What is "Add Low"?

unclebuck · #1 (**permalink**) 08-12-2008, 01:09 PM

Someone was talking about a prescription for multi-focal contact and used the term "add low." What does that mean?

pmc524 · #2 (**permalink**) 08-14-2008, 01:39 AM

This article may help you understand it a little more.

http://www.clspectrum.com/article.aspx?article=13108

unclebuck · #3 (**permalink**) 08-14-2008, 11:47 AM

Hi pmc524.

Thanks for the URL. I checked it out and it was kind of confusing.

Here's where I think they define "add high" and "add low." It says "The aspheric anterior surface creates a power gradient across the optic zone with more plus power centrally than in the peripheral area, thus creating the multifocal effect. The design is available in two add powers — low and high."

Okay, I read it over three times and I still don't understand. I wanted to know what "add low" means, and now I have to scurry to my dictionary and see if I can figure out what "aspheric anterior surface" and a "power gradient" means.

Sorry if it sounds like I'm being mean. I guess that's why I like Lens 101. It's usually a pretty simple site for a simple person like myself.

pmc524 · #4 (**permalink**) 08-22-2008, 09:59 AM

Sorry for the late reply but here goes; (remember i'm not an optometrist or dispensing optician)

my understanding anything on or bordering -2.50 and lower usually is a "low add" and anything above is a "high add".

low add can be compared to single vision lense and a reading glasses where high add is both, the reason the Dr would choose "low" over "high" in most cases is comfort, "high" maybe too strong and lead to headaches etc. this is how i understand the terms and their fittings.

i could be completely wrong

unclebuck · #5 (**permalink**) 08-22-2008, 10:43 AM

Quote:

Originally Posted by pmc524

Sorry for the late reply but here goes; (remember i'm not an optometrist or dispensing optician)

my understanding anything on or bordering -2.50 and lower usually is a "low add" and anything above is a "high add".

low add can be compared to single vision lense and a reading glasses where high add is both, the reason the Dr would choose "low" over "high" in most cases is comfort, "high" maybe too strong and lead to headaches etc. this is how i understand the terms and their fittings.

i could be completely wrong

Thanks for trying, pmc524. I'm still confused. Does "add" mean that something is actually being added to something else? If so, what's being added to what?

pmc524 · #6 (**permalink**) 08-22-2008, 11:14 AM

Quote:

Originally Posted by unclebuck

Thanks for trying, pmc524. I'm still confused. Does "add" mean that something is actually being added to something else? If so, what's being added to what?

The Dr measures your eyes to a standard, then corrects for your condition and i'm assuming "presbyopia" with B&L multifocals they correct only "low or high".

If your condition is mild, they use a "low add" and if it's serious, they'll use a "high add". "Add" in this case can be described as a power.

If your vision is just starting to get poor, they add a little or low power and if it's getting poorer, they add more or higher power.

When you're getting your eyes tested and they put that thing over your face and tell you to read the chart, they're adding low or high and then make the glasses or contacts from those results. All those little adjustments are your low or high additions.

I can't be anymore simpler than that, LOL one reason i never became a teacher

unclebuck · #7 (**permalink**) 08-22-2008, 11:39 AM

Quote:

Originally Posted by pmc524

The Dr measures your eyes to a standard, then corrects for your condition and I'm assuming "presbyopia" with B&L multifocals they correct only "low or high".

If your condition is mild, they use a "low add" and if it's serious, they'll use a "high add". "Add" in this case can be described as a power.

If your vision is just starting to get poor, they add a little or low power and if it's getting poorer, they add more or higher power.

When you're getting your eyes tested and they put that thing over your face and tell you to read the chart, they're adding low or high and then make the glasses or contacts from those results. All those little adjustments are your low or high additions.

I can't be anymore simpler than that, LOL one reason i never became a teacher

I think I understand now.

Have you ever used one of those fancy microscopes in biology class, the ones with "coarse" and "fine" focus? You use the coarse focus knob first to get the specimen mostly in focus, then you use the fine focus knob to move the microscope lenses just a hair to get the focus exactly right.

The "add" powers are kind of like the fine focus knob. They make tiny corrections to get the focus exactly right. Right?

pmc524 · #8 (**permalink**) 08-22-2008, 01:12 PM

Quote:

Originally Posted by unclebuck

I think I understand now.

Have you ever used one of those fancy microscopes in biology class, the ones with "coarse" and "fine" focus? You use the coarse focus knob first to get the specimen mostly in focus, then you use the fine focus knob to move the microscope lenses just a hair to get the focus exactly right.

The "add" powers are kind of like the fine focus knob. They make tiny corrections to get the focus exactly right. Right?

Yes, that's a good explanation.

harrychiling · #9 (**permalink**) 08-24-2008, 02:13 AM

A+ for the effort guys, some of what was posted could be correct. The doctor does measure your eyes, the focal length of the correction needed is expressed in diopters which are inverse meters of the focal length (example 1/focal length in meters).

When a bifocal contact is prescribed it is becuse a condition exists called presbyopia which can simply be put as the eye loosing it's ability to change focus. When we're young we can view a distant object and then quickly turn around and read a book 14 inches or so away from us. The eye actually manipulates the lens inside to change the power of the eye like a telescope of microscope like defined here. As we age this microscope gets stuck and just has a hard time getting to the fine focus (up close) like it used to so we need to add power to help it out. Ok lots of prep work for the answer but it's coming I promise.

So when the doctor measures for reading they will set and object lets say 30cm from the eye's and then put lenses in front of you until you can see a certain size text clearly. That power will usually range anywhere from +1.00 to +3.00 diopters, the manufacturers of some contact lenses take advantage of a the fact that we don't always llose all of our focusing ability so they make lenses in "low add" think of them as like a +1.50 and a "high add" think of them as like a +2.50 since the eye never loses all it's ability to acomadate or change focus, if your a +2.00 the +1.50 or "low add" would work well because you would rely on the eye to contribute +0.50 to the lens. Hope that helps.

unclebuck · #10 (**permalink**) 08-25-2008, 09:52 AM

Thank you for jumping in here harrychiling. I've read some of your earlier posts and it sounds like you know your stuff.

OK. I was able to follow you until you got to "So when the doctor measures for reading they will set and object lets say 30cm from the eyes and then put lenses in front of you until you can see a certain size text clearly. That power will usually range anywhere from +1.00 to +3.00 diopters."

Then you lost me.

One of my teachers once told me "Never accept an unclear answer." Maybe everyone else reading this is nodding and saying. "Okay, now I get it," but I guess I'm a little slow. You were talking about getting my eyes examined, then you were talking about contact lens manufactures. When does a "low" add become a "high" add? Is anything more than a +2 considered "high"?

Thank you for taking the time to explain this to someone as dense as me!