ga practical help

[brooke8283]

I will be taking the ga ldo practical next week. I have questions on some of the things on it. When measuring center lens thickness, do u actually measure at the center unlike the edge thickness? I am gettting mixed information. Also need help with the cataracts lenses.

[Fezz]

Hey Brooke-

Welcome to Optiboard!

Center thickness is...center thickness. Edge thickness is..edge thickness.

What are your cataract questions?

:cheers::cheers::cheers::cheers::cheers::cheers:

(I finally beat SnitGirl to a friendly welcome!)

[brooke8283]

I will be taking the ga ldo practical next week. I have questions on some of the things on it. When measuring center lens thickness, do u actually measure at the center unlike the edge thickness? I am gettting mixed information. Also need help with the cataracts lenses.

ok, so fezz, on the edge thickness plus lenses in center minus on edge? is that right? about the cataract lenses, do u still measure the center thickness on the bowl in center or the carrier? you also read these backwards in lensometer to pick up the high powers right? my help has given me mixed answers. i have to pass so ill take all the help i can get

[Fezz]

Brooke,

I apologize for my ignorance. I don't quite understand your question about thickness. I may be missing something. Could you help a goofus like me understand exactly what your asking? Thanks

[brooke8283]

Brooke,

I apologize for my ignorance. I don't quite understand your question about thickness. I may be missing something. Could you help a goofus like me understand exactly what your asking? Thanks

there are two different things right? edge thicknes and center thickness

[Fezz]

Yes!


A lens can be plus or minus, it doesn't matter=center thickness is the measurement in the center of the lens. Edge thickness is measured on the edges , plus or minus!

Hope that helps.

[AdmiralKnight]

Are you asking about minimum thickness in lenses? Tolerances etc? Or just in general? If you're talking which would be the thickest part, the edge on a minus is the thicker, and the center on a plus. I like the Diamond/Hourglass examples. plus lenses are like this <> and minus are like this |><|... still not 100&#37; sure what you're asking though hehe

[Diane]

ok, so fezz, on the edge thickness plus lenses in center minus on edge? is that right? about the cataract lenses, do u still measure the center thickness on the bowl in center or the carrier? you also read these backwards in lensometer to pick up the high powers right? my help has given me mixed answers. i have to pass so ill take all the help i can get

If you're taking the practical exam next week, these questions should have been more clearly explained by now. You should also have been practicing a lot by now, as well.

Calipers are used to measure thickness, of whichever meridian is asked. If the question is to give the center thickness, just measure the center and record your findings.

As far as cataract glasses, you need to read the distant power with the back of the lens on the lens stop and record the reading. The add power is determined by turning the glasses around and reading the distant portion of the lens (for reference only) then read the power through the segment and subtract the two. The add power is the difference between those two readings.

I'll wish you good luck, and if for some reason you don't pass, I would recommend a good lensometer course prior to sitting for the practical again. The Opticians Association of Georgia offers one a couple times each year.

From my perspective, the test is a relatively simple test and one that any optician with minimum competency could pass.

Hope this helps.

Diane

[HarryChiling]

What may be vague by center thickness is that you should measure the "Optical Center" Thickness and with edge thickness you should measure it at it's thinnest point.

For cataract lenses unless the question asks for front vertex power you will not flip the lens around to measure power, the exception to this is when you are reading the bifocal add power in this case the add will be the difference between the distance font vertex power and the near front vertex power. Hope that helps and good luck.

[Diane]

Let me try this. This demonstrates front vertex power and back vertex power. To read distant back vertex power. To compute the add, the power is the difference in the front vertex power of the distance and the front vertex power through the seg.

Diane