A painful, light-sensitive red eye may be inflamed beneath the surface.

A red eye is easy to dismiss as dryness, allergy, or pink eye. But when redness comes with deep aching, marked sensitivity to light, blurred vision, or new floaters, the inflammation may be inside the eye rather than limited to its surface. One important cause is uveitis.

Uveitis is a broad term for intraocular inflammation. It can affect the iris at the front of the eye, the vitreous and nearby structures in the middle, the retina and choroid at the back, or several regions at once. Some episodes develop suddenly and respond quickly to treatment. Others are recurrent or chronic and need coordinated long-term care.

Because untreated inflammation can damage vision—and because an infection can sometimes cause a similar appearance—uveitis should not be self-treated with leftover drops. A same-day or urgent examination is appropriate for a painful red eye with light sensitivity or reduced vision. Optima Eye Care provides emergency eye-care guidance for North York patients and can arrange ophthalmology or emergency referral when indicated.

The uvea is the vascular middle layer of the eye

The wall of the eye has several important layers. The white sclera forms much of the outer coat. The retina lines the inside and converts light into signals. Between them is the uvea, a layer rich in blood vessels and pigment.

The uvea has three connected parts:

• The iris is the coloured part visible at the front. It adjusts pupil size.
• The ciliary body lies behind the iris. It helps the lens focus and produces fluid for the front of the eye.
• The choroid lies beneath the retina and helps supply its outer layers.

Uveitis often involves neighbouring tissues as well as the uvea. Inflammation may affect the fluid-filled anterior chamber, vitreous gel, retina, optic nerve, or cornea. This is why symptoms, testing, complications, and treatment differ from one person to another.

Uveitis is classified by its main location

Location provides a useful starting point:

• Anterior uveitis affects the iris and sometimes the nearby ciliary body. It is often called iritis or iridocyclitis and is the most common form.
• Intermediate uveitis mainly involves the vitreous and peripheral structures behind the lens.
• Posterior uveitis primarily affects the choroid, retina, or both. Terms such as choroiditis, retinitis, or chorioretinitis may describe the exact tissue involved.
• Panuveitis means inflammation is present through the front, middle, and back portions of the uveal tract without one region clearly predominating.

The label does not by itself identify the cause. “Anterior uveitis” describes where inflammation is seen, just as “arthritis” describes inflammation in a joint. The next questions concern whether the episode is acute or chronic, one-sided or bilateral, infectious or non-infectious, isolated to the eye or associated with a systemic condition.

Symptoms depend on where the inflammation is

Acute anterior uveitis often causes a recognizable combination:

• a red eye, especially around the coloured iris;
• deep aching or tenderness;
• significant sensitivity to light;
• blurred or hazy vision;
• a small or irregular-looking pupil; and
• tearing without the prominent itch typical of allergy.

Bright light entering the unaffected eye can sometimes make the painful eye hurt because both pupils constrict together. This “consensual” light sensitivity can be a clue to inflammation involving the iris, but it is not a safe home test and does not confirm diagnosis.

Intermediate or posterior uveitis may produce floaters, hazy vision, missing areas of vision, distortion, or reduced colour and contrast. The eye may not be very red or painful because the inflammation is farther back. Some posterior conditions threaten sight while causing surprisingly little discomfort.

Symptoms can affect one eye, both eyes simultaneously, or one eye followed later by the other. They may appear over hours, days, or more gradually. Any new vision loss, cluster of floaters, or painful light-sensitive red eye deserves prompt assessment regardless of whether every textbook symptom is present.

Uveitis is not the same as conjunctivitis

Conjunctivitis inflames the thin membrane over the white of the eye and the inner eyelids. Viral conjunctivitis often causes watery discharge and may accompany a cold. Bacterial conjunctivitis can produce thicker discharge. Allergy usually causes prominent itch and commonly affects both eyes.

Uveitis is inflammation inside the eye. Deep pain, pronounced light sensitivity, reduced vision, new floaters, and redness concentrated around the cornea raise greater concern for intraocular disease. Uveitis usually does not produce the sticky discharge associated with some surface infections.

These patterns overlap. A corneal abrasion, corneal ulcer, scleritis, acute angle-closure glaucoma, or herpes infection can also cause a painful red light-sensitive eye. A subconjunctival hemorrhage can look dramatic but is often painless. Photographs and symptom checklists cannot safely distinguish all of them; the cornea, pupil, eye pressure, anterior chamber, lens, vitreous, retina, and optic nerve may need examination.

Sometimes no cause is identified

Uveitis can occur in an otherwise healthy person with no detectable systemic disease or infection. This is called idiopathic uveitis. “Idiopathic” does not mean the symptoms are imagined or the inflammation is harmless; it means no specific cause has been established with the information available.

