Ординатура / Офтальмология / Английские материалы / Modern Cataract Surgery_Kohnen_2002

Results

The group with the larger phacotmesis tip showed an obvious vibration of the eye that was transferred to the eyelid retractor. A positive side effect was that the parts of nucleus were loosened and therefore sucked off more easily. The flow of irrigation fluid was high (350–450 ml). Pressure changes were observed with collapse of the anterior chamber and forward movement of the posterior lens capsule. In 2 cases it came to a rupture of the posterior capsule. Three eyes showed a corneal decompensation on the first postoperative day that recoiled under adequate therapy rapidly. The intraocular pressure in this group decreased on an average from preoperative 15.7 3.1 mm Hg down to 13.6 3.1 mm Hg on the first postoperative day. The visual acuity on an average increased from

0.230.16 to 0.31 0.2 on the first postoperative day.

The group with the smaller phacotmesis tip showed a significantly lower

degree of vibration. The flow of irrigation fluid was less, the anterior chamber stable and the incision closed. No capsular ruptures were reported nor corneal decompensation. The preoperative intraocular pressure was on an average 15.8 2.4 mm Hg and on the first postoperative day 15.2 4.1 mm Hg. The visual acuity on average increased from 0.23 0.16 to 0.31 0.2 on the first postoperative day. During phacotmesis, small fragments of the nucleus were aspirated quite frequently by the tip resulting in a propeller like rotation.

Discussion

The principle of phacotmesis is well combinable with the classical phacoemulsification technique. Using the divide-and-conquer technique it supports splitting also denser nuclei with its cutting rotation and disassembling the nucleus after hydrodissection. The capsular ruptures in our series are not due to the principle rather due to intraocular pressure deviation due to inadequate incision closure. The relatively thick 2.5-mm tip strains the wound region and the teflon sleeve cannot seal it. The corneal decompensation we also rather put down to the high flow of irrigation fluid. After reducing the tip diameter to 1.8 mm and changing the sleeve material to silicone, these complications did not occur any longer.

A disadvantage was the obvious vibration of the bulbi because of rotation, particularly when using the thicker tip. They were decreased by reducing the lumen but still definitely there. Furthermore, small fragments of the nucleus were frequently aspirated by the tip causing propeller-like rotations.

Summing up, it may be said that phacotmesis seems to be suitable for denser nuclei from grade 3 onwards. The cutting rotation saves ultrasound energy

when dividing the nucleus. The rotation mechanism is adaptable to numerous phaco machines so it is not necessary to abandon one’s customary apparatus. The rotation though should give way to an oscillating movement similar to a vitrectomy cutter to reduce turbulence of nucleic fragment as well as bigger iris and sphincter damages through possible aspiration. Furthermore, other efficient and easier methods of dividing nuclei have been developed in the last few years [3–5] making an acquisition of a additional phaco tip superfluous.

References

1Anis AY: Phacotmesis: A new technique for automated small-incision cataract extraction utilizing a new surface discriminating instrument. Proceedings of the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Seattle, May 1993.

2Gimbel HV: Divide-and-conquer nucleofractis phacoemulsification: Development and variations. J Cataract Refract Surg 1991;17:281–291.

3Nagahara K: Phaco-chop technique eliminates central sculpting and allows faster, safer phaco. Ocul Surg News Int Ed 1993;4:12–13.

4Kammann J: Reversed tip and snip – A new phaco technique. Ocul Surg News Int Ed 1997;8: 18–19.

5Kammann J, Dornbach G: Rotbrauner Linsenkern? – 4-before-Phaco! Klin Monatsbl Augenheilkd 1997;210(suppl):13.

