Semi finished lens:
1. Semi-finished lenses need to have high qualified rate in power accurancy, stability and cosmetics quality.
2. High optical features, good tinting effects and hard-coating/AR coating results, realizing the maximum production capacity are also available for a good semi-finished lens.
3. Semi finished lenses can reprocessing to RX production, and as semi-finished lenses, not just superficial quality, they are more focus on the internal quality, such as precise and stable parameters, especially for the popular freeform lens.
4. Freeform lab requests for high quality of semi-finished lenses in precise and stable base curves/radiusg/thickness. Unqualified semi-finished lenses will lead to much waste in capacity, labor, clicking charge, delivery postpone, the consequence of which will be more than the
semi-finished lens cost.
Round top-28 optical lenses:
1. As the name suggests these lenses are designed to help with vision at 2 different distances. Round top lenses are usually made with the top part of the lens having the long distance prescription and the bottom part having the close work prescription.
Bifocals can be made with the reading portion in a number of different shapes.
2. Round top-28 are two prescriptions combined into a single lens.
Round top-28 were originated by Benjamin Franklin in the 18th century when he cut the halves of two spectacle lenses and fitted them into one frame.
Round top-28 are needed because the distance glasses do not suffice to focus sufficiently for near. As age increases, (in India 38-40 years is the presbyopic age) reading glasses are required to read at a comfortable distance. Rather than taking out the distance glasses and putting on near glasses each time, a person who wishes to work at the near point could use the lower segment comfortably.