Dear Student ,

Look, Railways have different eyesight condition sections based on which you can pass for different category after qualifying medical exam in different Railway Job posts.

Here is some details of it :

• A-1: —> Distance Vision: 6/6, 6/6 without glasses
• A-2: —> Distance vision: 6/9, 6/9 without glasses.
• A-3: —> Distance Vision: 6/9,6/9 with or without glasses (power of lenses should not exceed 2D)
• B-1: power of lenses not to exceed 4D (Distance Vision : 6/9 or 6/12)[ must pass colour vision]
• B-2:  same as B-2 , just need to pass Field of vision
• C-1: Distance Vision : 6/12 or 6/18
• C-2: Distance Vision : 6/12

You can check the brief details from here too :

https://www.rrbchennai.gov.in/downloads/recruitment_rules/medical_standard.pdf

Hope this helps !