CONTROL AND TAME

IRST STEPS

A capsulorhexis should always be well controlled and needs to be tamed if misbehaving. This may be easy or difficult according to the situation. General principles to be followed for a rhexis were mentioned in a previous article. To make a rhexis behave, the anterior chamber (AC) should always be full of viscoelastic and the anterior capsule flat. Good visualisation is vital, if required by staining with Trypan blue (0.06 per cent) and this is especially important in cases with poor red reflex (white or brown cataracts, vitreous haemorrhage etc); paediatric and other complex cataracts. Cortex should not be churned up which can hinder visualisation. All manoeuvres should be gentle and careful.

YOUNG CATARACT

Elastic nature of the capsule, positive vitreous pressure and low ocular rigidity create a tendency for a run-away rhexis – the younger the child, the stronger the tendency. Trypan blue staining gives better visualisation and makes the capsule stiffer. Aiming for a smaller size allows a final rhexis of the desired size as the elastic capsule stretches. The first nick should therefore be made smaller than in an adult cataract. The flap is lifted and the tear always directed towards the centre of the lens to avoid a run-away rhexis. High viscosity ophthalmic viscosurgical device (OVD), (Healon5 and Healon GV) may be used to maintain space and flatten the anterior capsule. Various other techniques such as vitrectorhexis, two incision push-pull technique, Fugo blade rhexis etc, have also been described. Depending on age, a posterior continuous curvilinear capsulorhexis (PCCC) may be required.

CALCIFIED OR FIBROSED CAPSULE

Seen in some hypermature cataracts, membranous congenital cataracts or as post-traumatic sequelae – the rhexis can be started in a normal area and circumnavigated around the affected area to include it. If not possible, micro-scissors or vitrector may be used in the affected zone in which case, subsequent manoeuvres should be as described for torn rhexis.

White cataract: Mature, white capsules are thin and together with increased intra-lenticular pressure increases likelihood of tears and run-outs. Capsular staining is vital. Oblique external illumination can help visualisation. Too small a rhexis carries risk of capsule blow-out, zonulodialysis, posterior capsular rent etc. Too large a rhexis has a tendency to run away.

INTUMESCENT CATARACT

These leak and make the aqueous cloudy. An initial aspiration with a needle from the centre of the capsule before initiating the rhexis can decrease the intra-lenticular pressure as well as leakage of obscuring lens material. In case of leak, AC should be washed and high viscosity OVD refilled. Once lens material is released, intra-lenticular support for needle capsulorhexis may be inadequate and a forceps may be required to continue.

SUBLUXATED CATARACT

The loose capsule offers inadequate resistance and initiation of rhexis may be done by a sharp needle or by side port knife. Larger subluxations may require rhexis by forceps. Rhexis should be centred on capsular bag and not on the visible portion of the lens. This may be done, if required, by centring the lens by engaging it with a Sinskey hook. Rhexis may be started small and if required spiralled around to enlarge. Adequate rim should be left on dialysed side to allow engagement by capsular hooks, segments or rings. Capsular hook should never be applied on incomplete rhexis to avoid run-out.

DIFFICULT VISUALISATION

This may be because of corneal opacities, white or brown cataracts, or because of poor red glow secondary to inadequate co-axial lighting/vitreous opacities such as haemorrhage or asteroid hyalosis. Visualisation can be enhanced by capsular staining, high magnification and co-axial lighting. An endoilluminator may be used for oblique illumination in corneal opacities.

SMALL PUPIL

Various pupil dilating techniques such as pupil stretching, iris hooks, Malyugin ring etc, may be used. With experience, the rhexis can generally be taken beyond the pupillary edge safely.

Small rhexis: Small rhexes are prone to zonular disinsertion and tears intra-operatively and capsular phimosis postoperatively. It may be enlarged by spiralling around. This may be done before ending the rhexis or after IOL implantation. In the latter case, a Vannas or a micro-scissors makes an oblique cut at the rhexis margin which is then spiralled around.

RUNAWAY RHEXIS

Little's Rhexis trick is used to effect a change in direction as soon as early tendency for peripheral extension is seen. The earlier it is performed, the easier it is to retrieve. AC is deepened with cohesive OVD and the flap laid flat. A forceps grasps the flap at the very root of the tear and pulls centrally to redirect the tear inwards. Blind pulling is avoided to avoid posterior capsular extension. In this case, can-opener capsulotomy from the opposite side connects to visible rhexis margin. Surgery should be as in torn rhexis.

Argentinian flag sign: This is the classical split rhexis in a Trypan blue stained, white, mature cataract and resembles the Argentinian flag. If it occurs, it may be saved by making a nick and tearing around circularly to join the other/both ends. However, if difficult, the tear may be converted to can opener capsulotomy. Surgery should be as in torn rhexis.

TORN RHEXIS

Only a continuous curvilinear rhexis can stretch. Tensile strength of the capsule is lost in case of any discontinuity, however small. All intra-capsular manoeuvres are avoided and the nucleus prolapsed out. Slow-motion phaco is then carried out extremely carefully. However, in case of doubt or lack of experience, it may be better to convert into an extracapsular cataract extraction.

POSTERIOR CONTINUOUS
CURVILINEAR CAPSULORHEXIS

Done in paediatric cataracts and with posterior capsular fibrosed plaques. A flap of posterior capsule is raised with 26 gauge cystitome and viscoelastic instilled through the nick. The flap is then torn in a continuous curvilinear manner. It
may or may not be combined with anterior vitrectomy.

* Dr Soosan Jacob is a senior consultant ophthalmologist at Dr Agarwal's Eye Hospital, Chennai, India and can be reached at: dr_soosanj@hotmail.com