consumer seeks info

bs · 10-27-2005, 11:19 AM

Hi.
1. I have found different levels of acuity with same rx and different lens materials.
2. If I have to tilt my glasses forward at the top, away from my face with lens bottoms pressing into lower eyelids, what am I doing; astigmatizing the prescription, or increasing the spherical power? or both? Thanks.

**QDO1** · 10-27-2005, 11:33 AM

Originally Posted by bs

Hi.
1. I have found different levels of acuity with same rx and different lens materials.
2. If I have to tilt my glasses forward at the top, away from my face with lens bottoms pressing into lower eyelids, what am I doing; astigmatizing the prescription, or increasing the spherical power? or both? Thanks.

1. It will be a fitting/setup/lens surfacing (quality) issue

A good dispener will be able to set the frame and lens up properly
2. You are doing a lot of things, what exactly happens will be prescription dependant. Again - a good optician will know that and sort it for you

**AWTECH** · 10-27-2005, 02:35 PM

You are either inducing or negating prism, which is bending of the lights ray due to the angle of light ray when it hits the surface of the lens. You could get a very slight technical spherical change however this would not be enough for the eye to even notice.

**mshimp** · 10-27-2005, 08:36 PM

By tilting the top of the lens away from your forehead and the bottom closer to your cheeks you are causing the optical centers(o.c.) to be raised.The effect of this is the potential of moving the o.c. to the center of your pupils. This would give you better vision.This is what AWTECH explained ,or in other words for every mm of vertical shift upward(for the o.c.) there are two degrees of pantoscopic tilt .

Also you are changing the vertex distance.The distance the lens are away from your eyes.Effectively giving you more plus power in a given RX.Though this perhaps is marginal.

Hope this helps