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TECHNIQUE

Modified hydrodissection to prevent intraoperative iris prolapse

Huynh, Michelle L. BA; Sanders, Riley MD; Sallam, Ahmed B. MD, PhD, FRCOphth

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Journal of Cataract & Refractive Surgery: December 2020 - Volume 46 - Issue 12 - p 1680-1681
doi: 10.1097/j.jcrs.0000000000000275
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Abstract

Hydrodissection is an important step of phacoemulsification surgery. This step usually consists of inserting a blunt cannula through the primary (phacoemulsification) corneal incision to inject a fluid wave of balanced salt solution under the lens capsule. As a result, the connections between the lens cortex and the nucleus are weakened and the nucleus can be mobilized within the capsular bag. A complication that can occur during hydrodissection is iris prolapse, in which a part of the iris slips through the ocular incision.1 The risk is higher in eyes with intraoperative floppy-iris syndrome that has defective iris tone, with shallow anterior chambers, or with imperfect wound construction.2,3 We describe a technique for decreasing the risk of iris prolapse during phacoemulsification surgery that relies on inserting the hydrodissection cannula through a side-port incision while simultaneously blocking the primary incision with the phacoemulsification tip.

SURGICAL TECHNIQUE

The eye is prepared and draped in the standard fashion for phacoemulsification surgery. Standard 1.0 mm side-port incision(s) and a main corneal incision (2.4 mm) are performed as preferred by the surgeon. Typically, the side-port incision is placed on the side of the surgeon's nondominant hand for access by the second instrument. The anterior chamber (AC) is filled with a cohesive ophthalmic viscoelastic device, and a 5.0 to 6.0 mm continuous curvilinear capsulorrhexis is then performed in the typical fashion. After capsulorrhexis, the phacoemulsification tip is inserted through the primary ocular wound into the AC with the sleeve and the tip occupying the main wound as usual (Figure 1). Next, the hydrodissection cannula is passed through the side-port incision using the surgeon's nondominant hand, advanced toward the lens equator opposite the wound, and then positioned under the edge of the capsulorrhexis (Figure 2). Fluid is then injected in the usual manner for hydrodissection and repeated as needed to ensure a complete wave in 1 or 2 locations as preferred by the surgeon (Supplemental Digital Content 1, Video 1, available at http://links.lww.com/JRS/A122). The nucleus is then rotated using the hydrodissection cannula or bimanually assisted with the phacoemulsification tip before the cannula is withdrawn from the AC. The phacoemulsification tip will already be in place for the next step of ultrasonic nucleus removal, and the rest of the procedure can be performed by the surgeon's usual method.

Figure 1.
Figure 1.:
The phacoemulsification tip is inserted into the primary wound prior to hydrodissection.
Figure 2.
Figure 2.:
The hydrodissection cannula is inserted through a side-port ocular incision while the phacoemulsification tip occupies the primary wound.

DISCUSSION

The Bernoulli principle states that an increase in velocity of an inviscid fluid is associated with a simultaneous decrease in pressure. As described by Allan in 1995, this principle best explains the mechanism of intraoperative iris prolapse during hydrodissection.1 During conventional hydrodissection, the fast fluid velocity caused by fluid injection in the anterior chamber results in a decreased pressure anterior to the iris root. As a result, the iris is pulled toward the incisional opening and is prone to prolapse.1 The risk of prolapse is higher if the iris tone is reduced as in intraoperative floppy-iris syndrome or if the corneal incision is too peripheral (a short wound) with little clearance between the internal opening of the corneal wound and the iris root (Figure 3).1–3

Figure 3.
Figure 3.:
(Left) Increased fluid velocity at the main wound (V2) compared with fluid velocity in the AC (V1) is associated with decreased pressure at the main wound (P2) compared with pressure in the AC (P1). There is also little clearance between the opening in the AC and the iris root (arrow). These 2 factors increase the risk of intraoperative iris prolapse. (Right) In the modified technique, the widened diameter of the phacoemulsification tip is associated with smaller differences in velocity and pressure between the opening of the AC (V2 and P2) and within the AC (V1 and P1). Moreover, placement of the phacoemulsification tip through the main corneal wound increases clearance between the opening in the AC and the iris root (arrow). These 2 factors decrease the risk of iris prolapse (AC = anterior chamber).

The proposed method for hydrodissection through a side-port incision while placing the phacoemulsification tip through the main corneal incision decreases the risk of iris prolapse through 2 mechanisms. First, the phacoemulsification tip provides a conduit for the fluid to egress from the AC and, therefore, lessens the increase in fluid flow through the corneal incision and the changes in the pressure gradient across the iris. At the same time, the more distal location of the tip inside the AC from the corneal incision provides more clearance between the opening in the AC and the iris root (Figure 3).

A limitation is that a learning phase might be associated with performing hydrodissection with the nondominant hand through the side-port incision. However, the learning curve is not steep given that cataract surgeons adeptly use their nondominant hand during several steps of surgery. It is possible to place an additional side-port incision at the side of the dominant hand in the initial learning phase or if the surgeon remains uncomfortable using their nondominant hand for this technique.

WHAT WAS KNOWN

  • Iris prolapse is a potential complication of hydrodissection.
  • The risk of iris prolapse is higher in patients with intraoperative floppy-iris syndrome (IFIS).

WHAT THIS PAPER ADDS

  • Insertion of the phacoemulsification tip into the primary ocular wound while performing hydrodissection through a side-port incision prevented iris prolapse.
  • This technique can be used routinely and might be especially useful in cases of IFIS, small pupils, or eyes with short corneal wounds.

REFERENCES

1. Allan BDS. Mechanism of iris prolapse: a qualitative analysis and implications for surgical technique. J Cataract Refract Surg 1995;21:182–186
2. Chang DF, Campbell JR. Intraoperative floppy iris syndrome associated with tamsulosin. J Cataract Refract Surg 2005;31:664–673
3. Ernest PH, Fenzl R, Lavery KT, Sensoli A. Relative stability of clear corneal incisions in a cadaver eye model. J Cataract Refract Surg 1995;21:39–42

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