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

RECOMMENDED READINGS

Buratto, L: Phacoemulsification: Principles and

Techniques, 1998.

Mendicute, J., Cadarso, L., Lorente, R., Orbegozo, J., Soler, JR: Facoemulsificación, 1999.

Seibel, BS: Phacodynamics: Mastering the Tools

and Techniques of Phacoemulsification Surgery,

Third Edition, 1999.

BIBLIOGRAPHY

Davidson J.: A comparison of technologically advanced ultrasonic tips. Advances in Technique & Technology, Alcon Surgical - April 1999, Part 2 of 2.

Fine, IH., Lewis JS, Hoffman, RS: New techniques and instruments for lens implantation, Current Opinion in Ophthalmology 1998, 9:20-25.

Fine, IH., Lewis JS, Hoffman, RS: Recent advances in phacoemulsification systems. Cataract Surgery: The State of the Art, Edited by Gills, H., Slack, 1998.

Fine, IH.: Total control phaco chop. Advances in Technique & Technology - Alcon Surgical, Part 2 of 2, April 1999.

Koch, PS.:Blades. Simplifying Phacoemulsification, Fifth Edition, Slack, 1997, 3:21-26.

Piovella M., Camesasca, F.: New phaco tips and handpieces. Atlas of Cataract Surgery,

Crandall, 1999, 5:42-47.

Salvitti, E.R: Flared tip technology. Advances in Technique & Technology, Alcon Surgical - April 1999, Part 2 of 2.

Seibel, B.: New phaco tips. Phacodynamics - Mastering the Tools & Techniques of Phacoemulsification Surgery, Third Edition, Section One:104111.

Technical advances in phacoemulsification systems, Ocular Surgery News, Feb. 2000.

General Considerations

Wehavepresentedthestep-by-steptech- nique of phaco during the transition including thefundamentalunderstandingofhowthephaco machine works (Chapter 7). The specific instrumentation, equipments and best systems used for phacoemulsification are discussed in Chapter 8.

Regarding instruments and use of equipment, it is essential to keep in mind that we should first train in order to thoroughly understand and command the subtleties of our phacoemulsifier before its clinical use. As frequently emphasized by Centurion, we will not be able to improvise or try to master it in the surgical suite.

Advantages of Phaco

It is also generally accepted that the main reasons why phacoemulsification has stimulated so much interest is because of the following advantages, all of which improve results:

1.Less ocular trauma induced.

2.Less postoperative inflammation.

3.Astigmatism induced is minimal or nil.

4.Postoperative refraction is more promptly stabilized.

5.Less risk of endophthalmitis.

6.Topical anesthesia can be effectively used.

7.Immediate physical and visual rehabilitation is attained.

Now let us consider fundamental concepts, measures, methods and techniques necessary to follow in order to master phacoemulsification.

Trauma-Free

Phacoemulsification

Considering that this procedure is very muchdevice-dependent,Centurionestablishes a tripod: physician-technician-machine. By individually organizing and interrelating the physician's role, his/her technician's important input and coordination, the functioning of the machine and the technique, we are able to perform the procedure free of trauma to our patients and less stress to the surgeon. This may be accomplished without changing the Operating Center's routine.

In this "trauma-free phaco," it is also important to achieve the following: 1) no delays of patients, anesthesiologists or the surgical team. 2) Perform a limited number of daily procedures with predictable results more days in the week which is preferable to a schedule of longer but less frequent operating days with a much larger volume of operations in one single day.

Perform 4 (four) cataract surgeries in one hour is as much as we should aim for. The objective is not to operate quickly but to take advantage of the results of a well-trained team that has adapted well to this system.

Faster Operations

Do They Sacrifice Patient Care?

If the operating team is really efficient, speed should not necessarily lead to lesser results. The key lies in the adroitness and perfect coordination among Centurion's "tripod: surgeon-technician-ma- chine". Making an operation safe and effective should be our primary goal. It is important to balance time, speed and safety, because in the end we all should aim for safe operations.

