Subluxated cataract - part 1 formulating a plan and becoming prepared

A subluxated cataract may be detected during routine preoperative evaluation or diagnosed intraoperatively. Whichever the case, the surgeon needs to have a plan for management - be it continuing with surgery or referring to a more experienced colleague. This article will discuss some of the strategies that can be employed depending on the clinical scenario. The article is divided into two parts – Part 1 here deals with formulating a plan and becoming prepared. Part 2 in the next issue of this column will deal with actual surgical principles.

PREOPERATIVE EVALUATION:

Successful surgery in subluxated cataract needs proper preoperative evaluation and diagnosis. Identifying conditions with zonular weakness such as pseudoexfoliation, trauma, Marfan's syndrome, ectopia lentis, hypermature cataracts, high myopia, megalophthalmos, post-vitrectomy eyes etc, is therefore paramount as these eyes need to be handled with extra care in order to avoid increase in the degree of subluxation.

Planning should be done preoperatively based on the degree of subluxation, the density of nucleus, cause of subluxation, as well as presence of other coexisting morbidity. Presence of vitreous in the anterior chamber (AC) should be looked for. Examination in the sitting posture on slit-lamp may be misleading in some cases and with the patient in the supine position under the operating microscope, the cataract may be found to be dangling into the vitreous cavity.

Intraoperatively, the extent of dialysis may be found to be larger than originally estimated on slit-lamp and the surgeon should be prepared to change plans to deal with such an eventuality. Necessary devices, sutures and equipment such as the vitrector should always be kept ready for use if required. A thorough retinal examination should be performed in cases with a view of the fundus, and a B-scan should be performed in cases with no fundus view.

THREE CLOCK HOURS SUBLUXATION:

Subluxations that are less than three-four clock hours can generally be handled by implantation of a capsular tension ring (CTR). The timing of insertion of the ring depends on the surgical situation. Kenneth Rosenthal MD explains: “The CTR should be implanted as late as you can but as early as you must.”

It may be implanted after cortical cleaving hydrodissection using either a CTR injector or by dialling it in. Depressing the ring down to the plane of the rhexis with a Sinskey Hook just before release ensures that the distal tip enters the bag. Good hydrodissection allows easier removal of cortex later in the surgery. Though the ring provides support to all further manoeuvres, it can trap cortex, making cortex aspiration difficult. The Henderson Ring has uniformly-spaced indentations on it that makes cortex aspiration easier. The CTR may also be inserted after nucleus removal, and in case of small subluxations, may be considered after cortex removal in the non-dialyzed area.

Zonular dialysis may extend if irrigation/aspiration (I/A) is performed in the area of dialysis as the capsular bag is not expanded. Lack of forniceal expansion also results in a floppy bag which can get aspirated into the I/A port. The CTR expands and stabilises the capsular bag, redistributes forces from stronger to weaker areas, makes the capsule taut, and gives counter-traction to all traction manoeuvres. It prevents extension of the dialysis as well as dropping of nuclear fragments, epinucleus or cortex through the area of dialysis.

FOUR-SEVEN CLOCK HOURS SUBLUXATION:

Any subluxation that is more than one quadrant needs scleral fixation of the bag. This may be done through various devices that are available. The Cionni Ring has a hooked element on one side for suture fixation to the scleral wall. The insertion of the ring, as well as timing of insertion, is similar to a CTR. A 9-0 suture or a Gore-Tex suture on a needle is passed trans-camerally through the eyelet and out through the scleral wall under a flap.

The knot is tied down after centring the bag. For larger degrees of subluxation, a double-hooked Cionni Ring may be used. One or more Ahmed segments along with a CTR implantation may also be used for the same purpose. A technique started by myself for the same purpose is the Glued Capsular Hook. The hooked element at one end engages the rhexis rim, and the haptic at the other end is passed trans-sclerally under a lamellar scleral flap to be tucked into a intrascleral Scharioth tunnel made at the edge of the scleral flap.

The degree of centration of the bag can be adjusted at any stage of surgery by altering the degree of tuck of the haptic. This allows sutureless trans-scleral fixation of the capsular bag and makes surgery easier and faster than having to pass long and thin needles across the AC as with sutured devices. Suture-related complications are also avoided. Intraoperative support can be enhanced by using standard trans-limbal capsular hooks as well, which are removed at the end of surgery. More than one Glued Capsular Hook may be implanted for larger subluxations. The hook gives scleral fixation and centration and a CTR is implanted for forniceal expansion.

MORE THAN EIGHT CLOCK HOURS SUBLUXATION:

Subluxations greater than two and a half quadrants may do better with lensectomy and secondary intraocular lens (IOL) fixation with the surgeon’s procedure of choice. This may be in the form of a glued IOL, sutured scleral fixated IOL or iris fixated IOL. AC-IOL, if chosen, should be done only with proper sizing. Scleral fixation of the bag may be opted for in certain select cases.

DANGLING SUBLUXATION:

Cataract removal with bag and secondary IOL fixation is preferred.

NON-PROGRESSIVE SUBLUXATIONS:

These are particularly amenable to sutured segments or the suturelessGlued Capsular Hook technique as described above.

PROGRESSIVE SUBLUXATION:

A well centred and supported IOL after surgery can undergo progressive subluxation with time because of progressive weakness of residual zonules. Lensectomy with secondary IOL fixation is preferred to attain long-term stability of the IOL. The supracapsular glued IOL technique that has been described by the author may also be opted for.