), it is difficult to tell whether lens opacity is a manifestation of the biology of schizophrenia or of poor eating habits.
Taken together, multiple and diverse risk factors existed for Mr. A’s cataracts. That cataracts most often develop slowly and over long durations undermines any presumption of a specific attribution for the lens changes observed in Mr. A. With so many confounding variables, it impossible to determine a single cause of Mr. A’s cataracts. Moreover, in my 3-year surveillance of ocular safety for AstraZeneca, which markets quetiapine, I have seen no clear signal emerge for toxicity in any part of the eye.
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