Material for 3 piece drill

[oxmoon]

What would be the best material for a high myope wanting a 3 piece drill? Script is -6.75 -4.50 X 88 and -7.25 - 4.25 X 96. Add is +2.75. Thanks.

[Chris Ryser]

I would guess that you will need some extra long parts to fill the holes that will be on the thickest side of the edges, as the - cyl is right on the vertical axis.

[WFruit]

In order of preference, from a lab point of view: Trivex, 1.67 (MR-10), 1.74 (HR-74 (Seiko))..... and that's it. Trivex is the best material for drills, and if it's not the best material for your patient's Rx, then it probably shouldn't be put in a drill mount. A/R is a must as well, and with that Rx, I would NOT high luster polish the edges either.

I'm sure someone will also mention Hi-Vex/Tribrid, which should also be great.

[Happylady]

I would use 1.74 and choose a size and shape that would minimize the edge thickness. I suggest a satin polish or an edge coat rather then a shiny polish or unpolished edge.

[EyeMaster]

As I recall 1.74 index really isn't very good for drill mounts because of the brittleness of the materials. Although with that correction (-7.25 - 4.25 X 96) it's not going to look very nice in any rimless

[mish]

Is there a difference between 1.74 Seiko, Optima, etc?

[WFruit]

Is there a difference between 1.74 Seiko, Optima, etc?

Yes. Seiko developed their own proprietary 1.74 material (HR-174). I don't know about Optima, but I know that Shamir, Shore, and Essilor use a MR-174 resin. According to Seiko, their material is more thermally stable, and better for drill mounts.

As far as 1.74 being to brittle for drill mounts, I've got three pairs of the Seiko 1.74 lenses in drill mounts and none have cracked, chipped, or split around the drill holes.

[jonah]

I would go with 1.67, as round of a shape as possible and no edge polish.
You may also want to consider adjusting the temples and bridge (as much as possible) prior to mounting.

I would only go with 1.74 if you feel really confident with drilling and mounting......

[DragonLensmanWV]

I'll chime in for 1.70 index. Way better ABBE than anything mentioned except Trivex.And you can just drill the lenses deep enough to hold the plugs and not even disturb the back surface. 1.70 is pretty tough stuff and it drills nicely.

[EyeCare Rich]

Wow, daring Rx for a drill mount. Hope they don't mind showing a little edge. I think Trivex would be a little to thick in this instance, I would probably use 1.67 if I had to make them, but hear good things about 1.74 Seiko, haven't used it though.

[J.P.]

The real questions are..... What is your A Measurement? and What type of 3 Piece frame are you using?

Silhouette Frame have worked well for me with Hyper Myopic RX's. Their drill posts are just over 3mm in length and their bushings are almost 7mm in length. I have had a patient with a -9.00 in a 48 A, then lens cam out to be 6mm Thick on the edge. You have to think your edge thickness as well as material. You just need to spend a few moments calculating your edge thickness. One of my OD's is a -8.50 and I spent the time custom making the size to make the edge thickness as thin as possible, and her -8.50's are 3.63 mm thin.

Your OD Lens:
In 1.74 with an A of 48mm your edge thickness should be around 5.58mm thick
In 1.64 with an A of 48mm your edge thickness should be around 6.26mm thick
You OS Lens:
In 1.74 with an A of 48mm your edge thickness should be around 5.68mm thick
In 1.64 with an A of 48mm your edge thickness should be around 6.14mm thick

With a 1.0 CT you may cut another 0.30mm from the edge thickness.

Your thickest point on OU is going to be Temporal and Nasal inferior on the lenses


Your difference in edge thickness is only 0.68 mm OD and 0.46 mm OS, which to the patient means nothing. You can sell them the 1.74 at a higher cost, but they will not be happy that it does not look any thinner then any other pair of glasses.

My suggestion is to spend the time with your frame and the patient, make a custom size and shape, calculate you sizes and thicknesses and then verify with your lab. Yes it's a lot of work on the front end, but it will keep you from having to remake or having an unhappy patient with their selection.