Ординатура / Офтальмология / Английские материалы / The Art and the Science of Cataract Surgery_Boyd, Barraquer_2000

surgeon is of its complete sealing. He proceeds with the removal of the opaque corneal button using a disposable Beaver knife and Castroviejo’s scissors (Fig. 190). The surgeon completes the procedure by bringing together the edges of the donor and recipient corneas, using 16 interrupted 10.0 nylon monofilament sutures. This approach undoubtedly reduces the long period of time during which the eye remains exposed, thus making surgery much safer.

Specific Recommendations

1) Padilha strongly recommends that the phaco procedure not be done using a clear cornea incision. Complications or difficulties may arise at the time of performing the penetrating graft. Consequently, use the sclero-corneal tunnel incision shown in Fig. 40-B.

2)The technique of phacoemulsification must be endocapsular, within the capsular bag, using the surgeon’s procedure of choice for management and disassembling the nucleus. This is with the purpose of preventing additional damage to the corneal endothelium. If necessary, the nucleus may be dislocated into the anterior chamber where it can be removed or into the iris plane (using Lindstrom’s iris-plane techniques - Figs. 136-139, Chapter 10). But repeatedly lubricating the cornea with dispersive viscoelastic.

3)If corneal edema deriving from the corneal disease itself is present and interferes with visualization of the intraocular maneuvers, the corneal epithelium may be completely removed to facilitate the surgeon’s adequate view of surgical maneuvers and instrumentation. (Editor’s Note: placing dispersive viscoelastic over the cornea will further facilitate the inner view by the surgeon).

PHACOEMULSIFICATION, IOL IMPLANTATION AND FUCHS’ DYSTROPHY

Preoperative Evaluation

These patients demand a meticulous preoperative evaluation before cataract surgery. This should not be limited to a good biomicroscopic examination with the slit lamp. Specular microscopy and corneal pachymetry may provide additional information of value to decide if a cataract extraction is sufficient or if a triple procedure is the most appropriate. These diagnostic examinations should be made if the equipment is available.

In the majority of patients, however, a detailed biomicroscopy may be sufficient to determine the amount of guttata and the extension of the corneal edema.

Role of Specular

Biomicroscopy and Pachymetry

In performing specular biomicroscopy, counting the endothelial cells is not sufficient to guarantee that an eye with cor-

or even worse, bullous keratopathy in the future. Analysis of the cell morphology provides important additional information for predicting the nature of postoperative complications after phacoemulsification or any other intraocular surgery.

Pachymetry offers a dynamic evaluation of these same corneas. Repetitive measures of the thickness of the diseased cornea may demonstrate how well its fluid system functions.

If there is considerable corneal edema, with an endothelial cell count of less than 500/mm2 and a central pachymetry up to 610 micra, the procedure of choice is performing combined surgery consisting of penetrating keratoplasty, cataract extraction and IOL implantation.

Special Precautions During

Phacoemulsification

1)The presence of cornea guttata or Fuchs’ dystrophy is not a contraindication to phacoemulsification, but it does require additional specific precautions. The surgeon must significantly decrease turbulence and maintain the anterior chamber with a sufficient quantity of BSS and viscoelastic to prevent contact between the nuclear fragments and the endothelium, particularly at the stage of aspiration of cortical remnants.

2)In corneas with Fuchs’ dystrophy, it

is very important to use dispersive viscoelastic for better adherence to and protection of the diseased endothelium. Be attentive in case the viscoelastic comes out through the wound. This makes it necessary to reintroduce it fairly often during the surgical procedure. This should be done through the sideport incision (Fig. 191). The phaco or the I/A tip should be kept functioning within the anterior chamber avoiding its removal and reinsertion back and forth through the main incision. This could lead to additional trauma.

3) During phacoemulsification, the maneuvers should be very delicate, using techniques that reduce the time and power of the ultrasound. Padilha considers that the phaco fracture or “divide-and-conquer” techniques, are the most indicated. When

emulsifying the last quadrant the surgeon must prevent fragments from moving into the anterior chamber and touching the endothelium (Fig. 192). The ideal procedure is to maintain a high vacuum power (150 mmHg or higher), keeping nucle-

ar fragments attached to the titanium tip and set in motion the pulse system of the equipment. If such fragments should move into the anterior chamber, dispersive viscoelastic substance should be used to prevent their touching the endothelium (Fig. 192).