Readiness and Know-How to Become

Efficient

Stephen Lane, M.D., has very positively emphasized that if you want to go faster, ignore what is happening inside the eye and concentrate on what is happening in the operating room (OR). Make sure that the OR staff is proficiently getting the cases in and out and moving the patients with readiness. If the surgeon is only working in one room, there is more time wasted moving a patient from one roomtoanother,gettingaroomcleanedup,and getting the next patient in, than during the

cataract operation itself. There are a series of steps to make the process flow efficiently.

I. Howard Fine, M.D., has pointed out that there is an emphasis today of cataract surgery being likened to a foot race. Some surgeons show videos with stopwatches. Just looking at their hands reflects how they rush rather than doing maneuvers that are appropriate for working inside the eye. Racing the clock is definitely not good for the patient.

In our teaching, it is important to convey that endothelial cell loss, iris trauma, incisions that do not heal, or broken capsules, may result because of a desire to do faster procedures. As a matter of fact, complications should be less because of the advanced technology we currently possess. If you have one or two operating rooms, efficiency is more connected to the turnover, not necessarily the individual case. Themostpracticalmethodtoobtainspeedwith efficiency is the one recommended by Centurion:usetwooperatingroomswithexactly the same equipment disposition -- theyarecloned rooms. This saves time because it is not necessary to change equipment; provides savings in maintenance and, most important: operating room staff can concentrate on the needs of the patient and the surgical team.

Anesthesia

Advancedorexperiencedphacosurgeons may use topical anesthesia alone or combined with intracameral irrigation anesthesia (Figs. 35, 36). You may find as in-depth discussion of this subject in Chapter 5. The other alternative, of course, is to have the assistant or anesthesiologist use peribulbar anesthesia, generally Xylocaine 2% + Marcaine 0.50%. This

type of anesthesia has the great advantage of enabling the surgeon to operate without any intenseemotionalinvolvementorrequiringthe more active cooperation needed with topical anesthesia. It is very comfortable to arrive at the operating room where two or three patients are already anesthetized and ready to begin surgery.

Theadvantagesoftopicalcombinedwith intracameralvsperibulbarareamplydiscussed

in Chapter 5. For experienced surgeons, the combined topical-intracameral approach is much preferred because of immediate visual recovery.

Fixation of the Globe

The experienced surgeon does not need to fixate the globe with sutures. Fixation by grasping the superior rectus muscle with forceps and placing a 6-0 silk suture through it, repeating the same maneuver with the inferior rectus,iscompletelyoutmodedforphacoemulsification. Besides, it leads to postoperative ptosis in a good number of cases.

ManysurgeonsutilizetheFine-Thornton fixation ring (Fig. 75 - Chapter 8), particularly during the construction of the limbal or the clear cornea tunnel incision. Other surgeons prefer to fixate the globe with a forceps.

THE INCISIONS

Phacoemulsificationisatwo-handedpro- cedure in most cases. Consequently there are two incisions done:

1)The Primary Incision.

2)The Ancillary Incision.

The Primary Incision

For experienced surgeons, the procedure ofchoiceisaself-sealingclearcorneal,stepped valvulated incision, performed temporally (Figs. 90-95). This incision is self-sealing and heals without sutures. It is shown in Figs. 90 and 91 (surgeon's view). Most surgeons do a two-stepclearcornealtunnelincisionasshown inFig.92,crosssectionview. Others preferthe three step corneal tunnel incision because they feel i t may add a factor of safety (shown in

Fig. 93, cross section view). When performing a two-step incision, the length of the tunnel is slightlylargertoensurethattheincisionwillbe self-sealing. A short tunnel may not self-seal (Fig. 92).

Essential Requirements for a SelfSealing Corneal Incision

To be safely performed, the clear cornea tunnel incision must be done with a sharp diamond knife (Figs. 77, 90, 91, 92, 93) although the presently available stainless steel disposable knives are also very sharp and useful (Fig. 76, Chapter 8). Sergio Benchimol, M.D., in Brazil, who was one of the first surgeons to popularize this incision in South America, starts the surgery with a selfsealing, small, 1 mm paracentesis side port incision (Fig. 41) and pressurizes the eye with

viscoelastic or saline solution through this side incision. Then he proceeds to perform the primaryself-sealingcornealincision,asshown in Figs. 90-93. The two-incision process, the sharpness and precision of the diamond knife and even the stainless steel blades, and the presence of viscoelastic in the pressurized eye make it possible for a valve-like self-sealing incision to be made in the cornea without damaging its structure.

