Cataract surgery can be complicated by presence of loose zonules

There are signs to look for preoperatively because zonular laxity is more difficult to detect after surgery has started.

Issue: July 2016

ByUday Devgan, MD

Loose zonules complicate cataract surgery because their laxity makes removal of the nucleus and cortex challenging and limits stability of the IOL. In some patients we are able to detect zonular laxity during the preoperative consultation. Severe laxity may result in subluxation of the cataract or marked phacodonesis, in which the cataract is seen to move or shake in response to ocular movement. Patients with visible pseudoexfoliative material on the anterior lens capsule are also at higher risk for loose zonules. Other signs may be more subtle, such as a shallow anterior chamber in the presence of a normal axial length. This may occur because the loose zonules allow the entire lens-iris diaphragm to push forward and compress the anterior chamber. A more difficult situation is to detect the presence of zonular laxity once the cataract surgery has already begun.

Beginning the procedure

Normal zonular tension allows the crystalline lens to be firmly in position with the anterior capsule held taut like the head of a drum. If we are using a sharp instrument such as a cystotome or needle to puncture the anterior capsule in preparation for the capsulorrhexis, it may be difficult to judge its tautness. When using the tips of the capsulorrhexis forceps to make the initial puncture, it is easier to detect the presence of loose zonules. Upon attempted puncture, the anterior capsule wrinkles, becomes focally depressed and resists penetration — much like an underinflated balloon (Figure 1a). This is the first sign that the zonules are weak and that the case will be technically difficult.

Creating the capsulorrhexis

At this point, the goal is to create a capsulorrhexis, safely remove the nucleus and cortex, and figure out a plan for stable placement of the IOL. In the case here, a sharp cystotome was used to puncture the anterior capsule and start the capsulorrhexis. When the forceps are used to continue the curvilinear tear, the capsule continues to wrinkle on both sides of the capsulorrhexis (Figure 1b). Care should be taken to create a round, well-centered continuous capsulorrhexis in order to maximize the options for IOL placement. The benefit to a sufficiently large capsulorrhexis of about 5 mm to 5.5 mm in diameter is the ability to bring the nucleus out of the capsule to avoid further damaging the zonules during phaco.

Cataract removal in the presence of loose zonules. Even though these forceps have sharp tips, they are unable to puncture the anterior lens capsule to begin the capsulorrhexis. The blue arrow indicates the radial wrinkles that are induced as the capsule is touched, which indicates a laxity. The yellow arrow shows the depression in the capsule, which is not taut (a). As the capsulorrhexis is performed, more wrinkles are evident at the edge (blue arrow) and flap (yellow arrow) (b). A technique to safely remove the nucleus is to first prolapse it out of the capsular bag by injecting balanced salt solution under the capsule edge (blue arrow) while making sure that the capsulorrhexis remains stationary (yellow arrow) (c). During cortex removal, the capsulorrhexis edge (blue arrow) is monitored for movement and the pupil margin is watched for a glimpse of the capsular bag equator because both are signs that the zonules are severely compromised (d).

Hydrodissection and phacoemulsification

Using balanced salt solution on a blunt 27-gauge cannula, the nucleus can be hydrodissected out of the capsular bag and brought into the anterior chamber (Figure 1c). The capsulorrhexis edge is watched to ensure that there is no movement. Dispersive viscoelastic is placed behind the nucleus to create a barrier in front of the posterior capsule, and an additional aliquot is used to further protect the corneal endothelium. At this point, the nucleus can be phacoemulsified and manually disassembled using the phaco probe and the chopping instrument. Because of the zonular laxity, be aware that when the last nuclear piece is removed, there is nothing to weigh down the capsular bag and that it may flop forward and become damaged by the phaco tip. The blunt side of the chopper can be used to keep the posterior capsule at bay during this step.

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Cortex removal

Cortex removal in the presence of zonular laxity can also be challenging because the cortex adheres to the capsule and must be stripped away, with countertraction being provided by the zonules. When quadrants of cortex are removed, the two areas to watch are the capsulorrhexis edge and the pupil margin (Figure 1d). The degree of movement of the capsulorrhexis edge correlates to the amount of zonular laxity. A lot of movement may indicate that the entire capsule will be aspirated out of the eye as the zonules break. The capsular bag equator should not be visible at the pupil margin. If it is, then there is likely minimal or no zonular tension in that meridian.

Role of capsular tension rings

Capsular tension rings may have a role in eyes with zonular loss or laxity, but they tend to work better in cases in which there is a focal defect. In these eyes, in which there are 2 or maybe 3 clock hours of zonular weakness or absence, the capsular tension ring, which is placed in the capsular bag and exerts outward pressure at the equator, can help distribute the forces evenly. However, in cases in which there is zonular laxity for all 360°, the benefit of the capsular tension ring is less certain, and it may even lead to complications.

In the next column, we will explore the options for IOL placement in these eyes.

For more information:
Uday Devgan, MD, is in private practice at Devgan Eye Surgery, Chief of Ophthalmology at Olive View UCLA Medical Center and Clinical Professor of Ophthalmology at the Jules Stein Eye Institute, UCLA School of Medicine. He can be reached at 11600 Wilshire Blvd. #200, Los Angeles, CA 90025; email: devgan@gmail.com; website: www.DevganEye.com.

Disclosure: Devgan reports no relevant financial disclosures.