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

people, or if the anterior chamber is shallow, the use of viscoelastic material is indicated. It is easier to introduce the IOL into the AC in the presence of viscoelastic, but manipulation of the lens into the final preferred position is more easily achieved in the presence of BSS. Viscoelastic is not contraindicated during manual small incision Mini-Nuc ECCE while using the anterior chamber maintaining system, but the BSS flow should be reduced or stopped. It is better to activate the ACM system during aspiration of the viscoelastic. This keeps turbulence and fluctuation to a minimum.

Pupil Enlarged by Increased IOP

Deepening the AC with the ACM and increasing the IOP from 10 mm Hg to 30-40 mm Hg, pushes the iris back and sideways, dilating the pupil mechanically beyond the pharmacological effect of the dilatation drugs. In certain cases the pupil stays extra dilated at the end of surgery because of a phenomenon known as reverse pupillary block. No long-term ill effects arise from this. After a few minutes the reverse pupillary block subsides, as pressure in the posterior chamber rises above that existing in the AC. The block can also be broken mechanically

by introducing a spatula under the iris. The pupil immediately becomes smaller, and the iris moves forward.

Advantages of the Continuous Flow of BSS during Manual ECCE

Removes debris: The anterior chamber is washed throughout surgery. All pigment debris is washed out, reducing to a minimum possible ill effects during the postoperative period.

Stops bleeding: When bleeding occurs in the tunnel or in the anterior chamber during surgery, it can be stopped by increasing the IOP. Moreover, no blood accumulates during surgery, as it is washed out by the continuous flow.

Frees cortex remnants: These remnants find their way out of the eye due to the continuous flow through the AC. The rest are aspirated by a 5 cc syringe with a cannula attached. The aspiration is usually performed at the final stage of the surgery before the ACM is pulled from the eye.

Removes viscoelastic: Viscoelastic material can and sometimes must be used during the surgery. It can be flushed out by fluid from the ACM or aspirated. Leftover quantities of viscoelastic are removed from their hidden locations with short bursts of BSS produced by a 1 cc syringe and cannula.

Cleans posterior capsule: A 1 cc syringe attached to the hydrodissector cannula is used to create an intermittent water jet effect on the posterior capsule to clean it from attached cortical material (Fig. 233). This

procedure is much more effective when the ACM is used. The freed cortical material is aspirated whenever it is separated form the capsule. Aspiration of cortical material directly from the posterior capsule involves much more dangerous manipulation, as most capsule tears occur during this stage of the surgery.

Prevents inflow : Hypotony, even if it occurs for a very short period, can cause inflow from outside the eye into the eye. With the ACM system, its active flow prevents foreign material from washing into the AC. By the same mechanism bacteria are partially prevented from entering the eye. If an instrument does carry bacteria to the AC, the bacteria may be washed out reducing the likelihood of endophthalmitis.

Complications

Posterior capsule tear: Tears in the posterior capsule are mostly caused by suction with the aspiration cannula. The presence of the AC maintaining system during unintended tear of the posterior capsule pushes the vitreous face backward. In 70% of cases of unintended tear of the posterior capsule, the vitreous face stays intact. When the vitreous face is intact, BSS does not enter the vitreous body, even if the IOP is 40 mm Hg.

The hypothesis that vitreous hydrates when in contact with BSS is not true. Hydration occurs only if the vitreous face is broken. During manual ECCE there is little turbulence or fluctuation; most of the time there is no movement at all. The amount of BSS used

throughout one modern ECCE procedure during 10 minutes of surgery is only 20 cc to 30 cc The amount of flow during each minute of the surgery is 2 cc to 3 cc. This amount produces the least possible turbulence. Controlled aspiration using a 5 cc syringe in the presence of a posterior capsule tear can be performed without vitreous engagement, and aspiration of cortical material in the presence of posterior capsule tear is continued until the capsule bag is free of cortex, without enlarging the tear.

The steady condition allows the surgeon to perform the most delicate maneuver possible, aspiration of cortical material lying on the vitreous face. This maneuver can be done only if the vitreous remains still, with no fluctuation.

Vitreous involvement: When vitreous enters the AC through a posterior capsule tear, vitrectomy must be performed. An existing ACM is a great advantage at this stage. Because an imbalance of inflow and outflow would aggravate the situation, Blumenthal recommends the paracentesis entrance for the vitrectome tip. Steady conditions during vitrectomy ensure the procedure can be performed in a controlled manner. Because the posterior capsule does not move in an uncontrolled fashion, enlarging the size of the tear can be avoided. Enlarging the posterior cap-

sule tear during vitrectomy reduces the option of choosing the bag as the best fixation site for the IOL.

