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It is useful because it records that the retinal effect was predicted before it was looked for.\nexposure: Electroretinography and histology in preclinical evaluation, with extended eye examination in clinical protocols and registry surveillance\nevidence_span: {\"source_cache\": \"artifacts/sildenafil-research/10703120.abstract.txt\", \"locator\": \"Indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"fc004205f7e036cf52e469c5f9941c4f69d216a012ccd8a588052b950c1077e6\", \"start_char\": 0, \"end_char\": 2146, \"text_sha256\": \"fc004205f7e036cf52e469c5f9941c4f69d216a012ccd8a588052b950c1077e6\"}\n[sil-p10703120] Ocular safety of Viagra, (sildenafil citrate). 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