Phaco chop technique for cataract surgery in the dog
狗白内障手术的 Phaco 切削技术

Christi Warren 克里斯蒂-沃伦Eye Care for Animals of Tucson, Tucson, Arizona, USA
美国亚利桑那州图森市动物眼科护理中心

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Abstract 摘要

Phaco chop is a bimanual phacoemulsification technique to remove cataracts. The technique was first presented at the 1993 3rd American-International Congress on Cataract, IOL, and Refractive Surgery in Seattle by Dr Kunihiro Nagahara. He compared the lens with a block of wood and by applying chopping forces parallel to the natural planes of the lens lamellae, as one does in splitting wood, a nucleus can be cleaved with surprisingly little force and time. Dr Nagahara used the phaco tip to impale and high vacuum to hold the nucleus while a second instrument, or chopper, hooked the equator and was pulled centrally, splitting the nucleus along its natural cleavage planes. This was a breakthrough for surgeons who had been utilizing several minutes of phaco energy sculpting grooves and bowls in a lens. Studies have shown that compared with fourquadrant ‘divide and conquer’, the phaco chop technique uses less phaco time and energy, significantly reducing endothelial cell damage. Other advantages of phaco chop include reduction of zonular and capsular stress because forces are directed toward an opposing instrument and the phaco tip is kept in a central ‘safe zone’ in the middle of the pupil. This technique has also been successfully adapted to the canine phacoemulsification procedure. The larger canine lens requires some modifications, and lenses with hard nuclear and cortical material may not be amenable to this procedure.
Phaco chop 是一种双臂乳化技术，用于摘除白内障。该技术由 Kunihiro Nagahara 博士于 1993 年在西雅图举行的第三届美国-国际白内障、人工晶体和屈光手术大会上首次提出。他将晶状体比作一块木头，通过施加与晶状体薄片自然平面平行的劈力，就像劈柴一样，以惊人的力量和时间劈开晶状体核。长原博士使用phaco刀尖刺入晶状体核，并用高真空吸住晶状体核，同时用第二个器械或切刀钩住晶状体核的赤道部，向中心拉动，沿着晶状体核的自然劈裂平面劈开晶状体核。这对于一直利用数分钟的 phaco 能量在晶状体上雕刻凹槽和碗状结构的外科医生来说是一个突破。研究表明，与四象限 "分而治之 "相比，phaco chop 技术使用的 phaco 时间和能量更少，大大减少了对内皮细胞的损伤。phaco chop 的其他优点还包括：由于力量被引导到一个对立的器械上，并且 phaco 尖端保持在瞳孔中央的 "安全区 "内，因此减少了晶状体和囊袋应力。这种技术也已成功应用于犬乳化手术。犬晶状体较大，需要做一些改动，而具有硬核和皮质材料的晶状体可能不适合这种手术。

Key Words: cataract, lens, phaco chop, phacoemulsification, dog
关键字：白内障、晶状体、超声乳化刀、超声乳化、狗

INTRODUCTION 引言

In 1993 at the 3rd American-International Congress on Cataract, IOL, and Refractive Surgery in Seattle, Dr Kunihiro Nagahara introduced a revolutionary phacoemulsification technique that involved chopping the lens nucleus utilizing a second instrument. He called the technique ‘phaco chop’. Dr Nagahara compared the lens with a block of wood. By applying chopping forces parallel to the natural planes of the lens lamellae, as one does in splitting wood, a nucleus can be cleaved with surprisingly little force and time. Dr Nagahara used the phaco tip to impale and high vacuum to hold the nucleus while a second instrument, or chopper, hooked the equator and was pulled centrally, splitting the nucleus along its natural cleavage planes.
1993 年，在西雅图举行的第三届美国-国际白内障、人工晶体和屈光手术大会上，Kunihiro Nagahara 博士提出了一种革命性的超声乳化技术，即利用第二种器械切碎晶状体核。他将这种技术称为 "phaco chop"。长原医生将晶状体比作一块木头。就像劈柴一样，在平行于晶状体薄片自然平面的方向上施加劈力，晶状体核就能以惊人的力量和时间被劈开。长原博士用phaco刀尖刺入晶状体，并用高真空吸住晶状体核，同时用第二个工具（即切刀）钩住晶状体的赤道部，向中心拉动，沿着晶状体核的自然劈裂平面劈开晶状体核。
This was a breakthrough for surgeons who had been utilizing several minutes of phaco energy sculpting grooves and bowls in a lens. Studies have shown that, compared with four-quadrant ‘divide and conquer’, the phaco chop technique uses less phaco time and energy, significantly reducing endothelial cell damage.

