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

Figure 212 (above): Cataract Surgery in Children

- Anterior Vitrectomy

With the anterior chamber filled with viscoelastic an anterior dry (that is, without infusion) vitrectomy is performed to avoid vitreous (V) remnants in the anterior chamber. This step should help eliminate any vitreous gel in the anterior chamber and near the posterior capsule. The vitrectomy probe (B) is inserted under the anterior capsulorhexis (A) and at the margin of the posterior capsulorhexis (P), always with the tip facing up, taking care not to touch any one of both capsules. This maneuver is preferably performed before the IOL implantation.

Figure 213 (right): Cataract Surgery in Children - Intraocular Lens Implantation

The anterior chamber and capsular bag are filled with viscoelastic. IOL (L) implantation within the capsular bag is the procedure of choice. It is important to use an acrylic lens. Anterior capsule (A). Posterior capsule (P).

IOL Implantation

Primary IOL implantation into the capsular bag is the procedure of choice. The risk of contact with vascular tissue and the possibility of inducing chronic inflammation is reduced as compared with implantation in the sulcus. For IOL implantation it is important to extend the incision to 3.5 or 3.8 mm to facilitate the implantation of a foldable acrylic IOL. Viscoelastic is injected between the anterior and posterior capsules to separate them. The acrylic lens is folded and inserted by the same technique used in the adult eye (Fig. 213).

The Posterior Approach to Cataract Extraction in Children

This has become a second option, and certainly not the procedure of choice. With significant advances in cataract removal in children through the anterior approach, the two or three port pars plana vitrectomy with removal of the posterior capsule and lens material and IOL fixation in the sulcus is left for cases in which a vitreoretinal operation is required as the primary procedure. This is the realm of the vitreoretinal surgeon. The anterior segment surgeon feels uncomfortable with this approach particularly when the technique done through the anterior segment is now so effective and the main controversies related to this surgery are almost a problem of the past.

CATARACT SURGERY IN UVEITIS

This is, indeed, one of the most delicate and complex situations in cataract surgery. In this volume it is fully discussed in pages 3133 and Fig. 22 (Chapter 2).

BIBLIOGRAPHY

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CenturionV,LacavaAC, DeLuccaES,BarbosaR: High myopia and cataract. Faco Total by Virgilio Centurion.

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Phacoemulsification: New Technology and Clinical Application (Thorofare, NJ: Slack, 1996), 161-80.

Dodick, JM: YAG laser phacolysis in new cataract techniques. Boyd’s World Atlas Series of Ophthalmic Surgery of HIGHLIGHTS, 1995; 5-130-131.

Dodick, JM, Christian J: Experimental studies on the development and propagation of shoch waves created by the interaction of short Nd:YAG laser pulses with a titanium target: possible implications for Nd:YAG laser phacolysis of the cataractous human lens. J Cataract Refract Surg 1991; 17:794-7.

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Overview

Although phacoemulsification followed by implantation of a foldable IOL is the “state of the art” technique and the operation of choice for many surgeons and patients, planned extracapsular extraction with an 8 mm incision and implantation of a rigid posterior chamber IOL is still used for a vast number of patients.

As a matter of fact, if we consider the day-to-day practice as performed by the majority of clinical ophthalmologists worldwide, planned extracapsular technique with a 8 mm incision and posterior chamber, in-the- bag implantation of a rigid PMMA lens or some other type of manual extracapsular continue to be: 1) the cataract surgical procedure performed on the largest number of patients who undergo cataract surgery; 2) the surgical technique done by the majority of clinical ophthalmologists throughout the world regardless of whether they are technically able to do phacoemulsification.

There are many first class surgeons who can perform a superior quality phacoemulsification but for a large number of patients they need to do manual ECCE. This is particularly true in less economically advanced societies.