The chance of identifying an association depends on the uveitis pattern, recurrence, age, examination findings, symptoms elsewhere in the body, geographic and exposure history, and test results. A single mild anterior episode may not require the same investigation as bilateral posterior inflammation or repeated attacks.

Testing every patient for every possible disease can produce confusing false-positive results. A targeted work-up guided by the eye findings and medical history is generally more useful than an indiscriminate panel.

Immune-mediated disease can involve the eye

The immune system normally controls infection and repairs injury. In autoimmune or autoinflammatory disease, it can also drive inflammation in healthy tissue. Uveitis may occur alongside conditions involving the spine, joints, skin, bowel, lungs, blood vessels, brain, or other organs.

Associations can include certain forms of inflammatory arthritis, ankylosing spondylitis and related spondyloarthritis, psoriasis, inflammatory bowel disease, sarcoidosis, Behçet disease, lupus, multiple sclerosis, and other less common disorders. The pattern of eye inflammation is not identical across these conditions.

Tell the clinician about:

• inflammatory back pain or prolonged morning stiffness;
• swollen or painful joints;
• psoriasis or unexplained rashes;
• recurrent mouth or genital ulcers;
• chronic diarrhea, blood in stool, or diagnosed bowel inflammation;
• unexplained cough or breathing symptoms;
• numbness, weakness, or other neurological symptoms;
• fevers, night sweats, or unintentional weight loss; and
• previous episodes of eye inflammation.

These symptoms do not prove a systemic cause, and their absence does not exclude one. They help determine whether family medicine, rheumatology, infectious disease, dermatology, gastroenterology, or another specialist should be involved.

Infection must be considered before suppressing inflammation

Viruses, bacteria, parasites, and fungi can cause or trigger intraocular inflammation. Examples include herpes simplex, shingles, toxoplasmosis, syphilis, tuberculosis, and infections that become more likely when the immune system is suppressed. Exposure and geographic history can matter.

An infectious and a non-infectious uveitis may both look inflamed, but treatment is not interchangeable. Steroids reduce immune activity. Given without appropriate antimicrobial treatment in certain infections, they can allow the organism to multiply and worsen tissue damage.

Tell the eye-care team about cold sores, shingles, recent fever or infection, immune-suppressing medication, cancer treatment, organ transplantation, intravenous drug use, tuberculosis exposure, travel, animal exposures, and sexual-health concerns relevant to infection risk. Medical conversations are confidential and accurate information protects vision.

Do not restart steroid drops from an older episode simply because the symptoms feel familiar. Recurrence should be confirmed, eye pressure checked, and infection considered first.

Injury, surgery, and medication can also matter

Blunt trauma can release pigment and inflammatory cells into the eye, damage the iris, cause bleeding, or produce inflammation called traumatic iritis. Pain and light sensitivity may begin hours after the impact even if the outside of the eye looks relatively normal.

Inflammation can follow eye surgery, and a mild controlled response may be expected during healing. Increasing pain, redness, discharge, or declining vision after a procedure is not something to monitor casually. Contact the surgical team immediately because infection inside the eye can be an emergency.

Rarely, a medication can be associated with uveitis or a uveitis-like reaction. Do not stop a prescription on your own. Bring a complete list of pills, injections, biologic treatments, supplements, eye drops, recent vaccinations, and medication changes so the ophthalmologist and prescribing clinician can assess timing and alternatives.

A history of one episode changes the conversation

Prior records are valuable. Bring the name of the diagnosis, which eye was involved, treatment used, taper schedule, laboratory or imaging results, and any ophthalmology letters. If you do not have records, a photograph of the old medication label or the dispensing pharmacy may help reconstruct the history.

Note whether previous attacks affected the same eye, alternated eyes, or occurred in both. Recall whether onset was sudden, whether floaters were present, and how soon symptoms returned after medication stopped. Recurrence pattern can guide investigation and longer-term planning.

An old diagnosis does not make every future red eye uveitis. Dry eye, allergy, infection, elevated eye pressure, and corneal injury remain possible. Conversely, a quiet-looking eye can still have posterior inflammation. Re-examination is more reliable than pattern matching at home.

How the eye examination detects inflammation

The assessment begins with visual acuity in each eye and a careful symptom and medical history. The clinician examines pupils, eye movements, colour vision when indicated, and the pattern of external redness.

A slit-lamp microscope uses a narrow beam to view the front structures at high magnification. In anterior uveitis, individual inflammatory cells may be seen moving in the fluid of the anterior chamber. Protein leaking from inflamed vessels makes the beam appear hazy, a finding called flare. Deposits can occur on the back of the cornea, and the iris or pupil can develop characteristic changes.

