Eyeglasses: What does Base Curve do?

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More specifically: what is the difference between getting a lense with a base curve of say, 6, and one of say 4?

For more information, here's the situation: I'm getting a new pair of glasses, broke the old ones (using an emergency pair now). To tell you how long I've had them, the old ones have glass lenses. There was a choice between plastic and glass at the time - let it just say I went with a more durable choice (scratchwise) as I know my history with glasses... (The frames are actually older - I go with something like the Marchon "flexon" frames and get new lenses put in the old frames).

Now the material of choice for lenses seems to be "polycarbonate". Glass actually either costs extra or takes longer. Call me old fashioned, but I'm not exited about this.

To get the base curve that I am told I need, I have to get "premium polycarbonate", which costs extra $, of course. This seems to be the product of mass production...

Of course the salespeople seem to think that I won't be able to see (correctly) if I go with the regular base curve. I know a little about optics, and how lenses work and this seems to be odd to me. The lense can be made to the correct power from any (within reason) base curve.

 

[i386]

Re: Eyeglasses: What does Base Curve do?

Sounds like a bunch of BS to me.

In contact lenses, base curve refers to the radius of the curve of the back of the lens. It needs to match the curve of your eye in order to fit corre4ctly. Has nothing to do with the prescription.

In glasses it refers to the radius of the curve of the front of the lens.



Either way, it's either the correct prescription or it isn't right?

 

[bucky7680]

Re: Eyeglasses: What does Base Curve do?

Base curve or front curve is an optical measurement of the lens where a zero or plano is flat like a table top and the higher the base curve the more curvature. Most glasses with no prescription are usually about a 6 base or about an 8 base on the wrap frames, the important thing for the lens to have no rx on them or plano power, the base or front and back of the lens have the same curve, the front being convex or plus, the back curve concave or minus.

 

[ehenry]

Re: Eyeglasses: What does Base Curve do?

Wheres LadyFish when ya need her? She can tell ya anything ya wanna know when it comes to the Peepers !