Prof. Dr. J. Kammann, Chefarzt der Augenklinik des St. Johannes-Hospitals, Johannesstrasse 9–17, D– 44137 Dortmund (Germany)

Tel. 49 231 1843 2241, Fax 49 231 1843 2508, E-Mail kammann@joho-dortmund.de

impossible to subluxate the nucleus safely into the iris plane or anterior chamber and thus it was necessary to employ posterior chamber, endocapsular phaco techniques. With most nuclei a nuclear cracking technique was used where the core nucleus was emulsified and the peripheral bowl of retained nuclear material and nuclear plate was infractured in a so-called ‘one-handed technique’ useful for soft nuclei in younger patients. Soon thereafter, hydrodissection and hydrodelineation became a standard part of the technique in order to loosen the nucleus and allow it to be rotated easier. With a small continuous tear anterior capsulectomy, the nucleus always remained localized in the posterior chamber. While there are many positive features to the endocapsular cracking techniques, they were more difficult to teach with a steeper learning curve. In addition, procedure times were somewhat longer than they had been with the iris plane technique. Furthermore, Dr. Lindstrom found a mild increase in the capsular tear rate from approximately 1 to 1.8%. On the positive side, visual recovery was very rapid, especially when foldable intraocular lenses were used, and most patients had a clear cornea on the first postoperative day. With time, the capsular tear rate was reduced to 1.3%, but the procedure required 10–15 min to complete. In addition in some instances, such as patients with loose zonules from pseudoexfoliation, the capsulorhexis was somewhat smaller, in the 4-mm range. In these cases other undesirable side effects were possible, such as the capsular-contraction syndrome.

Several Japanese investigators at the time suggested that retained subcapsular epithelium might play a role in postoperative inflammation and capsular opacity. Thus, the procedure was modified to incorporate larger diameter continuous tear anterior capsulectomies. With a continuous tear anterior capsulectomy of 5.0–6.0 mm the nucleus would often inadvertently partially or totally subluxate anterior to the capsular rim. The nucleus could simply be pushed back into the capsular bag and the procedure completed utilizing a nuclear fracture technique. It soon became obvious that subluxating the nucleus into the anterior chamber was advantageous, particularly in high-risk cases. When there was a large anterior segment, as in a myopic patient, a healthy cornea and a relatively soft nucleus, the nucleus could be subluxated to a position anterior to the capsular bag and then a deep anterior chamber phacoemulsification performed while supporting the nucleus with a nucleus rotator. The larger anterior capsulectomy allowed an easier phacoemulsification with no apparent adverse effect in regard to intraocular lens centration. Fundus visibility was good and the occasional case of capsular contraction syndrome disappeared. Capsular opacity rates appeared low and a small randomized study suggested that they were somewhat lower than with the smaller anterior capsulectomy utilized in the past. The impact of capsulorhexis size on capsular opacity rate and postoperative inflammation remains controversial with studies favoring both arguments.

The next influence came from David Brown, MD, and Bill Maloney, MD, who have championed the concept of supracapsular phacoemulsification where the nucleus is hydrodissected and tumbled prior to phacoemulsification. Although the technique was very efficient, it was not always easy to tumble the nucleus safely in every eye. Also, there was more postoperative corneal edema in these eyes compared to those treated with an endocapsular approach. However, use of this technique spurred the discovery that the nucleus could simply be supported in the plane of the iris and anterior capsular leaflet, rather than completely tumbling of the entire nucleus. Half of it could then be emulsified. Then, with a much smaller nuclear remnant, the remaining one half could be tumbled upside down and emulsified as in the classical supracapsular approach. The surgical technique was fast, simple and safe. The following day the corneas of these patients were similarly clear compared to those treated with an endocapsular nuclear fracture approach. The author chose to call the technique ‘tilt and tumble’and refined it so that it could be taught effectively to residents, fellows and other ophthalmologists with confidence. It is basically ‘back to Kratz’ with help from Brown and Maloney, in the capsulorhexis, hydrodissection, viscoelastic and modern phaco machine era. In the following paragraphs we will describe and illustrate this technique in enough detail to allow an ophthalmologist to evaluate it for his or her own patients.

