Often Pushing glasses is just a habit? 

This is not an subconscious gesture, it’s  a facial nerve feeling the sliding of the glasses.

When dispensing glasses, optometrists should carefully check the correct prescription parameters of the degree and pupil distance, so as to ensure that the glasses are fitted with the right comfort level. If you don't pay attention to pushing glasses often by hand, you should be careful that the glasses degree be deepen. If the glasses keep sliding, the focus of both eyes will not be in the scope of the glasses, which will increase the adjustment burden of the eyes and deepen the glasses degree.

There are clear technical requirements for pupil distance, horizontal distance and deviation of optical center, horizontal deviation of optical center on one side, vertical mutual difference, etc., so the glasses adjusted by optometrists should meet relevant standards and have the ability to correct vision.

What causes glasses to slip frequently?？

The high temperature in summer makes people's facial skin easy to produce oil and sweat, which is a good lubricant for glasses nose pads. Try to wipe the sweat on your nose, then you will feel glasses are more stable! 

A change in face shape can also cause glasses to sag and slip.For example, when you are heavy, then you lose weight, the glasses may become loose, unstable, and slide.

Long time wearing and often removal of glasses will easily lead to frame deformation. The front and back weight difference of glasses and size or plate type unsuitable will also lead to glasses easy slipping.

So you can't just rely on appearance preference, it's best to actually try on, choose a suitable for their own, quality glasses.