Eyeglasses of all types can be divided into two groups according to the function of their lenses. One main group is prescription eyeglasses, which are equipped with lenses with a power or certain powers. The other basic group is non-prescription eyeglasses. It is absolutely true that there are many ways to categorize the numerous spectacles produced by different manufacturers in the world. But lens power is one of the simplest approaches to such a classification. Eyeglasses in old days were all prescription ones because those wearers resorted to these devices solely for vision correction. Non-prescription eyeglasses are now available and popular in modern days. The emergence of non-prescription spectacles suggests that there are urgent needs from certain individuals to decorate their eyes. This is best testified by the prevalence of fashionable sunglasses. While non-prescription glasses are being enjoyed by more and more people who never need vision correction, prescription eyeglasses are still indispensible for those with defected eyesight.
In general, eyeglass users can buy a pair of prescription eyeglasses only when he or she has gained a valid prescription of the eyes. Such kind of eyeglass prescriptions can be determined by an eye doctor, either an optometrist or an ophthalmologist. An eye optician only has the right to provide eyeglasses according to a prescription given by an eye doctor. This is a strict requirement which is aimed to ensure eye safety for those wearers. In a serious case, an improper or out-of-date prescription may impair the wearer's eyes. Prescription eyeglasses will help the eyes refocus the entering eyes appropriately, which is called "correction" in brief. But a basis point is that such kind of correction can be precise only when the eyeglass lenses have the right power according to the wearer's eye condition. In a traditional way, most people trust eye doctors or practitioners when they want to buy prescription eyeglasses due to security concerns. In fact, other sources especially online eyewear stores can also provide safe prescription glasses. They can offer spectacles with vision correction exactly according to the prescriptions submitted by customers.
Dissimilar to prescription eyeglasses, non-prescription spectacles are designed to meet the needs for fashion. Many ordinary individuals and celebrities choose to wear designer sunglasses in summer days. Modern types of non-prescription eyeglasses usually incorporate the cut-edge fashionable tastes. Semi-frame and frameless eyeglasses are both stylish. In addition to special frame styles, non-prescription eyeglasses can also take use of unusual colored lenses. In some cases, those slightly tinted lenses can create an attractive effect. In a word, stylish elements are the key contributor to non-prescription glasses.
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