Old stock lenses

[ans546]

I'm wondering how long stock lenses be kept on hand - 3 years, 5 years? At what point should old stock lenses be replaced with new product?

[finefocus]

Put them in a lensometer and check; if the medicine has declined in potency, replace them. Otherwise, sell them fast, but discount them as a discontinued model.

[chip anderson]

Actually most plastics will yellow with time. Glass will sag with time but you won't live long enough for this to be a problem.

[FVCCHRIS]

We "Sag" at a much faster rate that is for sure! Yellowing is the only reason I've ever had to throw out stock and they were pretty old. I've still got some old Permalite lenses here that are ready to "roll" after sitting in the drawer for over 30 years. They are my old friends!:bbg:

[David_Garza]

We have lenses that are at least 5-8 years old (CR39 & POLY) and no way would I ever throw them out unused just because they may have an ever so slight yellow tint.

If a patient were to complain it would be easier and cheaper to make new lenses with the old stock than throw away unused product just because it's 'old'.

PS If you want to throw away unused stock lenses PM me and I will take them off your hands !

[Speed]

We have lenses that are at least 5-8 years old (CR39 & POLY) and no way would I ever throw them out unused just because they may have an ever so slight yellow tint.

If a patient were to complain it would be easier and cheaper to make new lenses with the old stock than throw away unused product just because it's 'old'.

PS If you want to throw away unused stock lenses PM me and I will take them off your hands !

Where in the dirty south is your office?

[David_Garza]

Durty.....not dirty......say it right!

[Dave Metzger]

I ran across glass lenses 52 mm round manufactured in Japan occupied Phillipines.

[Chris Ryser]

Only Cr39 lenses manufactured pre 1980 have yellowed. Anything made after that contains UV absorbers going up to 365nm and prevent yellowing.

The yellowed older ones are still tinting nicely , so can still be used.

Glass lenses do not sag, same as antique drinking glasses that still kept their shape over hundreds of years.

[Speed]

Durty.....not dirty......say it right!

Sorry, Durty. Now where?

[chip anderson]

Chris: All glass saggs given enough time. Have you ever seen a 200 year old structure with the origional windows? It ain't because they made glass poorly back then. The glass has slowly sagged toward the bottom.
I said the person wouldn't live long enough to for this to be a problem. Glass is also soluable in water given enough time, Priestly's super re-re-re distilled water turned cloudy and the etching line was appearent below the water line after sitting in some museum (the Smithonian, (I think) for 100+ years.

[rbaker]

If you have inventory, be it lenses or frames, lying around for three or more years you had best be reevaluating your purchasing procedures. Todays logistics allow a business to implement "lean" inventory control, that is to say, JIT "Just In Time" rather than JIC "Just In Case."

[David_Garza]

If you have inventory, be it lenses or frames, lying around for three or more years you had best be reevaluating your purchasing procedures. Todays logistics allow a business to implement "lean" inventory control, that is to say, JIT "Just In Time" rather than JIC "Just In Case."

Quite true! In my case I inherited all of the older stock lenses so I have tons on hand that came with the purchase of the business.....won't have to buy stock lenses for a LONGGGGG Time.

[zahid]

If anyone has Glass Single Vision or Bifocals lots in any Quantity, please feel free to inform us.
Vision International
ahmed@vision-international.com.pk