Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001

222 THE ART OF PHACOEMULSIFICATION

•It is not unusual to find quite dense plaques on the posterior capsule in some of these eyes. Some will polish sufficiently with a Kratz scratcher or similar device to avoid the need for further action until postoperative vision has been assessed. Others are so dense that the solution of choice is to perform a posterior capsulorrhexis. Sometimes these plaques actually are part of the posterior

capsule and when they abraded will come away leaving the hyaloid face exposed.

If as is suggested above a rhexis break has occurred, great care must be exercised in choice of IOL and site of implantation.

•Plate haptic lenses are not recommended as they may during unfolding extend the break. Even a 3-piece silicone IOL as it unfolds may do the same, due to the explosive nature of the release from the implanting device. However the new unfolder (Allergan) appears to overcome many of these difficulties though the authors would still recommend that the SI40 IOL with PMMA haptics is used.

•A lens which unfolds slowly and which is made from a material that causes minimal capsular contraction such as the AcrySof MA60 (Alcon) is ideal (Fig. 21.15). The lens is positioned with haptics at right angles to the break in the rhexis.

•If there are doubts about the status of any rhexis rim break, implant the IOL into the ciliary sulcus any IOL of sufficient length (greater than 12.5 mm) will suffice. The lens optic can then be pushed into the bag to give best stability.

Postoperatively

The majority of these patients have a normal postoperative course, they are placed on whatever the surgeon usually prescribes as medication. These eyes are probably more likely to exhibit corneal disturbance on the first postoperative day as greater intraocular manipulation than usual has been necessary.

Inderjit Singh

I N T R O D U C T I O N

Phacoemulsification cataract extraction has come a long way since the late 60s. There has been a considerable improvement in technique and in the equipment we use. Advances in software programs that allow the equipment to respond more intelligently and more precisely have also made the procedure safer. Phacoemulsification cataract extraction in routine cases can be difficult enough because conditions can change very rapidly which the surgeon has to consciously try to control. The technique becomes even more difficult to do in some situations which would be considered as difficult cases or challenges that the surgeon will meet at times. It is very important to have mastered a very structured and precise technique to be able to successfully operate on these challenging cases with minimal complications. The routine phacoemulsification technique a surgeon uses must be adaptable enough to use in these challenging cases without any major change.

General Considerations

The incisions used in these challenging situations can either be a clear corneal self-sealing wound or a scleral tunnel self-sealing wound. A two-ended technique is advocated for the phacoemulsification. In spite of a number of new techniques for the phacoemulsification itself, the technique that is most predictable, precise and repeatable is some form of nuclear divide and conquer.

It is important to minimize the excursion of the phaco tip in these cases and of all the various techniques, the split and lift technique is probably the most useful (Fig. 22.1). This technique allows the phaco tip to work within a small

In all the situations the smaller the phaco tip the more control there is within the eye and it also affords much better visualization within the eye of all the tissues. It is strongly recommended in these situations to use a microtip whether it is straight or curved. The microtip has a diameter of 0.9 mm compared to the larger tips of 1.1 mm. The port size is decreased by 48% and presents a larger metal surface. This improves efficiency in cutting by increased cavitation. The smaller port also decreases surge and minimizes collapses of the anterior chamber (Fig. 22.4).

Fig. 22.4: Curved micro tip for phacoemulsification.

Tip is 0.9 mm diameter. Bent tip more efficient

in these situations it is highly recommended to use some form of a curved tip, preferably a 90o tip which has been found to be most helpful (see Section on Small Pupils).

PHACOEMULSIFICATION IN DIFFICULT CASES 227

Fig. 22.6: Small pupil with posterior synechiae. On long-term miotics

Fig. 22.7: Iatrogenic distorted pupil. Note the exposed edge of IOL

Pupil Enlarging Surgery

There have been many methods through the decades to overcome small pupils.

•Keyhole iridectomy was the only method used particularly or extracapsular cataract extraction (ECCE).

•Iris sphincterotomies.

