Q: I have a patient who I suspect might have an intraocular foreign body, but his vision is normal. Does this make sense?

A: Although uncommon, it’s possible and it must be considered. Indeed, “most patients with foreign bodies who present to a primary care office have good vision,” says optometrist Brian Den Beste, of Orlando, Fla. Why? Because those with poor vision usually present to the ER with other serious injuries, such as from a motor vehicle accident, tire or battery explosion, or workplace accident, he says. 

Take, for example, the recent case that Dr. Den Beste saw: “This patient had an eye injury from chiseling an exposed nail head—a fragment broke off and struck the center of his cornea.”

Had the fragment penetrated? At first, it wasn’t obvious. “His vision was 20/40, the anterior chamber was deep and quiet, and initially it seemed due to the location of the injury on the visual axis and the concomitant epithelial disruption,” Dr. Den Beste says. “But he was referred to us because the injury was centrally located and he was a suspect for penetration.”

An intraocular foreign body (IOFB) is serious and can have devastating complications if missed.

“If the vision is reduced and the patient does have an IOFB, it’s usually from secondary infection, inflammation (vitritis), vitreous hemorrhage or associated retinal issues, like detachment, retinal hemorrhage or choroidal rupture,” Dr. Den Beste says. In addition, the FB can penetrate the crystalline lens and cause an acute cataract or subluxation.

Due to such serious ramifications, “one is always obligated to see if there is a possibility that the foreign body penetrated the eye,” he says. “Grinding and metal-on-metal histories should always alert the doctor of that possibility—whatever the vision.”

Could this corneal scar be a clue to something deeper?
In this patient’s case, not only was his vision still good, but his anterior chamber was quiet, and intraocular pressure and Seidel test were both normal.

Still, “I suspected the foreign body had penetrated [into the eye] because the slit-lamp exam showed a trail that was full thickness,” Dr. Den Beste says. Before dilation, a small injury to the anterior portion of the crystalline lens was visible. Upon dilation, a posterior subcapsular cataract was already forming.

Fundus evaluation is critical to tell if penetration has occurred, Dr. Den Beste says. In this case, “I found a large foreign body that stopped just short of the retina.”

Red blood cells or pigment in the vitreous are also signs that foreign matter has entered the eye or has caused enough percussion to create a tear in the retina.

“If the vitreous has too much blood or inflammation for visualization, then a B-scan can be of great assistance,” he says. “If the B-scan is not helpful or available, then an orbital CT scan (no contrast is necessary) will quickly give you the answer. If a CT scan is not available, then an X-ray will also work and is inexpensive, although it won’t help you localize the exact location of the foreign body.”

If an IOFB is in the orbit itself, removal is not usually required. “The chance of infection is always possible and is usually treated prophylactically,” Dr. Den Beste says.

In this case, the patient was sent for vitrectomy and the IOFB was removed. At the time of the pars plana surgery, the lens capsule ruptured and a total lensectomy was performed at the same time.

“This patient did well, but will need a secondary IOL or contact lens for final visual rehabilitation,” Dr. Den Beste says. “He could have lost his eye or had permanently reduced acuity if his primary care optometrist had not been suspicious and referred him on for further evaluation.”