if the cortex is cleaved from the capsular bag for 360 degrees, it is separated from the capsular bag but remains fused with the epinucleus. Therefore, the cortex is entirely removed during emulsification of the epinucleus. No irrigation and aspiration (I&A) is necessary. This eliminates the risk of ruptured posterior capsules during I&A. If the cortex is not entirely cleaved, it is usually significantly loosened from its capsular bag attachments. Hence, I&A is more easily performed. With cortical separation there is less traction on the zonules as cortex is pulled from the capsular bag during cortical aspiration. Subincisional cortex aspiration is enhanced, as it is less adherent to the capsular bag. Facilitated cortical aspiration minimizes the risk of capsular rupture during I&A. Second, less anterior segment manipulation is necessary if the capsular bag should be ruptured. This is due to the lack of need for I&A or to the necessity of minimal I&A. The risk of enlarging the tear or causing the need of increased vitrectomy is consequently decreased.

HYDRODELINEATION

Hydrodelineation is defined as the separation of the endonucleus from the epinucleus. It is generally performed immediately after hydrodissection.4 The same cannula is moved to the paracentral zone of the nucleus. It is then embedded within the nuclear substance. The cannula tip is moved forward and backward two or three times to create a track within the nuclear material. BSS is then injected slowly and firmly into the bulk of the nucleus. The BSS will find the surgical plane at the junction of the epiand endonucleus, thus creating the separation of these

FIGURE 7–3 Standard hydrodissection. Fluid wave passes between the epinucleus and cortex. Cortex is not cleaved from the capsular bag. The necessity for extensive irrigation and aspiration (I&A) with zonular traction is consequently necessary.

two entities. During the injection of BSS the surgeon will view the fluid as it separates the endonucleus from the surrounding epinucleus, creating a “ring” around the endonucleus (Fig. 7–4). The anterior chamber will deepen momentarily as BSS passes around the endonucleus and into the anterior chamber. It then shallows as the fluid advances out of the anterior chamber through the incision. Even after adequate hydrodelineation the endonucleus will not rotate independently of adjacent epinucleus and cortex.

Hydrodelineation is necessary in performing those phaco procedures requiring lens disassembly methodology.

COMPLICATIONS

Complications, which can occur during the hydrosteps, include inadequate cortical-capsular bag separation, misdirection of the fluid flow, zonular damage, tears of the anterior capsule, and tears of the posterior capsule (Table 7–1).

INADEQUATE CORTEX-CAPSULAR

BAG SEPARATION

If hydrodissection is inadequate, some areas of cortex will remain attached to the capsular bag (Fig. 7–5). Nucleus rotation will be difficult. Further hydrodissection in each quadrant for 360 degrees combined with gentle bimanual rotational forces on the nucleus, or even gentle viscodissection, will remedy this situation. Although not particularly serious a problem in routine cases, with zonular weakness such as in pseudoexfoliation, adherence of cortex

combined with rotational maneuvers may lead to further compromise of the zonules.

FLUID MISDIRECTION SYNDROMES

Misdirection of the fluid flow and tears of the zonules may occur separately or simultaneously. If the hydrodissection cannula is incorrectly placed deep to the iris but superior to the anterior capsule, the injection of BSS may pass through the zonules into the vitreous body (Fig. 7–6). Instantaneous increase of posterior segment volume, and vitreous hydration, will then cause shallowing of the anterior chamber. Subsequent hydrodelineation and phaco may become impossible. Treatment plans for this complication are illustrated in Chapter 8. The placement of the cannula or passage of BSS into the zonules may result in the severing of zonules. This may lead to unzipping of a small or large number of zonules. The ultimate outcome could be a small to large zonular dehiscence. Depending on the size and position of the zonular rent, an intracapsular support ring (Morcher ring) might be desirable (see Chapter 17).

TABLE 7–1 MOST COMMON CAUSES OF

CAPSULAR TEARS DURING HYDROSTEPS

Noncontinuous capsulorrhexis—visible or occult Pseudoexfoliation with friable capsule and weak zonules Mature cataract with poor view of the anterior capsule Relatively small rhexis in relation to maturity of the

cataract

Overzealous hydrodissection Viscodissection

Calcified posterior polar cataracts

FIGURE 7–4 Hydrodelineation. The endonucleus is separated from the epinucleus and cortex.

A second cause of both fluid misdirection and zonular damage may rarely occur. If a highly retentive viscoelastic, such as Vitrax, is utilized, the viscoelastic may impede egress of surplus hydrodissection or hydrodelineation fluid from the anterior chamber. This fluid, unable to leave the anterior chamber and under pressure, might pass through the zonules, or rupture them, causing chamber shallowing or zonular dehiscence as noted immediately above.5

CAPSULAR BLOCK SYNDROMES

In certain circumstances the lens can float anteriorally and literally seal against the capsular bag, trapping fluid, creating pressure, and tearing the anterior or posterior capsule. This is most likely to occur when the capsulorrhexis is too small for a mature cataract and, in addition, hydrodissection fluid is injected too vigorously. Fluid inflow exceeds the ability for fluid to egress. There is, therefore, a buildup of fluid behind the lens, which, under pressure, is pushed anteriorally and seals the anterior capsular rim against the nucleus. With continued hydrodissection, fluid pressure builds behind the lens until either the anterior capsule or posterior capsule ruptures (Figs. 7–7 and 7–8).6