Indications

The indications for the tilt and tumble phacoemulsification technique are quite broad. It can be utilized in either a large or small pupil situation. Some surgeons favor with small pupils where the nucleus can be tilted up such that the equator is resting in the center of the pupil and is then carefully emulsified. It does require a larger continuous tear anterior capsulectomy of at least 5.0 mm. If a small anterior capsulectomy is achieved, the hydrodissection step of tilting the nucleus can be dangerous, and it is possible to rupture the posterior capsule during the hydrodissection step. If, inadvertently, a small anterior capsulectomy is created, it is probably safest to convert to an endocapsular phacoemulsification technique or enlarge the capsulorhexis. If it is not possible to tilt the nucleus with either hydrodissection or a manual technique, the surgeon should convert to an endocapsular approach. Occasionally the entire nucleus will subluxate into the anterior chamber. In this setting if the cornea is healthy, the anterior chamber deep, and the nucleus soft, then the phacoemulsification can be completed in the anterior chamber supporting the nucleus away from the corneal endothelium. The nucleus can also be pushed back inferiorly over the capsular bag to allow the iris plane tilt and tumble technique to be completed.

In patients with severely compromised endothelium, such as Fuchs’ dystrophy or previous keratoplasty patients with a low endothelial cell count, endocapsular phacoemulsification is preferred to reduce endothelial. In a normal eye, corneal clarity on the first day postoperatively is excellent. Nevertheless, the tilting and tumbling maneuvers do increase the chance of endothelial cell contact of lens material compared to an endocapsular phacoemulsification. Therefore, the endocapsular technique should be employed in eyes with borderline corneas. The technique is a very good transition technique for teaching residents, fellows and surgeons who are transitioning to phacoemulsification, because it is easy to convert to a planned extracapsular cataract extraction with the nucleus partially subluxated above the anterior capsular flap at the iris plane.

Preoperative Preparation

The patient enters the anesthesia induction or preoperative area and tetracaine drops are placed in both eyes. The placement of these drops increases the patient comfort during the placement of the multiple dilating and preoperative medications, decreases blepharospasm and also increases the corneal penetration of the drops to follow.

The eye is dilated with 2.5% neosynephrine and 1% cyclopentolate every 5 min for three doses. Additionally, preoperative topical antibiotic and antiinflammatory drops are administered at the same time as the dilating drops. We favor the combination of a preoperative topical antibiotic, topical steroid and topical nonsteroidal. The rationale for this is to preload the eye with antibiotic and nonsteroidal prior to surgery. The pharmacology of these drugs and the pathophysiology of postoperative infection and inflammation support this approach. An eye that is preloaded with anti-inflammatories prior to the surgical insult is likely to have a much reduced postoperative inflammatory response. Both topical steroids and nonsteroidals have been found to be synergistic in the reduction of postoperative inflammation. In addition, the use of perioperative antibiotics is supported in the literature as reducing the small chance of postoperative endophthalmitis. Since the patient will be sent home on the same drops utilized preoperatively, there is no additional cost.

Our usual anesthesia is topical tetracaine reinforced with intraoperative intracameral 1% nonpreserved (methylparaben-free) xylocaine. For patients with blepharospasm a ‘miniblock’ O’Brien facial nerve anesthesia, utilizing 2% xylocaine with 150 units of hyaluronidase per 5 cm3 of xylocaine, can be quite helpful in reducing squeezing. This block lasts 30–45 min and makes surgery easier for the patient and the surgeon. Patients are sedated prior to the block to eliminate any memory of discomfort. One way to determine when this facial

nerve block might be useful is to ask the technicians to make a note in the chart when they have difficulty performing applanation pressures or A-scan because of blepharospasm. In these patients a mini facial nerve block can be quite helpful.

In younger anxious patients and in those with difficulty cooperating, we perform a peribulbar block. Naturally, general anesthesia is used for very uncooperative patients and children. While this is controversial, in some patients where general anesthesia is chosen and a significant bilateral cataract is present, we will perform consecutive bilateral surgery completely re-prepping and starting with fresh instruments for the second eye. Again, this is a clinical decision weighing the risk to benefit ratio of operating both eyes on the same day versus the risk of two general anesthetics.

