Two types of phaco incisions. Detail for scleral incision, side view: a to b: Initial groove is 1/3 to1/2 of scleral depth; if groove is too deep, bleeding may increase and entry into anterior chamber is likely to be too posterior, causing iris prolapse. a to l: Incision is traditionally 2–3 mm posterior to limbus. b to c: Tunnel is traditionally dissected past vascular arcade; if too long, ultrasound tip mobility is restricted and corneal striae decrease visibility. c to d: Short third plane is made by changing angle of blade prior to entering anterior chamber. In scleral incision, top view: e to a: Length of incision is determined by size of IOL. f to d: Initial opening into anterior chamber is usually 3.00–3.25 mm; after phacoemulsification, it is fully opened for IOL insertion. If opening is too small, irrigation flow is decreased, chamber tends to shallow, and heat buildup may cause burn. If opening is too large, excessive fluid egress causes chamber shallowing and iris may prolapse.