Near or Distance PD...

[EyeFitWell]

OK, maybe this is a stupid question, but I can't find it in my textbooks.

1. On a SV prescription for a child with hyperopia, do you use a distance PD or near PD?

Obviously, for myopia, a distance PD is used.
For NVO on a pt with presbyopia, a near PD is used.
But what about hyperopia? They're not really 'reading glasses' but the lens is a plus, and the focal point is relatively short.

2. While we're at it, how many of you use monocular PD's for a ST bifocal (or other visible bifocal)? Or, would you use a binocular for symmetry?

[scriptfiller]

I have always used the DPD for hyperopes.

I use a bino. PD for "visible" segment bifocals.

[chip anderson]

If the patient isn't symetrical, then the lenses shouldn't be either.



Chip

[CLANDGH]

Most of the time on a young child or infant the doctor is not only trying to help the child see better with lens power, they are also trying to help line the child's eyes up horizontally and to prevent the hyperopic child's tendency toward developing a "lazy eye." Often, power is tried first without prism. Using a monocular PD would not accomplish this. You would use the child's Distance PD divided equally in the glasses unless otherwise instructed by the doctor.

[CLANDGH]

Always use Monocular PD's for progressive lens designs, because the cosmetic problem of one seg closer to the nose or higher up isn't there to worry about. Also the reading area is smaller than a FT, and they have a corridor to move through. If they aren't centered Monocularly, the patient loses some usefull area. Also, make sure the manufacturer "etchings" are lined up square just like a FT if you want the patient to get the most use out of them.

On a FT, you have a much wider field of near vision, so you can get away with using the total PD to decenter them. If you split them, you will end up with a patient who will complain about the looks. It isn't optically as correct, but some of what we do is cosmetic too. Unless the patient has more than a 2 mm difference in Monocular PD, there should be no problem. Horizontal prism is tolerated a lot better than Vertical prism. In that occassional patient where you feel you must split the FT seg horizontally, there are ways to make them look the same, especially if you will be cutting off part of the seg at the bridge. Wider segs cut off at the bridge tend to look more equal in size than a smaller seg. Sometimes you can calculate the cut-off and use a wider seg on one side than the other, just make sure the vertical centers of the two seg widths are compatible.

[EyeFitWell]

Thanks for the responses...my main concern isn't so much about the bifocal senario.

It's about hyperopic SV. A doctor I work with always asks me to use a near pd because they are "reading" glasses, but I was taught that all myopic and hyperopic s/v lenses use a distance pd. Only when making reading or segmented bifocal glasses for presbyopia would I use the near pd.

If you agree that hyperopic S/V = distance pd, could you back it up with something so I can proove myself?

[scriptfiller]

If the RX is high enough, even a mm or two off can induce some mild prism.

Mono PD's especially if using aspheric lenses

[Judy Canty]

OK, maybe this is a stupid question, but I can't find it in my textbooks.

1. On a SV prescription for a child with hyperopia, do you use a distance PD or near PD?

Obviously, for myopia, a distance PD is used.
For NVO on a pt with presbyopia, a near PD is used.
But what about hyperopia? They're not really 'reading glasses' but the lens is a plus, and the focal point is relatively short.

2. While we're at it, how many of you use monocular PD's for a ST bifocal (or other visible bifocal)? Or, would you use a binocular for symmetry?

The focal point is where it needs to be to place an image on the retina, regardless of minus or plus power. If the eyewear is for distance vision, use a distance PD and I always recommend monocular PD's, especially for children.

[drk]

This is really simple:
1. Always monocular pds
2. Always distance pds unless it's an add. An add. An add. (I.e. your doc is wrong.)
3. Always individual fitting heights and p.d. for multifocals, unless you want to compromise optics for cosmetics (which I do, sometimes).

[chip anderson]

Ask yourself: "Am I an Optician or a cosmotologist?"

If the former, put the dam* PD and the seg, and the seg. ht. where it should be.

If the later, you can make a lot more money as a hair stylist.

Chip

[drk]

Chip, you know you won't make passes at a girl who wears glasses--with unequal seg heights and centration.

[EyeFitWell]

Ask yourself: "Am I an Optician or a cosmotologist?"

If the former, put the dam* PD and the seg, and the seg. ht. where it should be.

If the later, you can make a lot more money as a hair stylist.

Chip

LOL, now Chip, why can't I be both??;)

No, I agree, I'd always rather be as accurate as possible over symmetrical. However, an occasional patient wants the lines in the same spot...it's their money, if they understand the downside of symmetry, I let them have what they want.

[EyeFitWell]

This is really simple:
2. Always distance pds unless it's an add. An add. An add. (I.e. your doc is wrong.)

Thanks for the verification. I'm hesistant to argue with a Doc unless I'm certain on the topic. After all, I've yet to add all the fancy letters after my name, so what do I know! ;)

[EyeFitWell]

The focal point is where it needs to be to place an image on the retina, regardless of minus or plus power. If the eyewear is for distance vision, use a distance PD and I always recommend monocular PD's, especially for children.

I agree, but when the doctor walks over a 12 year old with, say, +1.25 sph OU, and tells mom she only needs to wear them when working on up close work, but not for distance activities such as TV, etc., it made me question whether this truly was a "distance" prescription.
In fact, a doc I work with frequently calls these glasses NVO and will write out the Rx as
"NVO OD +0.25 Add+1.00" Diagnosis is Hyperopia, and patient is a child (so it's not presbyopia). Since she's newish out of school, I thought maybe she had a newer/better understanding of hyperopia or knew something I didn't know, etc.

[CLANDGH]

4mm on a +1.25 Rx child isn't going to affect her one bit whether the Rx is primarily for Distance or Near. You are talking about .25 prism diopter in each eye which is a very small amount of prism in the horizontal meridian, probably when you accept an "average job" from your lab that is "only" a mm off PD it has more prism than that. When written as a bifocal Rx requiring NVO from a doctor, you should use Near PD, or you will not be following the doctor's instructions. But what do I know, I've only been doing this 36 years, have a couple of current state licenses, I've surfaced and finished, worked in both wholesale and retail stores, refracted, fit contact lenses, and Oh look, the certificates I have say I can use ABOM and OAAHF after my name along with a string of other titles. By the way, folks, we are cosmeticians along with being opticians. And, on many days, we are also phychologists, now if we could just get that bartenders license....

[Fezz]

This is a great time to open up communication between the Doc and the Dispenser! What a great opportunity for both sides to come together for the betterment of the patient! This type of situation has opened up many doors, many new and satisfied patients, and deeper respect between myself and the prescribing doctors!