What is the minimum distance one should maintain between the book and the eye while reading?

• The normal human eye can clearly see distant and nearby objects. However, it cannot focus on objects that are kept closer than 25 cm. 
• The optimal distance for reading is about 25 to 40cm from the eyes for decent magnification. If the book is kept very close or very far then it can strain our eyes and lead to eye troubles.

Therefore, 25 cm is the minimum distance one should maintain between the book and the eye while reading.