Position of the Clear Cornea Tunnel

Incision

The trend today is to make the clear cornea incision on the temporal side as introducedbyI.HowardFineandKimiyaShimizu, althoughShimizuisinclinedtoperformasingle plane incision, which is not generally accepted but he was a pioneer in the introduction of the clear cornea incision.

Reservations About the Clear

Corneal Incision

Some surgeons have reservations about the clear-cornea incision, particularly because of postoperative astigmatism and endophthalmitis. These usedtobetwo major complications ofclearcorneaincisions. Theseproblemshave been almost solved by making the wound as small as 3.2 mm or less at the temporal site and by using intracameral antibiotics as discussed in Chapter 4.

AdvantagestotheTemporalApproach

1)The approach to the anterior chamber is easier, especially in patients with a narrow palpebral fissure (Fig. 94).

2)Asinferiorductionoftheeyeballisnot required with the temporal approach, the iris plane is always kept at right angles to the microscope to provide good visibility.

3)As pointed out by Kimiya Shimizu, the cornea is oval and the optical center of the cornea deviates to the nasal area from the

anatomic center. Therefore, in the temporal approach, the incision's, the distance is about 1 mm more from the optical center as compared with a superior incision (Fig. 94). Thus, the operativeinvasiontothecornealcenterisminimal in the temporal incision. As a result, surgically induced astigmatism is small and recovery of visual acuity is fast. In addition, when working on clear cornea at the 12 o'clock position (closer to the optical axis than the temporal position) if there is a small amount of edema near the edge of the incision, being closer to the optic center of the cornea, may temporarily interfere with the immediate visual recovery aimed at with topical anesthesia and clear corneal incision.

4) The wound will not separate when blinking. The temporal incision, therefore, facilitates good adaptation of the wound.

5) In addition, there is more space for the surgeon's hands. The temporal approach makes the phacoemulsification itself easier because the eyebrow is not a barrier, and freer movements are possible.

AdditionalPatient'sComfortwith

Corneal Incision

Jack Dodick definitely prefers to do a clear cornea incision rather than the scleral tunnel procedure. Although he considers that both incisions are excellent and lead to the same outcome, patients tend to be more comfortable and satisfied with the clear cornea incision.

Using the scleral tunnel procedure, the surgeon cuts into the sclera, conjunctiva, Tenon's membrane, and some blood vessels, which takes perhaps 1 to 2 weeks to heal.

Although patients do not report having much pain, they do report a greater sense of awareness or discomfort for at least a week or so after the scleral tunnel procedure. With the clear cornea incision, on the other hand, the epithelium regenerates within 24 hours, much like it does after a corneal abrasion. Those patients who undergo a clear cornea incision report awareness of a sandy sensation which is virtually gone within 24 hours as the corneal epithelium is reepithelialized.

In many cases Dodick and many surgeons have done a scleral tunnel operation that turns out perfectly with 20/20 vision, and the patient still complains months and maybe even years later of an awareness or irritation in that eye. Creating a scleral tunnel wound leaves a scar at or near the limbus (Fig. 40), which Dodickbelievesinterfereswithtearfilmdistribution. Eventhough it heals beautifully, the interference with tear flow leaves patients with a vague awareness or irritation in the eye.

With a clear cornea incision, the limbus is never invaded, and a vascular scar is never created. Therefore, tear film distribution is never disturbed. The final reason Dodick chooses the clear corneal tunnel is that it is a much more cosmetic procedure. With the scleraltunnelincision,patientsoftenhaveared eye. No change is apparent in patients who have had the clear cornea incision just a few hours after the operation.

A postoperative photograph showing the barely visible scar of the corneal tunnel incision on the temporal side is shown in Fig. 95.

In Edgardo Carreño's experience, phaco through clear cornea is less traumatic, considering that there is no need for conjunctival dissection nor the use of cautery related to scleral tunnel dissection. There is also no possibilityofhyphemaandthereislesspostop-

erative inflammation because there is less trauma.

