Opinion on Adjusting ADD Power

[Quince]

Patient is very particular but thorough in his efforts for the perfect work environment. He has one pair FT28 for his desk which has triple monitors measured out, positioned, and bolted down. There is no problem with this pair- I'm only explaining this set to show how much effort he has put into this.

He now would like to get a progressive (has worn them before and understands differences in use) for his meetings. This pair is going to be fitted high because he will be using them mostly for his laptop. He will be able to gaze up at the clock or across the table at his company.

The tricky bit is this- we want to fill the power as prescribed for distance but need to adjust the reading power to a distance of 24". I have asked the doctor to adjust his ADD from the standard distance to the 24" the patient has requested (and also requested from the doctor) but I'm not confident in the feedback.

I do not know how specific doctors can set the prescription for specified ranges. Even though he has asked for the distance to be set to 14', I am under the impression that the adjustment would be too minuscule to change. BUT I do know that reading distances CAN be specified more accurately.

My question is this: Is there a formula to figure this out or does that need to be done in the chair?

RX reads:

+0.50 -0.75 x151
plano -0.25 x033

ADD +1.75

Doctor recommendation: lower ADD to +1.50

Does that seem like enough???

Thanks for any input!

[Robert_S]

Office lens?

[Quince]

Well my goal right now is too determine if a +1.50 ADD is too strong at 24" when he was prescribed +1.75 for 18". Thanks for the suggestion though!

[PRECISIONLAB]

In the FT28 scenario, optimum prescribed powers will be realized by the patient since there is a true distance and near provided by the lens. A progressive will not nor is it designed in this way. POW (Position of Wear), measurements will indeed provide ideal "grinding" of prescribed powers for best result. The slightest variation in head position, frame placement, gaze, actual focal point etc will affect ideal near power. Any reduction in ADD power will decrease "working distance" hence the Doctor recommended a .25 reduction. Will this provide an ideal Progressive pair for your patient? I'm guessing not but would not want to reduce any further. Let accommodation do the work.

[lensmanmd]

The IOT Office Reader 4 @ +1.5 add should do the trick.

[optical24/7]

Using the focal length formula, you usually use centimeters/mm's for length. Convert your inches into centimeters or mm's;

There are 2.54 CM's in an inch. There are 25.4 mm's per inch.

The formula for focal length is; 100/cm's or 1000/mm's

Convert your inches to cm's (or mm's)

24 (inches) x 2.54 = 60.96 cm's
24 (inches) x 25.4 = 609.6 mm's

Both will give you the same answer;

100/60.96 = 1.64
1000/609.6 = 1.64

Your answer is 1.64D has a focal length of 24 inches. Since you're using a PAL, either of the 2 add powers should be fine.

[Quince]

Awesome thanks everyone! Unfortunately this is a doctor who does not like to go the extra mile so I just wanted to make sure I was getting the necessary adjustment.

Special thanks to optical 24/7 for the math so hopefully I can figure it out for myself in the future

[drk]

Cranky OD, here.

1. You should always design the lens yourself. Don't call the OD back. He's given you the distance Rx, and you should work on your own to design lenses. It's an optician's specialty. Get a trial lens kit and/or do math.
2. Where does the trend of capitalizing "ADD" come from? It's add. I see it from CL companies with their multifocal fitting guides, and it's GOOFY.

[Robert Martellaro]

+0.75 -0.75 x151
+0.25 -0.25 x033

Satisfies the distance requirements, and enlarges the near zone by reducing the add power requirements. Don't do it if the eyeglasses will be used for general purpose/driving.

Start with a +1.25 add for 24". Let the client use a +0.25 flipper to choose between adds of +1.25 and +1.50. If J1 or J2 is equally clear, use +1.25. Take the +0.25 that you added to the distance and deduct it from the add.

+0.75 -0.75 x151 add +1.00
+0.25 -0.25 x033 add +1.00

Alternatively,

+1.00 -0.75 x151 add +0.75
+0.50 -0.25 x033 add +0.75

would enlarge the near zone even more, but show the client what +0.50 "over the top" does to the distance vision. Most will accept, but verify!

Don't set the fitting cross above the pupil to raise the near zone, instead use a very short corridor design with the fitting cross level with the pupil in the primary gaze.

This is one solution, but in most cases will be as sweet as a B.B King riff on payday.

Hope this helps,

Robert Martellaro

[Quince]

Cranky OD, here.

1. You should always design the lens yourself. Don't call the OD back. He's given you the distance Rx, and you should work on your own to design lenses. It's an optician's specialty. Get a trial lens kit and/or do math.
2. Where does the trend of capitalizing "ADD" come from? It's add. I see it from CL companies with their multifocal fitting guides, and it's GOOFY.

Hence:

"Special thanks to optical 24/7 for the math so hopefully I can figure it out for myself in the future " + now Robert as well!

I wrote ADD, as in add power, to differentiate between the additional power from the act of adding. Additionally, I tend to capitalize PL and SPH

[Tallboy]

Additionally, I tend to capitalize PL and SPH

Me too. Who ****** in your cheerios Dr. K?

I've calculated in the necessary addition powers for years, then I worked with an OD that accused me of changing his RX and I never did it again, now I do it again because he doesn't work here anymore.

[shanbaum]

Good point. In China, they call it "the A - D - D", enunciating the letters. So, poor capitalization can have undesirable side-effects!

Cranky OD, here.

1. You should always design the lens yourself. Don't call the OD back. He's given you the distance Rx, and you should work on your own to design lenses. It's an optician's specialty. Get a trial lens kit and/or do math.
2. Where does the trend of capitalizing "ADD" come from? It's add. I see it from CL companies with their multifocal fitting guides, and it's GOOFY.

[drk]

Additionally, I tend to capitalize PL and SPH

Now you've done it.

You are now QUINCE and TALLBOY, the unnecessary capitalizers.

[Kwill212]

Don't set the fitting cross above the pupil to raise the near zone, instead use a very short corridor design with the fitting cross level with the pupil in the primary gaze.

Robert Martellaro

This is the most important thing in the entire thread. You can not reduce the ADD(sorry drk) power in a PAL to increase working distance without usuing a very short corridor. If you use a normal corridor the power necessary to see at the requested 24" will be in the very bottom of the lens. It will not work. I have set up a few lenses with short corridor and intermediate add powers before for bus drivers and had success, but IMHO I think this patient would be much happier in an office lens. I have fantastic success with the IOT pure office lens. I would assume any office design would work well.