This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
True about color blindness -a) Age relatedb) Hereditaryc) Males onlyd) Female onlye) Can be treated 
Select and explain. 
A. ac, B. a, C. ad, D. ab
D: ab
Answer: D: ab 
Explanation: Colour blindness is mostly hereditary. However, one type of acquired colour blindness may be age related, i.e., Acquired blue colour defect (blue blindness). It occurs in old age due to increased sclerosis of the crystalline lens. It is owing to the physical absorption of the blue rays by the increased amber coloured pigment in the nucleus.
Colour blindness is more common in males (3-4%) than in females (0.4%). However, it can occur in both.
Currently, there is no treatment for colour blindness.