Fresnell prism -- What's the deal?

[eyeguy21]

Been in the business for a while now and doing Fresnells pretty regularly for about the last 12 years. My experience with them is that they're successfull about 40% of the time. I'm curious about other opticians experiences with these things and if anyone out there has any tips on: trimming the edges so they don't look like Frankenstein did them, applying them so they don't look like there's a fog on the lens, applying over AR and those types of things. I've tried just about everything. I've somehow wound up the prism guy at a group practice that's just full of MD's that absolutely love the stuff. We use Carl Zeiss labs (What's up Darryl Meister?) but they really don't know any more about them than I do. I've never had any formal training with them beyond the cute little pictures on the box. I've been getting by doing it the way I've been doing them but I still think they should look a lot better. As it is I trim them with scissors, then clean the lenses with alcohol. I then apply the prism to the lens in a sink full of warm water and wait for them to dry. Once dry I shave the excess material off the edges using an exacto knife or similar blade and walla done. That's what's worked best for me, any input on this is appreciated.

[optical24/7]

I see a lot of these from our practice also. I do much as you do (clean lens thouroughly, scissor larger than shape, use a sink full of water, ect) I make sure I run my fingers over both surfaces I'll be applying to make sure there are no small air bubbles on the surfaces. After fully pressing out any bubbles left I pat dry and use a new razor (new one every time). I pull (rather than push) the razor at a 45 degree angle in as complete single motion as possible. The 45 angle helps prevent the fresnel from lifting off from eyewire rim preasure. A continuous pulling of the razor also keeps the edges looking smooth. You can also use a paper hole punch to knock out a clean looking hole at rimless mounting points.

[eyeguy21]

So I assume that you have a similar issue to mine in that the edges look a bit choppy from time to time? I'm also curious as to your opinion (or anyone elses) as to how successful press on prism is for you. That's what I meant when I said they work about 40 - 50% of the time. In some cases we wind up spending 30min to an hour only to have to peel the prism off without them ever really trying it because it's a tough pill to swallow. I guess I got used to the high success rate of most aspects of this business and then there's Fresnell prism that has pretty evenly mixed results and a rather low success rate (plus a high price tag).

[optical24/7]

No choppy edges here! :bbg: If it's a binocularity issue, apply it to the non-dominate or worse v.a. eye. Explain it will take at least a week to evaluate if the prism will help and let them know that you can do a finalized Rx without the "lines". (if possible).

I would say we have closer to a 90% compliance with trying a fresnel. These patients have issues and you need to let them know that this is a more inexpensive way to verify a correct final Rx.

[FVCCHRIS]

Trace it out with a fine Sharpee, then use a drafting template with different curvatures to help you cut it out with an exacto knife(a sharp one)- and do it slow and carefully. I've never been a fan of these prisms, just too much time involved for something that the patient probably won't like. I know there are some circumstances where they actually do the trick but not very often. We used to use them for trial purposes before ordering the final Rx made up in the spectacles when the amount was a big change from what the patient was accustomed to.

[eyeguy21]

Depending on which circle I'm in I get different feedback on prism. However it usually doesn't take too long before I start getting the derogotory comments about them. When I add up the time it takes to get it done plus the overall cost to the patient and then factor in the amount of profit (We're basically selling them for cost) as well as the time we spend with the patient explaining them and the post care that goes into it, I cringe everytime. On the other hand I'm not sure there's a lot that can be done about it. Too bad there isn't a better solution. I figure the patients need SOMETHING and the doctors only have so many tools in the box to work with. But their aggravating for sure.

[Now I See]

I have a lady that comes in and will only wear a press-on prism, so that's what I do for her. (She started using press-ons at another office before she came to me.) I've tried to have the prism ground in, but she doesn't like it. I've spoken with her doc and he says her prism seems to fluctuate, and they are doing some other testing, but for years, she has been completely happy with her "removable" prism.

As far as applying them, I trace the lens shape on the prism, then use sharp scissors to cut it smoothly, I have always applied the prism under water with a tiny drop of dawn dish liquid added. And, if possible, I like for them to be left untouched overnight, seems to allow them to dry out better when they are not handled.

[FVCCHRIS]

I agree with you on the overnight bit, it does seem to promote a more secure prism.

[finefocus]

Disposable scalpels cut them very well. Lay the prism on a phone book (smooth side up!), lay the lens on top, pushing down fairly hard. Trace around with the scalpel, angling in a bit to get inside the bevel.

[DragonLensmanWV]

Heck, I just apply them, let them sit overnight, then just do a pin bevel on the back of the lens, cutting the prism off in the process. Perfect fit!

[obxeyeguy]

If I don't have the ability to let them sit overnight, I set the lens concave up in my Hilco tempmaster air heater with the heat control set to off and the fan on low.

[eyeguy21]

yeah, we don't really have time to let them set overnight. Our clientele are the types that mostly only have one pair of glasses and depend on them to get around so I'll have to try the frame warmer with the heat turned off trick. Plus we have horrible tools around here. You know, I work in a group practice with upwards of 40 doctors doing 500+ appointments in a day and countless surgeries but we're in a recession so all of a sudden we're completely broke. Anyhow, in optical we don't have a budget really for proper equipment so essentially I have basic optical tools (the necessities) and then tools that I make from office supplies (paperclips, push-pins etc.). So I don't have a hand wheel like Dragonlensman. I've keep asking though. Maybe someday one of the doctors will realize they can only drive one car at a time and therefore don't need six of them so I can get a hand-wheel.

[Strab]

If you want a much quicker way to get the lens dry and help it adhere...use rubbing alcohol instead of water and dry with hot air frame warmer. Works quickly. We do several of these a week and pt.'s have about a 90% rate of liking them. But we ALWAYS use them for atleast a week sometimes 2 weeks before allowing the pt. to determine if it is helping. Hope this helps :-)

Lovin' the hole punch idea for drill mounts!!!!