Incision

Fig. 6.43 Modified SST-USST for IFIS. The Flomax IFIS SST-USST

Arshinoff 2.7mm soft-shoulder diamond knife (Diamond Surgical Products), trying to lengthen the tunnel such that the corneal internal entry is slightly central to the papillary margin. The width of the knife is significant in that both incisions are intentionally tight in order to prevent leakage and iris prolapse.

3.The AC is then filled, through the phaco incision, with Viscoat (Alcon Laboratories, Fort Worth, TX), until the AC is about 70% full. Healon5 is then injected onto the surface of the anterior lens capsule, in the center of the AC, and it proceeds, pushing the Viscoat upwards and outwards, until the pupil stops dilating. It is important that the boundary of the Healon5/Viscoat be at the pupillary margin. This will later serve as a fracture boundary, and will help to keep the iris stable, and the pupil dilated, throughout the surgery. At this point the AC should be, over 90%, full of OVD and the eye should feel slightly firm. This step is a variation of SST.

4.BSS, or some of the nonpreserved lidocaine or phenylephrine is then injected slowly under the Healon5 layer, on the surface of the lens capsule, with the cannula aperture placed at the very center of the lens surface, to elevate the OVD soft shell, which is created above, off the lens surface, and create a water pocket on the lenticular surface which is confined to the lenticular surface, and not spilling over the iris surface. This is a variation of USST.

5.A routine capsulorhexis is then performed using a bent needle, beginning at the center of the lens, and being sure to keep the diameter of the capsulorhexis smaller than the pupil diameter. This will later act to confine the fluid flow into an area smaller than

the pupil, preventing turbulence from impacting the iris and the Viscoat layer, which would permit the pupil to constrict.

6.Hydrodissection is then performed with BSS on a 10 mL syringe with a 27 gauge hockey stick cannula, using small short pulses of BSS. As long as care is taken in performing the steps above, as well as in the placement of the BSS cannula, the BSS should be able to circulate around the lens and flow out of the eye, beneath the OVD shell, without disturbing the shell. If the OVD shell is disturbed in this step, and some OVD is lost, Healon5 is reinjected followed by BSS below it, before proceeding.

7.The Alcon Infiniti Phaco (or similar peristaltic) machine settings are adjusted to flow ≤20mL/min, vacuum ≤250mmHg, bottle height 75–80cm above patient’s eye, linear variable pulse mode. The procedure is performed using Phaco Slice & Separate or similar chopping technique, being sure to keep the Phaco tip at or below the capsulorhexis, and confining the fluid flow into the capsular bag [17]. All work is done in the capsular bag, and attempts to only engage the phaco into positions 1, 2 or 3 are made only with the phaco in the bag, and a piece of nucleus engaged. Unnecessary irrigation of the AC is avoided.

When the above steps are followed, paying careful attention to measuring the pupils preoperatively and creating tight incisions, Flomax cases become relatively routine procedures.

6.4.3 Discussion

Modern cataract surgery has brought modern challenges, due to new devices, methods, and patient medical status, and complicating systemic drugs. The recent move to smaller incision surgery, in the range of 2 mm, whether biaxial or coaxial, has changed our rheologic approach to phacoemulsification, but renewed attention is needed to understand what we are trying to do rheologically in different circumstances, and how the smaller incisions affect the rheological behavior of our OVDs, both in their surgical use and in later removal. A good understanding of rheological principles, however, in our new tighter environment, which in reality is changed only slightly from 3 mm incisions, can be used to create

any physical environment that we can invent, limited only by our imaginations. Cataract surgery really is just the application of rheology. The only two factors that make a difference in phacoemulsification are phaco power modulations, and our manipulation of the flow parameters (rheology) of our surgery. Rheology is by general consensus, a difficult subject, but understanding it, and its applications, makes us much better cataract surgeons, in any incisional environment.

Take Home Pearls

ßSmaller incisions make us less dependent upon high zero shear viscosity to maintain spaces, but

once an instrument is inserted into the eye, lower viscosity dispersives begin to leak out, destabilizing the created surgical microenvironment.

ßIn special situations, with anticipated difficult OVD removal (phakic IOLs, AC IOLs), visco-

adaptives are not the best choice of OVDs.

ßPreoperative dilation test should be used for all Flomax cases. If the pupil dilates to > 6.5 mm,

the case will not be difficult. If however, it dilates to <5.5 mm, difficulty can be anticipated and the IFIS SST-USST technique is used.

ßSmaller incisions generally make OVD techniques more stable and easier to perform.

References

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