A Visit to the Eye Doctor

I've been meaning to visit the optometrist,  I think that is an eye doctor, and get my eyes checked and possibly get new glasses. But that requires money I don't yet have. My mom said she could pull the money together. But money is tight for her. I don't have a lot of responsibilities at home so I told her I would cover it. In the end we decided to split the cost in 4 weeks. I feel bad when she has provided so much and has taken care of me these past 28 years and counting. I have a feeling I will have the money before she does though... What do you all think? I'm 28 years old, should I pay for it myself like I want to? Or let her spoil me when she is struggling herself with money? I already know the answer, I just want to hear varying opinions.