Location of Emulsification
The nucleus may be emulsified at various locations within the eye, including the posterior chamber, iris plane, and anterior chamber. The location determines which techniques are used to emulsify the nucleus.
The posterior chamber is a common location for nucleus disassembly and emulsification. Removal of the nucleus at this location is facilitated by hydrodissection and nucleus rotation. The advantages of posterior chamber phacoemulsification include a reduced risk of corneal endothelial trauma and the ability to minimize the size of the capsulorrhexis opening, which is helpful with suboptimal pupil dilation. Disadvantages include increased risk of complications because emulsification takes place closer to the posterior capsule, greater stress placed on the capsule and zonular fibers when the nucleus is being manipulated, and the need for sophisticated methods of nucleus splitting.
When phacoemulsification is performed at the iris plane, one piece (or pole) of the nucleus is prolapsed anteriorly. Once prolapsed, the nucleus can be manipulated with less stress on the posterior capsule and zonular fibers. Emulsification occurs between the corneal endothelium and the posterior capsule, thereby reducing the risk of damage to either structure.
This location is often suitable for the beginning phacoemulsification surgeon and advantageous in patients who have compromised capsular or zonular integrity. In patients with small pupils, this technique permits good visualization and enables safe emulsification. The disadvantages of working at the iris plane include difficulty prolapsing the nucleus and risk of damage to the corneal endothelium if the surgeon emulsifies the nucleus too close to the cornea.
This supracapsular approach involves prolapsing the nucleus through the capsulorrhexis during hydrodissection, which requires a medium to large capsulorrhexis and a relatively soft nucleus. This technique theoretically reduces the stress on the zonular fibers during manipulation of the nucleus. The risks include a greater chance of aspirating the iris in the phaco tip, as well as damaging the corneal endothelium. Nevertheless, phacoemulsification in a supracapsular location is useful in situations such as the presence of posterior capsule rupture. Using an OVD to protect the endothelium and minimizing phaco energy are recommended.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.