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Other advantages of phaco chop include reduction of zonular and capsular stress because forces are directed toward an opposing instrument and
这对于一直使用数分钟 phaco 能量在晶状体上雕刻凹槽和碗状结构的外科医生来说是一个突破。研究表明，与四象限 "分而治之 "相比，phaco chop 技术使用的 phaco 时间和能量更少，可显著减少内皮细胞损伤。

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the phaco tip is kept in a central ‘safe zone’ in the middle of the pupil.

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This makes phaco chop safer for patients with loose zonules
瞳孔中央的 "安全区 "内。

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这使瞳孔松弛的患者更安全地进行 phaco 切削。

Since Nagahara’s presentation, several forms of phaco chop have evolved. Dr Nagahara’s technique is a form of horizontal chop because of its analogy to cleaving a block of wood on-end. The chopper moves through the lens from the periphery to the center toward the embedded phaco tip.

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His method has also been termed ‘nonstop’ chop, because the chopping of the lens is performed without an initial groove. The horizontal ‘stop-and-chop’ method utilizes one central groove made with the phaco tip to facilitate the first chop and allow for additional space to chop and remove lens fragments.

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One study showed that nonstop chop and stop-and-chop methods were equally efficacious in removing cataracts.

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Vertical chop or ‘phaco quick-chop’ was introduced by Dr Vladimir Pfeifer and utilizes a sharp chopper spike to impale the lens in front of the centrally buried phaco tip. A shearing force is created when the chopper spike is depressed downward into the lens while the phaco tip simultaneously lifts the lens.

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In the vertical chop method, the chopper always stays centrally, rather than moving peripherally to centrally as in horizontal chop.
自 Nagahara 发表演讲以来，已经发展出多种形式的 phaco 切削。长原医生的技术是一种水平切削，因为它类似于在一端劈开一块木头。劈刀从晶状体外围向中心移动，朝向嵌入的 phaco 尖端。

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他的方法也被称为 "不停顿 "劈切，因为劈切晶状体时没有初始凹槽。水平的 "停止-切削 "方法是用 phaco 刀尖开一个中心槽，以方便第一次切削，并留出更多空间切削和移除晶状体碎片。

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一项研究表明，不停切法和停切法在去除白内障方面效果相同。

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垂直切法或 "phaco 快速切法 "由 Vladimir Pfeifer 医生提出，利用锋利的切刀钉将晶状体刺入中央埋入的 phaco 刀尖前方。当刀刺向下刺入晶状体时会产生剪切力，同时 phaco 尖端会抬起晶状体。

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在垂直切刀法中，切刀始终保持在中心位置，而不是像水平切刀那样从外围向中心移动。

Figure 1. Chang combination chopper on left and modified chopper on right.
图 1.左侧为 Chang 组合斩波器，右侧为改进型斩波器。

PHACO CHOP IN CANINE PHACOEMULSIFICATION
犬类超声乳化术中的 Phaco 切口

I have utilized the horizontal chop method most frequently in canine cataract surgery. Translation of the chop method to veterinary medicine has required some modifications, however, especially with instrumentation. The axial thickness of the human lens is

\approx 4 mm

. For successful chop, the chopper tip should be at approximately half depth,

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so chopper lengths average

1 - 2 mm

. The axial lens thickness of the cataractous canine lens varies from

\approx 6.4

8.4 mm,^{14}

or 8 to 11 mm in diabetic dogs.

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The short human chopper creates an inefficient chop in the larger canine lens. I have had a 4 mm modified Chang chopper (Katena, Denville, NJ, USA) manufactured for veterinary use (Fishkind-Warren chopper, Katena) and use it in medium to larger dogs (Fig. 1). I use the shorter chopper in my small patients.
在犬白内障手术中，我最常使用的是水平切削法。不过，将水平切削法应用到兽医领域需要进行一些修改，尤其是在器械方面。人类晶状体的轴向厚度为

\approx 4 mm

。为了成功切削，切刀尖端应位于大约一半的深度，即

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，因此切刀的平均长度为

1 - 2 mm

。白内障犬晶状体的轴向厚度从

\approx 6.4

到

8.4 mm,^{14}

不等，糖尿病犬的厚度为 8 到 11 毫米。

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短的人类切刀在较大的犬晶状体上产生的切削效率很低。我已经制造了一个 4 毫米的改良型张氏切刀（Katena，Denville，NJ，USA），用于兽医用途（Fishkind-Warren 切刀，Katena），并将其用于中型到大型犬（图 1）。我给我的小型患者使用较短的切碎器。

