Hi-Index

**majucalicut** · 10-08-2009, 01:22 AM

Dear All,

Is there is any instrument to find out the index of the lens fitted on a frame. When the customer came with a hi-index fitted on their frame.it is becoming a great confusion

**finefocus** · 10-08-2009, 01:09 PM

Yeah, I want to know that too. Poly has a audible difference, but how do you tell 1.6 from the other 1.6, or 1.58, or......? I know you could test for specific gravity or hardness or calculate thickness for comparison: Chris can fill a page with links and techniques, but how do you tell quickly while sitting at the table with a customer? Maybe you can't.

**cocoisland58** · 10-08-2009, 01:27 PM

I have never given it much thought. If I have a customer wearing a lens from an outside source and they want the same material, once I have determined by the "ping" that it is hi-index then they get a 1.67 because that is all I sell. If the lens needed only comes in 1.60 (haven't run into that) then they get that I guess but do you think they would notice a difference?

**scriptfiller** · 10-08-2009, 01:58 PM

Mass spectrometer. You could throw some shavings in there and see what their spectrum frequency is. That is, if the commonly used substrates have been measured for reference.

**sharpstick777** · 10-08-2009, 02:20 PM

If you carry stock lenses, they way i have done is to dot the OC on the old pair and measure the distance to the farthest edge. Then using stock lenses with the same RX in varius materials, see which thickness matches at that same distance from OC.

**finefocus** · 10-08-2009, 02:41 PM

Originally Posted by scriptfiller

Mass spectrometer. You could throw some shavings in there and see what their spectrum frequency is. That is, if the commonly used substrates have been measured for reference.

Sure, if I happen to keep a spectrometer at the dispensing table, but as a rule I don't. What about a small, simple device that measures resistance to a probe. Is there such a thing? Is the resistance of various materials sufficiently different, and sufficiently known, to make this practical?

**fagin** · 10-08-2009, 05:41 PM

a Lens measure, or lens clock, whatever you guys call it. If it is cailbrated for 1.523 as most are, you measure the surface powers with the lens measure, focimeter the lens to give you the actual power of the lens and then use your lens makers equation to recalculate the refractive index knowing the lens power and measured curves, simple.