Optical Centre

**majucalicut** · 12-05-2012, 05:55 AM

How can we mark the optical center of a finished lens manually(with out the help of lensometre). I think with the help of a light reflection we can mark. Any other method ?

**Wes** · 12-05-2012, 07:38 AM

Draw a a cross (2 perpendicular lines) on paper. Move the lens around in front of the cross. A lens with power will break the lines except when the oc intersects with the point where the lines cross. A toric lens will also break the lines at every meridian except the major meridians unless it is oriented with the major meridians in alignment with the lines on the paper.

**optical24/7** · 12-05-2012, 08:07 AM

Use a thickness caliper. On minus the OC is at the thinnest point, on a plus the thickest.

**Fezz** · 12-05-2012, 08:08 AM

Why would one want to do that (mark the optical center manually)?

**optical24/7** · 12-05-2012, 08:20 AM

Originally Posted by Fezz

Why would one want to do that (mark the optical center manually)?

1. You misplaced your lensometer and can't find it.

2. You took the bulb out of your lensometer to replace the one in your freezer.

3. To prove you're a Neanderthal optician and don't need no stinkin' lensometer.

**Jason H** · 12-05-2012, 08:27 AM

Zenni R&D center?

**Wes** · 12-05-2012, 08:41 AM

Originally Posted by optical24/7

1. You misplaced your lensometer and can't find it.

2. You took the bulb out of your lensometer to replace the one in your freezer.

3. To prove you're a Neanderthal optician and don't need no stinkin' lensometer.

4. You're blocking lenses in a major lab environment and some jerkoff missed spotting one and you don't feel like carrying it back to him.

**mdeimler** · 12-05-2012, 10:02 AM

Originally Posted by Wes

4. You're blocking lenses in a major lab environment and some jerkoff missed spotting one and you don't feel like carrying it back to him.

Guilty as charged...as the blocker, not the marker/spotter.

**GokhanSF** · 12-06-2012, 11:01 AM

Originally Posted by optical24/7

1. You misplaced your lensometer and can't find it.

2. You took the bulb out of your lensometer to replace the one in your freezer.

3. To prove you're a Neanderthal optician and don't need no stinkin' lensometer.

Or the guy just wants to show off... I am a super optician and no need for lensometer

**Wes** · 12-06-2012, 11:16 AM

Originally Posted by GokhanSF

Or the guy just wants to show off... I am a super optician and no need for lensometer

Focimeters/vertometers/lensmeters are/were not always available. The method I described was used by opticians of the past and current opticians that don't have the luxury of the right equipment to determine oc and axis. Along with neutralization, which is determining an unknown lens power by using known lens powers to neutralize with/against movement. And how did they know the "known lens" power? Focal length.