Progressive sunglasses

[OPTIDONN]

The other day I saw an add about KBCo's new progressive lens. In this add it mentioned that having a person in one progressive design for dress purposes and another design for sunglasses should not be that noticable for the patient. The reason behind this is that with sun glasses less light is transmitted onto the retina and because of this lack of light the eye cannot pick up on the subtle differances between the two styles resulting in very little non adapt. We have put patients in two drastically differant designs for dress and sun wear and we almost never hear the patient complain. Any body have any thoughts?

[For-Life]

I always use a less expensive design for the sun. Customers are quite appreciative of the second pair being less expensive, and we use a model that gives better distance. Reading is important, but not of huge importance for sunglasses.

[Pete Hanlin]

My thought would be that most PALs work fairly well, and people naturally understand that different pairs may feel and perform differently anyway.

For example, I own five or six pairs of shoes (having just moved, I can tell you my wife owns- well, let's just say more than five or six ;^). Anyway, the pair I mow the yard in perform their function admirably- they keep my feet from being pummelled by stubble, debris, etc. as I mow. They certainly aren't as comfortable as my lounging sneakers, but then again, my lounging sneakers probably wouldn't hold up to mowing duty quite as well. Likewise, the polarized sunglasses I wear while mowing aren't quite as nice as the ones I use for dress either.

While I believe there are performance differences between PAL designs, I also think most function quite well if properly fit.

[drk]

I believe that explanation is bogus.

Having said that, a progressive that maximizes distance zone width makes sense for sunglasses.

[William Walker]

I've had a few patients notice a difference in the progressive channels between dresswear and sunwear. I've even had patients notice the progressive channels differently when both pair have the same brand progressive. I've had those few patients go back with the doc and he gave me (and the patient) an explanation that seemed plausible, but unlikely to me. He said that in the sunglasses, allowing the pupil to open wider, will make the patient more aware of the periphery of the PAL.

Does anyone have any thoughts on this explanation?

Thanks

[Darryl Meister]

He said that in the sunglasses, allowing the pupil to open wider, will make the patient more aware of the periphery of the PAL

Essentially, the size of the blur spot formed on the retina by a power error (or lens aberration) is proportional to pupil size. Consequently, larger pupil diameters result in more "blur" for the same amount of power error. Further, as the pupil size increases, the aberrations of the eye become more apparent. However, I doubt that the pupil is much wider while wearing sunglasses on a sunny day than it would be under normal lighting conditions (unless the lenses were really dark). This would be more of an issue for vision under low-light conditions (reading in a poorly lit room, driving at night, etc.).

[OPTIDONN]

We have had several patients comming back complaining of the same thing. They can see fine out of thier dress glasses but not so well out of thier sunglasses (they were all progressive lens wearers). Everything on the sunglasses checked out fine. The rx, fitting, pd, base curve, lens design were all the same. Many even had the same frames for both sets. We used the above explanaition about pupil size to explain to the patient what was happening. We really had no idea! Could it be if the patient already had larger pupil size and if it dialted even more could that cause the above situation?

[William Walker]

Darryl:
You mentioned abberations of the eye. The only one I know of is the blur spot as a result of the macula. Are there any other abberations I might need to know of?

Thanks!

[Darryl Meister]

The eye actually suffers from the aberrations typical of an optical system, including spherical aberration, coma, chromatic aberration, et cetera.

[OPTIDONN]

I spoke with the owner of our store and he said that when he took the patients out side (he did it on a whim) they said that thier vision was better. They mainly complained while in the car and while inside. Could that contribute to the pupil dialation and cause some of the problems?

[jose2k]

honestly, i hate selling dress and sunglass progressives at the same time. i always have a patient that will switch from one pair to the other and tell me they can't see as well with the sunglasses... and apparently my boss doesn't think DUH!!! is an appropriate response =) while i don't think they can detect the difference in the progressives, always make sure they have abundant light before they slap on those sunglasses. heck, bring a flashlight and shine it in their face while they read... maybe they'll get the picture.. =)


joey

p.s. the way i understand it, the pupil controls the amount of light you get, and with sunglasses, even full dilation (w/o mydriatic of course) is not going to allow the same light in inside as it would outside. the decrease in light won't necessarily produce the aberration, but its like dimming the lights in a theater... you just can't focus on things as well, so the whole thing blurs. feel free to correct me

[Alvaro Cordova]

Darryl:
You mentioned abberations of the eye. The only one I know of is the blur spot as a result of the macula. Are there any other abberations I might need to know of?

Thanks!

Did you mean blind spot as a result of the optic nerve cup???

[OPTIDONN]

True Jose2k. The lighting in our store is fine it will never be as bright as natural light but it does the job. And yes the iris will constrict or dialate to controll the amount of light that enters the eye, it also helps to reduce aberrations such as spherical and coma. I was wondering if an already large pupil dialates behind dark sunglasses is it enough to allow oblique rays of light to enter the eye allowing it to pick up on the surface astigmatism that is part of the design on a progresive lens.

[jose2k]

i don't think it would and also when fitting the sunglasses, the patient usually doesn't wear the lens long enough for accomodation to finish. if you could convince them to wear them long enough before passing judgement it would probably be fine, and best of luck to you in that. your best bet would be to explain before you sell the lens that the vision will not seem as crisp at first and that it will take a small time to adapt.

joey

[OPTIDONN]

They all gave them a fair chance and wore them for several hours at a time. It seems that the people who wore them for longer periods noticed this the most.
Also this was not common for all patients. Thats what led me to believe that it could possably have something to do with pupil size. I don't think that the doctor documented any size. I could be totally off!

[jose2k]

i say we round em up, tag em, and release them back into the wild for further experiments. =)

we will call your new species the wide-eyed woollyknockers.

i think i asked our doctor about something similar, i'll see if he has anything new to add to the subject.

joey