October 2009




Left versus right: evaluating dexterity

by Matt Young EyeWorld Contributing Editor


Which hand is better at performing ophthalmic surgery—a dominant left or right one? It’s not a silly question when you consider new research findings that left-handed residents had fewer complications than right-handed ones when performing cataract surgery. “The incidence of posterior capsule tear and vitreous loss was significantly lower in cataract surgeries performed by left-handed residents,” according to lead study author Jae Yong Kim, M.D., Ph.D., Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea. “Handedness and patient age were significant predictor variables for these complications.”

The study, published in the June 2009 issue of the Journal of Cataract & Refractive Surgery, confirms previous reports that left-handed individuals have certain advantages that right-handed people do not, particularly in the surgical sphere.

Left vs. right hands

Dr. Kim retrospectively analyzed 1,730 surgeries undertaken by 36 residents over five years. Three of the 36 residents (8.3%) were left-handed. These three residents performed 170 (9.8%) of the cataract surgeries. “The rates of posterior capsule tear and vitreous loss were statistically significantly lower in surgeries performed by left-handed residents than in surgeries performed by right-handed residents,” Dr. Kim reported. “However, the BCVA [best-corrected visual acuity] and improvement in BCVA at the final patient follow-up visit was not significantly different between the 2 groups.”

Meanwhile, the surgical skill of all residents should have been fairly uniform, Dr. Kim noted. “Because all the residents in our study were from the same training program with the same year-to-year curriculum, the surgical experience should have been fairly uniform when the residents entered the fourth year,” Dr. Kim reported. “In the program, surgical volume for each resident is tracked throughout each rotation by the ophthalmology education office. If there is a large discrepancy in surgical volume between different residents, it is addressed and attempts are made to balance the surgical experience.”

Instead of the potential for superior skill among the three left-handed residents, Dr. Kim suggested their left-handedness itself may have contributed to fewer complications. “First, left-handed surgeons (forced to develop ambi-dexterity in a right-handed surgical environment) may be able to use their nondominant hand more effectively when required to use a secondary instrument or manage intraoperative complications,” Dr. Kim reported. To put it bluntly, Dr. Kim also suggested that left-handed surgeons “may be more talented.” “Left-handed individuals are considered to be more intellectual and artistic,” Dr. Kim wrote. Briefly, Dr. Kim cited a few studies that found, compared to right-handed people: “more caution and proficiency in neuropsychological testing of tactile-spatial ability among left-handed trainees,” and “functional asymmetry was less in a left-handed population.”

The studies don’t all support left- over right-handedness in the surgical sphere. One study, for instance, found that left-handed residents made more unnecessary movements, took a longer time, and made more errors than right-handed residents in undertaking virtual reality laparoscopy. Dr. Kim defended the study from potential criticism of the small number of left-handed residents included in the study. “Although the percentage of left-handed residents in this study was small (9.8%), it is similar to the percentage in the general population (11%),” Dr. Kim said. “Also, although the number of left-handed residents was small, the number of cases was more indicative than the number of residents.”

Dr. Kim explained that this study included the early period of learning cataract surgery in which all residents are more prone to error. “Therefore, we believe case number is the important unit to analyze,” Dr. Kim noted. Further, left-handed residents experienced their lower incidence of posterior capsule tear and vitreous loss even though most of their surgeries were performed earlier in the academic year because of rotation schedule. Meanwhile, Francis S. Mah, M.D, co-medical director, Charles T. Campbell Ophthalmic Microbiology Laboratory, University of Pittsburgh School of Medicine, Pittsburgh, found it surprising that left-handed residents performed better. “I would think that there would have been increased complications among left-handed residents—not that I have anything against left-handed surgeons,” Dr. Mah said. Dr. Mah, who is a right-handed surgeon, said he doesn’t believe left-handed surgeons are inherently inferior, but simply that right-handed preceptors might accidentally say the opposite of what they want left-handed residents to do. “It would be interesting to see if that same statistic holds up with right-handed faculty and left-handed faculty,” Dr. Mah said. Dr. Mah is also interested in seeing further research about why left-handed residents might perform better. “There has to be some practical, objective reason for this,” Dr. Mah said. In the future, Dr. Mah hopes to see a larger study with many more left-handed surgeons compared to more right-handed ones. A study with few left-handed residents means that there are relatively few procedures performed and perhaps less chance for complications to occur, he said.

Editors’ note: Dr. Kim has no financial interests related to this study. Dr. Mah has no financial interests related to his comments.

Contact information

Kim: jykim2311@amc.seoul
Mah: 412-647-2211, mahfs@upmc.edu

Left versus right: evaluating dexterity Left versus right: evaluating dexterity
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