Elmiron eye damage in the retina may not show up in a patient taking the medication until they have been on it for years.

Elmiron—known chemically as pentosan polysulfate sodium—is the only drug choice available that is approved by the U.S. Food and Drug Administration for the treatment of the bladder condition known as interstitial cystitis.

Elmiron mildly thins the blood and so has been known to help prevent blood clots from forming. It is primarily used to treat bladder pain and discomfort secondary to cystitis or urinary tract infection.

According to Healthline, information started coming to light last year concerning Elmiron’s toxic effect on the retina. This side effect wasn’t caught in clinical trials because a patient had to be on the drug for many years for it to develop.

Recently, scientific researchers continuing the investigation into alleged Elmiron eye damage presented additional evidence gathered in the intervening months at the annual meeting of the American Academy of Ophthalmology. As of Oct. 13, the study has not yet been published in a medical journal and subject to the criticisms and evaluation of peer professionals in the field.

According to Science Daily, three eye doctors at Kaiser Permanente in Northern California reviewed patients taking Elmiron after discovering one patient who had been misdiagnosed with a retinal dystrophy. That finding prompted a review of Kaiser Permanente’s full database of 4.3 million patients.

The review turned up approximately 140 patients whose intake of Elmiron averaged approximately 5,000 doses over a decade and a half of treatment. A little less than 100 of those patients agreed to come in for further evaluation with 22 revealing signs of toxic drug exposure along a continuum of exposure.

The researchers discovered about a quarter of patients with fairly long term exposure to the drug revealed signs of retinal damage. Researchers reported the damage in some cases could be mistaken for other conditions commonly known as age-related macular degeneration and pattern dystrophy.

What is clear from gathered data is that there is significant cause for patients starting on the drug to be carefully monitored. Part of the screening process to prevent Elmiron eye damage will likely be eye annual eye exams.

If minor damage is identified early, it can be stopped in its tracks by ceasing the medication under the guidance of the prescribing urologist. Due to this, researchers and ophthalmologists recommend regular screening interstitial cystitis patients on Elmiron.

What is Interstitial Cystitis?

According to Review of Ophthalmology, interstitial cystitis is a painful syndrome of the bladder and surrounding region which leads to urinary urgency and often discomfort during intercourse for female sufferers. It does mostly affect women, although men can suffer as well. One million U.S. citizens are expected to endure symptoms of interstitial cystitis.

Elmiron has been used for decades to treat the disorder, exposing countless people to these side effects that were occurring without notice. It wasn’t until last year, that the link between retinal damage and this bladder medication were discovered.

Consumers who were treated with Elmiron for years and later developed eye problems may be able to take legal action.