The eligibility in case of IAS for eyesight condition is given below
As given in the Mains notification (THE GAZETTE OF INDIA: EXTRAORDINARY, Civil Services-UPSC)
Limits of refractive error permitted -4.00 D (including cylinder) for Non- Pathological Myopia and +4.00 D (including cylinder) for Hypermetropia However lasik laser surgery correction is allowed for IAS and non technical services but not for Technical services like IPS, Indian Railway Traffic Services etc.
(Yet people with +6 eyesight have been able to get IPS, the only thing is that it should not be pathological and must have stablised. But you have to challenge the medical report for consideration, whereby a Expert doctors appointed by Government will look at your condition. Even if they give a negative report you still have the last option of knocking the doors of Judiciary).
Please find the pages of Gazette Of India (with regard to Physical Requirements for IAS) Attached. Refer to page 210 onwards.