Technical Information
Compare Special Base Options
For steeper curved frame selections, a suggested base curve is recommended to optimize the finished prescription result. If a base curve lens clock is not available, use the reference chart below to choose the closest matching curve and include this information with your order.
Lens Material Thickness Comparison
Compare the edge thickness of different GT Optical Lab lens materials under identical conditions. This example uses a -8.00 sphere prescription with a Ø70 mm blank to show how higher-index materials can reduce thickness and improve lens appearance.
Diameter Control Sliding Scale
Use the diameter control sliding scale to determine the smallest lens blank that safely accommodates the selected frame. Position the optical center over the center mark and choose the minimum diameter that clears all sides of the frame.
Diameter Reduction
Diameter reduction is recommended for hyperopic prescriptions whenever frame measurements allow. Selecting the smallest suitable diameter can reduce center thickness, lower lens weight, and improve the cosmetic appearance of the finished eyewear.
Progressive Sliding Scale
Use these fitting charts to support accurate progressive lens positioning, corridor selection, and frame compatibility.
Tint Color Scale
The tint color scale provides reference tones for standard index lenses. Printed colors may differ from the finished lens color, and tint appearance may vary depending on lens material, coating, and final processing.
Explanation of Progressive Engravings
Progressive engravings help identify lens design, corridor height, fitting height, index, addition, lens type, and brand markings. Use this guide to better understand permanent markings and verification references on progressive lenses.
Technical Information Chart
Review key lens material specifications including index, density, Abbe value, and UV cut information for GT Optical Lab lens options.
