It is common to see that many people around now are suffering from eye problems of various sorts. However, most of these errors are very common, and easy to treat- such as, nearsightedness, farsightedness, etc, can be cured with simple prescription glasses. However, other serious eye problems are not so easy to handle. For example, presbyopia is one of the most horrible eye diseases that people have ever met. This vision problem is firmly linked to age- when people are over forty, they run very high risk of getting it. With this problem, people may suffer from both near vision and far vision problems. But, with the development of technology in the industry, there comes some very special and effective devices for this problem- presbyopia glasses. However, these glasses can be categorized into several groups from the perspective of time. Here is a simple introduction about these eye wear.
Bifocals are the earliest forms of presbyopia glasses. They are said to be invented by Benjamin Franklin, the most reputable and outstanding state man and scientist in US. In his latter age, Franklin begins to devise some devices for his eye problems- he can not see clearly of neither nearby and afar objects. He succeeds! The invention is called bifocal glasses. This eyeglass is composed of two parts, namely the top part and the lower part- the former is for far vision and the latter is for nearby vision. Such design has really helped wearers a lot in seeing objects of different distance. Bifocal glasses still maintain great vitality even till to date.
People who often wear bifocals find that they can not see clearly of objects in intermediate distance, like arm-length. This is a real bothering matter. And some designers find it is possible to add another part in bifocal glasses- it is between the lower and the top part. They are thus called trifocal glasses. Trifocal eye glasses are composed of three parts, the lower part, the middle part and the top part. Each of these parts is responsible for different vision areas. The top lens is for far vision; the middle lens is for intermediate vision and the low lens is for nearby vision. With trifocal glasses, wearers can see objects at all distance.
However, there is a common problem in both bifocal glasses and trifocal glasses- a vision line is very evident in the place where lenses are jointed. This line will cause very radical vision changes when people see objects in different vision areas within short time. Some wearers even have suffered from dizziness or headache as a result. And some natural transition glasses are needed- also called no line glasses. These glasses are later called progressive glasses, which have a least 20 focus. All vision areas can be natural and easily transmitted with these glasses. And many symptoms in the other two glasses can be avoided.
Ultimately, all the aforesaid presbyopia glasses can solve the problem in a perfect way and are suitable for wearers with different vision needs.