Eye pressure is measured because inflammation can make pressure too low or too high. Steroid treatment can also raise pressure in susceptible people. A pressure reading is interpreted with the full examination rather than used alone to diagnose uveitis.

Dilating drops widen the pupils so the vitreous, retina, choroid, macula, and optic nerve can be examined. Dilation temporarily blurs near vision and increases light sensitivity, so bring sunglasses and avoid driving if vision is not comfortable or safe.

Imaging documents structures that cannot be judged from the surface

Optical coherence tomography, or OCT, creates cross-sectional images of the retina. It can detect swelling at the macula, the area responsible for detailed central vision, and track response to treatment.

Retinal photography documents lesions and change over time. Fluorescein or indocyanine-green angiography may be used by specialists to evaluate leakage and circulation in the retina or choroid. Ultrasound can help when a cataract, bleeding, or dense inflammation blocks the view into the eye. Wide-field imaging may show peripheral findings beyond a standard photograph.

Not every patient needs every test. The location of inflammation, clarity of the ocular media, visual symptoms, suspected cause, and prior results determine which imaging adds useful information.

Laboratory and medical investigations are targeted

An ophthalmologist may request blood tests, urine testing, chest imaging, or other studies based on the uveitis pattern and history. In selected cases, fluid from inside the eye may be tested for infection or malignant cells. Referral to another medical specialist may be needed.

A normal test panel does not mean the eye was never inflamed. Some immune-mediated diseases develop recognizable systemic features only later, and many cases remain isolated to the eye. New medical symptoms should be reported at follow-up even after an earlier work-up was unrevealing.

An abnormal screening test also does not automatically establish cause. Results are interpreted in context, sometimes with confirmatory testing, to avoid unnecessary treatment for an unrelated finding.

Treatment has two goals: control inflammation and treat its cause

For non-infectious anterior uveitis, corticosteroid eye drops are commonly used to suppress inflammation. The starting frequency may be much more intensive than ordinary eye-drop schedules and is adjusted as inflammatory cells decrease. The exact product, frequency, and taper must come from the treating clinician.

Dilating or cycloplegic drops may be prescribed to reduce painful iris and ciliary-body spasm and to lower the chance that the iris will stick to the lens. These drops can blur near vision and increase light sensitivity. They are therapeutic, not the same as routine redness-relief drops.

Intermediate, posterior, bilateral, or severe uveitis may require steroid tablets, injections around or inside the eye, an implant, or medication that modifies the immune response. Chronic immune-mediated disease is often managed by an ophthalmologist with uveitis expertise in coordination with rheumatology or another specialist.

Infectious uveitis requires treatment directed at the organism. An antiviral, antibiotic, antiparasitic, or antifungal medicine may be combined with carefully timed anti-inflammatory treatment. Suppressing inflammation without controlling the infection can be dangerous.

Never improvise a steroid taper

Stopping steroid drops too quickly can allow inflammation to rebound. Continuing a high dose longer than necessary increases side-effect risk. A taper is designed around the medication strength, starting frequency, examination findings, cause, duration, and response—not just how comfortable the eye feels.

Shake suspensions when the label instructs. Wash hands, keep the bottle tip away from lashes and skin, and use the correct eye. If several drops are prescribed, ask about spacing. Mark a written schedule or set reminders because complex tapers are easy to misread.

Call the treating office if a dose is missed, the bottle runs out, the pharmacy substitutes a product, or symptoms worsen during a taper. Do not double doses or borrow drops. Continue follow-up even after pain disappears; active inflammation can sometimes remain without obvious symptoms.

Steroid treatment requires monitoring

Corticosteroids can preserve vision by controlling harmful inflammation, but they also have meaningful risks. Eye drops, injections, implants, and systemic steroids can raise eye pressure, contribute to glaucoma, accelerate cataract formation, delay healing, and increase susceptibility to infection.

The balance is not simply “steroids are bad” or “steroids cure uveitis.” Uncontrolled inflammation itself can cause permanent damage. The safest approach is the lowest effective exposure within a monitored plan, with steroid-sparing immune treatment considered when repeated or long-term therapy makes that appropriate.

Do not skip pressure checks because the eye feels normal. Steroid-related pressure rise may be painless. Report halos, headache, nausea, worsening blur, or severe eye pain urgently, but remember that pressure can increase without these warning signs.

