ONLINE EXCLUSIVE
Cataract
January 2022
by Liz Hillman
Editorial Co-Director
While cataract surgery continually experiences advancement in technologies, techniques, implants, and calculations, one area that seems seldom discussed in comparison is incisions. A study that was published in late 2021 in JAMA Ophthalmology, however, took a look at the effect of incision shape on a cataract surgery complication in the setting of dense cataracts.1
Dai et al. conducted a double-masked, parallel, randomized clinical trial from July 2019 to January 2020 at the Zhongshan Ophthalmic Center at Sun Yat-sen University in Guangzhou, China, to evaluate whether a modified, trapezoid-shaped incision with an internal width of 3.0 mm vs. a conventional 2.2-mm incision had an impact on Descemet’s membrane detachments in cases of hard cataracts (grade 4.0 or greater based on the Lens Opacities Classification System III). A total of 130 eyes from 130 patients were randomized (65 to a conventional incision and 65 to a modified incision). The eyes in the modified group saw a Descemet’s membrane detachment incidence that was significantly lower at postop day 1. According to the authors, the length of the detachment and the maximal corneal thickness at the incision site were lower in the group with the modified incision. They did not observe a difference in BCVA, central corneal endothelium loss, or surgically induced astigmatism between the two groups at any follow-up point.
With these findings, the authors concluded that “modified 2.2-mm trapezoid incision phacoemulsification reduces the incidence of DMD for hard nuclear age-related cataract at postoperative day 1 and might be considered in patients at high risk of incision-related DMD, although the clinical relevance cannot be determined with certainty from this trial.”
Nathan Congdon, MD, MPH, Yizhi Liu, MD, PhD, Zhenzhen Liu, MD, PhD, and Lixia Luo, MD, PhD, who were involved with the study, expounded on the research in email correspondence with EyeWorld.
EyeWorld: Why research the effect of incision type on Descemet’s detachment?
Drs. Congdon, Yizhi Liu, Zhenzhen Liu, and Luo: Previous research has found that a 3.0-mm corneal incision led to larger surgically induced astigmatism (SIA) and a 2.2-mm incision led to a higher rate of Descemet’s membrane detachment (DMD), especially in patients with hard nuclear cataract. How do we combine the advantages of the two incision sizes and reduce the incidence of SIA and DMD? Based on this question, we designed this trapezoidal incision shape (with an internal incision width of 3.0 mm and an external width of 2.2 mm) to reduce the incidence of DMD without increasing SIA.
EyeWorld: Incision type for phacoemulsification cataract surgery is pretty standardized and accepted. What is the value in looking into new methods that are different than the “convention” in surgery?
Drs. Congdon, Yizhi Liu, Zhenzhen Liu, and Luo: We agree, […] however, with the development of refractive cataract surgery, cataract surgery is no longer defined as only a sight-restoring operation. Surgeons and patients pursue not only better visual acuity but also a higher standard of visual quality. Therefore, it’s necessary to find new methods to modify and improve conventional cataract surgery.
EyeWorld: Do you think that your findings support a shift away from using the conventional incision type to the trapezoidal shape that you describe? Are there certain types of patients that you think different incision types should be used for (patients with certain conditions that might be more prone to Descemet’s detachment from the outside for whom the trapezoid incision should be considered, for example)?
Drs. Congdon, Yizhi Liu, Zhenzhen Liu, and Luo: In our study, we found the patients having a high risk of DMD such as those with hard nuclear cataract or an unhealthy cornea would be most appropriate for this trapezoidal incision. In the future, we can choose different incision types according to such factors.
EyeWorld: What is your main takeaway/message for the U.S. cataract surgeon about your findings?
Drs. Congdon, Yizhi Liu, Zhenzhen Liu, and Luo: We hope to make American cataract surgeons more cautious about incision-related DMD, a common complication of cataract surgery. We hope that our American counterparts can try this trapezoidal incision in patients with a high risk of severe incision-related DMD so as to improve their prognosis and verify the safety and effectiveness of our novel approach in different clinical scenarios.
EyeWorld also reached out to Richard Hoffman, MD, who was not involved with the study, for his thoughts on the topic.
“It’s always interesting evaluating the incisions used for cataract surgery,” he said. “The thing to keep in mind regarding this study is that they were just evaluating the rate of DMD in patients with mature dense cataracts. The conclusions cannot be claimed for routine cataract surgery, which is usually in 2–3+ nuclear sclerotic cataracts—not 4+ NS cataracts. One would expect in these denser cataracts for the incision size and perhaps its architecture to reduce the incidence of incisional edema and perhaps reduce the rate of DMD at the incision since there may be more room for the phaco needle to maneuver and more maneuvering taking place.”
Dr. Hoffman also noted that the authors were looking at DMD at the incision, not complete DMD that affects the central cornea.
“DMD at the incision is a common occurrence and usually resolves without any sequelae. Thus, the clinical importance of DMD at the incision is minimal. If there were a higher incidence of complete or large DMD with the smaller incision size, this would be more clinically relevant and important,” Dr. Hoffman said.
About the physicians
Nathan Congdon, MD, MPH
Zhongshan Ophthalmic Center
Sun Yat-sen University
Guangzhou, China
Richard Hoffman, MD
Drs. Fine, Hoffman & Sims
Eugene, Oregon
Zhenzhen Liu, MD, PhD
Zhongshan Ophthalmic Center
Sun Yat-sen University
Guangzhou, China
Yizhi Liu, MD, PhD
Zhongshan Ophthalmic Center
Sun Yat-sen University
Guangzhou, China
Lixia Luo, MD, PhD
Zhongshan Ophthalmic Center
Sun Yat-sen University
Guangzhou, China
Reference
- Dai Y, et al. Incidence of incision-related Descemet membrane detachment using phacoemulsification with trapezoid vs conventional 2.2-mm clear corneal incision: A randomized clinical trial. JAMA Ophthalmol. 2021;139:1228–1234.
Relevant disclosures
Congdon: None
Hoffman: None
Yizhi Liu: None
Zhenzhen Liu: None
Luo: None
Contact
Congdon: ncongdon1@gmail.com
Hoffman: rshoffman@finemd.com
Yizhi Liu: yzliu62@yahoo.com
Zhenzhen Liu: 723179127@qq.com
Luo: luoll@icloud.com
