NASA Goddard Space Flight Center from Greenbelt, MD, USA, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
According to NASA, the only safe way to look directly at the uneclipsed or partially eclipsed sun is through special-purpose solar filters, like the eclipse glasses shown above. Failure to use appropriate filtration will result in permanent eye damage. Damage to the eyes comes predominantly from invisible infrared wavelengths, so if you are viewing the eclipse without appropriate solar filtration, you may not feel pain, but the resulting damage can still be catastrophic and irreversible. Even if 99% of the Sun's surface is covered during the partial phase of a solar eclipse, the remaining crescent is still intense enough to burn retinas. Check that your eclipse glasses are not scratched or wrinkled. Discard if your eclipse glasses have any damage.