Figure 192 (right): Phacoemulsification

in Fuchs’ Dystrophy - Ideal Procedure

During phacoemulsification, the maneuvers should be very delicate, decreasing the power of ultrasound to the minimum desirable, and using techniques that reduce the time of ultrasound. The ideal procedure is to maintain a high vacuum power (150 mmHg or more), keeping lens fragments attached to the phaco tip (P), and use the pulse system of the equipment. If such fragments should tend to move into the anterior chamber (white arrow), the dispersive viscoelastic (V) should be once more irrigated into the anterior chamber to protect the endothelium.

Figure 191 (left): Phacoemulsification in

Fuchs’ Dystrophy - Use of Viscoelastic

In such altered corneas it is very important to use dispersive viscoelastics (V) for better adherence to and protection of the diseased corneal endothelium. The lateral paracentesis or sideport incision (L) should be used for the intracameral injection of viscoelastic. The phaco tip introduced through the primary incision is not to be reinserted in and out, back and forth (T) for intraocular maneuvers . This could add trauma.

4) At the time of lens implantation, the first step should be the introduction of a

capsule well distended, especially if a foldable lens is to be implanted (Fig. 193). The next step is to lubricate the injector with dispersive viscoelastic to facilitate the delivery of the lens from inside the injector with the bag.

At the end of surgery, the aspiration of the cohesive VE will be easier and faster than the dispersive VE. In order to protect the cornea from any damage, the dispersive VE should not be removed aggressively although all VES should be removed. Administration of carbonic anhydrase inhibitors and betablockers during the immediate postoperative period is always recommended to inhibit elevation of intraocular pressure, especially in cases with some corneal disease.

Pharmacological Mydriasis

Phacoemulsification requires that the pupil be well dilated. Adequate exposure of the lens and the anterior capsule is

(Ocufen R ), which is administered every 15

combination is administered if, of course, no cardiovascular contraindications exist.

If this combination of medications is not effective, unpreserved adrenaline 1:1000 diluted in 10 ml of BSS may be injected into the anterior chamber at the beginning of surgery.

Mechanical Dilatation with Viscoelastics

In the presence of iris adhesions to the anterior lens capsule, Luntz mechanically separates them using a viscoelastic passed through a cannula. Once the synechiae have been separated, intracameral Epinephrine (adrenaline) is injected and in many instances the pupil will dilate adequately.

Mechanical Strategies

In patients who have a certain degree of iris atrophy that may be related to advanced senility, post uveitis, trauma or the long term use of miotics in glaucomatous eyes, the following options are available to obtain adequate exposure of the lens and the anterior capsule.

1. Stretching the Pupil

The pupil in most patients can be stretched to an adequate dilatation using two Kuglin hooks as advocated by Maurice Luntz, M.D. One Kuglin hook is inserted into a preformed temporal paracentesis and advanced to the opposite nasal pupil margin where the Kuglin hook engages the pupil margin (Fig. 194). The second Kuglin hook enters the anterior chamber through a preformed nasal paracentesis, is advanced across the anterior chamber to the opposite temporal pupillary edge, which it engages (Fig. 194). Both Kuglin hooks are now pushed toward the limbus, stretching the pupil horizontally until maximal stretching is achieved. There will inevitably be some small sphincter tears.

Both Kuglin hooks are now removed from the anterior chamber and re-entered into the anterior chamber through two preformed keratome incisiona one at 12 o’clock and the other at 6 o’clock (Fig. 195). One Kuglin hook is advanced across the anterior chamber to engage the pupil margin at 6 o’clock, and

the second Kuglin hook engages the pupil margin at 12 o’clock. Both Kuglin hooks are again pushed toward the limbus, facing each other, at 6 and 12 o’clock, thereby stretching the pupil vertically (Fig. 195). Once the maximal vertical extension is achieved, the Kuglin hooks are retracted. Intracameral epinephrine is injected, followed by intracameral viscoelastic. In those eyes in which the pupil margin in not significantly fibrosed and not too spastic, this maneuver can achieve a sufficiently dilated pupil to proceed with phacoemulsification. The technique using Kuglin hooks has also been advocated by

Miguel Padilha, M.D.

2) Mechanical Pupillary Dilators

In those cases in which the pupil margin is fibrosed or very spastic, one of the following procedures may be necessary.

