A great pair of glasses is created by the relationship between the customer’s lens powers and the customer’s frames.

You cannot have one without the other.

The greatest lenses ever made will not work well in a poorly made, poorly fitting frame.

The greatest looking, greatest fitting frame ever made will not work well if the lenses will not stay in them.

Super Important Here!

Frames have a base curve just like lenses do. Some lens powers and lens profiles or shapes do not do well in certain frames. The higher plus, the steeper or more curved the lens will be. A high minus will have little or no curvature of the lens. Should a frame be very flat (having very little face form), it will not hold a plus lens well. The reverse is true when we consider minus lenses in heavily wrapped shapes like sport sunglasses. One of the primary sources of lab delays is poor lens power – frame matching. 

What do I mean?

Notice that as minus become weaker or more plus the base curve increases and edge thickness decreases. When you get a high minus Rx you want to find a frame with little or no frame curve.

Notice that as plus lenses become stronger the base curve continues to grow steeper. This creates a steep curve on the edge of the lens. When you get a high plus you want to find a frame with some curvature.

Also see: Let’s Talk About Base Curves in the course, Finishing the Opticians Edge.

When you are faced with a very high minus prescription there are a couple of other things to look out for as well:

• Sometimes a lens edge can become so thick that the frame temple will not fully close. This is rare, but it can happen. We all make mistakes. If you don’t catch it during the sale you may well need to make things right later.
• A minus lens tends to have a “ledge” just behind the bevel. This ledge pushes the frame out creating spread temples and fitting issues. You can overcome some of that with heating and adjustments. The best solution is having the finishing work one by an experienced lab with a high-end edger that can “lap” the lens.

When you are faced with a very high plus prescription there are a couple of other things to look out for as well:

• You may need to add some frame curve to get a plus lens to fully sit in the frame bezel. Do that by “massaging” the frame with your fingers to increase the amount of curve.
• Plus lenses do not like to stay in a frame. The best solution is having the finishing work one by an experienced lab with a high-end edger that can adjust the lens bevel placement, angle and tilt to best match the frame.