Upon entering the surgical suite the patient table is centered on preplaced marks so that it is appropriately placed for microscope, surgeon, scrub nurse and anesthetist access. We favor a wrist rest, and the patient’s head is adjusted such that a ruler placed on the forehead and cheek will be parallel to the floor. The patient’s head is stabilized with tape to the head board to reduce unexpected movements, particularly if the patient falls asleep during the procedure and suddenly awakens. A second drop of tetracaine is placed in each eye. If the tetracaine is placed in each eye, blepharospasm is reduced. A periocular prep with 5% povidone-iodine solution is completed. We do not irrigate the ocular surface and fornices with povidoneiodine. Under topical anesthesia we have found that the patients note a significant burning. If a few drops leak into the eye this is certainly acceptable.

An aperture drape is helpful for topical anesthesia to increase comfort. We have noted that when the drape is tucked under the lids this often irritates the patient’s eye and also reduces the malleability of the lids, decreasing exposure. Since it is important to isolate the meibomian glands and lashes a reversible solid bladed speculum (Lindstrom/Chu Speculum – Rhein Medical) may be used. With temporal and nasal approaches to the eye, the solid blades of the speculum are not in the way. In those cases where a superior approach is planned, a Tegaderm drape is used, tucking it under the lids. In these cases, a Kratz-modified Barraquer wire is useful, as this enhances access to the globe. Nevertheless, we have been using a superior approach incision less and less.

Balanced salt solution (BSS) is used in all cases. For the short duration of a phacoemulsification case, BSS plus does not provide any clinically meaningful benefit. We place 0.5 cm3 of the intracardiac nonpreserved (sodium bisulfatefree) epinephrine in the bottle for assistance in dilation and perhaps hemostasis. We also add 1 ml (1,000 units) of heparin sulfate to reduce the possibility of postoperative fibrin. This is also a good anti-inflammatory and coating agent. At this dose there is no risk of enhancing bleeding or reducing hemostasis.

The lids are separated with a solid blade speculum. A solid blade Barraquer speculum or the Lindstrom/Chu aspirating speculum (Rhein Medical) which

Fig. 1. Paracentesis incision.

Fig. 2. Injection of nonpreserved xylocaine.

can be placed temporally or nasally, isolates the lashes. A final drop of tetracaine is placed in the operative eye or the surface is irrigated with the nonpreserved xylocaine. We do not like to utilize more than three drops of tetracaine or other topical anesthetic as excess softening of the epithelium can occur, resulting in punctate epithelial keratitis, corneal erosion and delayed postoperative rehabilitation.

Operative Procedure

The patient is asked to look down. The globe is supported with a dry Merocel sponge, and a counter puncture is performed superiorly at 12 o’clock with a diamond stab knife (Osher/Storz). The incision is about 1 mm in length (fig. 1). Approximately 0.25 ml of 1% nonpreserved methylparaben-free xylocaine is injected into the eye (fig. 2). We advise the patient that they will feel a ‘tingling’ or ‘burning’ for a second, and then ‘the eye will go numb’. This provides a psychological support for the patient that they will now have a totally anesthetized eye and should not anticipate any discomfort. We tell them that while they will feel some touch and fluid on the eye, they will not feel anything sharp, and if they do, we can supplement the anesthesia. This injection also firms up the eye for the clear corneal incision. We do not find it necessary to inject viscoelastic prior to constructing the corneal wound.

We perform a temporal or nasal anterior limbal or posterior clear corneal incision. We perform a modified Langerman incision. A groove is made

Fig. 3. Clear corneal incision.

400–500 m deep into the perilimbal capillary plexus just anterior to the insertion of the conjunctiva. Care is taken not to incise the conjunctiva as this can result in ballooning during phacoemulsification and irrigation aspiration. Some surgeons define this as being a posterior clear corneal incision and others as an anterior limbal incision. The anatomical landmark is the perilimbal capillary plexus and the insertion of the conjunctiva. When the groove is made there will be a small amount of capillary bleeding. Since the incision is into a vascular area, long-term wound healing can be expected to be stronger than it is with a true clear corneal incision. True clear corneal incisions, such as performed in radial keratotomy, clearly do not have the wound-healing capabilities that a limbal incision demonstrates where there are functioning blood vessels present.

