Base curve issues?

**shellrob** · 07-13-2005, 10:11 AM

Ok, my patient comes in and purchases lenses into his own frame. Single vision poly lenses w/ar because he's strickly using them for shooting. I order the uncut(stocked) lenses and edge them. Well, he cannot see anywhere outside the optical center. Hmmm. Didn't happen in his old glasses. His old lenses were poly ft28's in a 6.5 base curve. The new single vision lenses were made on a 5 base curve. I checked the rx and the pd and everything else. Do you think it's the difference in the base curve that causing his problem? I thought maybe it was the size of the frame, but it didn't happen in his old lenses.

I've come across this because of size, lens materials, changes in rx, but haven't had this big of difference in vision occur because of the difference in base curve.

I feel silly not knowing the reason.

**GOS_Queen** · 07-13-2005, 10:47 AM

Any change in the Rx ?

What about oc's ?

Is it now an aspheric poly (vs a spherical - I've seen issues with that before) ?

Karen

**shellrob** · 07-13-2005, 11:46 AM

Actually yes there was a change in the rx. Previous rx
0.00 -.50 x 80
+.25 -.75 x 110

New rx
+.25 -.50 x 65
+.75 -1.25 x 105

No change in anything else including oc hts and it's not aspheric.

CDOT · 07-13-2005, 04:44 PM

That power described in most stock lenses are mighty thin.. That along with the base curve difference from the previous pair makes me think that warpage would be the issue, Clock the lenses on the front curve at the 180 then at the 90, check a few places on the lens, the difference will be your warpage value.

**Jacqui** · 07-13-2005, 05:23 PM

It could very easily be the base cuve , have a pair sufaced in a 6.25 base and see what happens. I've seen this happen before and it will drive you nuts until you figure it out.

**OPTIDONN** · 07-13-2005, 10:03 PM

Did he use his other pair for shooting? He may notice the little differance in base curve and rx while shooting. Vision is a little more critical for sports like that and he may be more likely to notice any differance. Does he mainly notice it while he is shooting? I wonder if the head tilt (looking obliquely through the lens) could effect his vision?

**shellrob** · 07-14-2005, 07:00 AM

Well, he had ft28's as his shooting glasses in the same frame previously but decided he didn't need the bifocal this time around, so we made the single vision. I've actually made them twice and the same thing. The base curve is the only thing besides being single vision that is different. I know that he will have some distortion outside the oc because of how large the frame is, but he litterally cannot see clearly anywhere except the center. I'm thinking of just surfacing the job in the 6 base curve to see if that solves it. Just not sure. I don't want to keep making lenses for nothing.

**GOS_Queen** · 07-14-2005, 10:42 AM

Originally Posted by OPTIDONN

Does he mainly notice it while he is shooting? I wonder if the head tilt (looking obliquely through the lens) could effect his vision?

It could be that he is tilting his head differently in the single vision vs the bifocal. (thinking also of the change in the Rx he experienced)....

Good Luck !! (things like this make me want to :hammer: ) Be sure to let us know after you surface the 6 bc.

Karen

**shellrob** · 07-14-2005, 10:51 AM

Thank you all, I appreicate it and I'll surely let you know after I finish them.

**shellrob** · 07-25-2005, 04:50 PM

Bae curve was the problem. Surfaced them in the 6 base and no problem.

**omisliebling** · 07-25-2005, 10:05 PM

I have seen this many times before when patient takes his new Rx somewhere else, comes back and the only difference I can find is the base curve, I send them back to where they got the new glasses made with a note of patient's old BC, ask patient to come back and let me double check and make sure he/she is doing fine with the new BC and voila problem solved. I got in to the habbit of checking old BC to avoid this problem.

**shellrob** · 07-26-2005, 08:32 AM

It's the first time that it has happened to me in a very long time and at first I didn't even think of that, but then after thinking about it, it occured to me that it may be the problem and of course it was. I will definitly check from now on to avoid this occuring again.