In preparation to perform phaco chop, a 4-5 mm continuous anterior capsulorrhexis is performed. Trypan Blue (OV Blue, Ocularvision Inc, Solvang, CA, USA) aids in visualizing the anterior capsular edges during the chop, as capsular visualization is critical in preventing damage of the capsule with the chopper. Thorough hydrodissection/hydrodelineation is important in preparing for the chop technique and allowing for free rotation of the lens nucleus during the procedure.
在准备进行 phaco 切削时，要进行 4-5 毫米的连续前囊切除。胰蓝（OV Blue，Ocularvision Inc，Solvang，CA，USA）有助于在切削过程中观察前囊边缘，因为囊的可视化对于防止用切削刀损伤囊至关重要。彻底的水解剖/水划线对于准备切削技术和允许晶状体核在手术过程中自由旋转非常重要。

For right-handed surgeons, the phaco handle is held in the right hand and the chopper is held in the left. The instruments are inserted through two separate corneal incisions, as if holding a knife and fork on a dinner plate. With intumescent or hard lenses, I utilize the stop-and-chop method to allow more room for the initial insertion of the chopper under the lens capsule edge. The phaco tip deeply impales the lens proximally centrally and holds the lens with vacuum. The chopping instrument is passed under the anterior capsule edge, hooking the lens or lens nucleus at the equator (Fig. 2). The chopper is pulled toward the phaco tip. This manual energy compresses and fractures the nucleus (Fig. 3). This first fracture should completely dissect the lens or lens nucleus into two separate pieces. If a groove is
对于右撇子外科医生来说，右手握住 phaco 手柄，左手握住切刀。器械从两个不同的角膜切口插入，就像在餐盘上拿刀叉一样。对于膨胀型镜片或硬性镜片，我采用的是 "停-切 "法，以便有更多空间将切刀插入镜片囊边缘下方。phaco 刀头深深地刺入晶状体近端中心，并用真空吸住晶状体。切刀从晶状体前囊边缘下穿过，在赤道部钩住晶状体或晶状体核（图 2）。将切刀拉向 phaco 尖端。这种手动能量会压迫晶状体核并使其断裂（图 3）。第一次断裂应将晶状体或晶状体核完全切成两片。如果有凹槽
initially made, the fracture would occur along the groove. If this is not achieved with the first pass, additional passes or maneuvering of the chopper should be made until a complete split is achieved. The lens is rotated and a second chop is made, creating a small pie-shaped wedge (Fig. 4). The piece is removed by phaco-assisted aspiration and the process repeated until the lens or lens nucleus is completely removed. Epinuclear and capsular clean up are performed and the surgery completed.
如果在最初切割时，裂缝就会沿着凹槽出现。如果第一次没有达到这个效果，就应该再多做几次或操纵切片器，直到完全裂开为止。旋转晶状体并进行第二次切割，形成一个小饼状楔形（图 4）。用噬菌体辅助抽吸法取出小块，然后重复此过程，直到完全取出晶状体或晶状体核。晶状体外核和晶状体囊清理完毕，手术完成。

A thorough understanding of the principles that influence phaco machine settings is vital in achieving a proficient and safe surgery. The phaco machine must perform differently for each of the three basic steps in phaco chop: (i) chopping the lens, (ii) carrying the pieces toward the pupil center with the phaco tip, and (iii) using phaco-assisted aspiration to remove the pieces. Strong vacuum power to hold the lens on the phaco tip is important in the first two steps while followability is needed for the third step.
透彻了解影响 phaco 机器设置的原理对实现熟练和安全的手术至关重要。在 phaco 切削的三个基本步骤中，每一个步骤的 phaco 机器都必须有不同的表现：(i) 切削晶状体，(ii) 用 phaco 刀头将碎片带向瞳孔中心，(iii) 使用 phaco 辅助吸力去除碎片。在前两个步骤中，将晶状体固定在 phaco 尖端的强大真空力非常重要，而在第三个步骤中则需要可追踪性。

Strong vacuum is achieved with total occlusion and a tight seal around the phaco tip. Tip chatter will not allow a tight seal. Certain phaco machines such as the AMO Sovereign (Advanced Medical Optics, Santa Ana, CA, USA) have the capability of ‘burst mode’, which utilizes one burst of phaco power to impale the lens deeply without continued chatter. In lieu of ‘burst mode’, one could utilize a low pulse phaco to impale the lens. Vacuum is adjusted to hold the lens piece strongly without cavitation of the surrounding lens material and weakening the hold, as might occur if the vacuum is too strong. Too low a vacuum setting, however, will not hold the piece adequately. Additionally, the silicone sleeve of the phaco tip may be retracted slightly to expose more of the bare tip for a better seal. Finally, in softer lenses, a 0 degree phaco tip occludes and holds more easily because less of the tip must be buried for total occlusion.