The anterior chamber is then entered parallel to the iris at a depth of approximately 300 m or above the deepest portion of the groove. This creates a hinge type or Langerman type of incision (fig. 3). We prefer the width of the incision to be 1.75–2.00 mm and Dr. Lindstrom has designed a keratome with Storz with two small black lines which can serve as a guide to the surgeon in creating an appropriate width incision (Lindstrom Keratome/Storz).

In right eyes the incision is temporal, and in left eyes, nasal. This allows the surgeon to sit in the same position for right and left eyes. The nasal cornea is thicker, has a higher endothelial cell count and allows very good access for phacoemulsification. The nasal limbus is approximately 0.3 mm closer to the center of the cornea than the temporal limbus, and this can, in some cases where there is excess edema, reduce first day postoperative vision more than one might anticipate with a temporal incision. There also can, in some patients, be pooling of irrigating fluid. For this reason, an aspirating speculum is useful. It is also helpful to tip the head slightly to the left side. Nonetheless, in left eyes a nasal

clear corneal approach is an excellent option, particularly for surgeons who find the left temporal position uncomfortable.

The groove may be constructed by simply taking the keratome and tipping it up and utilizing the tip of the keratome. Some surgeons utilize a guarded knife to create a consistently deep incision. An astigmatic keratotomy blade can be quite useful in this regard. This blade can also be helpful when patients present with high astigmatism and an intraoperative astigmatic keratotomy is felt to be appropriate.

In some patients it may be safest to create a corneal scleral incision. Examples of these include patients who have had a previous radial keratotomy or demonstrate findings of peripheral corneal ulcerative keratitis, in some patients with very low endothelial cell counts, and any case where there is any significant peripheral pathology or thinning. The anterior limbal or posterior corneal incision described above can be made temporally, nasally, in the oblique meridian or even superiorly without induction of significant corneal edema or endothelial cell loss.

With a corneal scleral incision we will raise a small conjunctival flap with Westcott scissors. Prior to this, anesthesia can be provided by holding a Merocel sponge soaked in tetracaine or nonpreserved xylocaine in the area of the limbus where the conjunctival flap will be raised for 30–60 s. Mild cautery can be applied or one can utilize a Merocel soaked in thrombin 1/1,000 in BSS to effect hemostasis. If there is minimal capillary oozing the mild bleeding can also simply be ignored. Thrombin solution is also very useful in anterior segment reconstruction cases where excess bleeding is noted and may be safely injected into the anterior chamber if diluted in BSS.

We prefer to close all clear corneal incisions 4 mm with a horizontal mattress, X or single radial suture. The least early astigmatism is induced with the horizontal mattress suture. A corneal scleral incision 5.5 mm is also closed with one horizontal mattress suture. The incision, if 3 mm in length, tends to cause an induction of 0.25 0.25 dpt of astigmatism. If it is placed on the steeper meridian, it can therefore be expected to reduce the astigmatism somewhere between 0 and 0.50 dpt. If the incision is 4 mm in length, there usually is a reduction in astigmatism of 0.50 0.50 or 0–1.00 dpt if the incision is placed on the steeper meridian. In routine cataract surgery we do not utilize incisions4 mm. An incision in the 3-mm range will almost always be self-sealing. With modern injector systems most foldable intraocular lenses can be implanted through a 3-mm anterior limbal incision.

In select patients an intraoperative astigmatic keratotomy can be performed at the 7–8 mm optical zone. This can be done at the beginning of the operation. The patient’s astigmatism axis is marked carefully using an intraoperative surgical keratometer which allows one to delineate the steeper and flatter meridian and not be concerned about globe rotation. One 2-mm incision at a 7–8 mm