## **Core Concept**
The question tests knowledge of ophthalmological diagnostic tools, specifically the use of fluorescent dyes. Fluorescein is a commonly used dye in ophthalmology for diagnostic purposes. It is utilized to visualize the cornea, detect corneal ulcers, and assess retinal circulation.

## **Why the Correct Answer is Right**
The correct answer involves the administration route of fluorescein for ophthalmological diagnosis. Fluorescein is typically injected intravenously. This allows the dye to circulate through the bloodstream and illuminate structures within the eye under blue light during a fluorescein angiography, helping diagnose conditions like diabetic retinopathy, macular degeneration, and other retinal diseases.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because the specific route (intravenous) is crucial for systemic distribution and diagnostic imaging.
- **Option B:** This option is incorrect as it does not accurately represent the standard method for injecting fluorescein for diagnostic purposes.
- **Option C:** This option might seem plausible but is not the standard or preferred method for diagnostic imaging using fluorescein.
- **Option D:** This option is incorrect because, although topical fluorescein is used (e.g., for detecting corneal abrasions), the question seems to focus on a method that involves injection, implying a systemic or more comprehensive diagnostic approach.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that fluorescein angiography, which involves intravenous injection of fluorescein, is critical for evaluating the retinal vasculature and diagnosing various retinal diseases. This technique is non-invasive and provides valuable information on retinal circulation and pathology.

## **Correct Answer:** . Intravenous.