Semi finished lens:
Minus and plus semi-finished lenses
Lenses with different dioptric powers can be made from one semi-finished lens. The curvature of the front and back surfaces indicates whether the lens will have a plus or minus power.
Semi-finished lens is the raw blank used to produce the most individualized RX lens according to the patient's prescription. Different prescription powers request for different semi-finished lens types or base curves.
Rather than just the cosmetic quality, semi-finished lenses are more about the inner quality, such as precise and stable parameters, especially for the prevailing freeform lens.
1) What is the photochromic lens?
When photochromic lenses are exposed to UV light, trillions of photochromic molecules in the lens begin to change structure. This reaction is what causes the lenses to darken.
All lenses that adapt to light use photochromic molecules; the superiority of Transitions brand technology lies in our exclusive, patented formulas. Each formula is integrated into the surface of the lens. These molecules constantly and smoothly recalibrate so the optimal amount of light reaches your eyes whether you’re in bright sunlight, under cloud cover or indoors.
Photochromic lenses, often called transitions or reactolights, darken to a sunglasses tint when exposed to sunlight, or U/V ultraviolet, and return to a clear state when indoors, away from U/V light.
2) How do photochromic lens work?
Tiny molecules of silver halide and chloride are embedded within a photochromic lens which is invisible and clear until exposed to sunlight/UV rays. A chemical process takes place when exposed to sunlight/UV and the molecules effectively move, change shape and absorb the light. This process changes the molecules and they darken to a sunglasses shade/tint.