Locating vitreous strands is another very important aspect of the art of vitrectomy. Two-handed vitrectomy, during which the surgeon has a spatula in one hand and the vitrectome in the other, enables the surgeon to search for and locate vitreous fibers. Getting rid of all the vitreous strands, whether large or small, is essential. A quiet milieu allows the surgeon to search with the spatula carefully for strands over the iris and at the opening sites of the paracenteses and the tunnel. Eyes after such vitrectomy without strands in the AC have a very low rate of CME or iris deformation. In cases where the smallest vitreous strands remain, on the other hand, the incidence of CME is much higher.

Expulsive Hemorrhage Minimized by

Positive IOP: This rare phenomenon can be reduced to a minimum in routine cataract surgery, and in complicated or traumatic eyes by using continuous positive IOP during surgery. No hypotony occurs to cause leakage from, or rupture of choroidal or retinal blood vessels, especially when they are arteriosclerotic. Therefore expulsive hemorrhage or partial choroidal hemorrhage is mostly prevented.

Overview

We here present the Phaco Section cataract technique as developed by David McIntyre, M.D. one of the most talented and expert cataract surgeons in the U.S. We describe the evolution of his cataract surgery technique, present highlights of the procedure he has been using for 10 years, suggest how a surgeon can make the transition to the 5.5 mm wound Phacosection, and outline his surgical procedure step by step.

At present McIntyre continues to use a 5.5 mm, non-sutured self-sealing, corneoscleraltunnel incisionplacedtemporallyunder a peritomy, through which extracapsular cataract surgery is performed and a posterior chamber intraocular lens (IOL) is placed in the capsular bag. The intraocular lens is a 5.5 mm round, one-piece polymethylmethacrylate (PMMA) IOL placed in the bag, presently manufactured by Surgidev.

McIntyre uses an anterior chamber maintainer, capsulorhexis and the nucleus is sectioned into 2 or 3 fragments, occasionally 4, with few exceptions in ages under 50-55.

surgery, using Kelman's phacoemulsification technique. During the past 20 years he has devised a number of instruments and modified techniques, resulting in extracapsular surgery with smaller and smaller incisions. Currently theincisionisself-sealingandjustlargeenough for the IOL implantation.

From the perspective of results with patients, McIntyre has found no reason to return to the emulsification of the cataract nucleus with ultrasonic energy (phacoemulsification). Atthesametimehehas personally attempted to develop a number of mechanical devices to aid in cortex aspiration. With each device he has reaffirmed that he has greater control over the operation when he uses a completely manual technique.

Indications

McIntyre strongly believes that a basic advantage of the Phaco-Section is its applicability to all degrees of hardness of nucleus, from soft (+) to moderate (++), to fairly hard (+++)andtohard(++++), with truly minimal variations.

Evolution of Technique

McIntyre’s surgical technique has had a complex evolution. In 1974, he made the transition from intracapsular to extracapsular

PHACO SECTION MOST IMPORTANT FEATURES

The three separate tissue zones of the lens are shown in Fig. 239 to enhance the understanding of how Phaco Section works.

Figure 239: The Three Tissue Zones of the Lens

This anterior globe cross section shows the three separate tissue zones of the lens. Portions of the lens are shown removed to reveal the three dimensionality of these tissue zones. The rigid nucleus (N) is in the center. The second zone is the epinucleus (E), a firm or heavy gelatin material which is difficult to aspirate. The third and outer zone is the cortex (C) which is soft gelatin that is easy to aspirate, and lies just under the capsule (D). Note the 6 mm diameter circular capsulorhexis, which is large enough to allow the management of almost all nuclei by the phacosection technique. Air (A) is used to fill the anterior chamber during capsulorhexis to maintain the chamber depth and to eliminate the magnification effect of the corneal curvature.

The following are the most important featuresofMcIntyre’sPhaco-Section surgical procedure.

Capsulorhexis

Thisisperformedthroughtheincomplete tunnel incision that is perforated only by the cystotome.

McIntyre believes capsulorhexis offers several advantages in small incisionphacosectiontechnique. First, a 6 mm capsulorhexis is large enough to allow the management of almost all nuclei by the phacosection technique (Fig.241). Secondly,thecapsulorhexis actually gives a stronger margin to the capsulectomy than any of the "canopener" techniques. Consequently, there is considerably less risk of tears ofthecapsulectomymargin extending around the equator and to the posterior capsule.

