6.1 Pupil Dilation and Preoperative Preparation

ßDecrease the vacuum setting for initial B-MICS cases to help prevent chamber fluctuations due

to post-occlusion surge. Once the flow parameters are worked out and the chamber is stable, vacuum can be gradually increased.

ßThe phaco tip is used without a sleeve, but it is useful to place a cut-off sleeve on the phaco

handpiece to prevent spraying of BSS during ultrasound. The sleeve must be cut off very close to the hub – if the stump of the sleeve is longer than about 1 mm, it can limit the phaco tip’s excursion into the eye.

ßInitially, B-MICS makes nuclear disassembly easier in some aspects and more difficult in

others. It is made easier by improved chamber stability and followability, and it is made more difficult by the bulkier irrigating choppers and smaller, more restrictive incisions. Once adjusted to the instruments and smaller incisions, however, B-MICS is a superior technique for nuclear disassembly.

References

6.1Pupil Dilation and Preoperative Preparation

Mark Packer, I. Howard Fine,

and Richard S. Hoffman

Core Messages

ßManagement of small pupil may be successfully accomplished by means of any one or a

combination of the following techniques:

−Pharmacologic mydriasis

−Viscomydriasis

−Pupillary stretching techniques

−Pupil ring expanders

−Iris surgery

ßPreoperative preparation accomplishes multiple goals, including infection prophylaxis. Pre-

venting infection is a multi-factorial process involving positioning, prepping, and draping of the patient, and the use of antibiotics as well as surgical technique.

1.Little BC, Smith JH, Packer M (2006) Little capsulorhexis tear-out rescue. J Cataract Refract Surg 32:1420–1422

2.Fine IH (2000) Cortical cleaving hydrodissection. J Cataract Refract Surg 26(7):943–944

3.Khng C, Packer M (2004) Intraocular pressure during phacoemulsification [poster]. In: XXII Congress of the European Society of Cataract and Refractive Surgery, Paris, 18–22 September 2004

4.Fine IH, Hoffman RS, Packer M (2004) Optimizing refractive lens exchange with bimanual microincision phacoemulsification. J Cataract Refract Surg 30:550–554

6.1.1Managing the Small Pupil

The pupil that dilates poorly or is fibrosed or hyalinized is frequently associated with complications during cataract surgery. With endolenticular techniques, especially with nucleofractis procedures and chop techniques [1–4], pupils do not need to be as large as previously required. This is because, much of the procedure takes place in the endolenticular space, within the center of the capsulorhexis, rather than at the equator of the lens as in anterior chamber phacoemulsification [5] and nuclear tilt pupillary plane phacoemulsification techniques [6]. However, there are still numerous instances in which the pupil is inadequate to allow the surgeon to proceed and some form of manipulation or surgery is required.

6.1.2Techniques that Depend on the Manipulation of the Pupil

The surgeon may tailor the initial pharmacological intervention for pupillary mydriasis in cataract surgery to achieve greater dilation. The use of phenylephrine 10% and cyclopentolate 2% will sometimes produce more effective mydriasis than lower concentrations of these or other agents, especially when administered in multiple doses over 1 h. The use of preoperative nonsteroidal anti-inflammatory agents, such as flurbiprofen sodium 0.03% (Ocufen, Allergan) or suprofen 1.0% (Profenal, Alcon) mitigates any intraoperative pupillary constriction. Additionally, preservative-free epinephrine 1:10,000 may increase the diameter of the pupil, when injected into the anterior chamber at the start of surgery.

A viscoelastic device, particularly a high molecular weight product, can increase mydriasis by applying direct mechanical pressure on the pupillary margin during instillation. When poor mydriasis is due to the presence of posterior synechiae and there is adequate zonular support, the surgeon may insinuate the viscoelastic cannula between the anterior capsule and the pupillary margin and then inject the viscoelastic in order to disrupt the irido-capsular adhesions. The cannula is angled in a tangential fashion to create a viscoelastic wave, which will dissect the synechiae. Multiple injection sites may be utilized to free the pupil fully. Following dissection of the synechiae, additional dispersive viscoelastic may be injected in the center of the pupil to achieve even greater dilation of the pupillary margin.

Frequently, the pupil can be manipulated with the phacoemulsification handpiece. One can retract the proximal portion of the pupil through the incision with the sleeve on the phacoemulsification handpiece, and effectively enlarge its size. This technique requires a great deal of skill and may result in thermal injury with chafing of the pupil and focal depigmentation of the iris. Additional advantage can be obtained by using the second handpiece, in such a way as to stretch the pupil in front of the phacoemulsification tip, once again enlarging the pupil for adequate visualization of structures, just under the margin of the pupil. In other circumstances, a portion of the lens may be manipulated through the pupil to maintain the pupil in a semi-dilated state. The protruding portion of the nucleus can then be consumed by the phacoemulsification handpiece before repositioning the nucleus within the pupil.

Fig. 6.4 The Beehler pupil dilator effectively stretches the pupil to a diameter of 6–7 mm by creating tiny microsphincterotomies

The surgeon may accomplish mechanical stretching of the pupil with a variety of instruments. Frye [7] has taught a technique that he attributes to Keener of Indianapolis, Indiana. Here, two hooks engage the pupillary margin at opposite points and apply steady, gentle pressure across the full extent of the anterior chamber to produce a pupillary diameter of 5–6 mm. A second stretch placed orthogonal to the first increases the diameter further. Viscoelastic protects the anterior lens capsule during this maneuver.

