Polyhexamethylene Biguanide 0.08% Monotherapy for Acanthamoeba Keratitis: A Real- World Clinical Experience

Imagine your eye is a bustling city, and the cornea is its shiny, clear glass dome. Usually, this dome is safe, but sometimes a tiny, sneaky invader called Acanthamoeba (a microscopic amoeba) crashes the party. This isn't just a minor glitch; it's a full-blown siege that can turn the glass dome cloudy and ruin the view forever. For a long time, doctors in Spain were fighting this siege with a messy toolbox: some used homemade mixtures, others had to order special ingredients from abroad, and the recipes varied from doctor to doctor. It was like trying to put out a fire with different buckets of water, some leaking, some empty.

Then, a new, standardized "fire extinguisher" arrived in Europe: a drop called Polyhexamethylene Biguanide (PHMB) at 0.08%. A big clinical trial had already shown it worked well, but this new paper is like a field report from the front lines in Spain, checking if it works in the real, messy world of a hospital.

The Big Discovery
The researchers gathered a team of 14 patients who were under siege by this amoeba. They gave them only the new PHMB drops—no mixing in other drugs, just the single, standardized solution. Think of it as sending in one highly trained special forces unit instead of a confused crowd of volunteers.

The result? A perfect score for medical cure. 100% of the patients achieved a "medical cure," meaning the infection was completely cleared and the eye surface healed. However, the battle left some scars: 3 patients (21%) still required a "window replacement" (a corneal transplant) later on. But here is the key detail: they needed the surgery not because the infection was still active, but because the battle had left behind a permanent scar (a "central leukoma") that blocked the light. The infection itself was gone in all cases. The paper explicitly states that this success wasn't just a lucky guess; it confirms that the high success rate seen in the big, controlled trials can be reproduced in everyday hospital practice.

How Long Did the Battle Last?
Healing isn't instant. The patients had to use the drops for a while. The "median" time to victory was 122 days. That's about four months of diligent drop-taking. The treatment plan was strict:

• Days 1–5: One drop every hour while awake (a heavy bombardment).
• Days 6–12: One drop every 2 hours.
• Days 13–20: One drop every 3 hours.
• Day 21 onwards: One drop every 4 hours, continuing until the infection was gone (up to a maximum of 6 months).

Who Was in the Fight?
Most of the patients (10 out of 14, or 71%) were contact lens wearers, which fits the usual story of how these amoebas get in. However, the paper makes a crucial point: 4 patients were NOT contact lens wearers. This proves that you can't rule out this infection just because someone doesn't wear lenses. Sometimes, the enemy comes from other sources, like dirty water or previous eye surgeries.

The "Before" Picture
Before these patients got the right treatment, things were rough.

• The average time from when symptoms started to getting a confirmed diagnosis was 29.7 days. That's a long time to wait while the enemy digs in.
• Many had been misdiagnosed. Some were told they had a viral infection (herpetic keratitis) and were given the wrong medicine.
• When they arrived at the hospital, their vision was already blurry. Only 3 patients (21%) could see better than 20/40 at the start.

The Aftermath
By the end of the treatment, the city was safe again.

• Medical Cure: All 14 patients achieved a "medical cure," meaning the inflammation vanished and the surface of the eye healed.
• Vision: The median final vision was 20/20 (Snellen). That's perfect vision!
• Surgery? Three patients (21%) still needed a "window replacement" (a corneal transplant) later on. But here is the key detail: they didn't need it because the infection was still active. They needed it because the battle had left behind a scar (a "central leukoma") that blocked the light. The infection itself was gone.

Did It Hurt?
The treatment was surprisingly gentle, with no severe adverse drug reactions reported.

• Some patients had mild irritation (superficial keratitis), but it went away when they slowed down the drops.
• One patient needed special "autologous serum" eye drops (made from their own blood) to help a stubborn spot heal.
• The paper did note that one case of white cataract and one case of phosphate keratopathy occurred during the study, but the treatment itself was well-tolerated by everyone. No one quit because the drops were too painful or annoying.

What the Paper Says We Should (and Shouldn't) Do
The authors are very clear about what this means:

• Don't assume you need a mix of many different drugs. The paper shows that using only the PHMB drops (monotherapy) was enough to win, even in tough cases.
• Don't wait too long. The paper argues that the old way of fragmented care—where patients get misdiagnosed or sent on a long journey to find the right medicine—is a major problem.
• Do use steroids (anti-inflammatory drops) carefully. The doctors in this study waited until the eye surface had started to heal and the infection was under control before adding steroids. They found this was safe and effective.

The Bottom Line
This paper suggests that the new, standardized PHMB 0.08% drops are a game-changer. They turned a chaotic, often failing battle into a winning strategy with a 100% medical cure rate in this group. It proves that if you have the right tool, use it strictly, and follow a clear plan, you can save the city's glass dome, even if the enemy was tough, the battle lasted 122 days, and a few patients needed a little extra help (surgery) to clear up the scars afterward. The authors hope this success story will help doctors everywhere stop guessing and start using a proven, standardized protocol to save vision.