We would like to share several comments about the article by Kim.1 The author mentions that excessive ultrasound energy might be used in phacoemulsification of hard nucleus cataracts phacoemulsification. We have a small trick to reduce the ultrasound energy used and avoid “wasted” energy. Once the nucleus fragment is captured by the phaco tip and is ready for phacoemulsification, we compress the nucleus fragment toward the phaco tip to make it crack into smaller fragments. The nucleus material is not absolutely incompressible; once a piece of nucleus is captured by the phaco tip and compressed by the chopper, it usually cracks and turns into smaller fragments, even powder. (This is similar to compressing a piece of cracker and turning it into powder with 2 fingers.) We then use ultrasound energy to remove the mixture of small nucleus fragments and nucleus powder. This reduces the ultrasound energy because some of the nucleus has been “emulsified” by the compression.
Second, we have 2 methods to deal with the posterior bridging strands that connect nucleus fragments. The first is to capture a single nucleus fragment and pull it to the central anterior chamber. After it is pulled into the central anterior chamber, there will be a gap between the pulled nucleus fragment and the adjacent nucleus fragment. The chopper is then moved into the gap to cut the bridging strands beneath the pulled fragment, moving from near the posterior capsule to the central anterior chamber. This method usually separates one nucleus fragment from the others. If the first method does not work, we try the second one: We try to remove all of the hard nucleus and leave a shell of thin epinucleus consisting of pieces of thin nucleus attached to each other by the bridging strands. Ophthalmic viscosurgical device (OVD) is injected into the space between the posterior capsule and the shell. The OVD pushes the posterior capsule away while elevating the shell to the iris plane. This enables the phaco tip to enter the anterior chamber without irrigation. The chopper is used to “feed” the center of the shell, which is the junction of bridging strands and the phaco tip. Phacoemulsification is then started. The center of the shell will obstruct the phaco tip because of the vacuum. Phacoemulsification of the shell can be completed with minor ultrasound energy. Because the phaco tip is obstructed by the shell, a small amount of OVD is aspirated, making the procedure relatively safe to the posterior chamber.
Third, one problem with hard nucleus cataracts is phaco burn to the clear corneal incision (CCI), possibly due to the heat produced by the ultrasound energy. Although the flow can decrease the heat, it is sometimes not enough. We notice that phaco burn is more common at the anterior lip of the CCI. This may be because the phaco handpiece is vertical instead of fully horizontal during phacoemulsification, making the rubber tube at the phaco tip firmly attach to the anterior lip of the CCI. This may reduce the flow through this area and thus not decrease heat at the anterior lip. During phacoemulsification, we usually ask the assistant to drop balanced salt solution onto the CCI at 10- to 15-second intervals. This can decrease the heat and “cool” the CCI. Although most assistants pay attention to the transparency of the central cornea and drop balanced salt solution on this area, it may not protect the CCI from a phaco burn. This is because the anterior lip of the CCI is usually elevated by the phaco tip during phacoemulsification, making it higher than the plane where the balanced salt solution spreads. Besides, the balanced salt solution dropped on the central cornea usually fails to reach the posterior lip of the CCI, which is beneath the phaco tip. Dropping the BSS directly onto the CCI can decrease the heat conducted to this area, protecting the area above and under the phaco tip.
1. Kim HK. Decrease and conquer: phacoemulsification technique for hard nucleus cataracts. J Cataract Refract Surg. 2009;35:1665-1670.