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I use no greater than a 30 degree tip when dealing with hard lenses, being sure to bury the entire bevel within the lens to create a full seal. Followability during the third step (phaco-assisted aspiration) relies on flow rate or aspiration. Aspiration should be sufficient to attract pieces to a centrally held phaco tip.
在完全闭合的情况下，可实现较强的真空度，并在 phaco 刀尖周围形成严密的密封。针尖颤动会导致密封不严。某些 phaco 机，如 AMO Sovereign（Advanced Medical Optics，圣安娜，加利福尼亚州，美国），具有 "爆发模式 "功能，它利用一次爆发的 phaco 功率将晶状体深深地刺入，而不会持续颤动。如果不使用 "爆发模式"，也可以使用低脉冲 phaco 击穿晶状体。真空度的调节可强力固定晶状体片，而不会使周围的晶状体材料产生气穴，从而减弱固定效果，如果真空度太强可能会出现这种情况。然而，过低的真空设置将无法充分固定晶状体。此外，可以稍微缩回 phaco 刀头的硅胶套，露出更多裸露的刀头，以达到更好的密封效果。最后，在较软的镜片中，0 度的 phaco 针尖更容易闭塞和固定，因为要完全闭塞，必须埋入的针尖较少。

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在处理硬镜片时，我使用不超过 30 度的针尖，确保将整个斜面埋入镜片内，以形成完全密封。第三步（噬菌体辅助抽吸）的可跟踪性取决于流速或抽吸量。抽吸量应足以将碎片吸引到中心固定的 phaco 尖端。

Pre-set phaco machine parameters are only a starting point, and these parameters often require modification during surgery. Being familiar with your machine’s ability and having the knowledge and experience to know when to change vacuum, power, flow rate and aspiration during surgery is important, as every lens has its own unique hardness and brittleness.
预先设置的超声乳化仪参数只是一个起点，在手术过程中往往需要修改这些参数。由于每种镜片都有其独特的硬度和脆性，因此熟悉机器的性能并掌握相关知识和经验，知道在手术过程中何时改变真空度、功率、流速和吸力非常重要。

DISCUSSION 讨论

Like all surgical techniques, there is a learning curve to phaco chop. Complications with the phaco chop procedure include damage of internal structures with the chopping instruments. Improper placement of the phaco tip or chopping instrument may result in tears of the anterior capsule, dialysis of zonules or tears of the posterior capsule.

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与所有外科技术一样，phaco chop 也有一个学习曲线。phaco切削手术的并发症包括切削器械损伤内部结构。phaco刀尖或切削器械放置不当可能会导致前囊撕裂、小叶透析或后囊撕裂。

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Figure 2. The chopper passes beneath anterior capsule edge to hook nucleus equator. The phaco tip impales the nucleus proximally. The phaco tip will move rightward with a slight lifting motion. The chopper will move leftward with slight depression. Reproduced with permission from Chang.

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图 2.切刀从前囊边缘下方穿过，钩住核赤道部。phaco 刀尖在近端刺入髓核。刀尖会向右移动，并有轻微的上抬动作。切刀向左移动，略有凹陷。经 Chang 许可转载。

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Figure 3. The chopper chops against the phaco tip. Reproduced with permission from Chang.

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图 3.切碎器劈向 phaco 刀尖。经 Chang 许可转载。

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Figure 4. Chopping steps repeated after slight rotation. Reproduced with permission from Chang.

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图 4.轻微旋转后重复切割步骤。经 Chang 授权转载。

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Damage to the anterior capsule or zonules may occur if the surgeon loses sight of the anterior capsule edge and places the chopper on top of the capsule instead of under the leading edge. (Fig. 5a-c) Visualization of the capsular edge is
如果外科医生看不到前囊边缘，将切刀放在囊顶部而不是前缘下方，则可能会损伤前囊或小叶。(图 5a-c）囊边缘的可视化是

Figure 5. (a) Incorrect. The chopper is positioned too high. It will skim over the nucleus. An adequate chop is impossible. (b) Incorrect. Both the chopper and phaco tip are too high. © Incorrect. The chopper is placed outside the capsular bag, which will create a zonular dialysis on attempted chopping. Reproduced with permission from Chang.