•Iris sutures

•Modified iris tucking maneuvers.

•Modified radial iridotomies.

All the above methods have distinct disadvantages which included distorted pupil and increased bleeding from the pupillary edge during surgery and postoperatively. Theoretically there is an increased breakdown of blood-aqueous barrier causing increased inflammation and increased instances of cystoid macular edema (CME).

Some of these methods also required suturing of the cut pupils and this would involve extramanipulation with added risk of retraction syndromes. These methods also do not work very well on very small pupils (Fig. 22.8).

Fig. 22.8: Sutured keyhole iridectomy. Note trauma to iris tissue

Pupilloplasty Surgery

These methods involve using specially designed sutures that require multiple passes through the eye. Some of these methods also require sclerotomy. Again this method involves considerable manipulation of the iris tissue.

Iris Retractors

A number of iris retractors have recently come onto the market to keep the pupil enlarged. These include the following: De Juan flexible iris retractors (Grieshaber, Switzerland) Mackool iris retractors (Storz Instruments, St. Louis, Missouri) (Figs 22.9 and 10).

There are a number of problems that can occur with the use of the iris retractors. The proper placement of the paracentesis for these iris retractors is very important and the pupil has to be enlarged in a gradual and controlled fashion to prevent complications. The complications can occur with the use of iris retractors and include: (i) movement of the iris too anteriorly which can result with the

PHACOEMULSIFICATION IN DIFFICULT CASES 229

Fig. 22.9: Iris retractors for small pupil phaco

Fig. 22.10: Iris retractors. Note the number of retractors that may be required

phacoemulsification tip and instruments, (ii) the tendency to create a scaffold of iris tissue can occur if the corneal entry site hooks are too long, (iii) thermal or mechanical injuries can occur to the iris if the iris is moved too anteriorly by the retractors, (iv) tenting of the iris can occur intraoperatively if the position again is incorrect, and (v) too rapid a dilatation of the pupil may cause tearing of the pupillary sphincter.

PHACOEMULSIFICATION IN DIFFICULT CASES 231

Figs 22.11 to 22.14: Graether pupil expander (Eagle vision, Memphis Tennessee). Note: the strap engages the pupillary margin and keeps the pupil enlarged. The phaco tip is passed over the strap bridging the gap in the ring

Pupil Stretching Devices

These are appliances that can be temporarily placed inside the eye to stretch the pupil, such as:

•Hydroview Iris Protector Ring (Escalon-Trek Medical, Skillman, New Jersey).

•Graether Pupil Expander (Eagle Vision, Memphis, Tennessee) (Figs 22.11 to

14).

These external appliances, however, are not without their problems and possible complications. They take time to apply and because of the increased instrumentation within the eye, may cause endothelial damage. There is also significant increase in the manipulation of the iris to apply these devices successfully.

Pupil Stretching Techniques

Several methods have been described to stretch a pupil in order to enlarge it. Currently pupil stretching techniques are possibly the safest and most easily applied techniques for enlarging the pupil. The advantage of this technique is very small pupils with dense posterior synechiae that can easily be enlarged with this technique.

This technique can also be combined with small partial sphincterotomies at the pupillary margin, especially in those small pupils that have got dense fibrotic rings. The instrumentation that is required for this technique is now fairly simple and they include push/pull iris manipulation hooks, e.g. Kuglein hooks, the Graether Iris Collar buttons (Storz Instruments, St. Louis, Missouri). In a very small fibrotic pupils where sphincterotomies are required, intraocular scissors that have blades that can be rotated around 360 degree axis can be used, e.g. Sutherland scissors (Grieshaber, Switzerland) (Figs 22.15 to 17).

It is also very important to use a very retentive type of viscoelastic material which by itself can act as a tamponade to keep the pupil enlarged, e.g. Viscoat (Alcon, Fortworth, Texas).

It is not necessary to stretch the pupil in several directions. In most instances stretching from 6 to 12 O’clock is more than sufficient, however where there are numerous posterior synechiae a horizontal stretching in the 3 to 9 O’clock