1. in most cases, as a result of inconsistent leg angle the mirror, particularly larger offset, and angle;
2. nose pads the left or right is inconsistent, which is easily observed;
3. points, left and right leg bending length is inconsistent, bias is too short, pull to the side glasses;
4. about the individual wearing the face width of the differences or different left and right ear of front and rear position.
Long term wear these types of frames can cause dizziness, blurred vision and so on, will cause the main perspective of serious deviation.