The postoperative cosmetic appearance of the globe is better, the eye looks as if never touched (Fig. 95). The patient feels more comfortable because there are no sutures, no cautery has been done and there is no pain. The intraoperative time is less because several traditionalstagesoftheoperationhavebeeneliminated. Therefore, the cost is reduced.

Importance of the Length of the

Tunnel

Ideally, the part of the corneal tunnel itself should be about 1.75 mm (Fig. 93). A shorter tunnel (dotted line in Fig. 92) decreases the self-sealing rate, although the surgeon's visibility becomes better. Too long of a tunnel increases the self-sealing, but corneal folds sometimes disturb surgeon's visibility. Corneal endothelial damage also becomes greater as the distance between the phaco tip and

corneal endothelium becomes shorter. Thus, when the surgeon performs a corneal incision for the first time, it is recommended to make a rather shorter tunnel and to place 11-0 nylon single knot without being concerned with selfsealing.

Placing and Making the Primary

Incision

As emphasized by Kimiya Shimizu, the proper placement of the incision is important. If it is too anterior, the corneal tunnel becomes shorter,andtheself-sealingeffectisdecreased. In contrast, if it is too posterior, conjunctival bleeding and/or chemosis sometimes occur.

So, before incising the cornea, dry the incision site, make the vertical first step just anterior to the terminal conjunctival vessels, then insert and advance the keratome straight about 1.75 mm into the corneal stroma. Next, direct the keratome slightly downwards in the iris plane to perforate Descemet's membrane.

When the tip of the keratome appears in the anterior chamber, remove the Merocel sponge and release the counterpressure. After that, advance the keratome, swinging it to both right and left sides. By doing this, the incision may be conducted safely without causing the collapseoftheanteriorchamber. Thelengthofthe corneal tunnel is usually 1.75 mm, but if it is a complicated or hard nucleus case, it should be shorter. On the other hand, when the patient has good mydriasis or a shallow anterior chamber, the incision site should be a little anterior, and the corneal tunnel should be longer to prevent iris damage and/or iris prolapse.

Surgeon's Position

When the operator is right-handed and he/she is operating the right eye, sit at the 10.30 position. When operating on the left eye, sit at 4:00.

Controversy Over the Strength and

Safety of the Wound

One of the most controversial criticisms ofclearcornealincisionshasbeentheirrelative strength compared to limbal or scleral incisions. Mackoolhasdemonstratedthatoncethe incision width is 3.5 mm or less and the length of the tunnel 1.75 to 2 mm, there is an equal resistance to external deformation in clear corneal incisions as compared to scleral tunnel incisions. Ernest work as well has revealed that as incision sizes get increasingly smaller, 3mm or less, the force required to cause failure of these incisions becomes very similar for limbal and clear corneal incisions. This further documents the safety of corneal incisions.

The real issue for these various incisions is not healing but sealing. Fine feels that as long as an incision is sealed at the

conclusion of surgery and remains sealed, the time before complete healing of the incision is accomplished is almost irrelevant, especially since there is still a 6-day period in which limbal incisions are not healed. An analogy can be drawn to the sealing that takes place duringLASIK,inwhichthereisnofibrovascular healing of the clear corneal interface, which has little effect on the strength, effectiveness, or safety of the wound, and, in fact, is an advantage by limiting scarring and an inflammatory healing response.

Clear corneal cataract incisions are becoming a more popular option for cataract extraction and IOL implantation throughout the world. Through the use of clear corneal incisions and topical and intracameral anesthesia, we have achieved surgery that is the least invasive of any kind in the history of cataract surgery with visual rehabilitation that is almost immediate. Clear corneal incisions have had a provenrecordofsafetywithrelativeastigmatic neutrality utilizing the smaller incision sizes.

Inaddition,cornealincisionsresultinanexcellent cosmetic outcome.

Testing the Wound for Leakage

There are several methods to test the seal of the incision. For the most practical one, we referyoutoFig.73,Chapter7,andtheexplanatory text in the same page under this title.

Closing a Leaking Wound

Without Sutures

Professor Juan Murube, M.D.

(Madrid), has demonstrated the effectiveness of a very comfortable maneuver in order to close-shutaleakingwoundinsteadofhavingto suture it. Although a self-sealing, stepped valvulated corneal tunnel incision, 3.0 mm or