How to enable nightvision as a personal perk instead of a shared perk?

[Rainbow Kitty]

I have a friend using a character called the nightmare which has nightvision, but other characters around him can also make use of it. I want to be able to give my character nightvision but without others being able to make use of it. I've looked through the code and this is what I found.

local function NightVision(inst)
	if not TheWorld.state.isday or TheWorld:HasTag("cave") then
		inst.Light:Enable(true)
		nightVision = true
		print("NightVision On")
    else
        inst.Light:Enable(false)
		nightVision = false
		print("NightVision Off")
end
end

-- This initializes for both clients and the host
local common_postinit = function(inst) 	
	inst.soundsname = "maxwell"

	-- Minimap icon
	inst.MiniMapEntity:SetIcon( "nightmareplayer.tex" )
	
	inst:AddTag("monster")
	
	inst:ListenForEvent("respawnfromghost", function(inst)
	    --inst:DoTaskInTime(5, SpawnTerrorbeakpet(inst))
		inst:DoTaskInTime(0.5, NightVision) 
	end)
    
	inst:WatchWorldState("startnight", NightVision)
	inst:WatchWorldState("startday", NightVision)
	
	if TheWorld.state.isnight and nightVision == false or TheWorld:HasTag("cave") and nightVision == false then
		inst:DoTaskInTime(0, NightVision)		
	elseif not TheWorld.state.isnight and nightVision == true or not TheWorld:HasTag("cave") and nightVision == true then
		inst:DoTaskInTime(0, NightVision)		
	end
	
	inst.entity:AddLight()
    inst.Light:Enable(false)
	inst.Light:SetRadius(30)
    inst.Light:SetFalloff(0.9)
    inst.Light:SetIntensity(0.7)
    inst.Light:SetColour(180/255,195/255,150/255)
end

I'm not sure what to change to make the nightvision a personal perk.

Edited February 21, 2018 by Rainbow Kitty

[Aquaterion]

I'm guessing that they're not actually able to use nightvision, but instead are able to bask in his light, so if you reduce the radius of the light, it should be less accessible by others