关于签证照片的问题

I have a stupid question that I hope people with experiences can help clarify.

On the official Consulate website, it is stated that glasses are not allowed in the 签证照片. My parents are both near-sighted and they argue that on they did not see such a statement published at 上海中信银行.

My question is: are glass an absolute "no-no" or it is optional in the 签证照片?

Thanks in advance!