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Laser-assisted cataract surgery can enhance safety, improve results in challenging eyes

Femtosecond laser was used in a patient with against-the-rule corneal astigmatism and pseudoexfoliation.

Issue: January 10, 2015

ByWilliam W. Culbertson, MD

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The crystalline lens is bathed in aqueous humor and held in its resting position by zonules. Any compromise in zonular integrity threatens the crystalline lens position and makes cataract surgery more challenging and prone to potential complications. To avoid any intraoperative surgical surprises, it is essential to perform a comprehensive preoperative dilated ocular evaluation to assist in proper surgical planning. A new sign, called the anterior capsular snap, can result in intraoperative anterior zonular dehiscence in pseudoexfoliation with preoperative phacodonesis. In addition to phacodonesis, iridodonesis may be the initial telltale sign of compromised zonules. An important pearl is to examine the patient preoperatively in the supine position because a lens that appears easily accessible in the upright position may fall back well beyond the reach of the operating cataract surgeon.

Zonular dehiscence and compromise can often be due to pseudoexfoliation syndrome, ocular trauma and iatrogenic surgical trauma during cataract surgery. Other causes include high myopia, Marfan syndrome, Marchesani syndrome, homocystinuria, scleroderma, porphyria, hyperlysinemia and spherophakia. The key in these cases with a destabilized lens is to perform cataract surgery with the least amount of added iatrogenic intraoperative trauma to the lens and zonules. In this regard, to minimize zonular stress, a welcome addition to cataract surgery is the application of femtosecond laser technology in performing capsulorrhexis and lens fragmentation.

In this column, Dr. Culbertson illustrates the added value of laser technology in performing difficult cataract cases.

Thomas John, MD
OSN Surgical Maneuvers Editor

William W. Culbertson

There is currently tremendous interest in the potential of the femtosecond laser to improve cataract surgery. We often herald the precision and efficiency benefits of laser-assisted cataract surgery, particularly in the setting of premium IOL surgery, but a recent case illustrates the value of laser-assisted surgery in enhancing safety and improving results in challenging eyes.

The patient was a 74-year-old woman with 1.25 D of against-the-rule corneal astigmatism and significant pseudoexfoliation. She had grade 2.5 nuclear sclerosis in the right eye; her left eye had undergone standard cataract surgery with a toric IOL elsewhere 1 year earlier. Although that procedure was performed by an excellent surgeon, the result was unfortunate. According to the operative note, the capsular bag became loose during the capsulotomy due to torn or missing zonules, capsular and iris hooks were placed, and an anterior vitrectomy was required. A toric IOL was placed in the bag. Despite being sutured to the iris, zonular dehiscence led to decentration and malrotation of the toric IOL (Figure 1), leaving the patient with monocular diplopia and great reluctance to undergo surgery in her fellow eye.

Figure 1. Despite being sutured to the iris, zonular dehiscence led to decentration and malrotation of the toric IOL implanted in the patient’s first eye.

Images: Culbertson WW

After extensive discussion with the patient about risks and benefits, I performed cataract surgery on her right eye with the WhiteStar Signature phaco system (Abbott Medical Optics). Anticipating zonular issues in this eye as well, I elected to use the Catalys femtosecond laser (AMO) for several steps of the procedure and to implant a three-piece aspheric IOL (Tecnis 9003, AMO) instead of a one-piece toric lens. The capsule was loose, as it likely had been in the first eye, but surgery proceeded differently this time. At each step, laser assistance reduced the stress on the eye.

Capsulotomy

In contrast to a manual capsulotomy that requires some manipulation of the lens capsule, the anterior capsulotomy was performed with the laser ab externo, with no stress on the zonules or capsular bag. A 4.8-mm capsulotomy was performed.

Phacoemulsification

Thanks to the laser’s optical coherence tomography imaging, the lens can be softened in a grid pattern within 500 µm of the posterior capsule. The laser also segments the lens into quadrants, so I did not need to perform chopping maneuvers that might have put the lens capsule or zonules in this eye under stress. The fragments gently separated, and I was able to elevate them out of the capsular bag and aspirate in the anterior chamber with minimal phaco energy. Venturi fluidics are ideal in this situation because they allow the surgeon to keep the tip positioned centrally and anteriorly, drawing the fragments to the phaco tip with little stress on the zonules or capsular bag. I used a capsular tension ring to support the capsule, but no iris hooks or rings were required.

IOL and astigmatic correction

In eyes with pseudoexfoliation, one can anticipate that the lens capsule might not be stable enough to keep the lens perfectly centered postoperatively. Toric IOLs are particularly vulnerable to loss of effect with any shift or decentration of the capsular bag. Therefore, I decided to correct this patient’s astigmatism on the cornea, placing paired intrastromal astigmatic keratotomy incisions with the laser. Intrastromal astigmatic keratotomy was done at the 7-mm optical zone, with the intrastromal cut through the central 70% of the cornea. The laser’s OCT imaging guidance allows us to make these intrastromal incisions easily and predictably at the time of surgery, without any patient discomfort or chance of epithelial ingrowth. The three-piece IOL provides additional stability and support for the capsule. In addition, if the capsular bag becomes loose later on because of pseudoexfoliation, the three-piece IOL would be easy to suture to the iris using the two haptics of the IOL.

Figure 2. With the help of laser cataract surgery, the second-eye surgery proceeded much more successfully, with a well-centered IOL and incisional astigmatic correction.

Results

The lens was stable and well centered (Figure 2). On the first postoperative day, the patient’s visual acuity in the right eye was 20/30 without correction and subsequently improved to 20/20 uncorrected. Moreover, within a short period of time, she found that the good vision she enjoys in that eye reduced her awareness of the diplopia in the left eye, and she is now happy with her binocular vision.

This patient, who was reluctant to undergo eye surgery at all, is thrilled with the results and tells her friends that I am a “wonderful surgeon.” In fact, I simply took advantage of the capabilities of the femtosecond laser and Venturi fluidics to reduce the stress on the zonules at every step of the procedure. Laser-assisted cataract surgery allowed me to plan adequately for this complex eye and to prospectively adjust my surgery to suit the eye, rather than reacting to problems intraoperatively.