“As many of you know, I’ve lost my eyesight,” John said. “It’s hard for me to see it, but I love to hear it.”

The loss of his eyesight, he says, is a result of an eye infection he’s been dealing with since the summer, according to an Instagram post from September, which has left him with limited vision in one eye.

“I unfortunately lost eyesight in my right eye in July,” John said in an interview with Good Morning America on Nov. 25. “It’s been four months now since I’ve been able to see.”

John hasn’t disclosed the cause of his eye infection, but the musician admits he has been struggling. 

“I’m kind of stuck at the moment,” John told GMA. “Going into the studio and recording, I don’t know, because I can’t see a lyric for starters.”

Despite what he’s going through, John says he’s grateful for the care he’s received and the support around him. In his September post, John said he was feeling positive about the recovery he’d made so far.

“I am healing, but it’s an extremely slow process and it will take some time before sight returns to the impacted eye,” he wrote.

But how does an eye infection turn into blindness? Here is what you need to know.

What causes eye infections?

You can get eye infections from bacteria, fungi, parasites, or viruses, according to the American Academy of Ophthalmology (AAO). Eye infections can emerge from eye injuries, if you rub your eye after touching a dirty surface, or from sleeping in or wearing dirty contact lenses.

What types of eye infections are there?

The most common eye infection is pink eye, or conjunctivitis, often caused by the same viruses as the common cold. It leads to red eyes with a goopy discharge and is extremely contagious but possible to be treated at home. Depending on the type of bacteria, you may need antibiotics.

Other types of eye infections include:

• Corneal ulcer, also called keratitis (inflammation of the eye’s clear dome, or cornea)
• Endophthalmitis (painful infection inside the eye)
• Preseptal or orbital cellulitis (infection of the eyelids or the eye socket)
• Other viruses and sexually transmitted diseases (herpes, syphilis, gonorrhea, venereal warts, pubic lice, and HIV/AIDS)
• Sties

Certain types of eye infections can lead to blindness, especially if they go untreated.

How to spot an eye infection

Here are the symptoms to look out for if you’re concerned you have an eye infection:

• Eye pain or irritation
• Red eyes
• Light sensitivity
• Blurry vision
• Itchy or burning eyes
• Watery or thick discharge
• Swelling and redness of the eyelids

How to prevent eye infections

The Cleveland Clinic advises the following to minimize your risk of eye infections:

• Wash your hands frequently.
• Don’t rub your eyes.
• Wear protective eye gear when working or participating in sports. 
• Don’t share items that come in contact with your eyes, like towels or eye makeup.
• Throw out cosmetics after you’ve had an eye infection so you don’t get reinfected.
• Clean your contact lenses and contact lens case.
• Take allergy medication to avoid eye irritation.
• Contact an ophthalmologist if you have any symptoms of an eye infection.