HANDLE WITH CARE

Epinucleus and cortex removal is an integral part of cataract surgery, and unless done properly and carefully can lead to a posterior capsular rent in this last stage of surgery. A good cortical cleaving hydrodissection is critical for proper management of cortex. Hydrodelineation allows nucleus emulsification to be performed within a safe epinuclear shell which is then removed separately.

EPINUCEUS REMOVAL

The epinucleus is bowl-shaped and is removed in toto. The amount of epinucleus depends on the density of cataract and the depth of hydrodelineation. The softer the nucleus and the deeper the plane of hydrodelineation, the thicker the epinuclear shell. Unlike cortex which is stripped as sheets, the epinucleus breaks off in chunks.

Once the nucleus is removed, a loosened and free epinuclear bowl may be caught with the phaco probe in low vacuum and zero power, gently carouselled out into the anterior chamber (AC) and aspirated. Using high vacuum can result in break of occlusion and aspiration of small chunks of the epinucleus. If repeated at multiple points, this can convert the bowl into a plate and therefore should be avoided.

Epinucleus may also be visco-prolapsed and aspirated. Gentle but continuous injection of viscoelastic under the epinuclear bowl while gently depressing the posterior lip of the incision often allows the epinucleus to be prolapsed into the AC. If difficulty is still experienced, the irrigation/aspiration (I/A) probe may be used to remove the epinuclear shell.

This is done by gently tugging on the peripheral cortex all around using aspiration, which results in loosening of the epinucleus from all sides. Once freed and brought to the centre, it may be aspirated with the I/A probe using high vacuum (300-500 mmHg) with aspiration port facing up. In case of difficulty, the I/A probe may be nudged under the loosened and displaced epinuclear shell with aspiration port facing up.

CORTEX ASPIRATION

Bimanual I/A: This requires the construction of either one additional port 180 degrees away from the side port or two completely new ports 180 degrees apart. The main port is not used as it does not give a watertight fit around the bimanual instruments. It has the advantages of offering excellent closed chamber stability at all times, as well as being able to switch irrigation and aspiration between hands to gain 360-degree access to the capsular bag.

Coaxial I/A: The coaxial probe may also be used very efficiently, however sub-incisional cortex may be more challenging in this case. I/A probes may be made entirely of steel or may have a silicone sleeve which helps prevent wound leak. The irrigation ports must be placed perpendicular to the aspiration port and the sleeve should be adjusted to get the right amount of tip exposed. Straight, 45-degree or 90-degree tips may be used.

With the aspiration port facing up, peripheral cortical strands are engaged with low vacuum. Once the tip is completely occluded, vacuum is gently increased and the tip is moved towards the centre in order to strip the cortex as a sheet. The same is repeated at multiple points. Increasing vacuum while holding small wispy strands of cortex that do not completely occlude the tip does not prove effective, as occlusion of the tip needs to be achieved before increasing vacuum.

The port should never be facing down while aspirating cortex in order to avoid a posterior capsular rent. Blind manoeuvres should be avoided. With conventional cataract surgery, cortical strands always extend beyond the anterior capsule margin and are easy to engage, however in femtosecond cataract surgery, the laser also cuts the superficial cortex in line with the rhexis and necessitates having to go under the anterior capsule with the I/A tip in order to engage the cortex.

SUB-INCISIONAL CORTEX

With coaxial I/A, sub-incisional cortex may either be tackled first while the remaining cortex holds the bag open or may be left for last. The sleeve may need to be drawn back slightly to get better visibility and access to sub-incisional cortex, however an excessively drawn back sleeve may cause irrigation to come out of the main port while manoeuvring and this should be avoided.

Turning the aspiration port to either side helps to engage the cortex, but care should be taken to avoid shallowing of the AC and inadvertent engagement of the posterior capsule. CapVac mode used for polishing the capsule is very effective for removing sub-incisional cortex and offers a greater margin of safety. The peripheral cortex under the anterior capsule or the cortical strand on the posterior capsule may be directly engaged on this mode.

In case difficulty is still experienced, bimanual I/A can be used to easily remove the cortex. A Symcoe cannula introduced from the opposite side also serves the purpose well. Stubborn and difficult to remove sub-incisional cortex may be tackled after intraocular lens (IOL) placement. Dialling the IOL loosens the cortex. I/A may then be attempted with higher vacuum levels safely, as the IOL holds the posterior capsule down. The IOL is gently nudged towards the sub-incisional cortex with the left hand in order to push the posterior capsule away while aspirating with higher vacuum levels.

CAPSULE POLISHING

The anterior and posterior capsule can be polished to decrease the incidence of posterior capsular opacification, as well as to remove any plaques and residual lens epithelial cells. This should not be done in case of subluxated or posterior polar cataracts or with a posterior capsular tear.

CONCLUSION

To conclude, thorough and complete cortex aspiration must be aimed for as retained cortex can lead to inflammation, posterior capsular opacification, IOL decentration, and can promote capsular phimosis and cystoid macular oedema. Following basic principles of I/A allows easy management. The surgeon should have knowledge of different techniques that can be adopted in case difficulty is experienced.

Dr Soosan Jacob is Director and Chief of Dr Agarwal’s Refractive and Cornea Foundation at Dr Agarwal’s Eye Hospital, Chennai, India, and can be reached at: dr_soosanj@hotmail.com