A 33 year old man presents to AIIMS ophthalmology OPD with pain and watering of eyes. On examination there was a 3X2 mm greyish white corneal ulcer with indistinct elevated margins. The lesion is surrounded by feathery finger like infiltration into the adjacent corneal stroma. Minimal hypopyon is also observed. Based on the information provided the microbiological investigation should be directed against

## **Core Concept**
The clinical presentation described points towards a corneal ulcer with specific characteristics, such as a greyish-white appearance, indistinct elevated margins, and feathery finger-like infiltration into the adjacent corneal stroma. These features are suggestive of a particular type of corneal infection.

## **Why the Correct Answer is Right**
The description provided is highly suggestive of a fungal corneal ulcer. Key features that point towards a fungal etiology include the presence of a greyish-white corneal ulcer with indistinct elevated margins and feathery or irregular infiltrates extending into the corneal stroma. The minimal hypopyon can also be seen in fungal keratitis. Fungal keratitis is a serious condition that requires prompt and accurate diagnosis to initiate appropriate treatment.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Herpes simplex keratitis typically presents with a dendritic or geographic ulcer, not usually with a greyish-white ulcer and feathery infiltrates.
- **Option B:** Bacterial keratitis can present with a corneal ulcer, but the typical presentation is with a defined, round, or oval ulcer with a sharp, distinct margin and a more homogenous infiltrate, not usually feathery.
- **Option D:** Acanthamoeba keratitis, often associated with contact lens use, might present with a ring-shaped infiltrate or a more diffuse corneal involvement, and is less commonly described with the exact features mentioned.

## **Clinical Pearl / High-Yield Fact**
A high-yield fact to remember is that fungal keratitis is more likely to present with the described feathery, irregular infiltrates and a greyish-white ulcer, especially in a post-traumatic or agricultural setting. A definitive diagnosis often requires corneal scrapings or biopsy for culture and histopathological examination.

## **Correct Answer:** C.

✓ Correct Answer: A. Aspergillus spp.