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In-Office Finishing

Ferman Optometry offers custom cut opthalmic lenses.

Step One:  Lens Verification

After your frame selection, an order is sent to the lab with your custom lens parameters. We receive uncut lenses, verify that the lenses are correct, and use a device called a lensometer to verify the prescription. The lensometer is also used to locate the optical center of the lens. Special ink is used to mark the lens with dots, which are then used to prepare the lens for edging.


Step Two: Frame Tracing

The part of your frame that holds the lenses is measured. Exact dimensions are determined using a tracing stylus that measures every parameter to the nearest 0.01 mm. Data is then transferred to a lens blocking device. Here’s a 30-second video of the frame tracing process.


For grooved rimless frames – the lens is traced instead of the frame.

  • Frame size is measured
  • Center of the lens is determined
  • Lens is removed and placed on a special lens holder
  • Instead of the inside of the frame, the outside of the lens is traced.

Step Three: Lens Blocking

“Blocking” a lens is a process in which a plastic “lens block” is attached to the lens using a special adhesive pad. Your custom lens measurements are entered into the blocking device. A brown sunglass lens is ready for blocking in this image


The blocking device is equipped with a small camera, used to visualize the dots from Step 1. Using the frame trace data, your custom lens data, and the dots on the lens, the block is precisely placed onto the lens using a swing arm.

Step Four: Edging

The green block fits perfectly with a chuck on a lens-holding axle inside the edging chamber, allowing the lens to be held securely against the action of a grinding wheel. An arm with two feelers lowers to trace the exact thickness and curve of the lens – at the exact points that the finished lens will fit into the frame.


The lens axle spins the lens against the grinding wheel to achieve the correct shape. Other wheels create a bevel (raised area that fits into the groove of a frame), clean up the edges, and for grooved rimless frames – create the groove. Here’s a two-minute video of the lens tracing and edging processes.

The blocks are removed, and the lenses are inserted. One final verification by the optician and these eyeglasses are ready to be fitted!