1.499 S/F FLAT TOP BIFOCAL BLANKS
|MARTERIAL REFRACTIVE INDEX=1.499 TOOLING INDEX=1.530|
Semi finished lens:
Semi-finished lens is the raw blank used to produce the most individualized RX lens according to thepatient's prescription. Different prescription powers request for different semi-finished lens types or base curves.
The semi-finished lenses are produced in a casting process. Here, liquid monomers are first poured into moulds. Various substances are added to the monomers, e.g. initiators and UV absorbers. The initiator triggers a chemical reaction that leads to hardening or "curing" of the lens, while the UV absorber increases the UV absorption of the lenses and prevents yellowing.
The classic bifocal product for presbyopes:
Flat top lens are two prescriptions combined into a single lens. Flat top lens 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.
The flat top is also called the style multifocal lens. This design has a segment width that ranges from 25mm to 45mm. The Flat Top is regarded as one of the easiest multifocal lenses to adapt to, hence it is the most commonly used bifocal (FT 28mm is referred to as the standard size). This lens style is also one of the most readily available in almost any medium and including comfort lenses. The Flat Top utilizes the complete width of the segment giving the user a definitive reading and distance transition