**1. Introduction**

Cataract surgery is the most common ophthalmic surgery, and one of the most frequently performed surgeries in general. A "cataract" refers to a focal or diffuse opacification of the

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crystalline lens, a structure that is normally opticaly clear. Hardening and clouding of the lens may result in a progressive loss of vision depending on its size, location and density. It is typically bilateral, compromises visual acuity and contrast sensitivity and increases glare. Cataract may form at any age due to a number of different etiologies such as systemic metabolic disease, use of different medications, ocular trauma, but most often is age related. As the lens ages, it increases in weight and thickness and decreases in accommodative power. In crosssectional studies, the prevalence of cataracts is 50% in people between the ages of 65 and 74 and it increases to 70% in those over the age of 75 [1]. The pathogenesis of age-related cataracts is multifactorial and not completely understood. Different methods have been developed for cataract surgery, such as intracapsular and extracapsular extraction procedures, but the most common and widely accepted procedure is phacoemulsification, since its development in 1967, by Charles Kelman [2].

### **2. Phacoemulsification**

The procedure of phacoemulsification has gained increasing popularity worldwide, since the introduction of sutureless clear corneal cataract incisions, due to several advantages over the traditional sutured scleral tunnels and limbal incisions [3]. Several surgical approaches have been suggested to allow for a faster and easier phacoemulsification technique. The introduc‐ tion of clear corneal incisions to enter the anterior chamber and remove the cataract using phacoemulsification revolutionized cataract surgery [4]. This approach is the most popular and widely accepted. Clear corneal wounds have transformed cataract surgery by dramatically reducing surgical time, offering faster postoperative recovery, and lowering the induced astigmatism in comparison to scleral tunnel incisions [3].

#### **3. Scleral tunnel incisions**

Scleral incisions in phacoemulsification were firstly introduced by Girard and Hoffman [5]. The incision size is usually 3-7 mm in chord length [6]. Smaller incisions may be sutureless while larger tunnels often are sutured and periotomy is performed in both cases. Scleral tunnel construction could lead to several problems. An initial scleral tunnel that is too deep will create scleral disinsertion with exposure to the ciliary body leading to different problems with hemostasis, poor wound stability, early or posterior entry to the anterior chamber, and iris prolapse. On the other hand, an incision that is too shallow may result in tear of the tunnel roof and problems with water tightness of the wound [3]. Another thing that is of great importance is the length of scleral tunnel. A dissection that is too far into the cornea creates an anterior entry into the anterior chamber resulting in decreased maneuverability and corneal striae that interfere with visibility during subsequent steps. An incision that is too short would create problems with wound closure and iris prolapse [3]. Other complicaions include induced astigmatism, filtration, hyphema and Descemets membrane detachment.
