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How much power can you grind?
We have surfaced as much as 60 diopters of plus or minus. However, with the human eye having approximately 60 diopters of power we have found no reason to go beyond this amount. Cornea removal would be in the range of 40 diopters and the crystalline lens makes up for approximately 20 diopters.
How much prism can you grind?
In theory we can grind as much as 35 diopters of prism, but we are limited to lens blank thickness provided by lens manufacturers. We have ground lenses in the upper 20’s for customers. Opticians find it difficult to fit prism reaching upper limits due to weight and thickness with the lens so close to the patient’s face.
How long does it take to turn around a laminate job?
Laminate lenses generally take between 7 and 10 working days. The lenses are hand crafted and this process can be time consuming.
Prism segments and Franklins — what materials are they available in?
All materials except polycarbonate and Trivex. Transition lenses can be done as a Franklin style segment. Cement-on-segments can only be done on non-coated lenses; so high index materials need to be done as a Franklin style.
Can you laminate plastic and high index together?
At this time, no. For now only the same materials can be laminated together.
How high of plus power can be ground before we need to use a lenticular lens?
In 1.67 index, we can produce lenses in the +15 to +17 diopter range in some cases by grinding a convex curve on the back surface. However, this can pose a problem for the optician in fitting glasses with a strong plus back curve.
What is the thinnest available material?
The higher the index number, the thinner the lens can be. Be aware that the higher index lenses are more expensive to manufacture. Semi-finished blanks are already thin relative to other materials, so we are limited to how much power we can grind. The limitations are in the indexes of 1.70 and 1.74. Good choices to grind most high power prescriptions are 1.56 or 1.67 index.
What is the range in power on a progressive?
We are limited by manufacturers on base curves and the index of materials. In addition, the patient’s frame selection comes into play. In a high plus we can produce up to around +12, and in certain cases even higher. In a high minus we can achieve about -20. In these powers most patients will find it difficult to use a progressive due to the long travel the eye must go to get to the add power creating a lot of induced prism. Extreme powers are generally more comfortable and functional for the patient in a flat top style bifocal or trifocal.
Myodisks — what material and styles can they be done in?
Myodisks are for high minus power prescriptions so we recommend a high index material. We still can do myos in CR39 but it is not preferred due to power limitations and cosmetic look. There are different styles and designs that can be done. Call us and we can discuss the best options for your prescription. Some examples of different myos include: standard, blended, double standard and double blended and AOF (aspheric open field).
What material can we do slabs in?
All materials, except glass.