Enlarging dot sign in fundus fluorescein scanning is seen in –
**Core Concept**
The "enlarging dot sign" is a characteristic finding in fundus fluorescein angiography (FFA), which is a diagnostic tool used to visualize the blood vessels in the retina. This sign is associated with a specific retinal condition that affects the retinal pigment epithelium (RPE) and the photoreceptor layer.
**Why the Correct Answer is Right**
The enlarging dot sign is typically seen in central serous chorioretinopathy (CSCR), also known as central serous retinopathy (CSR). In CSCR, fluid accumulates beneath the RPE, causing a serous detachment of the retina. The enlarging dot sign is thought to represent the leakage of fluorescein dye from the RPE layer into the subretinal space, which appears as a expanding dot or spot in FFA.
• The enlarging dot sign is often accompanied by other FFA findings, such as a "smokestack" or "smoke ring" appearance, which are indicative of RPE disruption and photoreceptor layer damage.
• The pathophysiology of CSCR involves an imbalance of fluid and ion transport across the RPE layer, leading to the accumulation of fluid beneath the retina.
**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect as the "enlarging dot sign" is not typically associated with diabetic retinopathy, which is characterized by microaneurysms, hemorrhages, and hard exudates.
**Option B:**
This option is incorrect as the "enlarging dot sign" is not characteristic of age-related macular degeneration (AMD), which is associated with drusen, pigmentary changes, and geographic atrophy.
**Option C:**
This option is incorrect as the "enlarging dot sign" is not typically seen in retinal vein occlusion (RVO), which is characterized by retinal hemorrhages, cotton wool spots, and retinal edema.
**Clinical Pearl / High-Yield Fact**
The enlarging dot sign is a useful FFA finding that can help differentiate CSCR from other retinal conditions. It is essential to recognize this sign in combination with other clinical and FFA findings to make an accurate diagnosis.
**Correct Answer:** C. Central serous chorioretinopathy.