The opioid epidemic may be leading to a rise in cases of what's normally a rare eye infection, according to a report from an eye treatment center in New England.

From 2014 to 2016, health care providers at the center saw 10 patients with an eye infection called fungal endophthalmitis that was tied to injection drug use — most commonly, the use of heroin. That number is up from just three cases seen at the center from 2012 to 2014.

Injection drug use is known to put people at risk for fungal endophthalmitis, and the infection can cause serious vision problems, according to the researchers, from the New England Eye Center at Tufts Medical Center in Boston. Several patients in the new report became legally blind after their infections.

"Increasing rates of [intravenous drug abuse] in the New England region have placed more patients at risk for vision-threatening" fungal endophthalmitis, the researchers wrote in the April 20 issue of the journal JAMA Ophthalmology.

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Fungal endophthalmitis is an infection caused by a fungus that grows inside the eyeball. The use of injection drugs can allow the fungus to enter the bloodstream, and the fungus can then spread to the eye, the researchers said.

In the new report, six of the 10 patients reported having injected heroin , and one patient reported having injected buprenorphine, an opioid medication used to treat opioid addiction . The other three patients reported that they had injected drugs but did not say which drug they had used.

In nearly all of the patients, eye problems were their only symptom of infection; just one patient had fevers in addition to the eye infection. The most common eye symptoms in these patients were reduced vision, the appearance of "floaters" in a person's vision , eye pain and sensitivity to light. Some patients still had near-normal vision when they were seen by the doctors, but others could detect only hand motions, the report said. In all of the patients, just one eye was infected.

Nine of the patients were admitted to the hospital and received an injection of antifungal medications into their eyes, as well as intravenous or oral antifungal medications. One patient refused to be admitted to the hospital.

Five of the patients eventually required surgery to remove the clear, gel-like substance in the eye called the vitreous humor . In general, the patients who underwent this surgery had improved vision compared to those who didn't get the surgery. The five patients who received the surgery had 20/70 vision, on average, which is moderately impaired vision, while the three patients who didn't get the surgery had 20/300 vision, which is legally blind. (Two of the 10 patients did not follow up with their doctors after their initial visit to the clinic.)

The researchers noted that the patients with fungal endophthalmitis often have vague symptoms, such as reduced vision, redness and pain, which can lead to a delay in their diagnosis. One key factor that can lead doctors to suspect fungal endophthalmitis is if patients have a history of intravenous drug use, but patients may be hesitant to bring this up. In the new report, three patients initially denied having injected drugs but later revealed that they had used drugs, after they were "informed that knowledge of intravenous drug use was vital to making appropriate treatment decisions," the researchers said.

Thus, "a high clinical suspicion, detailed history taking, and open discussion with the patient are necessary for early and accurate diagnosis" of fungal endophthalmitis tied to injection drug use, the researchers concluded.

The researchers noted that they don't know for sure if the rise in cases of this eye infection seen at their center is entirely due to the rise in opioid use in the region. For example, because other doctors refer patients to the center, changes in referral patterns in the region could also lead to an increase, they said.

Original article on Live Science .