Question

A 17 year old girl with keratitis and severe pain in the eye came to the hospital, and Acanthamoeba keratitis was suspected. The patient gave a history of the following four points. Which one of these is NOT a risk factor for Acanthamoeba keratitis?

• A. Extended wear contact lenses
• B. Exposure to dirty water
• C. Corneal trauma
• D. Squamous blepharitis

Hint:

Acanthamoeba keratitis needs an outside exposure route: contact lenses, dirty water, or trauma. Lid margin disease does not fit that pattern.

Answer 1

The Correct Option is D

This question checks which of the four listed points is not a genuine risk factor for Acanthamoeba keratitis in a young girl with painful keratitis.

1. Extended wear contact lenses: wearing lenses for long hours, especially with poor lens hygiene or tap water rinsing, is the leading risk factor for this infection. This is a true risk factor.
2. Exposure to dirty water: Acanthamoeba lives in soil, dust, and untreated water. Contact with dirty water, ponds, or hot tubs is a well known route of infection. This is a true risk factor.
3. Corneal trauma: an injury, especially one involving soil or plant matter, breaks the corneal surface and lets the ameba enter. This is a true risk factor.
4. Squamous blepharitis: this is chronic lid margin inflammation, usually tied to Staphylococcus and to bacterial or marginal keratitis, not to Acanthamoeba, which needs an outside source such as lenses, water, or trauma.

The point that does not belong on this risk list is squamous blepharitis, since Acanthamoeba keratitis is tied to an outside exposure route and not to lid margin disease.

Let's summarize:

• Contact lens wear and dirty water exposure are the two classic risk factors for Acanthamoeba keratitis.
• Corneal trauma opens a route for the ameba to enter the stroma.
• Blepharitis raises the risk of bacterial keratitis, not Acanthamoeba keratitis.

So the correct answer is squamous blepharitis, option 4.