Uveitis can cause complications even after pain improves

Inflammation and its treatment can lead to:

• adhesions between the iris and lens, creating an irregular pupil;
• cataract;
• elevated pressure and glaucoma;
• abnormally low eye pressure;
• swelling of the macula;
• clouding or debris in the vitreous;
• retinal damage, scarring, or detachment;
• abnormal new blood vessels;
• optic-nerve involvement; or
• permanent reduction in vision.

The risk depends on location, cause, severity, duration, recurrence, and response. Follow-up examinations and imaging aim to detect complications before the patient necessarily notices them.

If vision remains blurry after the anterior inflammation looks quiet, the clinician may check for macular swelling, cataract, pressure change, corneal alteration, or another residual effect rather than simply increasing the glasses prescription.

Children can have quiet inflammation

Some childhood uveitis, particularly that associated with juvenile idiopathic arthritis, can develop with little redness, pain, or light sensitivity. A child may seem visually normal while inflammation is present. This is why children with certain arthritis patterns receive scheduled slit-lamp screening even when they have no eye complaints.

Parents should follow the screening interval set by the child’s rheumatology and ophthalmology teams. A routine school vision screen cannot detect anterior-chamber cells. Missed appointments matter because silent inflammation can still cause cataract, glaucoma, band-shaped corneal changes, or amblyopia.

A child with a new painful red eye, photophobia, floaters, or reduced vision needs prompt assessment regardless of known arthritis. Do not use a parent’s or sibling’s drops.

Recurring uveitis needs a written action plan

Some people experience one episode; others have recurrences separated by quiet periods or inflammation that returns whenever treatment is reduced. Ask the treating ophthalmologist what symptoms should trigger a same-day call, whether a direct pathway for urgent review is available, and whether any medication should ever be started before examination.

In most situations, the eye should be examined before steroid drops are restarted. A familiar ache could instead be herpes-related disease, a corneal ulcer, or high eye pressure. If a specialist has given explicit individualized instructions for recurrence, follow those instructions rather than general online advice.

Keep an updated medication and diagnosis list on your phone. Include allergies, systemic immune medications, infectious history, and the contact information for the ophthalmologist and other specialists. This can prevent delay when a flare begins outside regular office hours.

Practical comfort measures while awaiting care

Sunglasses can reduce brightness outdoors and may help temporarily indoors, but they do not treat inflammation. Keep the environment comfortably dim without staying in complete darkness for days. Avoid driving while vision is blurred or pupils are dilated.

Remove contact lenses and leave them out until an eye-care professional confirms it is safe to resume. Avoid eye makeup during an acute red-eye episode so debris and products do not complicate the examination. Do not patch the eye, because occlusion can hide worsening redness and does not treat uveitis.

Use only medications already approved for the current episode. Ordinary lubricating drops may ease surface irritation but will not control intraocular inflammation. Redness-relief drops can temporarily narrow surface blood vessels and create false reassurance.

Do not delay care while searching for the perfect pair of sunglasses or waiting to see whether sleep fixes the problem. Uveitis symptoms deserve assessment because the diagnosis is made by examining inside the eye.

When to seek emergency care

Arrange urgent same-day eye assessment for:

• a painful red eye with sensitivity to light;
• new or worsening blurred vision;
• new floaters or a sudden increase in them;
• recurrence of suspected uveitis;
• increasing symptoms during a medication taper;
• redness or pain after eye surgery, injection, or significant injury; or
• an eye symptom occurring with immune suppression or serious infection risk.

Go to an emergency department for sudden severe vision loss, major eye trauma, a severe headache with nausea and a painful red eye, neurological weakness or speech trouble, or other symptoms suggesting a broader medical emergency. Call 911 when appropriate and do not drive yourself.

Flashes, a curtain or shadow in the vision, and a sudden shower of floaters can indicate a retinal tear or detachment as well as inflammation and require urgent dilated assessment. Our flashes and floaters guide explains these warning signs in more detail.

Uveitis assessment in North York

Uveitis is not one disease and is not always visibly dramatic. Anterior inflammation may cause a painful light-sensitive red eye, while intermediate or posterior disease may be noticed mainly as floaters and blurred vision. Causes range from an isolated immune event to systemic inflammatory disease, infection, trauma, surgery, or medication.

Optima Eye Care can assess new symptoms for North York patients, check the anterior chamber, eye pressure, and dilated retina, and coordinate urgent ophthalmology or medical referral. Established uveitis generally requires ophthalmology-led treatment and monitoring because medication choices, tapering, systemic investigation, and complications can be complex.

If you have a painful red eye, marked light sensitivity, new floaters, or reduced vision, request urgent guidance and describe those symptoms when you contact the clinic. Do not restart an old steroid drop while waiting unless the ophthalmologist responsible for your care has explicitly instructed you to do so for this episode.