Talk to Eye Specialist on Eye Sight Suddenly Going Weaker And Weaker

Hello, It's been few months since she started complaining about bot seeing writings on the board. She is a medical student. She get her eye sight checked from her hospital. They said sight is okay. Then covid break. She was home, but she was saying its getting more and more weak. A weak ago we took her to a doctor, he recommended glasses. But she is saying 'I feel like it's going weaker day be day'. Any suggestions, what could be the reason, and what should be done?