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图 5. (a) 不正确。斩波器位置太高。它会掠过原子核。不可能进行充分的斩波。(b) 不正确。切碎器和 phaco 刀尖都太高。(c) 不正确。切刀放置在囊袋外，尝试切削时会产生带状透析。经 Chang 许可转载。

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improved with the use of a vital stain such as Trypan Blue, and is most useful when working on white opaque cataracts. A larger capsulorrhexis is also helpful in preventing anterior capsular damage.

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Also, the initial groove created in the stop-and-chop method allows more room to insert the chopper for the first critical chop, especially when the lens is large, intumescent or hard.
使用胰蓝（Trypan Blue）等重要染色剂可改善白内障的染色效果，在治疗白色不透明白内障时最有用。较大的囊口也有助于防止前囊损伤。

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此外，在停止-切削法中形成的初始凹槽可以为插入切刀进行第一次关键切削留出更多空间，尤其是当晶状体较大、膨胀或较硬时。

Zonular dialysis may occur during lens rotation if hydrodissection is incomplete. Thorough hydrodissection ensures that the lens will easily rotate. Complete hydrodissection can be difficult in the dog due to sticky cortex or if the lens is intumescent. I find that the Chang hydrodissecting cannula (Katena) provides a broad-fanned stream of fluid to aid in dissection, plus it has a sharp bent tip to hook the lens and test its ability to rotate. Zonular dialysis or posterior capsular rupture can occur if the phaco tip pushes too hard on the lens during impalement.

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This can be prevented by using sufficient phaco power to impale the lens without exerting too much downward pressure. Also, preplacement of the chopper around the lens equator provides counter-traction when impaling the lens.

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如果积水分解不彻底，晶状体旋转过程中可能会发生晶状体透析。彻底的水力切割可确保晶状体轻松旋转。由于皮质粘稠或晶状体膨胀，在狗身上很难进行完全的水压解剖。我发现 Chang 水动力解剖套管（Katena）可以提供宽阔的液体流以帮助解剖，而且它有一个锋利的弯曲尖端，可以钩住晶状体并测试其旋转能力。在植入过程中，如果 phaco 刀尖对晶状体的推力过大，可能会发生晶状体透析或后囊破裂。

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这种情况可以通过使用足够的phaco功率来植入晶状体而不施加过多的向下压力来避免。此外，在植入晶状体时，将切刀预先放置在晶状体赤道部周围可提供反牵引力。

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A chopper that is elevated during the chopping maneuver will not compress and fracture the lens completely. (see Fig. 5a,b) For complete chop, the chopping instrument is maneuvered under the anterior capsule on its side and the handle turned upright which point the chopper head down. The chopper head should move in a deep and even plane while being drawn toward the embedded phaco tip. It is also incorrect to press down on the limbus with the chopper or phaco handle.

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This will depress the globe and rotate it away from the surgeon. Visualize moving the instruments as a seesaw over the limbus to prevent this natural tendency.
在切削过程中，如果切刀抬高，就不会完全压迫和压碎晶状体（见图 5a、b）。(见图 5a,b）要完全切碎晶状体，应将切碎器械侧向前囊下方，并竖直转动手柄，使切碎器头部朝下。切刀头应在一个深而均匀的平面上移动，同时朝向嵌入的 phaco 刀尖。用菜刀或 phaco 手柄向下按压边缘也是不正确的。

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这会压迫眼球，使其远离外科医生旋转。将器械视作跷跷板在边缘上移动，以防止这种自然趋势。

I have also found that there are some cataractous lenses that are not amenable to the chop method. Those lenses which have hard nuclear and cortical material in seemingly one massive chunk may not allow room to pass the chopper under the lens capsule for a horizontal chop. The chop method is also difficult in cases in which rotation of the lens cannot be achieved despite hydrodissection.
我还发现，有些白内障镜片不适合使用切削法。那些硬核和皮质材料似乎是一大块的晶状体，可能不允许将切刀通过晶状体囊下进行水平切削。另外，在水切割后仍无法实现晶状体旋转的情况下，也很难使用切碎法。

In conclusion, phaco chop is a new and interesting technique that may provide advantages in the canine patient similar to that of the human patient over other techniques that utilize more phaco power and time.
总之，phaco chop 是一种有趣的新技术，与其他需要更多 phaco 功率和时间的技术相比，它可以为犬类患者带来与人类患者类似的优势。

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