Create Ortho Screen EdgeColliders2D - Collider Edge

ScreenEdge.cs

// perspective camera, get far clip plane edges in world space (z is set to 0)
var bottomLeft = (Vector2)cam.ScreenToWorldPoint(new Vector3(0, 0, cam.farClipPlane));
var topLeft = (Vector2)cam.ScreenToWorldPoint(new Vector3(0, cam.pixelHeight, cam.farClipPlane));
var topRight = (Vector2)cam.ScreenToWorldPoint(new Vector3(cam.pixelWidth, cam.pixelHeight, cam.farClipPlane));
var bottomRight = (Vector2)cam.ScreenToWorldPoint(new Vector3(cam.pixelWidth, 0, cam.farClipPlane));

Debug.DrawLine(bottomLeft, topLeft, Color.red, 33);
Debug.DrawLine(topLeft, topRight, Color.green, 33);
Debug.DrawLine(topRight, bottomRight, Color.blue, 33);
Debug.DrawLine(bottomRight, bottomLeft, Color.magenta, 33);

ScreenEdgeCollider.cs

using UnityEngine;
using System.Collections;

public class ScreenEdgeCollider : MonoBehaviour 
{
	void Awake () 
	{
		AddCollider();
	}
	
	void AddCollider () 
	{
		if (Camera.main==null) {Debug.LogError("Camera.main not found, failed to create edge colliders"); return;}

		var cam = Camera.main;
		if (!cam.orthographic) {Debug.LogError("Camera.main is not Orthographic, failed to create edge colliders"); return;}

		var bottomLeft = (Vector2)cam.ScreenToWorldPoint(new Vector3(0, 0, cam.nearClipPlane));
		var topLeft = (Vector2)cam.ScreenToWorldPoint(new Vector3(0, cam.pixelHeight, cam.nearClipPlane));
		var topRight = (Vector2)cam.ScreenToWorldPoint(new Vector3(cam.pixelWidth, cam.pixelHeight, cam.nearClipPlane));
		var bottomRight = (Vector2)cam.ScreenToWorldPoint(new Vector3(cam.pixelWidth, 0, cam.nearClipPlane));

		// add or use existing EdgeCollider2D
		var edge = GetComponent<EdgeCollider2D>()==null?gameObject.AddComponent<EdgeCollider2D>():GetComponent<EdgeCollider2D>();

		var edgePoints = new [] {bottomLeft,topLeft,topRight,bottomRight, bottomLeft};
		edge.points = edgePoints;
	}
}