Cataract chopping techniques, developed for safe and fast removal of dense cataracts, allow easier mechanical nucleus separation and reduce intraocular tissue damage by using less ultrasonic power. Such procedures include the phacochop and the stop-and-chop techniques.1,2
Here, we present a modified nonsculpting technique for grade 3 to 4 dense cataracts. This lift-and-crack technique, which uses minimal ultrasound energy and applies minimal stress to the capsular bag and the zonules, is particularly useful in the presence of an incomplete capsulorrhexis and/or zonular weakness in less than two quadrants.
SURGICAL TECHNIQUE
Under local or topical anesthesia, a temporal self-sealing
clear corneal incision is created with a 2.8-mm diamond
knife, and a sideport is made with a microvitreoretinal
blade 30° to 45° degrees from the main incision
(preferably 30° because the chopping maneuver will be
easier to manipulate). Trypan blue dye is applied under
air in the anterior chamber to stain the anterior capsule.
In all cases, a large anterior capsulorrhexis (6–7 mm
diameter) is attempted.
High intralenticular pressure in eyes with dense cataract frequently leads to peripheral extension of the capsular tear and an incomplete capsulorrhexis. Therefore, we make use of the advantages of the soft-shell technique, initially applying a dispersive ophthalmic viscosurgical device (OVD) such as Viscoat (Alcon Laboratories, Inc., Fort Worth, Texas) to protect the endothelium. Afterward, a cohesive OVD such as Provisc (Alcon Laboratories, Inc.) is introduced into the anterior chamber to prevent collapse and to avoid an errant radial capsular tear.
The phaco tip is used to grasp the nucleus centrally with high vacuum (approximately 350 mm Hg), and the nucleus is elevated with a tilt so that it protrudes outside the capsular bag distally. Then the chopper is used to segment the nucleus centripetally, with a maneuver that starts from the lens equator (or just behind) and uses the vector forces efficiently to cleave the nucleus without applying additional stress to the capsular bag or the zonules (Figures 1 and 2).
The nucleus is then cleaved and segmented into smaller triangular sectoral pieces, which are emulsified with the following parameters: 250 to 400 mm Hg vacuum, 30 mL/min aspiration flow rate, and 120 mm infusion bottle height. Phacoemulsification power is titrated according to the density of the nucleus, generally ranging from 25% to 60%. The I/A tip is used to clean any residual cortical material, and the IOL is implanted in the bag or in the sulcus, with proper positioning of the haptics perpendicular to the axis of the capsular defect or tear.
DISCUSSION
Chopping techniques achieve fast and safe cracking of
the nucleus. Several unique characteristics of our lift-andcrack
technique are favorable in grade 3 to 4 dense
cataracts, particularly in the presence of an incomplete
capsulorrhexis and/or zonular weakness. Lifting the distal
nucleus is beneficial because it brings the nucleus through
the anterior capsular opening and partially out of the capsular
bag, so that chopping and phacoemulsification are
performed at the pupillary plane. High vacuum is applied
to the central nucleus, preventing transmission of stress
to the zonules in the presence of a large anterior capsulorrhexis.
In techniques in which the whole lens is prolapsed
into the anterior chamber, excessive tilt of the nucleus
may lead it to skim over the corneal endothelium in eyes
with a shallow anterior chamber. But with manipulations
performed in the pupillary plane, as in our technique, the
capsular bag and zonules are protected from excessive
stress, and the corneal endothelium is spared the deleterious
effects of phacoemulsification power
In conventional phacoemulsification techniques such as divide-and-conquer and phaco-chop, significant ultrasound energy is required for segmentation and complete removal of dense nuclei. After a central groove is created, in situ forceful outward separation of the large, hard nucleus may transmit excessive stress to the capsular bag and zonules. This stress increases with further maneuvers to divide the nucleus into smaller pieces due to inadequate space in the bag. Additionally, such maneuvers frequently remain inefficient for cracking. Proceeding to phacoemulsification after incomplete separation of nuclear pieces may lead to greater risk of decreased capsular and zonular integrity. Increased stress on the capsule may eventually lead to posterior capsular rupture or zonular dehiscence, particularly in eyes with an incomplete capsulorrhexis due to peripheral extension of the tear or zonular weakness.
In the lift-and-crack technique, the positioning of and distance between the chopper and the phaco tip maximizes the efficiency of the vector forces when the chopper is moved centrally to cleave the nucleus into two segments. Therefore, unsuccessful cracking attempts are unlikely. This horizontal chopping technique also removes the need for grooving the central nucleus and decreases use of phacoemulsification power considerably. Additionally, the chopper does not pass beneath the nucleus, unlike in peripheral chopping techniques where the chopper may slide over the nuclear surface with any tilt of the nucleus, risking posterior capsular integrity.3 In our technique, the surgeon can continuously observe the tip of the chopper, increasing the safety of the capsular bag.
The tilt-and-chop technique4 uses a similar method of chopping. The distal edge of the nucleus is tilted from the capsular bag by digging the phaco tip into the nucleus, proximal to its center, and pushing posteriorly. The chopper is then placed around the lens equator or behind the nucleus, and a horizontal chop is performed. In our opinion, the maneuver of depressing one edge of the nucleus to elevate the other may further stress the capsule and the zonules. However, when the nucleus is grasped centrally and lifted up with high vacuum, the only force applied during chopping will be toward the center of the phaco tip.
CONCLUSION
The lift-and-crack technique we present is a modification
based on recent trends in chopping. It seems to be particularly
useful in eyes with dense cataracts, especially in the
presence of an incomplete capsulorrhexis or zonular weakness.
The technique has allowed us to perform phacoemulsification
in such usually risky cataract cases with minimal
risk to the capsular bag, the zonules, and the endothelium.
We have enjoyed successful outcomes in challenging cases
that other cataract surgeons were hesitant to undertake.
Hanefi Cakir, MD, practices at the Turkiye Hospital Eye Clinic, Istanbul, Turkey. Dr. Cakir states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: haca61@gmail.com.
Canan Asli Utine, MD, MSc, is an Assistant Professor of Ophthalmology at Yeditepe University, Istanbul, Turkey. Dr. Utine states that she has no financial interest in the products or companies mentioned. She may be reached at tel: +90 212 2114000; fax: +90 212 2112500; e-mail: cananutine@ gmail.com.
