Base curve changed?

**Monkeysee** · 10-12-2004, 06:14 PM

I just finished an order for a sv lens -3.00-4.00x85. The OD specified a 2 base lens be used, which is what it was, I checked before edging, and Im fairly sure I checked uncut at the 180 once lenses were dotted up. Now that I have edged the lens I am getting a reading of 4 base on the front? eyesize is a 52.. Don't recall this happening before, but then I dont get orders where the base curve is specified by the OD. Is the lens a bit too tight (looks fine)? If I measure the base curve at 90 not 180 it reads 2? Did I measure wrong or can the curves change after lenses are edged?

**Joann Raytar** · 10-12-2004, 10:10 PM

Are the lenses Poly or 1.0 CT?

**chip anderson** · 10-12-2004, 10:35 PM

What does it clock un-mounted?

**Monkeysee** · 10-12-2004, 10:42 PM

I didn't think to check unmounted, lenses are plastic reg. index ground at wholesale lab. I've heard of the base readings changing once mounted, but this just seems like alot....and I know I checked lenses before edging (picky customer)....I don't know a whole lot about base curves though...

**Monkeysee** · 10-13-2004, 08:34 PM

...well this became a non issue... the job was dispensed as is to pt. this morning. The curve read 2.75 when lens was unmounted which suggests frame pressure, right? Rather than risk taking the lens down a bit to relieve the pressure and make the lens too small, it was left alone. The patient has no lens in the other side of his frame and previously wore glass FT28 with a 4.00 base.(cataracts)..... I dont know why at 2 base curve was specified?? and probably never will....hadn't seen this sort of thing before, but then I don't clock all the lenses once they've been edged...does anyone?

**chip anderson** · 10-13-2004, 09:48 PM

A good optician always checks every mounted lens for frame/mounting/screw pressure and relieves same.

Chip

How you checks? With a colmasoce (polariscope) of course.

**Monkeysee** · 10-13-2004, 10:02 PM

Thanks you're right, I check for signs of stress visible to naked eye, under fluorescent desk lamp, and against louvered window in my lab (it really makes any waves in the lens stand out), but I'm afraid my polariscope is gathering dust...I think I'll put it next to the hand edger tomorrow!!:o

(the above mentioned lenses were checked using one of those polarizing "sleeves" that folds in half which you hold over the lenses-when I think of a polariscope I think of the illuminated one that is attached to my thermal hardex unit). Also could you give me a hint, should there be no signs of stress on the lenses? seems to me when I do that I end up with a too small lens?