Approach to a red eye: Clinical sciences

A red eye is a key indication of ocular inflammation. Common causes of red eye include vision-threatening conditions such as angle-closure glaucoma, globe rupture, scleritis, uveitis, keratitis, corneal injury, and hyperacute bacterial conjunctivitis. On the other hand, benign causes of a red eye include subconjunctival hemorrhage, conjunctivitis, blepharitis, and keratoconjunctivitis sicca.

Now, if your patient presents with a red eye, first perform a focused history and physical examination. Your patient will report redness of one or both eyes, and the physical exam will reveal conjunctival hyperemia. At this point, diagnose ocular erythema and assess for red flags that indicate an immediate threat to vision. These include severe pain; decreased visual acuity; photophobia; pupillary changes; increased intraocular pressure, also known as IOP; anterior chamber inflammation; and corneal epithelial defects. If any of these red flags are present, assess for an emergent underlying cause.

First up is angle-closure glaucoma! These patients are generally 40 years of age or older and report severe eye pain, blurry vision, and headache with nausea. They may even see halos around lights or have a family history of angle-closure glaucoma! The physical exam will show a dilated unreactive pupil; a hazy cornea; and conjunctival injection, commonly referred to as blood shot eyes, which is redness due to dilation of the conjunctival blood vessels. At this point, consider angle-closure glaucoma and make an emergent referral to the ophthalmology team. A gonioscopy exam that reveals an angle between the iris and cornea of 20 degrees or less confirms the diagnosis of angle-closure glaucoma!

Here’s a clinical pearl! While not required for the diagnosis of angle-closure glaucoma, fundoscopy, slit lamp examination, and tonometry are also helpful tools. Both fundoscopy and slit lamp examination will show a shallow anterior chamber and an enlarged optic cup, which is the area in the center of the optic disc that increase in size as optic nerve fibers are lost; whereas tonometry will reveal an IOP greater than 21 millimeters of mercury, often ranging between 50 to 80 millimeters of mercury!

Next up is globe rupture! Your patient will report a history of trauma, blurry vision, and severe pain. The physical exam will show local tenderness, a teardrop-shaped pupil, and shallow anterior chamber. In this case, consider a ruptured globe, and make an emergent referral to the ophthalmology team for further evaluation. The slit lamp exam might reveal foreign bodies, corneal lacerations, defects of the iris, and a hyphema, which is a collection of blood in the anterior chamber. The CT scan of the head and orbits may show foreign bodies or an orbital wall fracture. These findings confirm a diagnosis of globe rupture!

Moving on to scleritis, or inflammation of the sclera. Your patient will report severe pain, blurry vision, and photophobia; and they may have a history of autoimmune disease. The physical exam will reveal normal pupils and decreased visual acuity. At this point, consider scleritis and promptly refer your patient to the ophthalmology team. A slit lamp exam will show inflamed scleral vessels and the CT scan of the orbits will reveal scleral enhancement. These findings confirm a diagnosis of scleritis, which can affect not only the sclera, but the cornea, adjacent episclera, and underlying uvea!

Here's a clinical pearl! At least half of cases of scleritis are linked to an underlying autoimmune condition. So always evaluate your patient for autoimmune disorders if you diagnose scleritis!

Now let’s move on to uveitis or inflammation of the uveal layer of the eye. These patients report moderate to severe pain in the affected eye, as well as consensual photophobia, which is pain when light is shone in the unaffected eye. They may also have a history of autoimmune diseases such as systemic lupus erythematosus or rheumatoid arthritis; infectious processes, such as lyme disease, syphilis, or herpes simplex; as well as use of certain medications, such as checkpoint inhibitors for cancer treatment or the antiviral cidofovir.

On physical exam, pupils will appear constricted or irregular. You will also observe ciliary flush, which is the presence of a ring of red or violet spreading around the cornea, signifying inflammation. At this point, consider uveitis and promptly refer your patient to the ophthalmology team. A diagnosis of uveitis is confirmed when a slit lamp examination reveals cell and flare, where “cell” refers to a collection of white blood cells layered within in the anterior chamber; and “flare” refers to a hazy appearance of the aqueous humor due to an increased concentration of protein.

Let’s move on to keratitis, or inflammation of the cornea. These patients report pain, photophobia, tearing, and blurry vision. They often have an underlying autoimmune disease, like rheumatoid arthritis, or an infectious disease, such as herpes simplex virus. The physical exam will reveal normal pupils and decreased visual acuity. At this point, consider keratitis, and promptly refer your patient to the ophthalmology team. Slit lamp examination with application of fluorescein stain may show cell and flare and diffuse fluorescein uptake in a branching pattern, causing opacity of the cornea. These findings confirm a diagnosis of keratitis!

Your patient will report moderate to severe eye pain, photophobia, and blurry vision, and may report chemical exposure or having a foreign body in the eye. Physical exam will show normal pupils; and you might observe decreased visual acuity as well as a visible corneal injury or foreign body. With these findings, consider corneal injury. and promptly refer your patient to the ophthalmology team. Slit lamp examination with fluorescein stain will show uptake of fluorescein at the site of the corneal epithelial defect, confirming the diagnosis of corneal injury!