Don’t count on the moon to protect your eyes from frying during the Great American Eclipse.

Proper eye protection is essential to preventing serious and potentially permanent vision damage. Ophthalmologists agree that eye injuries can occur instantaneously, and the eyes can experience discomfort within several hours after exposure.

“The sun is incredibly bright – some 400,000 times brighter than a full moon,” said Dr. Linda Chous, vision expert and chief eye officer at UnitedHealthcare.

“Any amount of exposure can cause short-term and long-term damage,” Chous added.

Signs of damage to watch for include sensitivity to light, eye pain or loss of vision in one or both eyes, according to vision experts.

However, even in the absence of eye pain, it is still likely that the eyes have experienced some level of damage, said Dr. Howard Purcell, senior vice president of customer development at Essilor of America.

“With some diseases like glaucoma, there’s no pain associated with it,” he said. “The same thing [applies] here; the individual is unlikely to feel any pain at all.”

Following a solar eclipse in the United Kingdom in 1999, public health officials reported a surge of calls from those with apparent eye injuries. A week after the eclipse, at least 14 cases of permanent damage were confirmed.

It has been stressed countless times that ISO-approved glasses are the only kind that should be worn while viewing the main event.

The American Academy of Ophthalmology and the American Astronomical Society recommend wearing eclipse glasses that are ISO 12312-2 certified.

“Be aware that it doesn't matter if glasses are darker or polarized,” said Dr. Lisa Park, ophthalmologist and associate professor of ophthalmology.

“The most important criteria is that the wavelengths of light are blocked by the filter, which is why the certification is relevant,” Park said.

The only period in which it’s safe to remove protective eye gear is during the few brief minutes of totality, when the moon eclipses the sun completely.

“Even if there’s an edge of the sun that’s still visible, you’re still at risk,” Purcell said.

While viewing the eclipse without proper eye gear may not completely blind you, the sudden flood of light can cause long-term conditions, including solar retinopathy.

It happens when a sun burns a hole in the retinal tissues.

“This is a permanent damage that can be created on the retina, the back of the eye – kind of [like] the film of the camera, if you will,” Purcell said.

The eyes can also be impacted in the short term by the sunburnlike photokeratitis, which occurs when the cornea is scorched from the intensity of the sun, according to vision experts.

In the wake of recent reports of fake solar eclipse glasses being sold, it’s essential that spectators ensure that their eyes are properly protected.

“There are about 13 different brands that are ISO approved,” said Purcell. “It’s really important that you’re making sure you’re getting them from those particular brands.”

Ophthalmologists recommend that those impacted by any sun-related vision damage visit an eye care professional immediately.