Hi
1) Since you are suffering from progressive rare eye condition,, you should escalate to Human Resources or Managing Director of your company and get relieved at the earliest.
2) Your manager seems to be acting illogical as he does not understand the risks involved in keeping you under notice period , despite the fact that the risks involved are mutual and destructive (for the company as well as individual)
3) Please speak to your Human Resource team and if they fail to respond, escalate to your managing director. At least one of them will be sane enough to relieve you instantaneously without burdening you.
4) Assuming even after writing letters to both Human Resources team and your managing director , both of them do not grant you a favourable decision, you may handover the lap top and other assets to the company to your relatives and get admitted in the hospital.
5) No employer can withhold the employee or his salary for not serving notice period when the employee is seriously sick(in your case affecting eyesight) that too at the risk of the employee and the company.
Hope this information is useful.