---
title: "Acanthamoeba keratitis | Eye Health Guide"
description: "What Acanthamoeba keratitis is, why contact lens wear and tap water raise risk, symptoms, diagnosis, and why early treatment protects sight."
url: https://eyehealthguide.org/conditions/acanthamoeba-keratitis/
source: Eye Health Guide
licence: "General information only. Cite the URL and the named medical reviewer."
---

Condition

# Acanthamoeba keratitis

Medical reviewer [Mr Mohamed Mohyudin](https://eyehealthguide.org/reviewers/mohamed-mohyudin/)· Last recorded site review July 6, 2026

### About this review

This page inherits the site’s previous review record. A separate, current article sign-off has not yet been recorded.

[How review works](https://eyehealthguide.org/reviewers/) · [Official biography & credentials](https://mohamedmohyudin.co.uk/author/mohamed-mohyudin/)

Quick answer

Acanthamoeba keratitis is a corneal infection caused by Acanthamoeba, a micro-organism found in soil, dust and water. It is uncommon but can threaten sight. Contact lens wear — especially with tap water, poor hygiene or sleeping in lenses — is the main risk in many countries. A painful red eye that does not improve needs same-day specialist assessment.

### On this page ⌄

1. Your next step
2. What it is
3. Who is at risk
4. Symptoms
5. Diagnosis and treatment
6. Prevention
7. Related conditions
8. Related symptoms
9. Practical guides
10. Frequently asked questions

## What it is

Acanthamoeba keratitis infects the clear cornea at the front of the eye. Unlike mild conjunctivitis, it penetrates corneal tissue and can cause ring-shaped ulcers, severe pain and scarring. It is harder to treat than bacterial ulcers and may need months of antiseptic drops.

## Who is at risk

Most cases occur in contact lens wearers. Risk rises with:

- Rinsing or storing lenses in tap water, or swimming or showering in lenses
- Sleeping in lenses not designed for overnight wear
- Poor lens hygiene or using contaminated lens cases
- Recent corneal injury or exposure to soil or stagnant water
- Using steroid eye drops without treating infection

## Symptoms

Symptoms can mimic other red-eye problems early on, which delays diagnosis.

- Severe eye pain out of proportion to how the eye looks
- Redness, watering and marked light sensitivity
- Blurred or hazy vision
- A feeling of something in the eye
- Sometimes a ring-shaped white-grey area on the cornea

## Diagnosis and treatment

Specialists examine the cornea with a slit lamp, may take corneal samples, and sometimes use confocal microscopy. Treatment is with antiseptic drops such as chlorhexidine or polyhexanide, often for many months. Steroids are avoided until infection is controlled. Late cases may need corneal transplant.

## Prevention

Never expose contact lenses to tap water, pool water or saliva. Follow replace-and-clean schedules, rub and rinse reusable lenses with fresh solution, and replace lens cases regularly. Remove lenses before swimming or bathing, and seek same-day care for a painful red eye during lens wear.

## Related conditions

## Related symptoms

## Practical guides

## Frequently asked questions

### Can tap water cause Acanthamoeba keratitis?

Yes. Tap water and recreational water can harbour Acanthamoeba. Lenses and cases should only contact sterile lens solution, never water.

### How is Acanthamoeba keratitis different from pink eye?

Pink eye usually affects the surface membrane and is often milder. Acanthamoeba infects the cornea, causing disproportionate pain and vision blur that worsens without specialist antiseptic treatment.

### Can Acanthamoeba keratitis cause blindness?

It can scar the cornea and reduce vision if diagnosis or treatment is delayed. Early specialist care greatly improves outcomes.

### Should I stop wearing contact lenses if my eye is red?

Remove lenses immediately and do not reinsert until an eye professional clears you. A painful red eye during lens wear needs same-day assessment.

Your next step

## Take this to your appointment

Write down what has changed, when it started, your current medicines and the questions you want answered. Take these to your eye-care appointment.

Sudden loss of sight, severe eye pain or a dark curtain across vision needs immediate assessment. Do not wait to complete a worksheet.

## Sources for this information

These references support the information on this page. Follow the linked source for its full context.

- [Acanthamoeba keratitis - Moorfields Eye Hospital](https://www.moorfields.nhs.uk/eye-conditions/acanthamoeba-keratitis)