Article

SPOTLIGHT ON TECHNOLOGY & TECHNIQUE

In pursuit of a perfect capsulorhexis

The Zepto precision pulse capsulotomy device provides a promising alternative.

All surgeons strive for a continuous, if not perfect capsulorhexis in cataract surgery. We intuitively expect more consistent effective lens position, less tilt and phimosis when the optic edges symmetrically and minimally overlap. To referral sources, seeing pristine capsulotomy at the slit lamp bespeaks care and mastery. Some eyes with intralenticular pressure, pediatric cataracts, miosis and zonular pathology challenge even the most experienced surgeons amongst us. Complications at this early stage of surgery can lead to a cascade of undesirable complications and repercussions.

These realities underlie the initial enthusiasm for femtosecond laser-assisted cataract surgery. Those who haven’t adopted are hampered by:

  • Reports of capsular tags and breaks with a weakened edge compared to manual rhexis, most likely due to the postage stamp application of femtolaser energy with micromovements of the target tissue.
  • The substantial financial investment required, which demands a larger surgical suite footprint, maintenance and significant per-case fees.
  • Logistical burdens of the technology, creating inefficiency.
  • The unnecessary pressurization of the eye and sometimes disturbing appearance of subconjunctival hemorrhage.
  • Chair time and complexity, as well as justification of billing.

These factors have spurred the development of alternate technologies to automate this critical step in phacoemulsification, level the playing field for inexperienced surgeons and deliver more consistently optimal outcomes for complex cases even in the best of hands.

Of the modern devices, the first to the U.S. market is the Zepto precision pulse capsulotomy (PPC) (Mynosys). It was CE marked in 2015 and recently FDA approved.

HOW IT WORKS

The working end of the Zepto PPC consists of a disposable round silicone suction cup with an elastic nitinol ring that delivers nonthermal electrical waveform pulses to the anterior capsule instantaneously for 360 degrees. This causes a rapid phase transition of the trapped water molecules and leads to the capsulotomy effect.

The surgeon introduces it through a 2.2-mm incision as it is collapsed by a central rod. Then, the surgeon withdraws it with one finger while holding the handpiece, which allows expansion of the ring to its original circular shape once within the anterior chamber. The PPC can be centered on the coaxially sighted visual axis under topical anesthesia or placed as desired to center the capsulotomy as in the case of a subluxated crystalline lens. The edges of the ring can be insinuated under a miotic pupil to create the ideal capsulotomy opening beyond the pupil edge when indicated, but it fits within the space provided by available pupillary expansion rings. Because of its uniform and 4-millisecond pulse delivery, the Zepto PPC is safe for intumescent lenses without fear of capsule edge escape or lens milk causing incomplete tissue lysis.

The Zepto energy-producing unit is a small console — its plug requires only a standard wall outlet. Depressing the power supply first activates suction to oppose the anterior capsule tissue to the ring. After establishing suction — assessed by observing microbubble movement — the surgeon delivers the electrical pulse uniformly, producing a free, circular capsule cap. The learning curve is fast and minimal; less than a handful of cases.

PRACTICE BENEFITS

The device is less expensive than laser technology, and the disposable intraocular portion is anticipated to add sensibly to the per-case cost. There is no interruption in the normal flow of surgery. The device simply replaces the cystotome and/or forceps capsulorhexis maneuver, causing no change in the use of viscoelastics or the technique of hydrodissection. Unlike the femtosecond laser, the Zepto energy does not affect the underlying cortex and therefore does not require a change in irrigation or aspiration technique or the ease of removal compared to standard manual rhexis.

RESULTS

The Zepto PPC has demonstrated reliability and zonular and endothelial safety in the preclinical setting.1 The resultant capsulotomy is two to four times more resistant to tearing than either femtosecond laser or even manual capsulotomy in paired cadaver eye studies.2 This phenomenon is best explained by the appearance on scanning electron microscopy of a perfect uniform folded upward edge along the 360-degree border of the lysed tissue (Figure). Normal tissue is thus presented to any intraoperative stresses such as capsule retractors. The resultant capsular opening (5.20 mm on average) virtually always overlaps the optic edge uniformly as anticipated. In a clinical study of both routine and challenging cases, including those with corneal opacities, 6 clock hours of subluxation withstanding capsular expansion hooks, small pupils and intumescence with the Zepto showed no complications.3

Figure. This scanning electron micrograph following Zepto capsulotomy shows the smooth edge with the treated edge reproducibly folded upwards. This is considered the explanation for the increased resistance to tear even compared to manual rhexis.

ANOTHER POTENTIAL USE

The Zepto PPC is capable of hyaloid-sparing posterior capsulotomy with posterior optic capture into Berger’s space in the preclinical setting. I first performed this procedure in the postmortem rabbit eye, and it is something that I hope will change the future of standard cataract surgery. This addition to routine surgical technique, more daunting psychologically than physically, has the capacity to eliminate secondary cataract and the need for YAG laser posterior capsulotomy in all patient age groups — a truly premium procedure. The manual technique of posterior capsulotomy is well established for efficacy, safety and reproducibility. However, it is not currently within the wheelhouse of the average cataract surgeon despite its wide reaching and profound benefits.4

Once the Zepto rolls out and is widely adopted as I expect, I hope this potential off-label application will be studied and perfected possibly in the fourth quarter of this year.

CONCLUSION

Given the ongoing reduction in reimbursement, it remains to be seen whether cataract surgeons will embrace automation of the anterior capsulotomy maneuver for routine cases or reserve it for complex and pediatric cataracts. I suspect, however, that once familiar with this cost-effective device they will embrace it. OM

REFERENCES

  1. PPC; preclinical safety and performance of a new capsulotomy device. Ophthalmology. 2016; 123:255-264.
  2. Thompson VM, Berdahl JP, Solano JM, Chang DF. Comparison of manual, femtosecond laser and PPC edge tear strength in paired human cadaver eyes. Ophthalmology. 2016; 123;265-274.
  3. PPC; Initial clinical experience in simple and challenging cataract surgery cases. Waltz K, Thompson VM, Quesada G. J Cataract Refract Surg. 2017; 43:606-614.
  4. Menapace R. Posterior capsulorhexis combined with optic buttonholing; an alternative to standard in the bag implantation of sharp edged intraocular lenses? A critical analysis of 1000 consecutive cases. Graefes Arch Clin Exp Ophthalmol. 2008;246:787-801.