Alternatively, the Beehler pupil dilator (Moria #19009) is uniformly applicable in front of small pupils. Inserted through a 2.5-mm single plane clear corneal incision, it usually stretches the pupil to 6–7 mm, while creating tiny microsphincterotomies circumferentially around the pupil (Fig. 6.4). The pupil can then be mechanically reduced at the end of the procedure with a Lester hook supplemented with an intraocular miotic agent. Pupils enlarged in this manner maintain a good cosmetic appearance and an ability to react to light, but may require a miotic agent for some time after cataract surgery to prevent the formation of irido-capsular synechiae.

Recently, we have seen a renewed interest in the use of iris hooks as described by McReynolds [8]. Mackool [9] has designed self-retaining titanium hooks that can be placed through paracenteses, so that the pupil can be positioned and held in a widely dilated state in a triangular or square shape, to adequately perform

phacoemulsification, regardless of the initial size of the pupil. Although this procedure is somewhat timeconsuming and results in considerable fluid loss from the eye, as a result of leakage through the paracenteses during phacoemulsification, it is an effective method of pupillary dilation and visualization of the structures for phacoemulsification. De Juan designed disposable nylon hooks with an adjustable silicone retaining sleeve that can be used through smaller paracenteses. Although more expensive, they may offer some additional advantages as reported by Nichamin [10], particularly the facilitation of hook removal through the paracentesis incisions.

Pupil ring expanders represent another option in the surgical armamentarium for small pupil cases. The Hydroview Iris Protector Ring (Grieshaber) forms a compressed oval in its dehydrated state. It can then be placed in the anterior chamber through a 3-mm incision and inserted into the small pupil. This hydrogel device expands with hydration, and captures the pupillary margin by means of flanges. The ring can be manipulated to expand the pupil as it hydrates. The device then remains in place for the entire surgical procedure, including implantation of the intraocular lens. The Graether silicone pupil expansion ring (Eagle Vision, Inc., Memphis, TN) offers another injectable option for maintaining dilation.

The Morcher Pupildilator Type 5S is a solid polymethylmethacrylate (PMMA) ring that is placed at the pupillary margin and expands the pupil through 300° of even tension, thus reducing the likelihood of iris sphincter tears and postoperative pupillary deformity. The ring may be introduced into the anterior chamber with forceps and then placed within the pupillary margin with a small hook. The central segment of the ring is manipulated into position, first in apposition to the distal pupillary margin, and then the ends of the ring are placed with the aid of eyelets on the ring. Following implantation of the intraocular lens, the ring is removed by first freeing the ends from their point of apposition with the pupil by means of the small hook and again placed in each eyelet. The ring may then be withdrawn from the anterior chamber with forceps. An injection device is also available for the ring from Geuder (Figs. 6.5 and 6.6).

The Malyugin Ring (MicroSurgical Technologies) features an innovative design that resembles a fourcornered paperclip (Fig. 6.7). It is placed in the eye with an injector and can also be removed with the same

Fig. 6.5 The Morcher Pupildilator may be injected via a device available from Geuder, as seen in this case of floppy iris

Fig. 6.6 The Morcher pupildilator in place, permitting capsulorhexis and the completion of the surgery

injector, by freeing the proximal corner of the device with a hook and then grasping it with the retractable arm of the injector.

6.1.3 Iris Surgery

A variety of techniques using iris surgery enable the enlargement of the pupil. A proximal sphincterotomy can be performed by grasping the superior sphincter and pulling it out of the incision. A small segment of the sphincter can be excised, after which the iris is repositioned [11]. While this procedure results in a

Fig. 6.7 The Malyugin ring: (a) Inserting the ring by capturing the distal papillary margin within the leading spiral. (b) Continuing insertion by capturing the inferior and superior papillary margins

in the ring. (c) Capsulorhexis with the ring in place. (d) Removing the ring at the conclusion of the case by grasping the proximal spiral with the retractable arm of the injector

permanently enlarged pupil that may be somewhat oval in shape, it does frequently achieve adequate dilation for the completion of the surgery. This has been found especially useful in glaucoma patients undergoing cataract surgery, and may be combined with a small inferior sphincterotomy.

Superior sector iridectomy is frequently performed for pupillary enlargement. However, this technique subjects the patient to glare and other undesirable retinal images postoperatively, because of the permanently enlarged pupil and the potential for edge effects from lenses and haptics, uncovered by the prominently enlarged pupils.

A modification of the superior sector iridectomy, which tends to give adequate dilation for surgery and yet, is less of a problem postoperatively, is the superior midiris iridectomy followed by sphincterotomy. This

allows the pillars of the iris to come together more closely following the completion of the surgery, than that done by sector iridectomy.

Many surgeons use a suture to close the sphincterotomy at the completion of the surgery, hoping to avoid potential sources of glare and trying to achieve a more cosmetically acceptable appearance, postoperatively. These sutures may be preplaced through the clear cornea. The posterior loop is drawn out of the peripheral iridectomy with a hook prior to sphincterotomy. Alternatively, the suture may be placed through the clear cornea at the end of the surgical procedure. The ends are drawn out of the cataract incision and tied in the same way as originally described by Worst and reported by Drews [12].

Masket [13] has described a technique for using a preplaced suture in the inferior or distal portion of the