A good example of this situation is the experience of Everardo Barojas, M.D., from Mexico, one of Latin America’s most respected ophthalmic surgeons and teachers. He performs a first class phacoemulsification and teaches the technique to his residents. But in his extensive work with patients in the

rural communities which he spontaneously serves, he does the “envelope extracapsular technique” initiated in the 1960’s by Baikoff and revived in 1982 by Galand. All his residents learn how to perform the planned extracapsular with 8 mm incision, the envelope extracapsular, as well as phacoemulsification.

Barojas and collaborators have selected the “envelope extracapsular” procedure for rehabilitation of large numbers of patients at a time considering cost, time it takes, safety and good results.

Advances in Manual Extracapsular

In the past few years, the technique of planned ECCE has progressively and substantially improved. In addition, small incision or medium-small incision manual extracapsulars have stimulated the interest of a good number of clinical ophthalmologists in different regions who have chosen to do these manual techniques instead of undergoing the learning process of phacoemulsification even though some of these “small incision” manual extracapsulars are not easy to do. These techniques are presented in this Chapter.

Advances in extracapsular surgery are related to better instruments, viscoelastics, the application of nuclear fragmentation techniques, advances in IOL technology, irrigating solutions and the methods to minimize infection and postoperative inflammation as presented in Chapter 4 of this Volume. The

application of these advances is a long step forward for manual extracapsular as well as phacoemulsification, which is a mechanical extracapsular. As a matter of fact, a good number of steps used in phacoemulsification, such as continuous circular capsulorhexis have been incorporated into the modern methods of ECCE. All of these factors make manual extracapsular a very good operation. The essential difference with phaco regarding results is that with a very well done phaco and topical anesthesia the patient has almost immediate visual rehabilitation and minimal inflammation, in contrast to a very well performed ECCE in which final visual recovery may take 6-8 weeks, although the visual acuity is practically the same at the end of this period. There may also be more inflammation with ECCE.

Regional Predominance of

Phacoemulsification

Phacoemulsification is predominant essentially in the U.S. and Western Europe, where it has become the number one technique for most ophthalmic surgeons. In many instances, this is because their patients demand and expect a very rapid visual rehabilitation and have the economic means to receive the benefit of the high technology required for phaco. In other geographical regions, phacoemulsification continues to gain ground, but essentially in teaching centers and private practice.

Because manual planned ECCE is still extensively used, we have selected Professor

Joaquin Barraquer, M.D., from Barcelona to present his technique of a flawless planned extracapsular. There is no one better suited for this task.

ANESTHESIA

At the Barraquer Ophthalmology Center in Barcelona, we continue to find general anesthesia administered by an expert anesthesiologist the procedure of choice even with ambulatory surgery. With this type of anesthesia, the surgeon does not need to depend on the cooperation of the patient. Hypotony of the eye is excellent. The surgeon can perform the complete procedure with optimum control and safety.

Nevertheless, because many eye centers and clinical ophthalmologists throughout the world routinely use local anesthesia, both techniques are here described.

General Anesthesia

(as Performed at the Barraquer

Ophthalmology Center)

Pre-induction

Midazolam (1-5 mg, intravenous, anxiolytic).

Induction

Propophyl (1-3 mg/kg, intravenous, hypnotic)

Succinylcholine (1 mg/kg, intravenous, muscular relaxant for orotracheal intubation).

Adjunct Medications

Analgesics: alfentanil (0.5-1.0 mg) or pentazocine (15-30 mg) intravenous.

Neuroleptics: droperidol (2.5-5.0 mg, intravenous)

Vagolyptics: atropine (0.5-1.0 mg, intravenous)

Curare: atracurium besylate (0.25-

0.50mg, intravenous as muscle relaxant) Antiemetics: ondansetron (4 mg) and/or

metoclopramide (10 mg) intravenous.

Maintenance

Halogenated ethers for inhalation anesthesia (sevoflurane or isoflurane), occasionally complemented by nitrogen protoxide (N2O) 50%.

Ventilation

Spontaneous respiration, if possible, depending on the type of patient and surgery. Assisted or controlled ventilation if necessary.

