Peripheral radial chop technique for phacoemulsification of hard cataracts

Phacoemulsification has gained acceptance as the standard technique for cataract surgery. It is widely used for extraction of almost all kinds of cataractous lenses.¹ A method that protects intraocular tissues, especially the corneal endothelium, from surgical damage and has minimal complications rates is the objective. Many variations on phacoemulsification techniques have been described to decrease the total ultrasound time and energy used during nucleus emulsification.² However, difficult cataracts such as hard cataracts are still the challenging cases for surgeons. We describe a technique of chop phacoemulsification of hard cataracts that results in minimal damage.

METHODS

Patients
This prospective study comprised 107 consecutive eyes of 98 patients with age-related hard cataracts having modified phacoemulsification between January 2003 and January 2004. The mean age of the 51 women (55 eyes) and 47 men (52 eyes) was 67 years (range 56 to 78 years). The degree of nuclear hardness in all eyes was more than grade IV according to Emery and Little nuclear hardness classification. Exclusion criteria were corneal disease or opacity, glaucoma, uveitis, pupillary dilation problem, high myopia and previous ocular trauma or surgery.

Surgical procedure
Phacoemulsification was performed by the same surgeon. After local or topical anesthesia, a clear corneal tunnel incision of 3.2 mm or 2.8 mm was made according to the preoperative corneal curvature.³ And another self-sealing clear corneal incision was made as a two-side port. Following the injection of chondroitin sulfate 4%-sodium hyaluronate 3% (Viscoat, Belgium) into the anterior chamber, a 6.0 mm continuous curvilinear capsulorhexis was performed. Complete hydrodissection was done using a flap-tip cannula and phacoemulsification was performed as follows: Phaco tip down slope buried in the eccentric nucleus opposite to the main incision, and the large nucleus was hold with the phaco probe using high vacuum. Next the chopper was placed posterior to the corresponding part of the nucleus. Vertically chopping of nucleus in small scope was performed after the nucleus was pressed between the chopper and phaco tip and the chopper was pulled toward the phaco tip (Fig. 1). And then chop at next one hour o'clock region by rotating the nucleus. After repeated chopping 3 or 4 times at 3 or 4 clock hours position, one or more small wedge-shaped pieces of nucleus were created and emulsified in the capsular bag (Fig. 2). Removal of peripheral nucleus provided adequate space for easy emulsification of uncovered central hard nucleus by routine skill such as phaco-chop technique (Fig. 3). After cortical cleanup, intraocular lens was implanted finally. The Bausch & Lomb Millennium phacoemulsifier (USA) was used with the preset parameters of power less than 30%; vaccum, 150 mmHg; and bottle height, 85 cm when a DP8145 phaco tip was used, and vaccum, 380 mmHg; bottle height, 95 cm when a DP8245 phaco tip was used.

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Fig. 1. The phaco tip is embedded diagonally down into the eccentric nucleus opposite to the main incision; the nucleus is held with the phaco probe using high vacuum, and the chopper is placed posterior to the corresponding part of the nucleus. Then vertically chopping is done by pulling the chopper to the phaco tip in the periphery.
Fig. 2. The same procedure shown in Fig. 1 is repeated one o'clock away from the first chopping position, producing a small wedge-shaped piece.
Fig. 3. The peripheral nucleus is removed with a space left.

RESULTS

The mean ultrasonic power applied was 14.7%, ranging 9% to 19%, and ultrasonic time was 1.98 minutes, ranging 1.55 to 3.18 minutes. There were 6 cases (5.6%) of posterior capsule rupture with tearing scope less than 60%. After anterior vitrectomy, intraocular lens were implanted, including 4 for capsular bag and 2 for ciliary sulcus.

One day postoperatively, corneal edema was present 7 eyes (6.5%) and disappeared about 3 to 5 days later in the early stage of application of this technique, and 13 eyes in the late stage presented edema for only one day. At 1, 7 and 30 days postoperatively, the eyes with uncorrected visual acuity 0.5 or better accounted for 76.42%, 87.16% and 90.67% respectively. The mean endothelial cell loss rate one month postoperatively was 9.74%, ranging 8% to 17%. No serious complications were noted.

DISCUSSION

Performing phacoemulsification on hard cataracts tests the skills and experience of the surgeon. The chances of intraoperative complications are high in the hands of surgeons who deal with such cataracat occasionally. And it is also still a challenge for experienced surgeons. Therefore many surgeons hesitate to perform phacoemulsification and advocate manual extracapsular cataract extraction (ECCE).⁴ However phacoemulsification is preferred as it ensures smaller surgical incision and quicker visual rehabilitation.

Most complications of phacoemulsification result from ultrasonic power and time.^5-8 Ocular tissue injury, especially irreversible corneal endothelial cell loss becomes prominent for hard cataracts.⁹ Many variations on phacoemulsification techniques have been described. Except for up-to-date surgical instrument and viscoelastic solutions such as Viscoat and irrigating solutions such as BSS Plus,^10,11 chop techniques of mechanical nucleus-separation reduce the damage to intraocular tissue for less ultrasonic power needed.^12-14

In cracking techniques, the division of the nucleus is achieved by outward separation. A forceful outward separation may transmit excessive stress to the capsular bag and zonules in hard and large cataracts. Chop techniques also depend on vacuum to help divide the nucleus. However, the chop action does not always completely divide the nucleus of extremely hard cataracts. When the division is incomplete, the fragments are held together at the central plate. This makes in-the-bag emulsification difficult and risky. And chopping provides little room for the nuclear pieces to move, the first of these pieces being the most challenging to remove.¹ Moreover, it is inevitable for impairment of endothelial cells caused by the upward ultrasonic wave and energy.¹⁵ Therefore, we developed a peripheral radial chop technique for endocapsular phacoemulsification with low energy.

In our study, chopping the peripherial relative soft nucleus first made low ultrasonic power needed and surgical manipulation easier. It decreased the risk of posterior capsule rupture and zonular dialysis. After removal of small pieces of part of relative soft nucleus, the remaining nucleus would float in the capsular bag and was emulsified easily by routine technique for additional space allowed for. At the beginning of emulsification, several peripheral vertical chopping at about 3 to 4 different position created a relative loose cataract nuclear in the periphery, which made it easy to perform further chopping. And embedded down-slanted phaco tip descreased undesirable energy loss⁵ and the damage to endothelial cells. Finally, manipulation at the endocapsular plane reduced the intraocular tissues damage further. On the whole, vertically chopping the relative soft nucleus in the periphery first enabled an easy first crack and initial removal of a segment of nucleus. Once the first segment is removed, it is often easier to manipulate and rotate the remainder of the nucleus.¹⁶

Usually for a soft or medium-hard nucleus, the epinuclear shell acts as a cushion,¹⁷ which should be removed at last. But for hard and large nucleus, the cushion protection of epinuclear shell was absent. It is very important to use the chopper to protect the posterior capsule from damage. This is an important safety issue that should not be overlooked while performing this technique. It will not increase the risk of posterior capsule rupture rate in the hands of an experienced surgeon. And the results in our study showed the safety of the modified technique for phacoemulsification with quick visual rehabilitation and no serious complications.

In conclusion, less phaco power and phaco time were needed, and stress on the zonules and damage to intraocular tissues were minimized. Phacoemulsification of hard catracts in the bag was safe and effective using peripherial radial chop technique.　　

REFERENCES

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