Goggles protect a swimmer's eyes when in the water. The protection is provided primarily by the lens and gasket, or seal, that surrounds the edge of the lens. The lens is typically made of a polycarbonate that is shatter-proof, though not scratch resistant. The seal is made of either hard rubber, silicone or foam.
Most goggles include a lens, gasket, straps and case. The lenses are typical optical grade to ensure clarity in the water. They can be mirrored, tinted or clear. Mirrored and tinted lenses offer UVA and UVB protection and are a smart choice for swimmers using outdoor pools. The gasket choices are driven primarily by comfort and personal choice. Foam gaskets may not last as long as rubber or silicone, though they may initially feel more comfortable. The most popular strap types are two piece--two straps that wrap around the head individually--or a one piece that splits at the back to cover the back crown of the head. Straps are made of either rubber or silicon. Goggles come with either a polyester case that is hard-sided or a soft case that protects the lenses from scratching.
The high tech materials of today's goggles are a far cry from what was initially developed. Swimmers of the early 1960s wore goggles so painful that they could be worn for only part of the workout. The eye pieces dug into the swimmer's eyes and the rubber straps made painful grooves in the swimmer's face and head. Nowadays, the materials used for goggles enable speed, comfort and durability.
Given the advances seen in the Beijing Olympics of 2008, it's likely goggle technology will be the next to advance. Goggles are already being introduced that use new levels of technology. You can measure your speed and heart rate. Microprocessors can count your laps for you and track your acceleration in the water, making even a recreational swimmer's workout more efficient.
Check the manufacturer of any goggles you might purchase. Cheap manufacturing from cheap materials leads to leaky goggles and frustration in the pool. Make sure that the gaskets are sealed tightly to the lens as no high tech material can withstand water if it's not properly adhered to the lens. Also be sure that there are variable nose bridge pieces as your nose may be wider or narrower than average. If you're buying for children, make sure their goggles fit properly as eye damage can occur from goggles that have been fitted too tightly to young swimmer's faces. The high-tech material used in gaskets should minimize the lines that you see around your child's eyes. If those lines don't fade after a few minutes out of the water, check the goggles fit and the gaskets for leakage.