Common vision issue could lead to missed cancer warning, study finds

About 8% of men are estimated to have a form of color vision deficiency (CVD), compared to 0.5% of women, according to global statistics.

The condition, in which patients see and identify color differently, could cause people to miss blood in their urine, which is a vital sign of bladder cancer.

Blood in the urine is the most common first sign of the disease and is often the impetus that leads to diagnosis, according to researchers at Stanford Medicine.

Since colorblind people fail to recognize blood in their urine, they may be delayed in seeking care, which can lead to worse outcomes, the findings suggest. Bladder cancer is about four times more common among men than women.

Senior study author Ehsan Rahimy, M.D., adjunct clinical associate professor of ophthalmology at Stanford Medicine, commented in a press release that he's "hopeful this study raises some awareness, not only for patients with colorblindness, but for our colleagues who see these patients."

Dr. Douglas Lazzaro, a professor in NYU Langone's Department of Ophthalmology, said the inability to recognize the color red in this scenario is a "real risk."

"My guess is that many doctors may not be looking closely enough at the medical record to pick up on this eye problem, leading to delays in diagnosis as the patient may not be able to see the issue," he added.

Dr. Don Railsback, optometrist and CEO of Vision Care Direct in Kansas, agreed that people with known CVD and their clinicians should "pay close attention."

"This is the kind of small detail in a medical history that can change how we counsel patients on the symptoms they should never ignore," he told Fox News Digital.

Railsback, who was not part of the research, added that if the color of urine looks "off" - for example, is tea-colored or unusually dark - the patient should be checked "promptly."

"This study is a strong reminder to tailor health guidance to real-world differences and variations, including color vision," he said.

For colorblind individuals, Railsback recommends asking their primary care physician for a urine test at annual visits. If something seems unusual, they should ask a spouse or partner.

Fox News Digital reached out to the study authors for comment.