Question

Causes of microbial corneal ulcer.

Hint:

Trauma, contact lens use, and pre-existing eye conditions are major risk factors for microbial corneal ulcers. Prompt treatment is crucial to prevent complications.

Answer 1

Microbial corneal ulcers are caused by infections of the cornea by various microorganisms. These infections can lead to significant vision impairment and require immediate treatment.

Step 1: Bacterial Causes of Microbial Corneal Ulcer:
1. Pseudomonas aeruginosa: This is a common causative organism, particularly in contact lens wearers, causing rapid corneal ulceration and a risk of perforation.
2. Staphylococcus aureus: Often associated with post-traumatic infections and can lead to severe corneal damage.
3. Streptococcus pneumoniae: This pathogen can cause aggressive corneal ulcers, especially in children, and may lead to scarring.
4. Other bacteria: Haemophilus influenzae and Moraxella species can also cause corneal ulcers, often in individuals with pre-existing conditions like blepharitis or conjunctivitis.

Step 2: Fungal Causes of Microbial Corneal Ulcer:
1. Aspergillus species: Commonly found in soil and decaying matter, leading to fungal keratitis after trauma with plant material.
2. Fusarium species: Also associated with outdoor injuries, particularly those involving organic matter, and can cause severe scarring.
3. Candida species: These fungal infections are more common in immunocompromised patients and can be challenging to treat.

Step 3: Viral and Parasitic Causes of Microbial Corneal Ulcer:
1. Herpes Simplex Virus (HSV): A leading cause of recurrent corneal infections, often presenting with dendritic ulcers that affect the corneal epithelium.
2. Acanthamoeba: This parasitic infection occurs primarily in contact lens wearers, especially those who use contaminated water to clean lenses, leading to painful ulcers with ring-shaped infiltrates.