What is the difference between conjunctivitis and keratitis?

Generally, conjunctivitis and keratitis are common eye diseases, and their main differences include the site of infection, symptom presentation, impact on vision, causative factors, and disease course and prognosis. A detailed analysis is as follows:

1. Different sites of infection: Conjunctivitis occurs in the conjunctiva, the transparent membrane covering the inner surface of the eyelid and the front part of the eyeball; keratitis occurs in the cornea, the transparent tissue at the front of the eyeball. The two diseases affect distinctly different anatomical structures—one superficial and the other deeper.

2. Different symptom presentations: Conjunctivitis is characterized by conjunctival congestion, increased eye discharge, itchy eyes, or a foreign body sensation, with mild pain; keratitis presents with severe eye pain, photophobia, tearing, and dark red ciliary congestion around the cornea. The discharge is minimal and mucoid, often accompanied by eyelid spasm.

3. Different impacts on vision: Conjunctivitis does not involve the cornea, which is the refractive medium, and typically has no significant effect on vision, except for temporary blurred vision due to discharge blocking the line of sight; keratitis causes decreased corneal transparency, directly affecting vision, and delayed or inadequate treatment may lead to permanent visual impairment.

4. Different causative factors: Conjunctivitis has a wide range of causes, including bacterial or viral infections, allergic reactions to pollen or dust mites, and physical or chemical irritants such as sand or cosmetics; keratitis is mainly caused by infections and injuries, with allergic factors being rare.

5. Different disease courses and prognoses: Conjunctivitis has a short course and usually resolves within 1-2 weeks with proper care, with a good prognosis and no sequelae; keratitis has a longer course requiring weeks or even months of treatment. Untreated cases may lead to corneal scarring, sometimes requiring surgery, and the prognosis is poorer compared to conjunctivitis.

It is recommended that when experiencing eye discomfort, patients should avoid rubbing their eyes to prevent worsening the condition. If symptoms mainly include itchy eyes and excessive discharge, initial eye cleansing with normal saline may be helpful; however, if severe eye pain or vision loss occurs, prompt medical attention is necessary. Maintaining good eye hygiene and avoiding sharing items such as towels in daily life can help reduce the risk of these diseases.