High Index versus Poly

[whitneyd74]

Hi everyone!

How do you explain the difference between high index and polycarbonate to your patients? I know that high index is thinner, but is that the only benefit to the patient?

Sorry if this is a repetitive question, but I have searched the other posts and I can't find anything specific as far as what to say to patients.

Thanks so much for all of your help!

-Whitney

[melthemadhatter]

I always explain to people that light travels faster in Hi Index vs. poly, thus providing clear vision. Itell them that since poly is softer it is more impact resistant, but light travels slower causing more distortion. I hope this helps.:)

[chip anderson]

You might also mention that poly distorts colors and other images more.
Poly scratches much more easily.
Poly is easily eaten by chemicals such as acetone.
The only reasons to use poly are: It's light weight, and to protect the dispenser from lawyers.

Chip

[whitneyd74]

Than why do so many people prefer poly? That's amazing! GREAT tips! Thanks, Chip and Mel!

[melthemadhatter]

1) It's cheaper to make, and is marked up considerably making a good profit.

2) Impact resistant.

3) Most places sell it because of those reasons.

I personally sell it only to people who are wearing it already, and to children. Other than that, I use CR 39, high index or trivex.

Polycarb has to be cured for a year. If not it will develop stress cracks. Being the demand is so high, they are not curing them as long, so more cracks.

I do not wear it because with my whacked out prescription i will go batty. Hi index for me!

That's my take on it.

[rbaker]

Than why do so many people prefer poly? That's amazing! GREAT tips! Thanks, Chip and Mel!

Probably because the have never worn a CR-39 or crown glass lens.

[finefocus]

I always explain to people that light travels faster in Hi Index vs. poly, thus providing clear vision. Itell them that since poly is softer it is more impact resistant, but light travels slower causing more distortion. I hope this helps.:)

Actually, it travels slower, which is why you don't need as much of it to bend light the same amount.
Also, what high index do we mean? Some high indexes are higher that other high indexes. Do you think of 1.55/1,56/1.58 as HI ? Or do we start at 1.6, 1.67, and 1.70? Or do we need 1.74 to be truly "high" index?

[melthemadhatter]

Actually, it travels slower, which is why you don't need as much of it to bend light the same amount.

Indeed. I stand corrected! I was thinking one thing, but typing another. I must have been thinking of Spectralite..:o

[Scrumblydumpus]

I know the chain I used to work for would push poly more than any other lens type.

When the big chains push something I suppose it probably affects the consumers perceptions. If a consumer walks into a big chain and then writes them an estimate with the "best" lens material available and they do it for poly (assuming they trust the mctician working there) that consumer now thinks poly is the best available material.

now that I have escaped the chains... of the chains... I see that poly is really only good for its impact resistance when you dont (for some reason) want to use trivex.

[chip anderson]

You could tell them it's cheap because there was so much of it left over from ship's hole liners after WWII. They had to do something with it.
In fact if it's so cheap why do sheets of it cost more than sheets of plexiglass at the Home Depot?

[cocoisland58]

I recommend poly specifically for weight and safety. Hi index for cosmetic reasons or for better visual acuity. I try to keep it simple.

[MarcE]

You might also mention that poly distorts colors and other images more.
Poly scratches much more easily.
Poly is easily eaten by chemicals such as acetone.
The only reasons to use poly are: It's light weight, and to protect the dispenser from lawyers.

Chip

Poly distorts colors more than 1.67?? I thought they were pretty much the same.

Poly doesn't scratch, the hard-coat scratches. The scratch-resistance is only as good as the hard-coat. There are good and bad. Same with high-index. I also needs a hard-coat. Every type lens needs a hard-coat except CR and glass.

The other reasons to use poly are low cost, thin centers are available, relatively high index, and to prevent chipping and flaking in rimless.

I know lots of people are down on poly and I will admit that it is never THE BEST choice. But it is very often the best compromise lens in terms of light weight, thinness, toughness, and availability.

[chip anderson]

Poly do scratch, dat why it need hard coat. Duh.

Un coated you finger nail or even your finger pad enough to scratch it.

[OptiChick21]

My POV

Wow chip, you really do come off as a grumpy old man sometimes... LOL. :p

Anyhoo, we really dont have very many problems with poly compared to what I've heard in the past, like many many moons ago when poly was considered not as clear as plastic. I guess in a high Rx comparison, hi index would be a little clearer, maybe little less distortion, but we still use poly quite often. These days especially, I find our patients dont want to spend much over what their insurance will cover for them, so poly is a great bang for your buck option. We always use poly for children, safety glasses and for our monocular pt's too. We consider 1.56 and 1.60 mi-index's and 1.67 and 1.74 are hi index. I guess to summarize I would say poly is thin, lightweight and impact resistant... where hi index can be even thinner and great for hi Rx's.

[DragonLensmanWV]

Wow chip, you really do come off as a grumpy old man sometimes... LOL. :p

Anyhoo, we really dont have very many problems with poly compared to what I've heard in the past, like many many moons ago when poly was considered not as clear as plastic. I guess in a high Rx comparison, hi index would be a little clearer, maybe little less distortion, but we still use poly quite often. These days especially, I find our patients dont want to spend much over what their insurance will cover for them, so poly is a great bang for your buck option. We always use poly for children, safety glasses and for our monocular pt's too. We consider 1.56 and 1.60 mi-index's and 1.67 and 1.74 are hi index. I guess to summarize I would say poly is thin, lightweight and impact resistant... where hi index can be even thinner and great for hi Rx's.

My suggestion as a former really high myope is to scrap the 1.67 and 1.74 index and use the 1.70. Better ABBE means clearer vision.