one more thing about p.d.s

[Dr. Bill Stacy]

As long as I'm tuning in on P.D.s, I'll pass along a little gem I think I might just be the first to discover. I have measured P.D.s on some very fat people and some very skinny people and sort of have this impression that very fat people have wider p.d.s than do their skinny friends. I got the notion that maybe it's orbital fat pushing the eyes forward and outward due to the outward orientation of the roughly pyramidal shaped orbits.

I got a chance to test this thesis a couple of times when two of my morbidly obese patients got gastric bypass surgery and lost an extra person or so in weight very rapidly. I was right. The p.d.s in these two people reduced by 3 or 4 mm. One was male and the other female.

The geometric model of the skull makes this another reason to retake p.d.s from time to time. I'd like to call this the P.D.Variation due to Obesity Syndrome or PDVOS.

I presume this is the same reason people with graves disease not only get exophthalmos, they often even get exotropia at the same time. I'll be more attentive to the p.d.s of graves disease patients too.

[Tallboy]

You post some very interesting things Dr. Bill.

I will keep this phenomena in mind when fitting such patients who have had major weight loss.

[Dustin.B]

The more I think about it the more it makes sense though I had not considered it before.
Thanks for the info!

[Dr. Bill Stacy]

Yeah, it goes both ways, but those stomach procedures produce weight losses that are so rapid that it's startling. Going the other way is very gradual as is most weight gain, so it can sneak up on you. BTW I always re-measure kids when they are growing, as their p.d.s often grow a mm or 2 in 1 or 2 years, even with normal weight.

[smallworld]

Great post! I never thought to recheck PD's after weight loss. I work in a surgery/specialist medical center and now you have me thinking about how this must apply not only pre and post orbital surgery for my Grave's patients, although my two are still fluctuating prism 13 to 22 diopters Fresnel. But what about orbital fractures, pre and post brain tumors, I can see other implications for your knowledge. Thanks!

[Dustin.B]

Definitely measure kids every time, at least I always do. Fun parts making a game of it for the littler ones.
" Do you see that light in back there? I need you to tell me when it changes from green to red, its really important that you do."
After I get the measurement they always ask why too. I tell them its the low battery light. Gets a good laugh usually.

[Lelarep]

I did see a patient once that had a significant PD shift, much more so for one eye than the other, after a stroke that caused unilateral visual issues that have since resolved. I'm guessing it has something to do with a change in the occulomotor balance, since that was what was impacted by the stroke?

[mervinek]

I measure kids every year, but didn't think about the weight factor for adults. I usually only check Pds on adults occasionally. Usually it's if our computer system is changed or if the last optician to work with the pt wasn't me! I will keep this in mind. Thanks for bringing it up!

[Craig]

Great insight and I just thought is was done so we had an easier time making glasses for the pumpkin heads of the world!

[Uncle Fester]

Is there more than anecdotal evidence of increased astigmatism associated with excess weight? I think I read about that somewhere recently. Maybe here?

[mervinek]

Is there more than anecdotal evidence of increased astigmatism associated with excess weight? I think I read about that somewhere recently. Maybe here?

Interesting! I suspect that would be true. Anyone have evidence on that?

[Dr. Bill Stacy]

Never seen any data on it but I wouldn't be surprised. One of my long time keratoconus patients has been morbidly obese since I've known him, over 20 years. One eye perforated and accidentally became aphakic during the corneal transplant, so it's about +10.00 - 8.00 x some axis. The other eye spectacle Rx is not measurable, but is about -18.00 - some irregular astigmatism. We just refit his left eye with a scleral lens and for the first time in years is reasonably comfortable.

I think anything that causes the eye to bulge forward will change the corneal toricity to some degree due to differences in lid pressure on the globe.

[ak47]

Sure, pd measurements get bigger as people get bigger and vice versa. I've always noticed that. Just another great reason to take a new measurement every time a patient orders new specs. Measure one more time, cut one less time.

[colem84]

Usually I'll measure the PD if it's the first time I've seen someone in 12+ months. If the pt was just in a few months prior, I'll copy the last one. Plus, retaking PDs helps limit remakes :)

[smallworld]

Never seen any data on it but I wouldn't be surprised. One of my long time keratoconus patients has been morbidly obese since I've known him, over 20 years. One eye perforated and accidentally became aphakic during the corneal transplant, so it's about +10.00 - 8.00 x some axis. The other eye spectacle Rx is not measurable, but is about -18.00 - some irregular astigmatism. We just refit his left eye with a scleral lens and for the first time in years is reasonably comfortable.

I think anything that causes the eye to bulge forward will change the corneal toricity to some degree due to differences in lid pressure on the globe.

We fit keratoconus patients in specialty contacts all the time. I don't think weight has as much effect as the disease itself. We have a post corneal transplant patient who still has a couple of stiches imbedded who wants a piggyback. My doc said he needs a scleral to vault the cornea, but doesn't think you can piggy back. I agreed that wouldn't work. Still working on a solution. SynergEyes needs to invent a skirted scleral.

[Dr. Bill Stacy]

Your doc is right, go for the sclerals. You'll need a fitting set, but I think they are returnable. You'll need to learn the technique for getting them out. Insurance pays big time for sclerals, so make sure your fees are up there.

[smallworld]

We do sclerals. I'm saying the patient wants piggyback and you can't do piggyback with sclerals. We have so many fitting sets, Rose K, AKS, Kerosoft IC, Standard scleral, you name it. I do medically necessary every week I swear.

[Dr. Bill Stacy]

We do sclerals. I'm saying the patient wants piggyback and you can't do piggyback with sclerals. We have so many fitting sets, Rose K, AKS, Kerosoft IC, Standard scleral, you name it. I do medically necessary every week I swear.

Patient is demanding it for comfort? I'm amazed at how everyone likes the comfort of the sclerals, including the pickiest and most sensitive. So try the piggyback on a regular rgp and after the pt balks at that mess, have a backup scleral to try... There's always synergyze Kone lens. Pretty much a skirted scleral

[smallworld]

Too bad synergize are not FDA approved for post corneal transplant. She wears piggy back on her eye that hasn't had transplant and loves it. But I think her stitches also effect the fit of the gas perm. I think doc said the stitches will "kick it off " her post surgical eye. We used paragon with a flexlens plano ( soft lens with a center depression that holds the gp over the center of the cornea) before, but she didn't like that.

[Dr. Bill Stacy]

Too bad synergize are not FDA approved for post corneal transplant. She wears piggy back on her eye that hasn't had transplant and loves it. But I think her stitches also effect the fit of the gas perm. I think doc said the stitches will "kick it off " her post surgical eye. We used paragon with a flexlens plano ( soft lens with a center depression that holds the gp over the center of the cornea) before, but she didn't like that.

Yeah, you could go off label and make sure they vault. No chance of getting those last sutures out of there?

[smallworld]

True. Imbedded. I'm currently working on five med necessary