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For years, she had assumed that the strange sensation in her right eye was just a part of a changing body, nothing worth troubling over.

Fortunately for the unidentified 67-year-old woman, doctors preparing her for routine cataract surgery last November discovered the source and removed it. Unfortunately for the squeamish, the cause was the stuff of nightmares: The woman’s eye had become home to a hard, bluish mass of nearly 30 contact lenses held together by mucus.

The lump the medical team discovered was composed of 17 contact lenses, they reported this month in BMJ, a medical journal. On further examination, they found 10 more.

“We were all shocked she had not noticed!” Dr. Rupal Morjaria, an ophthalmologist in Britain and one of the three authors of the report, said in an email.