A) Plastic Iris Hooks (Alcon-

Grieshaber) are inserted through four paracentesis incisions in the cornea (Fig. 196) as advocated by Luntz as well as Padilha. The hooks engage the pupil margin at the 10:00 o’clock, 2:00 o’clock, 4:00 o’clock and 8:00 o’clock meridians, and the pupil is forcibly enlarged by pulling the hooks outward and fixing their positions. Metal hooks are also available but Luntz considers that plastic hooks are less traumatic to the pupil.

When the pupil margins are heavily fibrosed this method will not achieve adequate pupil dilation, or the pupil margin may be severely traumatized.

Padilha considers that, of all the available mechanical resources, the one that has contributed the most safety and satisfaction in the management of small pupils is the flexible iris retractor (Alcon-Grieshaber) (Fig. 196). These retractors are extremely useful, even if placing them requires extra time. After the placement of the first or the second retractor, the anterior chamber may need to be refilled

with viscoelastic to facilitate the introduction of the other two.

B) The Beehler Pupil Dilator

Padilha uses this instrument when the other options outlined above have not been effective. This dilator, made by Moria, in France, allows dilatation in three directions with only one maneuver (Fig. 197). Moreover, it provokes a discrete retraction of the iris in the direction of the corneal or scleral tunnel incision.

C) The Silicone Expander Ring

In more severe cases, Padilha uses a silicone ring with an indentation, which fits all along the edge of the pupil. This presents some advantages. Using this technique the iris fits like a tire around the ring, which is like an iron wheel (Fig. 198). Among its disadvantages is the fact that it can loosen itself easily with intraocular maneuvers during the phaco procedure. Known as Graether’s pupil expander (EagleVision #1540) it has three components: the preloaded expander, a disposable insertor and a glide retractor of the iris. (The use of this ring is controversial - Editor).

Padilha emphasizes that stretching maneuvers using mechanical dilators may induce a certain degree of iris atony. This predisposes the iris margins to insinuate into the titanium tip, during the phaco maneuvers, leading to injury of the sphincter and the iris tissue. The same can occur with sector iridectomies, which can also predispose the iris to the development of synechiae to the anterior capsule during the postoperative period, requiring the administration of miotic drops for some time.

Overview

The complex repair of an eye injury is best when a team which shares anterior and posterior segment skills work together in primary and secondary management.

Almost all bad results following ocular trauma occur in injuries involving the posterior segment, particularly when the lens is also damaged

Assessment of the Injured Eye

The circumstances of the injury and the early clinical assessment give important information that will determine the early management and help to predict complications.

As pointed out by Michael RoperHall, M.D., an accurate history is essential. This can be very helpful in indicating the nature and extent of injury. The true history is sometimes elusive, especially when children are involved, or there is potential for litigation.

The injuries that cause traumatic cataract occur not only from serious penetrating trauma, but also from blunt injury. Most blunt injuries are not severe enough to cause rupture of the sclera. In evaluating and managing all blunt injuries, it is important to recognize that each ocular tissue, from the cornea to the posterior choroid, may have been damaged by the impact. Therefore, management is based on identifying the affected tissues, understanding the pathophysiology of events that can occur after a blunt injury, and anticipating possible secondary complications.

Highlights of Examination

The ophthalmologist must examine the patient carefully. The examination should begin with an assessment of the visual function, if there is light perception or light projection. The prognosis is better if there is good light projection. Then the eye should be examined in the usual way with the direct ophthalmoscope and the slit lamp. In many cases the fundus cannot be visualized because of the presence of opaque media: cornea, lens, and vitreous hemorrhage. The presence of a foreign body must be definitely excluded. It is important to search for anatomically related trauma. Individual intraocular structures are not often damaged alone.

In severe injuries, the full extent of damage is obscured by blood or opacities in the media . Special assessment is needed before planning surgery to establish the extent of damage and the visual potential. There may be no light perception in the presence of a complete vitreous hemorrhage - until the hemorrhage clears. In such cases diagnostic imaging is invaluable.

Diagnostic Imaging

B-scan ultrasonography should be used to identify the presence of a foreign body and where is it precisely located, the amount of vitreous hemorrhage present and the condition of the retina. Ultrasound imaging also demonstrates changes in lens position; posterior rupture of the lens; cyclitic