Commentary: Advances in anterior vitrectomy

The human crystalline lens is a biconvex structure enveloped in a thin capsular bag. The capsule is thinnest (2–4 microns) at the central posterior pole, making it vulnerable to rupture during surgery. Posterior capsule rupture (PCR), or posterior capsule rent, is defined as a breach in the integrity of this posterior capsule. Its incidence during cataract surgery has been estimated to be around 0.45%–7.9%, depending on the experience of the surgeon. A PCR can cause the vitreous to prolapse into the anterior chamber (AC) and even become incarcerated in surgical incisions. This can potentially lead to serious vision-threatening complications like retinal detachment, cystoid macular edema, and endophthalmitis.[1]

It is imperative for cataract surgeons to diagnose a PCR at an early stage and be prepared with a structured disaster plan. The most critical step in PCR management is clearing the prolapsed vitreous and removing the residual lens fragments without disturbing the rest of the vitreous.

Kasner et al. pioneered anterior vitrectomy (AV) in the late 1960s and popularized the “manual sponge and scissors vitrectomy.”[2] However, it can cause severe vitreoretinal traction and subsequent retinal breaks. Hence, automated vitrectomy is the current preferred technique. However, in the absence of modern equipment, surgeons may sometimes need to resort to the old technique. The automated AV requires instrumentation for visualization of the vitreous, performing vitrectomy, and providing infusion. The visualization of the vitreous in the AC can be facilitated with the help of triamcinolone injection or an endoilluminated infusion cannula.[3]

The instrumentation required for infusion during automated AV has undergone several modifications. Dry AV includes injecting an ophthalmic viscosurgical device (OVD) while simultaneously performing vitrectomy. However, it can lead to complications like hypotony, scleral in-folding, miosis, and, even suprachoroidal hemorrhage.[4] Although it may be used to manage a small PCR, infusion should be used for the management of a large PCR. The infusion may be either coaxial or bimanual. The coaxial device has a single instrument that contains all the components of infusion, aspiration, and cutting. Such an arrangement is similar to the phacoemulsification probe and hence is comfortable for the anterior segment surgeon. However, this approach has lower efficiency as the vitreous is pushed away from the cutter by the fluid from the irrigation port. Also, it can lead to hydration and turbulence in the vitreous, which can cause vitreous prolapse and retinal traction. Currently, most surgeons prefer the bimanual technique with a separate infusion line. The infusion line in the bimanual technique can be inserted either through the limbus or the pars plana. Similarly, the vitrector can be inserted through the limbus or the pars plana.[4] Ryoo et al. showed that the posterior approach has comparatively lower complication rates.[5]

There have been several modifications in the bimanual AV. Nanavaty et al. described the “face down” AV. The technique involves performing initial vitrectomy at and under the plane of PCR with bevel facing posteriorly followed by clearing of the vitreous from the AC. This reduces the length of traction between the cutter and the vitreous base, thereby reducing the risks of retinal tears.[6] Park et al. described the injection of air bubble into the Berger’s space before performing AV. They proposed that the air bubble served as a barrier between the OVD-filled AC and the posterior segment of the eye, preventing vitreous prolapse into the AC and lens material from dropping posteriorly. It also helps in visualization of the vitreous at the air/vitreous interface.[7] Taggart et al. described tri-manual AV, in which they separated the irrigation, aspiration, and pneumatic vitrector lines. They proposed that such a system might be advantageous in removing the remnant epinuclear and cortical material in the presence of PCR.[8]

The larger residual nucleus material can be removed from the bag by converting the surgery into small incision cataract surgery (SICS) or extra capsular cataract extraction (ECCE). On the contrary, smaller pieces can be removed with the help of either a Sheets glide or techniques like visco-shield or intraocular lens scaffold.[4]

Bausch and Lomb[9] made a recent development in the field of vitrectomy. They developed hypersonic vitrectomy (HV) that used ultrasound power to cut the vitreous. It received the United States Food and Drug Administration (USFDA) approval in April 2017, while the first human trial was performed at Dr. Agarwal’s Eye Hospital, Chennai, India. This new technology uses a single lumen needle which vibrates at a high frequency (27–31 kHz) with a linear displacement of 60 μm. This is sufficient enough to liquefy the vitreous in front of the port, which is then aspirated continuously as the port remains open permanently. This makes the process of vitreous liquefaction smooth, thus reducing the vitreous traction. Apart from its advantages in posterior vitrectomy, it can also be beneficial for management of PCR as it can be used for performing AV as well as the removal of the remnant lens material. It provides the advantages of reduced vitreous traction and incidence of transient hypotony. However, it has few disadvantages including heavy weight of the handpiece which can lead to hand fatigue as well as higher chances of ocular tissue thermal burn.[9]

We congratulate the authors for describing a case where they successfully managed a case of PCR with HV.[10] Further prospective, comparative studies with large sample sizes are required to compare the efficacy and safety profile of HV with guillotine vitrector in the management of PCR.