Fig. 31. Deep sclerectomy with viscocanalostomy: limbal landmarks. The green arrows designate the anterior and posterior limit of the surgeons blue zone. The anterior limit is designated by the green arrow with the yellow border and the posterior limit is easiest to see designated by the scleral spur (green arrow with black border). This zone is usually 1.2 to 1.5 mm in anterior to posterior width but varies considerably between eyes. Limbal anatomic clues will vary depending on the depth of the flap. The deep flap dissection verifies the presumed location of the scleral spur seen in Figure 27. In congenital glaucoma eyes, the scleral spur may be found considerably more posterior to this figure.