Capsulorhexis

Since the time of its description by Howard Gimble and Thomas Neuhann in 1985, capsulorhexis remains the key phase of any safe phacoemulsification procedure.

In the absence of forceps of a size appropriate for 1.4 mm microincisions, for some years the procedure had to be performed with cystotome 26 G needles, which represented some difficulties for surgeons used to Utratta or Corydon forceps.

For most surgeons wishing to transition to bimanual phaco, the capsulorhexis forceps enables perfect control of the circular and continuous cutting process of the anterior capsule by providing a good diameter while avoiding prejudicial rhexis discharge towards the equator [of the crystalline lens].

A distal control forceps, such as a vitreoretinal surgery forceps, and having a smooth tip, prevents surge upon introduction into the chamber. Larry Laks designed the Duet® bimanual capsulorhexis forceps which can be introduced through an incision of less than 1mm, with a short beak and a smooth introduction tip facilitating manipulation inside a microincision. Other short beak forceps are available on the market, such as the Verges and Fine forceps.

A viscoelastic substance combining both dispersion and cohesion agents (Rhexéal®) is particularly appropriate for use in bimanual phaco. The viscoelastic agent is injected into the anterior chamber by placing the canula at 6 o’clock in order to evacuate the aqueous humour; the pressure of the viscous substance increases pupillary mydriasis.

Most surgeons will perform capsulorhexis with a fine 23 G forceps specially designed for this highly important moment. Its beak has a cutting end that makes it possible to perform initial capsulotomy without introducing other instruments. This forceps has a retractable beak in the tip, which makes the manoeuvre more precise when gripping the capsule at the upper end of the capsulotomy.

A continuous circular incision is obtained by means of tangential traction and centripetal movements by taking back the capsular flap at its hinge at approximately every 60o of rotation under strong magnification from the operative microscope. Rotation can be clockwise or anticlockwise depending on the surgeon’s customary practice. It is sometimes difficult to turn the capsulorhexis when approaching the forceps entry site because of the reduction in mobility of the latter through the incision. The forceps can then be introduced through the other incision and the rhexis can be completed with the non-dominant hand. This bimanual strategy, which seemed very bold at first, in fact enables better visualisation of the end of the capsulorhexis and also makes it possible to anticipate use of both hands in the bimanual technique.

The size of the capsulorhexis conditions the surgery and the post-operative sequelae. A capsulorhexis that is too small makes surgery more difficult, with an increased risk of zonular disinsertion and capsular rupture during surgery. Special care needs to be devoted to the edge of the rhexis during phacochop so as not to injure it. For safe use of choppers, the minimal recommended capsulorhexis size is 5 mm. In the post-operative phase, a small capsulorhexis creates a risk of capsular phimosis that is prejudicial to the patient’s visual recovery.

With narrow pupils, i.e. in practice less than 5 mm before the injection of the viscous agent, Prolene iris retractor hooks should be used without hesitation to facilitate capsulorhexis and the further development of the procedure.

With white cataract or poor visualisation of the anterior capsule, visual control must be improved by means of capsular staining. Injecting trypan blue (BCC®) at the beginning of the procedure before the viscoelastic agent facilitates visualisation of the capsular incision.

In the event of leakage from the capsulorhexis towards the periphery, additional injections of viscous agent enable the surgeon to retract the pupil and again to visualize the end of the rhexis, to repair the capsule and to restore depth to the anterior chamber. In most cases, taking back the flap with the forceps together with a centripetal action enables the practitioner to recentre the rhexis and to continue the procedure as planned.

In other cases, taking the capsulorhexis back up in the opposite direction from the initial opening ends with the formation of a rupture line, so that it is then better to convert to coaxial phacoemulsification. In fact this rupture line subjected to the strong infusion flow rate necessary for bimanual phaco creates excessive exposure to capsular rupture.