Using dispersive viscoelastic, there is one report of the development of instantaneous pupillary block due to retained viscoelastic between the lens, capsule, and iris, acting like glue and thereupon sealing the lens to the iris. In this report unenlarged meiosis was noted to be a causative factor. Lack of recognition of this episode could lead to fluid misdirection syndromes when accompanied by continued irrigation of BSS into the anterior chamber.7

These two syndromes may be avoided if the surgeon (1) creates an adequately sized capsulorrhexis in relationship to the size and consistency of the nucleus; (2) injects fluid slowly; (3) depresses the central nucleus after hydrodissection to force fluid trapped behind the nucleus, around the equator, and into the anterior chamber, so that the posterior capsule is decompressed; and (4) depresses the posterior lip of the incision to release excess BSS and viscoelastic.8

NONCONTINUOUS CAPSULORRHEXIS

Tears of the anterior capsule, either visible or occult, occur when the capsulorrhexis is not continuous. If

FIGURE 7–6 A cannula inadvertently placed under the iris but over rather than under, the anterior capsule. Injected fluid passes into, and is trapped within, the retrolental space. As the anterior chamber shallows, intraocular pressure is significantly increased.

FIGURE 7–5 Incomplete hydrodissection. Part of the nucleus remains adherent to the capsule. The nucleus will be difficult to, or may not, rotate.

recognized, after infusion of viscoelastic, one edge of the discontinuity can be grasped with capsulorrhexis forceps, and by bringing the tear back into the capsulorrhexis, it is blended, once again creating a continuous capsulorrhexis.

Predisposing factors include:

1.small pupils making visibility of the capsulorrhexis difficult,

2.positive posterior pressure from all causes creating the vector forces that encourage the capsule to tear peripherally,

3.long axial length with excessively deep anterior chambers and weak zonules,

4.short axial length with crowded anterior chambers and the tendency for centripetal tearing,

5.pseudoexfoliation with fragile capsules and weak zonules,

6.mature white or black nucleus with poor capsular visibility and thin fragile capsules, and

7.advanced age with thin fragile capsules.

Small notches or tears in the rhexis act as weak points and focus the vector force of the expanding capsule during the hydrosteps. With the force of the fluid stream filling the bag and pushing the nucleus superiorally, the defect at the notch or tear will split outward toward the equator, stopping at the equator 75% of the time. However, 25% of the time it extends through the equator and into the posterior capsule. The surgeon will see the nucleus “pop” up into the anterior chamber. The new rent in the anterior capsule will be visible. Unfortunately, it is impossible at this juncture to know whether the tear has extended through the equator, compromising the posterior capsule. Even if the tear does not presently extend into the posterior capsule, it perhaps could extend during ensuing phaco steps. The surgeon

FIGURE 7–7 A small rhexis large cataract. The nucleus seals against the anterior capsule. Fluid egress is blocked. Increased fluid pressure causes rupture of the posterior capsule.

must therefore react to preserve the capsule and prevent enlargement of the tear.

The continuation of the procedure is performed in a manner that will allow emulsification without creating undue force on the ruptured capsule. In addition, if the vitreous face is exposed, it should be sequestered from the emulsification so as not to produce its disruption. This is accomplished by installation of a dispersive viscoelastic (Viscoat) beneath the nucleus, gently elevating it to the plane of the iris. The same viscoelastic is then placed above the nucleus to shield the endo-

FIGURE 7–8 Incomplete capsulorrhexis. Pressure of the hydrodissection causes extension of the torn anterior capsule. It is surgically observed as a “pop” when the capsule splits and the nucleus moves anteriorally.

thelium. Emulsification is then accomplished within the layers of viscoelastic. Viscoelastic is replenished as necessary to sequester the posterior capsule/vitreous face and the endothelium from the phaco procedure. Alternatively, if sclerocorneal, the wound can be enlarged for an extracapsular removal. If clear corneal, the wound can be sutured and a new scleral wound created for the extracapsular removal of the nucleus.

POSTERIOR CAPSULE RUPTURE

Rupture of the posterior capsule during hydrosteps occurs infrequently in the absence of the extension of an anterior capsular tear. It is reported to occur in 0.04% of cases.9

Predisposing factors include:

1.small pupils making visibility of the capsulorrhexis difficult,

2.long axial length with excessively deep anterior chambers and weak zonules,

3.short axial length with crowded anterior chambers and the tendency for fluid pooling collection behind the nucleus,

4.pseudoexfoliation with fragile capsules and weak zonules,

5.mature white or black nucleus with poor capsular visibility associated with thin fragile capsules,

6.advanced age with thin fragile capsules, and

7.the proportional relationship of the size of the capsulorrhexis to the size of the nucleus.

Item 7 may be of particular importance. If the capsulorrhexis diameter is too small to allow egress of hydrodissection fluid trapped deep to the nucleus, progressive expansion of the posterior capsule and eventual capsular rupture may occur.

Three unique circumstances may give rise to posterior capsular tears during hydrosteps:

1.Patients who have dense or calcified posterior subcapsular cataracts may have invasion of the posterior capsule with lens epithelial cells. Hydrodissection will tear the posterior capsule around the central plaque, creating a central defect in the posterior capsule.

2.Patients who have undergone previous vitrectomy may have an iatrogenic preexistent defect in the posterior capsule created inadvertently by the retinal surgeon.

3.The surgeon may inadvertently pass the hydrodissection cannula too far peripherally during the hydrodissection. This will result in the cannula passing through the equatorial capsular bag, splitting it. This tear may propagate into the posterior capsule at any time throughout the remainder of the procedure.