Everything You Always Wanted to Know About…Posterior Capulsar Rent
This is the second part of a series by Dr Soosan Jacob MS, FRCS, DNB
This is the second part of a series by Dr Soosan Jacob MS, FRCS, DNB
A posterior capsular rent (PCR) should be recognized immediately since continuation of surgery can lead to various complications such as enlargement of tear, vitreous prolapse, nucleus drop, loss of capsular support (including the rhexis), and an increase in the risk of posterior segment complications such as retinal tears, detachment, and cystoid macular oedema.
Signs a PCR has occurred include sudden deepening of the anterior chamber (AC), transient pupil dilation, challenging nuclear rotation, and decreased nuclear fragment followability. Other signs include an area of clear red reflex, visible PCR margins, striae on the posterior capsule, difficult cortex aspiration, and pupillary peaking. Surgeons should be on the lookout for the presence of material such as ophthalmic viscosurgical device (OVD), cortical material or nuclear fragments within the vitreous.
The pupillary snap sign described by Ronald Yeoh refers to a sudden pupil constriction during hydrodissection and signifies a blown-out posterior capsule.
Some common principles of PCR management include maintaining AC depth by injecting viscodispersive OVD before withdrawing instruments; using viscodispersive OVD as a shield or scaffold below nuclear fragments to prevent nucleus drop as well as vitreous aspiration. Other management practices include supplementing topical anaesthesia with sub-Tenon block and/or intracameral, preservative-free Xylocaine; using slow motion phacoemulsification and irrigation/ aspiration (I/A) with low flow, low vacuum, and lowered bottle height; using bimanual I/A and appropriately directing irrigation to avoid vitreous hydration and fragment drop.
Proper vitreous management is critical and includes identifying vitreous using preservative-free intravitreal triamcinolone acetonide (IVTA) and bimanual vitrectomy. The surgeon should avoid vitreous traction at all times. Management also includes using a high cut rate and low vacuum; using the vitrector in the appropriate mode (irrigation-cut aspiration) to always cut vitreous before aspirating; using 23- or 25-gauge pars plana vitrector to alternately cut vitreous and aspirate cortex by shifting modes using the footswitch. A pars plana approach to vitrectomy is thought to have advantages as it pulls prolapsed vitreous back into the posterior segment instead of pulling more vitreous forwards as an anterior vitrectomy might.
Continuing from part one of this multi-part series where we discussed management of PCR without vitreous loss, a posterior continuous curvilinear capsulorhexis (PCCC) is a useful manoeuvre to know in cases of small, central rent without vitreous loss as it prevents any further extension of the PCR and allows in-the-bag IOL implantation. The PC is flattened using OVD, and micro forceps are used to carefully convert the tear into a PCCC.
PCR WITH RETAINED NUCLEAR FRAGMENTS AND VITREOUS LOSS
It is important to avoid vitreous traction and rent enlargement. After injecting dispersive OVD over the rent, the phaco or I/A probe is gently withdrawn. Any residual nuclear fragments are assessed and dispersive OVD is instilled behind the fragments to keep them from descending. If none have dropped into the vitreous, the priority is localising them safely in the AC over the iris to avoid nucleus drop.
IVTA-assisted anterior vitrectomy is then done to remove prolapsed, entangled vitreous before proceeding with either nucleus or cortex removal. Bimanual vitrectomy is preferred as it has advantages of 360-degree access between opposite ports and the ability to direct irrigating flow away from the rent and fragments, thus preventing vitreous hydration and increasing vitreous prolapse and fragment drop into the vitreous cavity.
Once prolapsed vitreous is removed, the nuclear fragments are emulsified using slow motion phaco. Surgeons should use either viscodispersive OVD as scaffold or, more preferably, a pre-placed IOL as scaffold.
Whole nuclei or large pieces, especially if hard, may be managed by conversion to extracapsular cataract surgery. For this, suture the phaco incision and make a separate corneo-scleral or scleral incision. Pieces are brought into the AC using a Sinskey hook. After suitably protecting the endothelium using viscodispersive OVD, use a vectis to bring them out through the new incision. Extract the pieces, then suture all large incisions before proceeding to operate under closed chamber conditions.
Complete cortex aspiration with bimanual I/A, always stripping towards the rent to avoid extension of the PCR. Constantly look for accidental vitreous aspiration and, if present, immediately stop I/A to avoid vitreous pull and risk of retinal traction and detachment. Continue I/A again only after vitrectomy. Finishing dry aspiration of the cortex is also possible using a bent cannula. Surgeons can access the capsular bag and the cortex from the posterior aspect via pars plana ports or sclerotomies created for a glued IOL. Use a pars plana vitrector in irrigation aspiration-cut mode. An anterior chamber maintainer (ACM) or a trocar- ACM (TACM; as described by Agarwal et al) may be used for infusion if desiring a second instrument in the other hand.
If the nucleus or fragments descend into the anterior vitreous, a few described manoeuvres can bring them into the AC. Posterior-Assisted Levitation (PAL) may be used to levitate a nucleus or fragment which is lying just posterior to the PC through a pars plana approach. However, this can potentially cause vitreous and retinal traction, so perform with care. PAL used with Viscata can stabilize and elevate a descending nucleus. It’s possible to use sleeveless phacotip-assisted levitation (SPAL) for an entire nucleus or fragments that dropped into the posterior segment. Finish the core vitrectomy and release the fragment completely before attempting to lift it with the sleeveless phaco probe. Brought into the AC, the nucleus is then emulsified using IOL scaffold technique or extracted after enlarging the incision. Unless well experienced, all situations with a descended nucleus are best managed by a vitreoretinal surgeon.
THE IOL SCAFFOLD TECHNIQUE
As described by Agarwal et al, a foldable IOL is pre-placed within the AC, over the iris, and under the nuclear fragments so the haptic of the IOL occludes the pupil and compartmentalises the anterior and posterior segments. Importantly, it also prevents fragment drop, vitreous prolapse, and PCR enlargement. The surgeon may remove the cortex before placing the IOL or afterwards by introducing the bimanual I/A probe under the IOL. Another approach to strip the cortext includes a posterior approach with a vitrector. The IOL is finally translocated into the sulcus or as per the surgeon’s choice of IOL fixation.
In the absence of iris support, the IOL may be pre-placed into the sulcus. If there is not adequate iris and capsular support, consider the glued IOL scaffold technique. In that case, the nucleus is brought anteriorly into the AC, and a glued IOL is fixed below the iris plane to act as a scaffold during phacoemulsification.
Dr Soosan Jacob is Director and Chief of Dr Agarwal’s Refractive and Cornea Foundation at Dr Agarwal’s Eye Hospital, Chennai, India, and can be reached at email@example.com.
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