Which of the following is NOT considered a topical diagnostic agent?

Indocyanine Green is classified as an intravenous diagnostic agent primarily used in angiography, particularly for assessing choroidal blood flow and retinal vascular conditions. Unlike the other options, which are used topically for surface staining and evaluating ocular conditions, Indocyanine Green is administered via injection. Fluorescein, Methylene Blue, and Rose Bengal are all utilized in ocular diagnostics to stain tissues or highlight abnormalities in the cornea and conjunctiva. This distinction in administration routes and applications is what makes Indocyanine Green the correct answer, as it is not considered a topical agent.