Fig. 26.7 (a) Color photograph showing end-stage thioridazine toxicity with diffuse loss of pigmentation. (b) FA shows diffuse atrophy of the retinal pigment

epithelium and choriocapillaris, optic atrophy, and vascular attenuation. This severe end-stage disease resembles ocular findings seen in choroideremia

Toxicity with Crystalline Deposits

Tamoxifen

Tamoxifen (Nolvadex, AstraZeneca, Wilmington, DE), an estrogen antagonist, is commonly used in the treatment of metastatic breast adenocarcinoma and more recently has been used at a higher dosage in the treatment of advanced glioblastoma. Toxicity is frequently asymptomatic, but may cause vision loss with dyschromatopsia [31]. White refractile deposits appear in the posterior pole (Fig. 26.9a, b), which may be associated with pigmentary changes and, in advanced cases, cystoid macular edema (CME) with angiographic leakage (Fig. 26.10). In patients receiving highdose tamoxifen, peripheral retinal crystals may also develop [32].

Asymptomatic crystals may be observed closely, but discontinuation of the medication is generally recommended in patients with CME or

visual loss [33]. The successful use of intravitreal pegaptanib (Macugen, Eyetech, New York, NY) and/or bevacizumab (Genentech, South San Francisco, CA) to treat CME associated with tamoxifen retinopathy has been reported [34].

Canthaxanthine

Canthaxanthine (Orobronze, Dewitte, Greenville, SC) is a carotenoid pigment used therapeutically for vitiligo and photosensitivity disorders. In some nations, the drug is sold as an over-the- counter oral tanning agent. Toxicity may be asymptomatic, but a ring of yellow-orange crystals is noted in the macula [35], (Fig. 26.11) associated with various abnormalities in electrophysiologic testing [36]. Imaging of the crystals with spectral domain OCT has been reported [37]. Upon discontinuation of the medication, the crystals typically resorb and the electrophysiologic parameters improve [38].

Fig. 26.10 (a) Color photograph of tamoxifen crystalline retinopathy in a patient with advanced glioblastoma being treated with high-dose tamoxifen. (b) FA documents diffuse cystoid macular edema (CME). (c) Time domain OCT confirms the findings of diffuse CME, while

(d) a follow-up OCT several months later, following administration of intravitreal bevacizumab, shows resolution of the CME. The findings were bilateral (Images courtesy of David Sarraf, M.D., Los Angeles, CA)