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Femtosecond laser eases surgery involving brunescent cataract with known zonular weakness

In this case, two types of capsule retractors were used without causing anterior capsular tears.

Issue: November 10, 2014

ByNicole R. Fram, MD

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Cataract surgery has evolved over time from large-incision intracapsular surgery to large-incision extracapsular surgery to modern day small-incision phacoemulsification, which provides optimal vision with little or no iatrogenic corneal astigmatism postoperatively.

Even with these technological advances, the complexity and surgical challenges often parallel the increased density of the cataract, making the procedure more difficult when the cataractous lens is brunescent. Potential complications associated with brunescent cataract phacoemulsification include corneal endothelial damage and endothelial cell loss, corneal entry wound site thermal burn, zonulysis, posterior capsular rupture and dropping the nucleus into the vitreous cavity. The surgical challenge increases further when there is a brunescent cataract and pre-existing zonular dehiscence that destabilizes the cataract. Hence, it is essential to have a complete preoperative assessment to help in the proper planning of the surgical approach in these complicated cases.

The application of femtosecond laser technology to cataract surgery greatly facilitates a predictable capsulorrhexis without zonular stress along with nuclear softening before phacoemulsification using phaco power modulations with lower ultrasonic energy. Such an approach, combined with capsular stabilization devices, dispersive viscoelastic endothelial protection and favorable fluidics of lowered flow rate, can provide a safer approach to managing complicated cataract cases. Present day application of advanced technology platforms can offer safer cataract surgery with a favorable outcome and a satisfied and happy patient.

In this column, Dr. Fram describes her technique in a stepwise fashion in managing complicated cataract cases with zonular weakness using femtosecond laser and phacoemulsification.

Thomas “TJ” John, MD
OSN Surgical Maneuvers Editor

Cataract surgery in the setting of zonular weakness or dehiscence can present challenges for even the most expert surgeon. Although these difficult cases can most certainly be tackled manually with great success, femtosecond laser technology may add reliability and reproducibility to these cases.

Figure 1. A patient with spherophakia variant and zonular dehiscence for 180° in both eyes presented with an early brunescent cataract in the right eye.

Images: Fram NR

The case presented demonstrates the use of the Catalys femtosecond laser (Abbott Medical Optics) to assist in the creation and centration of the capsulorrhexis and segmentation of the lens in a patient with diffuse zonulopathy and brunescent cataract.

The case

A 79-year-old woman with a history of spherophakia variant and diffuse zonular weakness in both eyes presented with an early brunescent cataract in the right eye (Figure 1). The plan was to use the femtosecond laser to achieve centration of the capsulorrhexis, as well as to fragment the lens, potentially decreasing the energy necessary to remove the lens during phacoemulsification.

The first step is to determine if the pupil dilates appropriately to use the scanned capsule option for laser capsulotomy centration. Many femtosecond platforms center the capsulotomy based on the dilated pupil. The scanned capsule option available on the Catalys laser platform is unique in that it allows for centration of the capsulotomy based on the capsule center and can result in more accurate centration in these challenging cases. If the pupil is irregular secondary to an iridodialysis caused by trauma, it may be necessary to perform custom capsule centration (Figure 2). In this case, the pupil dilated adequately, and the scanned capsule mode was used to create a 5-mm laser capsulotomy. Note the visibility of the equator of the lens confirming greater than 180° of zonular weakness (Figure 3). A 5-mm capsulotomy size was chosen based on the large brunescent nucleus and risk of future capsule contraction associated with smaller capsulorrhexis sizes in cases with zonular compromise. A lens segmentation pattern was then used to soften the nucleus to assist in lens removal.

Figure 2. An irregular pupil secondary to an iridodialysis caused by trauma.

Figure 3. The visibility of the equator of the lens confirms 180° of zonular laxity.

The “waffle” lens segmentation pattern created by the femtosecond laser can result in a decreased red reflex and anterior lens capsule visualization. Thus, trypan blue is used to stain the anterior capsule before removal of the laser-created capsulotomy. Staining the anterior capsule also enhances visualization during placement of the capsule retractors. If the capsulotomy is not free floating because of significant lens tilt, the capsulorrhexis can be completed manually to avoid unwanted anterior capsular tears.

Dispersive viscoelastic is then placed between the lens and the anterior capsule to create a potential space for capsule retractor hooks or capsular tension segments. In this case, two types of capsule retractors, MST and Yaguchi-Kazawa, were used (See video at http://video.healio.com/video/Marie-Holland;Ophthalmology). After the anterior lens capsule was secured, gentle hydrodissection with balanced salt solution and viscodissection with a dispersive viscoelastic were performed, and the lens was removed with phacoemulsification. Although the lens segmentation softens the nucleus, a brunescent lens requires a shallow groove before cracking the nucleus to avoid undue stress on the already weakened zonules.

When to place the capsular tension ring (CTR) is always a dilemma because the ring can pin the cortex and make removal challenging. A scalloped Henderson ring can be used if you need to use the CTR before cortex removal. It is important to note that the CTR will assist in cases with less than 3 clock hours of support for posterior chamber IOL centration; however, if there is greater than 3 to 4 clock hours of zonular dehiscence, fixation with a sutured capsular tension segment or Cionni ring modification is indicated.

In this case, a bimanual approach to cortical removal was used, and the bag was constantly re-inflated with a dispersive viscoelastic to loosen the cortex and push the floppy bag posteriorly. Because there was greater than 180° of zonular weakness, I elected to use two Ahmed capsular tension segments (FCI Ophthalmics) fixated 180° apart. A conjunctival peritomy was made followed by a groove 1.5 mm to 2 mm posterior to the limbus. A 23-gauge MVR blade was used to make sclerotomies 1.5 mm posterior to the limbus in the groove and 2 mm apart.

Gore-Tex suture (off label CV8 thread; TTc-9 needle) was loaded into the islets of the two CTRs and retrieved through needleless recovery through the sclerotomies with the use of MST microsurgical instruments. The segments were then placed in the capsular bag and fixated with a slip knot subsequently buried in the sclerotomy on respective sides.

Summary

This case demonstrates a challenging scenario of a brunescent cataract with known zonular weakness that was made easier by the femtosecond laser. The stability and integrity of femtosecond laser-generated capsulotomies have come into question because of recent reports evaluating light microscopy and scanning electron microscopy of laser-generated vs. manual capsulorrhexes. The concern regarding laser-generated capsulotomies is the occasional tags and bridges rather than free-floating capsulotomies that could result in anterior capsular tears if the surgeon does not carefully inspect the borders of the capsulotomy. It has been speculated that potential causes include laser misfiring, docking tilt or corneal folds causing impedance of the laser capsulotomy completion. It is suspected that changes in patient interface to avoid folds in the cornea, adjustment of spot size separation and liquid interface technology could improve the precision surrounding laser-generated capsulotomies.

Fortunately, in this case, capsule retractors were used after a femtosecond laser-created capsulotomy without consequence of anterior capsular tears. In fact, we reviewed 11 cases of laser-generated capsulotomies across two platforms (Alcon LenSx and Catalys) requiring capsule retractors and found that all cases were able to withstand the manipulation. As long as there is adequate surface area of the retractors and careful attention to not tighten the retractors too aggressively, laser-generated capsulotomies appear to sustain the challenge.