My youngest is 4, and we went in about 9 months ago for our annual family checkup (my husband wears contacts, and this was her first eye exam). We noticed about a month before our appointment, that she would wink really hard sometimes when she was talking to us (like she got something in her eye), and a couple of times, we'd notice her eye turn in just a little bit.
When we went in for her appointment, they put her on a machine to get a preliminary reading on her prescription (she peeks through a hole at a farmhouse in the distance, and they bring it in and out of focus to measure the changes in her eye). When the doc saw the results, he put her back on the machine, to test her, himself. When he got the results again, he had his assistant check herself on the machine, to make sure it wasn't broken. Most people see 20x20. Her vision was 20x200, but when she would wink hard or cross the eye, she could compensate, and bring it up to 20x100.
My daughter's prescription is +8.25 in one eye, and +7 in the other, both with a significant astigmatism. We ordered glasses through our doc (Trivex lenses), and went to LensCrafters to get a "spare pair" of polycarbonates (she wore them in the interim, until her "everyday eyes" came in). Her everyday glasses are wire frames, so they're lighter and more comfortable. Her spares are a little big on her, but they have plastic temples, so as she grows, they can move the bend further back, and they'll last longer.
We've had to use her spares once or twice, when a lens fell out or got scratched. Early on, there was an occasion where she was really frustrated/mad, and took it out on her glasses. After mangling her glasses and making a lens fall out, I made her sit in time-out until I could fix them. They bent back into shape fairly easily, but unfortunately, I couldn't get the lens back in, so we took them up to LensCrafters to get them fixed. All the while, she was hollering at me to give her the spares. I explained that we have spare glasses only for when she -accidentally- breaks hers. She can't wear her spares right now, because if she gets mad again and breaks them, she'll have -no- glasses.
After being legally blind for an hour or so, and realizing what life would be like without them, she hasn't mangled her glasses, since. She's always been very careful with them (aside from the aforementioned temper tantrum), and has gotten so used to wearing them, she sometimes accidentally climbs into the shower with them on.
Our doc said that he starts most kids in contacts at around 10, but given how active she is, that we could try them if we'd like. After getting her used to them over a couple of weeks, it got much easier to get them in and out, but overall, I think she's more comfortable in her glasses.
Our daughter is also on swim team (and we have a pool), so we ordered two pairs of prescription swim goggles. We ordered two sets of lenses, along with one pair of black eyepieces, and one pair of blue eyepieces. Our original intent was to have one pair for home, and one for her swim bag, and when we were assembling them, we decided to have two different color eyepieces for each pair, so she could easily determine which eyepiece goes on which eye (because they're two different prescriptions). This is the place where we ordered them from, and the goggles we got. They can convert his prescription for goggles (glasses are different from contacts and from goggles, depending on how far they are from the eyes), but I'd recommend checking the prescription with your doc, before you order them.
http://asightforsporteyes.com/hilcospt.htm
Best wishes,
M.