Monitoring

Electrocardiogram (EKG) Pulsioximetry (Oxygen saturation) Non-invasive blood pressure (NIBP)

every 3 minutes.

Capnography (expired CO2) and respiratory frequency.

Muscular relaxation.

Awakening and Recovery

Oxygenation 100% and control of vital signs. Cholinesterase inhibitors (neostigmine and/or edrophonium) if curare has been used.

Local Anesthesia

With this type of anesthesia very good hypotony and akinesia can be achieved. If sedation is adequate but not excessive, minimal patient cooperation will be sufficient. Barraquer believes an expert anesthesiologist should always be available to ensure that the patient is controlled, even if local anesthesia is used.

Sedation

Propophyl, alfentanil, midazolam. The dosage depends upon the patient’s weight and age.

The patient should be oxygenated during the anesthetic and surgical procedure because sedation causes respiratory depression.

Peribulbar Injection

Two injections are administered: Ante-equa- tor injection - Inferotemporal Site.

1.An inferotemporal injection at the intersection of the temporal lateral third and the two medial thirds of the inferior orbit, just anterior to the equator (Fig. 214). A 23 gauge needle 25 mm long is used.

2.A superonasal injection (Fig. 215). A 25 gauge needle 16 mm long is used.

Technique for Peribulbar Injection

First, the inferior temporal rim of the orbit is identified by palpation, and the eyeball is displaced with the finger. The needle is always introduced in the direction of the orbit until it touches bone. At this point the needle is lowered, following the rim of the bone. Three to 4 cc of local anesthesia are injected. Then the same maneuver is performed at the superior nasal point. Massage is applied to the globe for a few seconds. A Honan balloon is placed over the globe with a pressure of about 40 mm for 5 to 10 minutes (Fig. 96).

Extracapsular Cataract Extraction with an 8 mm Incision (ECCE)

At the beginning of the operation, the pupil must be adequately dilated (8mm or more. We use cyclopegics and tropicamide every 30 minutes, beginning 3 hours before surgery. Diclophenac is added to reduce the tendency for the surgical maneuvers to cause pupillary constriction. Atropine is not recommended because we want prompt recuperation of normal pupillary reaction the first day after surgery.

Anesthetic Medications

5 cc lidocaine 2%, plus 5 cc buvicaine 0.75%, plus hyaluronidase 100 UI plus adrenaline 1:200 000 (3 to 4 cc in the injection inferiorly and 3 to 4 cc in the injection superiorly. This combination lasts for almost 2 hours).

Monitoring

Electrocardiogram (EKG) Pulsioximetry (Oxygen saturation) Non-invasive blood pressure (NIBP)

every 3 minutes. Muscular relaxation

Incision

A traction suture is applied in the superior rectus muscle. A fornix-based conjunctival flap is prepared. The conjunctiva is separated at the limbus either with a razorblade knife or with Wescott scissors. If the scissors are used, the dissection is completed with the same scissors.

Light bipolar diathermy is used to coagulate the bleeding vessels, especially in the anterior part of the sclera and at the sclerocorneal limbus, where the incision will be made to extract the nucleus and to introduce the IOL.

An 8 mm-groove is made approximately 0.5 mm from the limbus with a dia-

mond knife, a Desmarres scarifier, a disposable knife, or a razorblade knife. The depth of the groove is approximately two-thirds of the scleral thickness and represents the first step of a two-plane incision to be completed later. This two-plane incision facilitates better apposition of the wound edges, thereby improving wound closure and reducing postoperative astigmatism induced by the sutures. The surgeon should avoid overlapping the wound edges. (Fig 216).

Continuous Curvilinear

Capsulorhexis

A viscoelastic substance is introduced in the anterior chamber through a paracentesis (Fig. 217) to maintain adequate depth and to facilitate the deep, horizontal incision (second step) and anterior capsulorrhexis. The horizontal incision is started with a disposable knife at one of the ends of the predetermined groove and continued over approxi-