Third, the use of air provides significantbenefitinthecapsulorhexis. Air is maintained in the anterior chamberveryeasily after thepuncture incision of the cystotome needle (Fig. 241). The presence of air in the anterior chamber makes visualization

and control of the fragment of anterior capsule much easier for the surgeon. Lying on the surface of the cataract as it is torn around the circle, the fragment is very easily visualized.

And finally, and perhaps most importantly, when the fluid is removed from the anterior chamber and is replaced with an air bubble, the magnification effect of the cornea is almost entirely neutralized, so that it is easy to understand the actual dimensions. When the anterior chamber is filled with fluid, the cornea becomes a 15% magnifier on average, making the capsulorhexis appear much larger than it really is.

Completing the Tunnel Incision

After the capsulorhexis has been completed, the surgeon must complete the tunnel primary incision into the anterior chamber. There is a paracentesis just to the

right end of the tunnel incision, but the tunnel has been perforated only by a needle (the cystotome)uptothispoint. McIntyreenlarges the primary incision by grasping the margin of the scleral lip with a colibri forceps and passing a 15-degree supersharp blade through the cystotome puncture to slightly enlarge the incision. Then, with the double-bevelled crescent knife, he enlarges the opening into the anterior chamber to the full length of the tunnel incision, which is 5.5 mm to 6 mm (Fig. 241).

The Dynamics of the Self-Sealing

Incision

McIntyreusesananalogytohelpexplain the dynamics of the self-sealing incision. Shallowness of the tunnel is important in preventing frequent hyphema. Deep tunnels tend to have frequent hyphemas; superficial tunnels tend not to result in frequent hyphema. McIntyre’s analogy is a great circle, which is the shortest distance between two points on the surfaceofthe sphere, a common concept used in navigation (Fig. 240). On the eye the ends of an incision can be connected by a great circle around the globe. If any pressures and traction occur, there is a tendency for a wrinkle to develop that connects the two ends of the incision along the great circle.

Consequently,ifascleralflapisfashioned following the curve of the limbus, that scleral flap must be sutured in position because any deformity of the globe will cause the eye to wrinkle along the great circle connecting the two ends of the incision. The scleral flap wouldbecomeafree,non-supportingstructure. In contrast, a frown-type incision that has a

concavity facing the great circle that connects the two ends of the incision does not allow any stretching or raising of the flap. This is the reason the superficial layer of dissection in a tunnel has a very firm, unyielding geometry which to resists deformity or increased pressure within the globe. As long as the incision is concave to the great circle, a satisfactory self-sealing tunnel can be created.

With the exception of children, the tunnel incision is sutured only in approximately 1 of 300 cases.

Anterior Chamber Maintainer

The anterior chamber maintainer that McIntyre uses is a threaded or screw-like tip of metal tubing attached to a silicone tube, which is then attached to the hub of a needle. It can be plugged into a fluid source and has a flexible connection with the eye (Fig. 241). The internal diameter of the metal tubing is 0.6 mm. The threaded outer surface of the tube is able to grasp the corneal paracentesis very firmly so that when this has been screwed into the cornea it will hold in that position even when the eye is rotated rather vigorously.

At the conclusion of the procedure it must be unscrewed to be removed. During its introductionthesiliconetubeandthemaintainer tip itself have a stylette passed into them; the resulting rigidity allows the turning process, andaroundedpointatthetipsallowsittoeasily pass through the paracentesis. The fluid source for the chamber maintainer is balanced salt solution (BSS), which contains additional antibiotics for prophylactic purposes and is supported on an electric IV (intravenous) pole

so that the static height, and thereby the gravitational force, on the fluid that is entering the anterior chamber can be easily adjusted. The infusion tubing that comes from the BSS bottle to the table also has a roller valve so that the assistant can turn the maintainer system on and off as needed throughout the procedure.

Aspiration of theAnteriorCortex and

Epinucleus

With the tunnel completely opened and with the chamber maintainer operating and its pressure somewhat elevated, the surgeon does the preliminary aspiration of the cortex and

epinucleus overlying the anterior surface of the firm central nucleus using a 21-gauge cannula (Fig. 241). McIntyre is careful to create a gutter or furrow around the equatorialareaofthenucleus,thusallowing ittomoreeasilycomeupfromtheremaining epinuclear "bowl". This is performed without any hydrodissection.

Mostexperiencedsurgeonsareaware of a complication that is frequently disastrous for the patient: the combination of posterior capsule tearing or rupturing with loss of vitreous and with portions of nucleus retained in the posterior segment.

