The large-size glasses is much broader than usual myopia glasses, which means the optical center between the glasses would therefore becomes broad. A myopia glasses wearer whose PD is shorter would cause the focus error of the optical center between the pupils and glasses. That means it could easily cause the eye fatigue and blurred vision. So long-time wearing would make your vision become worse.
The original lens of large-size glasses is plastic (http://www.finestglasses.com/
The curvature of optical center and edge varies according to the myopia glasses. There is a strict requirement on ophthalmology:
Provisions of Ophthalmology:
1. The error between the pupils and the optical center should be limited into 2mm;
2. The higher the ametropic degree is, the less the error between the pupils and the optical center is.