"A bluish foreign body" turned out to be a "hard mass" of 17 lenses stuck together with mucus, and 10 more were then found under further examination.
A report in the BMJ said she had worn disposable lenses for 35 years, and had not complained of any irritation.
But after they were removed, she said her eyes felt a lot more comfortable.
Specialist trainee in ophthalmology Rupal Morjaria told Optometry Today: "None of us have ever seen this before.
"It was such a large mass. All the 17 contact lenses were stuck together.
"We were really surprised that the patient didn't notice it because it would cause quite a lot of irritation while it was sitting there.
"She was quite shocked. She thought her previous discomfort was just part of old age and dry eye."
The case report said the patient had poorer vision in her right eye and deep-set eyes, which may have been a factor in the lenses becoming lost.
Association of Optometrists spokeswoman Ceri Smith-Jaynes said losing contact lenses in the eye was a common problem but they usually worked their way out.
"They are normally hiding, folded up under the top lid of the eye," she said.
"They can't go any further up than that because there is a pocket.
"It's the same under the bottom lid - the lens can only be in one of those places."