Several complications could occur during the transition to bimanual phaco as a result of the related learning curve. They should be managed with great care and, ideally, prevented altogether.
Corneal complications
Superior corneal oedema is a frequent occurrence in the transition to bimanual phaco. Proper construction of the microincisions, instruments of a diameter appropriate to the width of the microincisions and minimising the number of times instruments are inserted and withdrawn during the procedure are essential measures. A Polysiloxane antioedematous collyrium will help resorb extensive oedemas.
Corneal burns can be prevented by avoiding incisions that are too tight around the phaco probe, by minimising US time and power and by using cold BSS at 4°C to irrigate the cornea. Fortunately such burns remain exceptional, at a rate of approximately 1/1000 according to Olson. If corneal burns do occur, it will be necessary to suture at the end of the procedure in order to prevent leakage.
Tears in Descemet’s membrane are linked to improper use of the phaco probe, which should be introduced with the bevel oriented downwards. Reapplying the Descemetic flap will be facilitated by injecting an air bubble at the end of the procedure.
Iris complications
In the event of mydriasis of less than 5 mm before the injection of the viscous agent, Prolene iris retractor hooks should be used without hesitation to facilitate the procedure, preventing injury to the iris caused by the phaco probe during aspiration or emulsification manoeuvres.
A hernia of the iris can occur with incisions that are made too far posterior, or are too short or too wide. The likelihood of hernias is increased by the significant irrigation pressure required by bimanual phaco. Reintegration often takes place at the end of the procedure, using viscoelastic agent, and only exceptionally requires peripheral iridectomy.
Complications during emulsification of the nucleus
If the US probe should not properly emulsify the nuclear fragments, verify that it is properly screwed onto the handpiece, that the aspiration is not plugged up by a piece of nucleus, and that the US power is not set too low by reference to the hardness of the nucleus.
During emulsification of the nucleus quarters the practitioner should also consider increasing the pulse per second frequency to reduce the rebound effect that moves the nuclear fragments away from the US probe. This measure makes it possible to both regain emulsification efficacy and reduce heating in the US tip.
Posterior capsular rupture
The practitioner must realise as soon as possible when a rupture of the posterior capsule occurs during bimanual phaco in order to prevent a drop of the nucleus into the vitreous body. The following signs call attention to the potential presence of vitreous substance in the anterior chamber: Sudden collapse of the anterior chamber, increase in pupillary diameter, difficulties in nuclear rotation and finally, inefficiency of aspiration accompanied by an abnormal downward shift of the nucleus.
Bimanual phaco is performed with a closed eyeball by means of leakproof microincisions that reduce the tendency for vitreous substance to enter the anterior chamber. Vitrectomy is not necessary in the event of capsular rupture without egress of vitreous substance. It is nonetheless necessary to reduce infusion pressure and to continue the procedure with a reduced aspiration rate to prevent a hernia of the vitreous body from developing.
On the other hand, leakproof microincisions facilitate bimanual anterior vitrectomy in the event of egress of vitreous substance into the anterior chamber. The practitioner must avoid the use of anterior chamber vitreotomes with coaxial infusion, which necessitate the enlargement of the microincision, aggravating the capsular lesion, hydrating the vitreous substance and overall promoting prolapse of the vitreous body into the incision. Bimanual vitrectomy with separate infusion as in vitreoretinal surgery makes it possible to cut the vitreous body in the posterior segment with the vitreotome while the infusion remains in the anterior chamber without aggravating the situation.
When the nucleus falls into the vitreous body
With a large rupture of the posterior capsule, the nucleus can fall into the fundus. Nuclear fragments and the epinucleus are highly antigenic and would cause a phacoanaphylactic reaction requiring their extraction. It is then necessary to perform pars plana posterior vitrectomy using perfluorocarbon liquid to cause the ectopic fragments to float up to the surface and to remove them from the retina. Cataract surgeons who are not familiar with these techniques should refer patients to a retina specialist.
Expulsive haemorrhage
Expulsive haemorrhage is a rare occurrence in bimanual phaco, as the microincisions prevent the protrusion of the intraocular content associated with this frightful complication. Its onset is announced by a abrupt darkening of the pupillary reflex and sudden ocular hypertonia. It is then necessary immediately to withdraw the intraocular instruments, quickly to suture the incisions and to perform two posterior sclerotomies at 4 mm from the limbus.
When is a changeover recommended ?
- When faced with a rupture line in the capsulorhexis, it is best to convert to coaxial phaco or extracapsular extraction.
- When faced with a rupture of the posterior capsule during hydrodissection, with the nucleus falling into the vitreous body, it is necessary to convert to pars plana vitrectomy with the use of perfluorocarbon liquid.
- In case of capsular rupture with an egress of vitreous substance early on in the procedure when creating the grooves, the surgeon will need to convert to manual extracapsular extraction using a Snellen lens loop.
- When faced with a capsular rupture with a migration of nuclear fragments into the vitreous body, it is necessary to convert to posterior vitrectomy with the use of perfluorocarbon liquid.
- If a capsular rupture with egress of vitreous substance should occur at the end of bimanual phaco, it will be necessary to carry out bimanual anterior vitrectomy.
