## **Core Concept**
Ophthalmia neonatorum, also known as neonatal conjunctivitis, refers to conjunctivitis that occurs within the first month of life. It is primarily caused by infectious agents acquired during passage through the birth canal. The most common pathogens include bacteria, viruses, and Chlamydia.

## **Why the Correct Answer is Right**
The correct answer involves identifying the most commonly associated pathogens with ophthalmia neonatorum. Among the given options:
- **Gonorrhea (a)**: Neisseria gonorrhoeae is a well-known cause of ophthalmia neonatorum. It can cause severe purulent conjunctivitis in newborns.
- **Chlamydia (c)**: Chlamydia trachomatis is another leading cause of ophthalmia neonatorum, often resulting in inclusion conjunctivitis.

## **Why Each Wrong Option is Incorrect**
- **Option B: H. Influenzae**: While Haemophilus influenzae can cause conjunctivitis, it is less commonly associated with ophthalmia neonatorum compared to gonorrhea and Chlamydia.
- **Option D: Pseudomonas**: Pseudomonas aeruginosa can cause various infections, including ocular infections, but it is not a primary cause of ophthalmia neonatorum.
- **Option E: Staph. aureus**: Staphylococcus aureus can cause conjunctivitis but is not as commonly linked to ophthalmia neonatorum as gonorrhea and Chlamydia.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that ** prophylaxis against gonococcal ophthalmia neonatorum is routinely administered to newborns** using erythromycin or tetracycline ointment. This practice significantly reduces the incidence of gonococcal ophthalmia neonatorum.

## **Correct Answer: C.**