A 2-year-old girl with a full-scale IQ score of 135 is the youngest U.S. member of Mensa -- an accomplishment attributed in large part to a simple pair of glasses.

Emmelyn Roettger, from the Washington, D.C., area was admitted to the prestigious high-IQ institution in March, a month before her third birthday, msnbc.com reported.

As a baby, Emmelyn's slow development led doctors to warn her parents that she might have "unspecified delays," but her mom's insistence that her daughter's vision be tested found the cause of her issues: poor eyesight.

"It turned out that she just needed glasses!" mother Michelle Horne said. "It was so obvious that any delays she had were vision-related. From there on out, she just took off."

Emmelyn began recognizing letters at 15 months and was writing them before she turned two. Within months she could write her own name and count to 100 as well as in lots of two, five and 10.

In an effort to prove her daughter was not suffering delays as a doctor continued to insist, Horne tracked down intelligence tests and found the little girl was right at the top for her age, recording an IQ of 135.

Her remarkable abilities were relayed to Mensa, and the group quickly welcomed the girl into the fold.

"My husband thought it was a silly idea at first," Horne said. "I was looking for support, though, and I thought Mensa could be another resource for us."

Newscore contributed to this report.