Removal of residual cortical material following phacoemulsification can at times be challenging and can lead to posterior capsular rupture. Understanding the principles and techniques of irrigation and aspiration (I/A) will enable the surgeon to use a structured approach and allow for safe and efficient evacuation of residual cortex.
II. CORTEX ANATOMY
During cataract surgery, lens cortex can be encountered surgically in 2 layers: supranuclear cortex and peripheral cortex. Surgically, cortex exhibits a high degree of “followability.” Cortical material flows to the I/A tip easily and is likewise able to be aspirated without difficulty. The same is not true of more solid, stiff nuclear material.
- Epinucleus, or supranuclear cortex, refers to the soft, continuous region of cortex surrounding the nucleus. Hydrodelineation will often produce this epinuclear shell.Careful manipulation of the epinucleus can allow for its removal as a single bowl.
- Peripheral cortex, as the name implies, is located beneath the anterior capsule, into the equatorial region, and lines the posterior capsule. Peripheral cortex tends to have a more fibrous texture. Under the anterior capsule and in the equator, intralenticular cells retain a pseudofibrous metaplastic capability. These cells are also involved in thickening of the anterior lens capsule, which leads to firm attachments of the cortex to the capsule in these locations. Intralenticular cell attachments are not present adjacent to the posterior capsule. This differential property is important to consider during aspiration of cortical fibers, as peripheral cortex requires a stripping action from the equatorial and anterior lens capsule in order to achieve a meticulous cortical cleanup.
Although a variety of hand piece configurations are available, most aspiration instruments use a 0.3-mm side-ported orifice. This size allows for efficient aspiration, while minimizing inadvertent lens capsule entrapment. Cortical aspiration can be performed using a coaxial or a bimanual technique.
A. Coaxial Versus Bimanual
Both irrigation and aspiration of the I/A instrument typically coexist on a coaxial hand piece with an outer irrigating sleeve surrounding a central aspirating port. Since most cataract surgeons still employ coaxial phacoemulsification, coaxial I/A remains a popular choice. However, subincisional cortical cleanup can sometimes be difficult.
Bimanual I/A separates the I/A portions into separate hand pieces. These smaller hand pieces fit through smaller wounds, including paracentesis ports. The hand pieces can be inserted interchangeably, allowing access to all subincisional locations (Figure 15-1). In addition, the irrigating hand piece can be directed to control fluid inflow away from suspect areas such as capsular tears. The use of smaller incisions also allows for better control of fluid inflow and outflow, providing improved anterior chamber stability.
One small disadvantage to most bimanual techniques is that they require a second paracentesis port, since the main wound is often too large to maintain adequate seal with insertion of a small diameter bimanual instrument. An alternative option is to use a standard coaxial hand piece for irrigation through the main wound, with the smaller bimanual hand piece for aspiration through the paracentesis. The larger diameter coaxial hand piece provides the high flow needed to maintain the anterior chamber and obviates the need for additional incisions. As an alternative to automated bimanual systems, nonautomated bimanual I/A instrumentation can also be used with similar advantages (Simcoe I/A). These manually controlled I/A devices provide a very controlled cortical cleanup and are especially useful in the setting of a posterior capsular rupture.
B. Soft Versus Metal Sleeve
Traditional coaxial I/A hand pieces consist of a metal irrigating sleeve with a central metal aspirating port. However, given the smaller diameter of I/A versus phacoemulsification hand pieces, these metal sleeves allow for wound gape and subsequent anterior chamber instability. Newer silicone soft sleeves are available that provide for tighter wound seals and more stable anterior chamber maintenance. These benefits of chamber maintenance extend also to viscoelastic removal and may improve intraocular lens (IOL) rotational stability.
C. Irrigation and Aspiration Tips
Coaxial I/A hand pieces come in a variety of tip angles, with a side aspiration port. A straight tip allows for easy access to cortical material 180 degrees from the main incision (Figure 15-2). However, subincisional cortex can be difficult to reach with this tip. A 90-degree tip, conversely, provides for more facile subincisional cortex removal (Figure 15-3) but can be a hindrance when approaching cortical material opposite the incision. Intermediate tips, such as at 45 degrees or “banana” shaped, can be helpful for all-purpose use. For capsular vacuuming, roughened tips or silicone tips can be used to enhance posterior capsule polishing. Some surgeons are using silicone tips for all parts of the cortical removal. In addition, disposable tips may reduce the likelihood of debris retention and clogging as can be present in reusable metal tips.
Most surgeons adapt their I/A settings based on situational and personal preference (Table 15-1). For cortical I/A, high vacuum settings allow for ease in epinuclear removal and cortical stripping. Capsular vacuum settings, however, demand much lower vacuum and aspiration rates. While capsule may still be incarcerated at these low settings, the safety margin is greatly enhanced when working near the posterior capsule with this mode. Removal of viscoelastic is usually under both high vacuum and aspiration rate settings to promote adequate irrigation of the anterior chamber.
*Dikutip dari Buku Essentials Of Cataract Surgery 2nd Ed, halaman 149-152