You can use hamsandwich updated module for it and it efficient.
PHP Code:
/**
* Description: Whether or not the player is being flashing. (flashbang grenade explosion)
* blindTime is the time you are considered as being blind. (holdTime * 0.33).
* Forward params: function(this, Float:blindTime, Float:duration, Float:holdTime, alpha);
* Return type: None.
* Execute params: ExecuteHam(Ham_CS_Player_Blind, this, Float:blindTime, Float:duration, Float:holdTime, alpha);
*/
Ham_CS_Player_Blind
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