Hydro manoeuvres are essential basic techniques in modern phacoemulsification (PEA). They use fluid to separate tissue layers within the lens, facilitating nucleus mobilization and removal.
The term hydrodissection was introduced in 1984. It was described as a method to inject irrigating fluid and separate the lens nucleus from the cortex in planned extracapsular cataract extraction (ECCE). Later, multilamellar hydrodissection, involving injection into multiple layers, was reported. Hydrodelineation and cortical cleaving hydrodissection were also developed.
The main purposes of hydro manoeuvres are as follows:
Hydrodissection and hydrodelineation are easily confused, but they involve different layers.
Hydrodissection
Layer separated: Between the lens capsule and the cortex
Purpose: To free the cortex-nucleus complex from the capsule, allowing the nucleus to rotate freely within the capsule
Confirmatory finding: A fluid wave that spreads around the posterior capsule
Effect: If cortical cleavage is successful, separate cortical removal may become unnecessary
Hydrodelineation
Layer separated: Between the lens nucleus (endonucleus) and the epinucleus (perinuclear cortex)
Purpose: To separate the endonucleus into a smaller piece, facilitating nuclear management
Confirmatory finding: A circumferential golden ring along the boundary between the endonucleus and epinucleus (golden ring)
Effect: The epinucleus acts as a protective cushion for the posterior capsule, preventing posterior capsule rupture
If only hydrodissection is performed without hydrodelineation, the perinuclear cortex is also divided during nuclear chopping. Nuclear fragments may adhere to the cortex, making it difficult to bring them to the center. When both are performed, the perinuclear cortex remains undivided and acts as a cushion during ultrasound manipulation.
Hydrodissection is a procedure that separates the lens capsule from the cortex. Hydrodelineation is a procedure that separates the nucleus from the epinucleus. They involve different layers, and both play important roles in nuclear management and posterior capsule protection.
Hydrodissection uses a syringe with a cannula.
This is the most widely used technique. The steps are as follows:
The same maneuver may be repeated in the opposite distal quadrant. If the nucleus can be easily rotated with the cannula, hydrodissection is successful.
In very soft or very hard cataracts, it may be difficult to find the appropriate cleavage plane.
The sign of success is the observation of a fluid wave spreading around the posterior capsule. If the nucleus can be easily rotated with the cannula after the maneuver, sufficient separation has been achieved. In hydrodelineation, the appearance of a circumferential golden ring is the indicator of success.
Although hydrodissection is a basic technique, improper performance can lead to serious complications.
Posterior Capsule Rupture
Cause: Increased intracapsular pressure due to excessive fluid injection.
Prevention: Avoid excessive irrigation. Be especially careful when operating through a side port, as OVD does not leak out and intraocular pressure rises sharply.
Management: If capsular block occurs, relieve intracapsular pressure by trenching or chopping.
Irrigation Fluid Misdirection Syndrome
Cause: Irrigation fluid passes through the zonules and breaks the anterior hyaloid membrane, flowing posteriorly.
Symptoms: Anterior chamber shallowing due to ciliary block.
Management: Mild cases may resolve after waiting about 10 minutes. Severe cases may require vitrectomy.
Anterior Capsule and Iris Complications
Anterior Capsule Tear: A small continuous curvilinear capsulorhexis can cause a crack in the anterior capsule when a hard, large nucleus is dislocated forward.
Iris Prolapse: More likely in cases of intraoperative floppy iris syndrome (IFIS) or shallow anterior chamber.
Nucleus Dislocation into Anterior Chamber: Gently reposition into the capsular bag and perform nuclear reduction if necessary.
Capsular blowout is more common in cataracts with a fragile posterior capsule. Risk is high in posterior polar cataract, after vitrectomy, traumatic cataract, and also in femtosecond laser-assisted cataract surgery (FLACS) where gas is trapped in the capsular bag. Characteristic findings include the “pupil snap sign” and nucleus drop.
Hydrodissection is contraindicated in posterior polar cataract. Due to adhesion between the posterior capsule and the opacity, there is a very high risk of posterior capsule rupture from increased intracapsular pressure. Instead, perform hydrodelineation to separate the nucleus from the epinucleus. Proceed carefully with low aspiration pressure and low aspiration flow rate. See the section “Management of Posterior Polar Cataract” for details.
This technique uses the dynamic irrigation pressure from the phaco tip sleeve irrigation ports instead of the conventional cannula-based hydrodissection.
The main advantages are as follows:
Irrigation hydrodissection contributes to the minimally invasive nature of all cataract surgeries, including difficult cases such as zonular weakness, shallow anterior chamber, intraoperative floppy iris syndrome, microphthalmos, fragile posterior pole, hard nucleus, and anterior capsule tear.
This technique requires specific machine settings; standard settings may not achieve sufficient effect.
| Surgical System | Aspiration Method | Irrigation Pressure |
|---|---|---|
| Signature PRO | Venturi | 60 cmH₂O |
| Centurion | Peristaltic | 36 mmHg |
| INFINITI | Peristaltic | 60 cmH₂O |
The procedure consists of two steps.
For posterior polar cataracts, hydrodissection is contraindicated because the posterior capsule is adherent. Instead, perform hydrodelineation to separate the nucleus from the epinucleus.
The surgical device requires low aspiration pressure and low aspiration flow settings, and the surgery time is longer than usual. If the nucleus hardness is grade 2–3, standard PEA is selected; if the opacity is large and grade 3 or higher, intracapsular cataract extraction with intraocular lens suturing may be considered.
Reported techniques for posterior polar cataracts include the posterior capsulorrhexis method, inside-out delineation method, bimanual method, layer-by-layer method, and oval capsulorrhexis method.
The hydro-infusion method maintains a constant anterior chamber volume in a closed eye, greatly reducing the risk of complications such as anterior chamber collapse, intraocular pressure spikes, and IMS that occur with conventional methods. It can also be applied to difficult cases such as zonular weakness and IFIS, contributing to minimally invasive cataract surgery.
The effect of hydro-maneuvers is based on the layered structure of the lens. The lens has a layered structure from the outside: capsule, cortex, epinucleus, and endonucleus.
In hydrodissection, irrigating solution is injected into the interface between the capsule and cortex to hydrodynamically release adhesion. In the cortical cleavage method, tenting of the anterior capsule allows efficient fluid flow between the capsule and cortex. The shear effect of the fluid removes equatorial lens epithelial cells, suppressing postoperative posterior capsule opacification 1).
In hydrodelineation, irrigating solution is injected into the nucleus parenchyma. The fluid selectively spreads along the path of least resistance at the boundary between the endonucleus and epinucleus. This separation allows the epinucleus to act as a protective layer for the posterior capsule, preventing contact of the ultrasound tip with the posterior capsule.
With a flat-tip cannula, the fluid stream is ejected as a single laminar plane, making it easier to dissect along a specific interface. With a round tip, the fluid stream becomes three-dimensional, tending to cause multifaceted and irregular dissection.
In FLACS, anterior capsulotomy and nuclear fragmentation are performed with a laser. However, if gas generated by laser irradiation is trapped within the capsular bag, intra-capsular pressure may rise abnormally during hydrodissection. For this risk specific to FLACS, the safety and efficacy of the perfusion hydrodissection method are being evaluated.
The perfusion hydrodissection method, by avoiding pressurization and collapse, is expanding its application to difficult cases. Studies are also underway on the infiltration of irrigation fluid behind the posterior capsule and its effect on the anterior hyaloid membrane, showing that intra-capsular pressure rise is suppressed compared to conventional methods.
