Prescription Eyewear

Paddlers who require prescription glasses have a unique problem with paddling. They need something that can survive dunkings and not get pulled off your face. Two approaches are usually advised - get contact lenses or get special glasses for water sports.

Contact Lenses

There are a lot of options in contact lenses today and each type is preferred by different paddlers. In general, contact lenses do not come off easily in the water. If you open your eyes completely underwater, they will likely stay in place most of the time, especially in fresh water. Squinting, so the the lens is held by the edges will help ensure that they don't come out. Keeping your eyes closed underwater is best. If you really prefer to open your eyes underwater, wearing protective goggles is an option.

Removing and inserting lenses in the outdoors can be a challenge. Wind can play havoc with the lens while it is on your finger - keep out of the wind while handling the lenses. Standing in front of a mirror over a sink is a luxury that you'll miss in the outdoors. You have to get used to cleaning your hands and handling the lenses in a "dirty" environment. I use the mirror on my hiking compass, propped on a rock or some such - you can also use a signal mirror or ask one of the ladies on the trip if she brought her compact :-).

Contact lens options:

• Hard vs Soft - I've only worn soft, so I can't comment with experience on hard lenses. Some folks specifically require hard or soft lenses, so for them, choosing is not an issue. However, if you are free to choose, it is likely that soft lenses are the best choice. They stick well to the eye and are quite comfortable.
• Extended wear vs Daily wear - Extended wear lenses advertise that it is ok to sleep with them in. Daily wear must be removed every night and cleaned before reinsertion. The ones you can sleep with are advantageous in that the paddler can go on an overnight trip without having to worry about cleaning the lenses and ensuring the level of hygiene required to do this safely. However, there is some resistance to sleeping while wearing lenses among professional opticians and ophthamologists. While some think it's ok, others think it's a bad idea. Having worn these kinds of lenses in the past, I'd not recommend them.
• Conventional vs Throw-away - Daily throw-away lenses get rid of the problems of cleaning lenses and carrying around the cleaning chemicals. You wear the lenses for a day and then throw them away - the next day you put in a new pair. Conventional lenses and long-term throw away (i.e those that you use for several weeks or months before throwing away) are essentially the same from a kayaking standpoint - you have to carry around the cleaning agents.
• Single vision vs Bifocal or Astigmatism correction - There are contact lenses available for almost any prescription. However, almost all of them are conventional or long term wear type. Only a limited number of prescriptions are available for astigmatism correction with daily wear throw-aways - you'd be lucky to find one that matches.

Glasses

Any type of glasses will require a retainer band to keep them on. Chums, Croakies and other brands are available. You can also get a floating band pad so that if the glasses do come off, they won't sink to Davey Jones Locker.

If you are going to use glasses of any kind for whitewater paddling, you should ensure that you have the strongest, shatterproof lenses. Polycarbonate lenses are the best choice at this time.

• Regular glasses - These might be fine for sea kayaking if you use an adequate band to hold them on. You're taking your chances with them if you are into whitewater or surf kayaking. For rough conditions, you might consider a second pair with cheap, but tough, lenses - i.e don't bother with coatings and special features. That way, if you lose them, you aren't out as much money and your regular glasses are still in storage so you can drive home. Better to get specialty glasses.
• Sunglasses with prescription lenses - Many high-end sunglasses can be fitted with prescription sunglass lenses. Look for polarized lenses. Don't bother with expensive, snazzy sunglasses (too $$$) - look at good quality mountaineering or serious outdoor sunglasses. These will have tougher frames and may have features that allow easy and solid attachment of a band to hold them on. Good for sea kayaking, less so for WW and surf.
• Sport sunglasses with prescription lens add-ons - Lots of the fancy wrap-around sports sunglasses can be fitted with prescription lenses. Most of them use a small(ish) frame that clips into the sunglass frame or onto the nosepiece. Make sure you add a band to hold them on. Good for sea kayaking, less so for WW and surf.
• Prescription Sport sunglasses - I like these more than the sports sunglasses. The difference is that these are a glasses frame with the wrap-around sunglass part clipped on (rather than the glasses part clipped on). The sunglass portion is polarized and can be flipped up or removed for dark conditions. Much more practical than conventional sport sunglasses with prescription lens add-ons. One brand is Rx Sun Pro, but there is no info on them on the web - this brand is also made cheaply; good idea, crappy implementation.
• Prescription Swim Goggles - Many brands of swim goggles are available with prescription lenses. The cheapest option is basic "drop-ins", which are made available with integer or fractional diopter values (say half diopter increments), not custom prescriptions. If you have special needs, like different prescriptions in each eye or astigmatism, these can be also be obtained, but at a higher cost. Most of these lenses can also be polycarbonate-coated for scratch resistance. Bifocal lenses for swim goggles are also available, but are generally not worth the added cost -- the area of view is very small.
• Prescription whitewater and surf goggles - These are the best solution for some whitewater and surf kayakers. Search the web for surf and water sports prescription goggles. Some brands, like Barz, provide for prescription goggles that are larger than swim goggles. You might look like a space alien at the take-out, but at least you'll see clearly during the day.

Note that wrap-around sunglasses are generally better than conventional sunglasses when it comes to getting rid of glare and light from the side. Mountaineering glasses often have side covers that do the same.