Finding stability in unstable lenses

March 15, 2013

Cases illustrate utility of laser system when unstable lenses are present

Take-home

One surgeon relates her clinical experience with a laser system that enhances cataract procedures, even complex cases involving patients with unstable natural lenses.

 

By Anna Fakadej, MD; Special to Ophthalmology Times

A need for technology among surgeons that significantly improves their ability to perform cataract procedures always exists, even in complex cases involving patients with unstable natural lenses.

One such platform (Catalys Precision Laser System, OptiMedica) combines a femtosecond laser, integrated 3-D optical coherence tomography (OCT) imaging, and pattern-scanning technology. The system can create a precise, free-floating capsulotomy successfully and quickly and soften the cataract into tiny fragments, allowing complete removal of the natural lens without loss of nucleus posteriorly.

The rationale for using the system in these cases is multifactorial. In addition to an ability to create precise and effective incisions, it includes a number of key features that improve surgeon experience and confidence during the procedure. The liquid optics interface gently stabilizes the patient while providing a clear optical path for the laser. The integrated 3-D OCT imaging provides a sophisticated view of ocular structures preoperatively, which helps prevent unwelcome surprises during surgery and better prepares the surgeon for what he or she will find.

In addition, the system’s customized 3-D treatment mapping creates safety zones that ensure laser pulses are applied only to the intended areas.

Case background: +6 nuclear sclerotic trauma-induced subluxated lens

The utility of the system when unstable lenses are present can be illustrated by several cases. The first was a 72-year-old male who had a +6 cataract with trauma-induced subluxated lens and zonule loss in one eye. Although the lens was not mobile, it was unstable. Thus, the best place for the lens implant was the capsular bag, if it could be preserved.

Another consideration was the risk that the lens might completely dislocate during surgery. I concluded that using the laser would soften and break the lens into such small, well-defined fragments that a retinal specialist could then safely remove with little difficulty if dislocation did occur during ultrasound phacoemulsification due to the loose zonules.

In addition, the patient was elderly and had multiple medical problems that hindered his ability to lie still for the prolonged time required for a cataract procedure. Being able to create an intact, perfectly round capsulotomy with a softened nucleus with the system was an option that would both decrease the time of surgery and improve its safety.

Case outcome

During preparation for surgery, the integrated OCT revealed that the lens was partially tilted into the anterior chamber, something that had not been apparent in previous examinations. These detailed anatomical images were helpful in planning the surgery because they confirmed the location of zonular weakness. The system was able to compensate the applied lens softening treatment for the subluxated lens and fully complete the capsulotomy without attachments in less than 4 seconds.

The lens material was very dense (a +6 nuclear sclerotic cataract), but since the nucleus had already been softened and fragmented, a lower ultrasound phacoemulsification power could be used to remove the lens. The entire nucleus and all of the cortical material were removed with the bag remaining intact and without capsular or iris hooks. However, the zonules tore when the capsular tension ring was inserted, a result of the bag’s inherent weakness, and the IOL could not be placed in the bag.

The patient underwent a vitrectomy, and ultimately his postoperative best-corrected visual acuity (BCVA) was 20/100 due to retinal pathology.

The laser-produced capsulotomy was far less traumatic to the zonules than a manual procedure would have been. In this situation, even gentle pulling for the capsulorhexis would have been detrimental since the patient had 4 to 5 clock hours of zonule loss. Capsular and iris hooks also would have been needed to hold the lens in place, and a tension ring or suture segment probably would have been needed midway through phacoemulsification.

However, doing so would have made it much harder to remove the cortical material. All of these steps would have lengthened what proved to be an exceptionally long case-2 hours and 15 minutes-even with the femtosecond laser. In addition, a higher level of phacoemulsification power also would have been necessary, increasing the risk of energy damage and tissue injury.

In summary, the treatment helped identify a surgical plan for the dense subluxated lens in advance of entering the eye and provided extra control and safety for a very challenging case.

Case background: bilateral nuclear sclerotic cataract with phacodonesis

The second and third cases involved a male patient aged 56 years. His left eye had a 4 nuclear sclerotic (NS) cataract with phacodonesis, and the right eye had a 3.5 NS cataract, also with phacodonesis.

A work-up exploring several possible causes of the phacodonesis was negative, and since the patient denied any history of trauma, the reason for the instability was never determined. In clinical examinations, all zonules appeared to be present. It was likely that increased instability would have led to lensectomy via vitrectomy, and the patient agreed to the cataract procedures using the system.

Case outcome

The system’s OCT clearly demonstrated that both lenses were tilted into the anterior chamber and that they were not actually subluxated and could be safely softened. Since the nucleus was extremely dense in both eyes, it would have been difficult to phacofragment the quadrants with a traditional manual ultrasound technique via a posterior chamber approach.

The system successfully completed the capsulotomy and nuclear fragmentation in both eyes, creating a completely free-floating capsulotomy on each eye in less than 4 seconds. Liberal safety zones were programmed for both eyes.

In the first eye, a capsulotomy was created and the nucleus was softened enough for the entire lens, including cortical material, to be removed with the capsular bag intact. The patient coughed during lens fragmentation, which triggered the force sensors on the system to stop treatment safely and release suction on the patient. The capsulotomy was complete but lens softening was not completed. During the challenging intraocular procedure, the patient coughed again during implantation of a tension ring and the bag collapsed. As a result, an anterior chamber IOL was implanted. Although a full treatment was not possible, the capsulotomy was free-floating because of the short treatment time. With other laser technology requiring a longer treatment time, the capsulotomy might not have been completed, and the case would have been more complex.

The entire lens of the second eye was successfully removed, and the IOL was placed in the capsular bag with a tension ring. The grid-softening pattern in this patient’s first eye was 350/350, but because the patient had squeezed his eye during the first procedure, a 500/500 grid pattern was used in the second eye to lessen the amount of laser treatment. Surgery on the first eye lasted 1 hour, 15 minutes; the second surgery was completed in 45 minutes.

At last examination, the patient’s BCVA was 20/40 in the first eye and 20/20 in the second. IOP was within normal limits in both eyes, and at 6 months the IOLs appeared to be stable.

Summary

In all three of these cases, surgery had to be approached with exceptional care and caution due to the instability of the lens. Prior to firsthand laser cataract surgery cases with phacodonesis and subluxated lens, it was unclear whether the lens instability would cause skip areas in the capsulotomy or incomplete lens softening. When the lens is moving in the eye, a laser could theoretically penetrate too deeply. However, I did not have these laser-related complications in these difficult cases. Even in a lens with missing zonules, the system performed precisely and accurately, correctly compensating for the tilted lens and creating a safety margin for the capsule. The laser’s performance was impressive.

In some settings difficult cases, such as the ones described above, may be assigned to less experienced surgeons. The system will make these cases easier for surgeons at every level of experience, improving results by eliminating inconsistent manual steps and making cataract surgery more precise and reproducible.

Anna Fakadej, MD, FACS, FAA, is a refractive cataract surgeon in practice at Carolina Eye Associates, Southern Pines, NC. She may be reached at 910/295-2100; anna_fakadej@carolinaeye.com. Dr. Fakadej did not indicate a financial interest in the subject matter.