ask the labs

Pogressive Solutions

Susan Tarrant

CORRIDOR CONSIDERATIONS

Q For progressive lenses, what are the pros and cons to fitting a short corridor design into a lens with a large B?

A In PALs, the main negative to fitting a short corridor is that you will have a smaller intermediate area. The distance zone would stay the same, so if the patient normally looks down to read with a progressive in a different frame and lens, this might feel unnatural. This can be off-putting for a patient, and could lead to a non-adapt. The most comfortable solution for a progressive lens-wearing patient would be to have all pairs made with a similar corridor so the patient’s adaptation would be the same.

Let’s Hear From You

The only real advantage to it is that if your patient needs to use the reading zone without gazing down. With a shorter corridor, he will get to the reading area much easier and quicker.

—Beth Showalter, ABOC, president, ICE-TECH Advanced Lens Technologies, Atlantic Beach, FL

MATCHING PALS

Q If I need to replace one lens in a patient’s eyewear but do not have access to his past records, how can I make sure the new Rx matches the existing one? Also, is this doable with a progressive lens?

A All PALs have an engraved marking, so as a lab we can identify the progressive lenses to match them. But determining the lens material in order to match the lens can be done by listening!

If the eyecare professional understands the difference in the sounds of the various materials, it can help him to identify the correct material of the lens. For instance, when the ECP drops the lens on a table or desk, CR-39 material sounds heavy, while polycarbonate has a “cling” sound, and the sound of mid-index and high-index is in between a light “cling” and heavy sound.

Once the correct lens material is determined, the ECP should then find the engraved marker on the temple side of the lens and look directly under it to find the add power. He or she can then look up the engraved marking symbol in the American Optometric Association (AOA) progressive identifier manual. Use the PD ruler and put it on the 180 line; the manual will tell the ECP what the progressive is and where to set the cross above the 180 line.

Of course, a lensometer will help the ECP obtain the actual Rx. If still stymied, the ECP can reach out to his or her partner lab for help.

—Jean Pollard, customer service supervisor, Robertson Optical Laboratories, Inc., Columbia, SC