This pertains to kid's and adult's eye health directly from the eye Doctor

Viewing the Sun for even a scant few seconds can cause irreversible damage. 

The human eye normally allows light rays to channel, unhindered, to the macula, which is the central vision of the eye. In a matter of seconds, direct viewing of the sun can cause damage to the retina. 

In children's eyes the optical media comprised of the cornea, natural crystalline lens, and vitreous humour, are more transparent and clear and do not filter as much harmful UV rays when compared to adult eyes.

Here are more facts and tips; and myths debunked:

A little sun damage in the macula has a significant negative effect. The cells in the macula are not built to withstand that high energy from direct sun rays for very long.  When they are damaged they are damaged beyond repair. This is clinically known as a macular hole secondary to solar burn.

Common, and very exacting clinical scanning laser diagnostic tests can give a quantitative measure of its severity. These olar burns are also visible and can be diagnosed with common clinical ophthalmic tools. The size of a macular hole is proportional to the time spent looking at the sun. 

Supervise kids closely. Do not let them peek around solar glasses or look directly at the sun.

 Kids are inquisitive and naive, but this is not the occasion to let them learn from their mistakes!

Children's eyes are especially susceptible to damage from the exposure to sun's rays. 

Adult eyes are also easily susceptible to solar burns.

The macula in the eye is an area of approximately 500 microns (think 8-10 human hairs) in diameter wherein reside photoreceptors known as cones. (The rest of the entirety of the retina is comprised of rods.) The macula of the retina is also much thinner that the surrounding retina it and even microscopic disruptions in the layers of this delicate structure will result in a permanent decrease in visual acuity. 

The visual system is comprised of the eyes and adnexa, the optic nerves, optic chiasm, lateral geniculate nuclei, optic tracts and optic radiations. in children there is some plasticity in the brain (occipital cortex) up until about age 6 after which time the visual system is pretty much “set in stone”. That's the only part of the visual system that grows in childhood. The rest is essentially fully formed at full-term birth. Children are born with one set of cones in the macula and if they are damaged, they don’t get replaced or regenerate.

More myths debunked:

Myth: kids will grow out of a solar macular burn. 

If kids get a solar burn they won't grow out of it. There is no cure for a macular solar burn on the retina. Retinal tissues do not heal or regenerate or get better… once they are burned, it is forever. There is no medicine or surgery or transplant or exercise or salves or drops or treatments in the research pipeline to recover 20/20 vision. Even young babies would have permanent damage. It doesn't matter if you're tough or smart or athletic or have strong eyes. The tissues of the retina are very very delicate. 

Myth: Solar Burns are temporary, like a skin sunburn:

Once the delicate layers of the macula of the retina are disrupted from the high energy of direct solar rays, they don’t regenerate and fall back into normal configuration. 

In the case of a macular solar burn patients sometimes see improvements but they don't recover full vision. 

Myth: solar burns to the eye cause blindness.

Solar burns of the macula, per se, do not lead to blindness but they can cause a dark spot in the central vision and a reduction in visual acuity and color perception.

Myth: Adults don’t get solar burns of the eye:

Adult eyes may have some natural brunescence to the crystalline lens that filters and scatters some ultraviolet rays in ambient light, but not enough to even remotely be protective enough to view the sun directly.  

Myth: You’re OK if you look at the sun using your peripheral vision:

The peripheral retina can sustain damage of several hundred microns in diameter without any significant effect in overall vision. But an open eye directed towards the sun versus just normal ambient light is like comparing a fire hose to sippy straw. Even using your peripheral vision will cause damage to the entirety of the eyes inner structures.

Two or three pairs of sunglasses should be enough protection:

Welding glasses are Neutral Density 11 at the minimum. The sun’s energy is stronger than a welding arc. If you stacked enough sunglasses, you could likely view the sun directly.

ANSI standards suggest neutral density filters of 11 or more are sufficient to block out harmful ultraviolet rays.

Safety standards include ISO 12312-2 International Safety Standard and Shade #14 welder's glass (compliant with ANSI/ISEA  Z87.1) both of which are also recommended for safe solar viewing.