Ask the Labs
By Joseph L. Bruneni

PROGRESSIVE PROTOCOL

Q We recently had a patient who was having trouble accessing her near correction, but only in her right lens. I understand that there are a number of diagnostic steps that a dispenser should follow to assess the problem before blaming it all on the lens design and/or returning it for a non adapt. What are the proper steps to follow?

--Michelle Reilly, Eye to Eye Contact, Havertown, Pa.

A The best dispenser is a cautious dispenser. Your wise question illustrates what labs report as a common occurrence--replacing progressives before analyzing the problem.

The suggested procedure is this: First, using the engraved marks, find the position of the fitting cross and mark it. With the glasses in place (assuming they are properly adjusted), verify how the fitting cross sits in front of the eyes. This helps verify both fitting height and PD. Metal and rimless usually have adjustable pads and with these you can often vary the fitting height by several millimeters.

If the problem is at near, use a reading card and, testing each eye individually, have the patient hold the card where it is most clear. This can reveal a number of problems and guide you in correcting the problem.

In the case you cite where the problem is isolated in one eye, it's probably going to require replacing the lens, but first you must determine the problem.

The most likely problem is an incorrect PD or fitting height for that lens.

The leading PALs publish helpful troubleshooting tips, and your laboratory can usually help as well.

DIG OUT THE SLIDE RULE

Q I'm a licensed optician in Washington State. On the ABO exam, they asked what were the pounds of pressure on a lens at impact on the drop ball test. I had trouble with this question. Would you help me out?

A Every authority we asked had to do considerable calculations to come up with the answer. Without being critical of your state, it seems to be an impractical technical question for dispensing opticians.

Without elaborate test equipment, the best way to ensure proper testing is to use a regulation drop ball testing device, dropping the proper size ball from the specified height. The technical answer to your question follows: With regard to the "pressure" exerted using the 5/8-inch drop ball from 50 inches, one must relate this to the energy imparted. The ball weighs ~15.7 grams. When dropped from 50 inches, this ball hits the lens surface at a velocity of 16.37 feet/second. At that velocity, this ball exerts an impact energy of 0.197 joules or 0.145 feet/pounds.

--Dick Whitney,
American Optical Lens Co.

Order More File Cabinets

Q I work at an optical lab/manufacturer on the East Coast. We have been keeping our original job tickets and orders from day one for record-keeping purposes. The question has been raised (now that this paperwork is taking up a lot of space): Do we need to keep these for a minimum amount of time to comply with any FDA regulation, if there is such a thing? Or can we discard them? Any information you can provide would be most helpful.

--Karl A. Meyer, LO, final inspection group leader, Hoya Lens of America

A The FDA regulation states that records must be kept for three years. This information is referred to in paragraphs E and F of the FDA
regulation. They state that invoices and records of sale and the results of the testing be kept for a period of three years. The government agency also requires keeping a description of the test method and of the test apparatus for three years.

--Dan Torgersen, OLA technical director

If you have a question you'd like to have answered in Ask the Labs, send it to Joseph L. Bruneni. Fax: 310-533-8165. Phone: 310-533-4975. E-mail: joe@bruneni.com. Or mail questions to: Vision Consultants, 2908 Oregon Court, #I-2, Torrance, CA 90503. An archive of past Ask the Labs columns can be found on the Eyecare Business Website at www.eyecarebiz.com.