Subluxated cataract – Part 2 surgical principles to be followed in surgery
Everything you want to know about subluxated cataract surgery - Part 2
Fig A: Rhexis is initiated on the side of intact zonules and then carried around; B: A good
hydrodelineation allows easy extraction of nucleus; C,D: The bag is stabilized with capsular
hooks prior to phacoemulsification and cortex aspiration.
Prior to subluxated cataract surgery, it is important to get an informed consent from the patient regarding the risks and complicated nature of surgery, the possibility of the surgeon having to change plans intraoperatively, as well as the need for postoperative monitoring and follow-up. My last column (EuroTimes July/Aug 2016; Vol 21, Issue 7/8, pp56-57) dealt with planning and preparation for a subluxated cataract. This article deals with surgical principles to be followed in subluxated cataract surgery.
An anterior chamber (AC) maintainer may be inserted to provide continuous low flow infusion in order to prevent chamber fluctuations and shallowing of AC, both of which can predispose to extension of dialysis and vitreous prolapse. A trocar AC maintainer is easy to insert, sits tight in the incision and does not accidentally slip out.
Phaco incisions should be well constructed and leaking incisions should be avoided. They should be oriented away from the zone of dialysis to prevent extension of dialysis from movements of the phaco tip. Intravitreal triamcinolone may be used for identifying any prolapsed vitreous, and if present can be removed with a vitrector.
This is constructed with either a cystitome or a rhexis microforceps, though the latter may give better control in these tough cases. A dispersive viscoelastic can be used to cover the area of dialysis. It is often easier to initiate the tear in the area of intact zonules where the capsule offers sufficient resistance.
The initial puncture may be difficult and a bent 26-gauge needle can be used to initiate this. A laser capsulotomy may be opted for if sufficient anterior capsule is visible. Whichever the technique, care should be taken to leave an adequate rim in the area of dialysis for engagement of the rhexis by a segment or hook. One of the challenges experienced is to obtain an adequately sized rhexis, large enough to perform phaco manoeuvres, especially if the lens is only partially in the pupillary zone.
With a mid-dilated pupil, iris hooks can help carry the rhexis under the pupil. Alternatively, the cataract may be brought into better view by gently engaging and pulling on the nucleus with a Sinskey Hook. With soft nuclei, a small rhexis may be sufficient and can be secondarily enlarged later.
Hydrodissection and hydrodelineation are carried out gently, but meticulously, to free the nucleus. The cannula should be inserted carefully to avoid enlarging the dialysis. A cortical cleaving hydrodissection helps with easier removal of cortex later. Vigorous nuclear rotation should be avoided and a well-defined golden ring after hydrodelineation is generally a sufficient enough sign to confirm that the nucleus is free.
These are inserted via paracenteses and used to engage the rhexis rim for intraoperative support. More than one hook may be used.
CAPSULAR TENSION RING (CTR):
The introduction of the CTR by Hara et al in 1991 played a key role in making subluxated cataract surgery easier and repeatable. It expands and stabilises the capsular bag and redistributes forces from stronger to weaker areas. The capsule is made taut and all traction manoeuvres become easier and safer to perform.
Larger eyes require a larger CTR. Timing of insertion depends on the surgeon’s choice as well as the characteristics of the eye. It should not be implanted with an incomplete rhexis for fear of extension of rhexis. With minimal subluxation, the nucleus can be removed before CTR implantation, as the epinucleus helps in keeping the bag expanded.
However, with larger subluxations, a CTR may be inserted earlier to give forniceal expansion and to keep the bag expanded during intraocular manoeuvres. If the surgeon is unsure about being able to successfully complete surgery with an in-the-bag intraocular lens (IOL), an option is to pass a 10-0 nylon suture through the eyelet of the CTR before insertion, to allow easy explantation in case of a posterior capsular rent.
Any movement that can increase the stress on zonules is avoided. With soft cataracts, the nucleus may be gently prolapsed out, whereas with harder nuclei, a vertical chop while supporting the nucleus well with the embedded phaco probe can be used to divide the nucleus.
Sculpting should be avoided to avoid pushing on the nucleus. Supra-capsular phacoemulsification should be performed as much as possible. Slow motion phaco with low flow rate, low vacuum and low infusion bottle height is preferred. During insertion or removal of instruments from the eye, the AC should not be allowed to shallow.
The CTR can trap cortex and make its aspiration difficult. The Henderson Ring has evenly spaced indentations all around that can make cortex aspiration easier. Cortex should be pulled in a tangential manner and not perpendicular to the fornix, to prevent stress on zonules and to allow easier stripping from around the CTR. Bimanual irrigation/aspiration (I/A) is very useful for ease of access. Capsule polishing can cause the lax posterior capsule to get caught in the I/A port and repeated attempts should be avoided. Any plaque can be handled by a YAG capsulotomy at a later date.
My personal preference is to implant a three-piece IOL with the haptics aligned in the zone of dialysis. A three-piece IOL has the added advantage of easy closed chamber conversion into secondary fixation, as a glued IOL or iris-fixated IOL in case of a delayed dislocation or progression in subluxation.
Some surgeons prefer a slowly opening one-piece acrylic IOL as this allows sufficient time to place the IOL within the bag and to orient the haptics along the zone of dialysis. Centration of the IOL should be assessed. Larger optic diameter IOLs may be preferred to avoid excessive effects of minimal decentration. IOL stability in the frontal and sagittal plane should be confirmed at the end of surgery.