Sunglasses are the choice of almost every person to prevent bright lights and harsh glares from discomforting or hurting eyes. Doctors tell that the ultraviolet radiation and the blue light are dangerous to the eyes and will cause serious eye problems. In fact, the earliest sunglasses are widely used in the 1900s by the famous film stars to avoid being recognized by fans. Since then the sunglasses are widely known and in the 1940s the sunglasses are considered as the stylish accessories especially when at the beach. Until now, the sunglasses are developed into many styles and types, such as the common sunglasses worn by people with good eyesight, prescription sunglasses with bifocal, trifocal or progressive lenses, sunglasses being tinted different colors, sunglasses with different frames and so on.
The sunglasses in not limited to the sunlight protection only in the modern sunglasses making industry. They integrate the eyesight correction function too, so the prescription sunglasses come into being having the function of correcting many eyesight problems. Sunglasses with bifocal are one typical type of the prescription sunglasses.
Being a little advanced than the normal prescription sunglasses, the sunglasses with bifocal are able to deal with the two or three eyesight problems simultaneously, usually the myopia and presbyopia, or the hyperopia and presbyopia, and sometimes the astigmatism is also extra contained. Being human centered designed by the designers, the top part of the lenses is expected to focus on the far objects and the bottom part is expected to focus on the near objects. In fact, the bottom part is usually called the reading lenses as the special design for the old people with presbyopic problem.
Nowadays, the most widely accepted styles of sunglasses with bifocal are the D-segment one, with 28mm width and 7 mm length. Expect for the lenses with this type, you can also find lenses with larger D-segment which all depends on your demands. So remember for people with presbyopia problems, please do not choose the cheap presbyopic sunglasses with the same standard. The low quality sunglasses may worsen your eye condition.
You are supposed to go to the doctor for a careful eye check and choose the most suitable sunglasses with bifocal for you. Besides, you can choose any color tinted sunglasses as you like. Try on every pair to match your personality and temperament well, including the lenses color and frames. But keep that in mind, the key point is the structure of the lenses fit with your eye condition well.
Though the coming of prescription sunglasses with trifocal and multi-focal are invented in the need of the optical glasses market, the sunglasses with bifocal are still welcome by most people as its strong function, high quality and reasonable price. Owing a pair of sunglasses with bifocal is necessary for eye protecting and clear world seeing for the people over 40. Besides, the sunglasses can be used as a gift to the elder, which is quite sweet and friendly.