(Reuters) - Eye doctors who had braced themselves for at least a few patients after a dazzling solar eclipse swept the United States cautiously exhaled on Tuesday, with some hospitals reporting zero cases of damaged vision so far.

Slideshow ( 2 images )

One man showed up at a New York City hospital on Tuesday with a damaged retina after acting on the mistaken belief he could safely stare at an eclipse through a hole punched in a garbage bag.

But most signs pointed to people heeding medical advice that it is never wise to gaze at the sun without eye protection, even when some of it is shaded by the moon, as it was above the heads of tens of millions of Americans on Monday.

Some ophthalmologists, however, believed they would see a small number of people with blurry vision in the coming weeks, when putting off a sometimes costly or inconvenient visit to a doctor became untenable.

“I’m sort of amazed so far that we haven’t examined anybody who has damage,” Dr. M. Edward Wilson said by telephone from the Medical University of South Carolina’s Storm Eye Institute in Charleston.

It was a similar story at the University of Kansas Health System in Kansas City, New York City’s Health + Hospitals/Bellevue, the University of Nebraska Medical Center in Omaha and the Casey Eye Institute in Portland, Oregon: not a blurry eye in sight.

At Nashville’s Vanderbilt University Medical Center, however, seven people were scheduled to see doctors with concerns from viewing the eclipse, Dr. Shriji Patel said.

“We have opened extra clinics over the next three days, and I’m expecting them to be full,” he said.

Direct exposure to the sun’s ultraviolet radiation even for a fraction of a minute can be enough to overwhelm the photoreceptor cells lining the back of the eye. The symptoms -- blind spots and blurriness -- become apparent in the following hours. It can take months, but the retina can largely heal itself if the damage is not severe.

In the largest investigation into an eclipse’s effects on a nation’s ocular health, doctors found 70 cases of sun-damaged retinas after an eclipse shadowed the United Kingdom in 1999, according to a 2001 paper published in Eye, a medical journal.

The paper noted this was a low incidence for a country then home to some 55 million, and symptoms cleared up for all 70 people within six months.