McIntyre believes that this complication indicates potential loss of control by the surgeon during portions of the operation when aspiration is being used. During removal of the lens material, the cataract should be seen as being formed of three separate tissue zones (Fig. 239). Starting from the center is the nucleus, a rigid material that is too viscous to allow aspiration. The second zone is the epinucleus or, as it is often called, the epinuclear bowl. The epinucleus is a relatively firm gelatinous material with an intermediate degree of viscosity, which can be aspirated with sufficient vacuum. The third zone is the peripheral cortex, which lies just under the capsule surface. This gelatinous zone is of a very low viscosity and is freely aspirated.

This perspective of the three zones of the cataract clearly reveals an important safety factor in aspiration. Whether using manual or mechanical methods, the surgeon has more control when aspirating from the less viscous cortex toward the highly viscous nucleus.

Ontheotherhand,thereisapotentialloss of control and an extreme danger when aspiratingfrom the more viscouselement, such as the epinucleus, toward the peripheral cortex. In this circumstance when the aspirating

Figure 241: Aspiration of Anterior Cortex and Anterior Epinucleus

The following illustration depicts the surgeon's view of a left eye. Temporal (3 o'clock) is at the bottom and nasal (9 o'clock) is at the top. First, an anterior chamber maintainer (M) is inserted nasally. A 6 mm circular capsulorhexis (A) is performed. The 5.5 mm frown shaped scleral tunnel (T) incision is completed. A specially sharpened 21 gauge cannula (D) is introduced through a paracentesis made to the right of the scleral tunnel incision. Inset shows detail of the tip of the cannula. The port of the cannula is directed posteriorly to aspirate the central cortex (C), and epinucleus (E) overlying the anterior surface of the firm nucleus (N). A furrow is created around the equatorial area of the nucleus.

instrument clears a portion of the viscous epinuclear material, the cortex will then move through the aspirating system at a much greater velocity, challenging the control of the surgeon to avoid impaction and probable tearing of the posterior capsule.

Phacosection

Following the preliminary aspiration of cortex and epinucleus from the front surface of

the nucleus, McIntyre does a hydrodissection of only the central hard nucleus using a 27gauge, slightly narrowed and slightly curved cannula (Fig. 242). With this hydrodissection he also tilts forward the margin of the nucleus nearest the incision. Then the nucleus itself can be divided into a number of fragments using the technique called Phacosection (Fig. 243). This term, which McIntyre finds very useful, originated with Peter Kansas in New York. The procedure involves dividing the nucleus into a number of fragments, the number being determined by the size and hardness of the nuclear material, usually 2 or 3, occasionally 4. Each of these fragments is then individually surrounded by a layer of heavy viscoelastic material (Fig. 244) and simply extracted from the anterior chamber with their protective viscoelastic coating using a pair of instruments designed for this purpose (Fig. 245).

Removal of Epinucleus and

Cortical Cleanup

Following the removal of the divided nucleus particles, the epinucleus is then removed as a second stage. The epinucleus is hydrodissected from its attachment to the peripheral cortex (Fig. 246). In most cases the epinucleus is a continuous structure which can be hydrodissected, brought forward into the anteriorchamber,andhydraulicallyexpressed. The epinucleus is not removed by aspiration.

The third stage of the cataract tissue removal is simple aspiration of the residual cortex. The only stages of the procedure performed by aspiration are the preliminary aspirationoftheanteriorcortexandepinucleus, and then the final cleanup of the residual peripheral cortex. In this way the process of aspirating from a more viscous to a less viscous

mediumisavoided. Thereby,thesurgeon avoids losing control and destroying the continuity of the posterior capsule.

Transition from Extracapsular Extraction to Phacosection

McIntyre believes it is easier for the ophthalmic surgeon who is accustomed to standard, conventional large-incision extracapsular surgery to make the transition to small-incision phacosection (5.5 mm) than to phacoemulsification. The small incision phacosection technique offers thesurgeonsomeverydistinctadvantages on his/her patient’s behalf in comparison with the conventional large-incision plannedextracapsular. Theseadvantages are: more safely, a much more rapid recovery,amuchmoredurableeyeduring

Figure244(above):SurroundingNuclear Pieces with Viscoelastic

Each fragment of nucleus is individually surrounded by a layer of heavy viscoelasticmaterial viaacannulathrough the tunnel incision. The viscoelastic (V) is shown being placed between the two hard nucleqr fragments (N). This will assist in protectingintraocularstructuresduringtheir removal. The anterior chamber maintainer

(M) is still turned off.

Figure 243 (left): Phacosection of the Nucleus

A spatula (S) is introduced through the scleral tunnel incision (T) and placed behind the nucleus (N). A single cutter (R), also introduced through the tunnel incision, is used to section (arrow) the nucleus. The anterior chamb er contains viscoelastic with the anterior chamber maintainer (M) turned off during this sectioning.