|1.56 Semi Finished Photochromic Round Top Lens(Brown/Gray)|
Material: 1.56 Index Resin(Ne=1.56, Abbe=43, Specific Gravity=1.14)
Segment Placement=5mm down~5mm in
Add Power: +1.00 to +3.50 in 0.25D steps
|CONVEX SURFACE||CONCAVE SURFACE|
|Mominal Curve||True Curve|| |
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.
|The molecules in photochromic technology work by reacting to UV light. However, temperature can have an effect on the reaction time of the molecules. When the lenses become cold the molecules begin to move slowly. This means that it will take somewhat longer for the lenses to adapt from dark to clear. When the lenses become warm the molecules speed up and become more reactive. This means that they will fade back faster.|
RT-28 Bifocal lens:
The lower half of a bifocal lens contains the near segment for reading and other close-up tasks. The rest of the lens is usually a distance correction, but sometimes has no correction at all in it, if you have good distance vision.
One popular fused bifocal is the round seg bifocal. Round-top bifocals are further described by the width of the near segment, measured in millimeters (mm). The most popular RT bifocal is the RT-28, a round-top bifocal with a near seg that is 28 mm wide.
An advantage of round seg bifocals is that the line separating the distance and near zones of the lens tends to be less noticeable than the upper line of a D-seg bifocal.