Pain in one eye usually comes from something minor and treatable, like a scratch on the surface, dry eyes, or sinus pressure. But because some causes require prompt attention, it helps to understand what different types of eye pain feel like and what they point to.
The pain itself is your best clue. A gritty, stinging sensation suggests a surface problem. A deep ache behind the eye points to sinus issues, inflammation, or nerve involvement. Sharp pain with vision changes is the combination that needs the fastest response.
Surface Problems: Scratches, Dryness, and Foreign Bodies
The most common reason for sudden pain in one eye is a corneal abrasion, a small scratch on the clear front layer of the eye. This happens easily: a fingernail, a contact lens edge, dust, or even rubbing your eye too hard can do it. The pain is sharp and immediate, and your eye will water heavily and feel sensitive to light. The good news is that most corneal abrasions heal within 24 to 72 hours without lasting damage. Larger scratches covering more than half the corneal surface can take four to five days.
If you still have symptoms after three days, or if the pain is getting worse rather than better each day, that’s a sign something else may be going on, like a trapped foreign body or an infection developing at the scratch site.
Dry eye can also cause a burning, gritty pain that tends to affect one eye more than the other. It’s worse after long stretches of screen time, in air-conditioned rooms, or on windy days. Contact lens wearers are especially prone. Unlike a scratch, dry eye pain builds gradually and improves with lubricating drops.
Sinus Pressure and Congestion
Your sinuses sit directly behind and around your eye sockets, so when they’re inflamed or infected, the pain can feel like it’s coming from your eye itself. The type of sinus involved determines where you feel it. Infection in the ethmoid or sphenoid sinuses (the ones deep behind your nose) produces pain directly behind the eye. Frontal sinus infection creates pain across the brow and forehead. Maxillary sinus infection causes aching over the cheeks that can radiate up toward the eye.
Sinus-related eye pain has a distinct quality: it’s a constant, dull ache without throbbing or pounding. It gets worse when you bend forward, cough, or strain. Pressing on the bony area around your eye socket or along the bridge of your nose will increase the pain if sinuses are the source. If you also have nasal congestion, thick nasal discharge, or a recent cold, sinuses are a likely culprit.
Infections: Conjunctivitis and Beyond
Bacterial conjunctivitis (pink eye) often affects just one eye. It causes redness, soreness, and a sticky yellow or green discharge that can crust your eyelid shut overnight. Viral conjunctivitis tends to produce a more watery discharge and frequently starts in one eye before spreading to the other within a few days. Both are common and typically resolve without complications, though bacterial cases often benefit from antibiotic drops.
A more serious infection is orbital cellulitis, an infection of the tissue surrounding the eye. This causes pain, swelling, difficulty moving the eye, and sometimes vision changes. It can develop from a sinus infection that spreads. This one needs immediate treatment.
Inflammation of the Eye Wall
The white of your eye has layers, and inflammation at different depths causes very different symptoms. Episcleritis affects the outermost layer and looks alarming (a red patch on the white of one eye) but causes little to no actual pain. It usually resolves on its own.
Scleritis affects a deeper layer and is a different story entirely. It produces severe, deep aching pain that can wake you up at night and may radiate to your forehead, cheek, or jaw. Light sensitivity is common. Scleritis sometimes signals an underlying autoimmune condition and needs treatment to prevent damage to the eye.
Cluster Headaches
If your right eye pain comes in intense episodes that last 15 minutes to a few hours, especially if they happen around the same time each day, cluster headaches are a strong possibility. These headaches are one-sided and center on the eye and temple area. The pain is burning, sharp, or stabbing, and it’s often described as one of the most intense types of pain a person can experience.
During an attack, the eye on the affected side may tear up, turn red, or develop a droopy eyelid. Your nostril on that same side may run or feel congested. These headaches tend to occur in “clusters” over weeks or months, then disappear for a period before returning. They’re uncommon but frequently misdiagnosed as sinus headaches or migraines.
Optic Neuritis
Optic neuritis is inflammation of the nerve that connects your eye to your brain. It almost always affects just one eye. The hallmark symptom is a dull ache behind the eye that gets noticeably worse when you move your eye side to side or up and down.
Along with the pain, most people experience some degree of vision loss that develops over hours to days. Colors may look washed out or less vivid than normal, and some people see flashing or flickering lights with eye movements. Vision typically improves over several weeks to months. Optic neuritis can be an early sign of multiple sclerosis, so it’s evaluated carefully even when symptoms are mild.
Acute Angle-Closure Glaucoma
This is the eye emergency most people have never heard of. It happens when the drainage system inside the eye suddenly becomes blocked, causing pressure to spike rapidly. Normal pressure inside the eye ranges from 10 to 21 mm Hg. During an acute attack, it can surge above 40 mm Hg.
The symptoms are hard to miss: a painful red eye, blurred vision, halos around lights, headache, and nausea or vomiting. The pupil on the affected side may appear fixed and dilated. This combination needs emergency treatment within hours to prevent permanent vision loss. If you’re experiencing severe eye pain with any of these accompanying symptoms, go to an emergency room.
Corneal Ulcers and Contact Lens Complications
A corneal ulcer is an open sore on the cornea, usually caused by infection. Contact lens wearers are at higher risk, especially those who sleep in their lenses, swim with them in, or don’t clean them properly. Symptoms include moderate to severe eye pain, a sudden inability to tolerate your contact lenses, redness, and decreased vision. Unlike a simple abrasion, a corneal ulcer can cause lasting scarring if not treated promptly.
Patterns That Point to the Cause
Pay attention to what the pain feels like and what comes with it. A gritty, stinging pain that started suddenly after something got in your eye points to a surface injury. A deep, steady ache that worsens when bending over suggests sinus involvement. Pain that flares specifically when you move your eye could indicate optic neuritis. Intense, time-limited attacks with tearing and a stuffy nose on the same side fit the pattern of cluster headaches.
Certain combinations are red flags that warrant same-day evaluation: eye pain paired with sudden vision loss, pain with a visibly abnormal pupil, pain after trauma to the eye or face, or severe pain with nausea and vomiting. Pain that’s mild, started recently, and improves on its own is far less concerning, but any eye pain lasting more than a couple of days without improvement is worth having examined.