I believe the hard glass spectacle lenses reflect the sound and bounce it back towards surrounding hard surfaces, hence causing a pseudo echo effect. This in turn disproportionally corrupts sound wave constants, therefore destroying any possibility of perceiving a true stereo image. This whole problem is of course made much worse every time the listener or other spectacle wearers in the room move their heads. My advice would be to wear contact lenses as these are made of softer less reflective material.