We read with interest the recent publication by McKay et al. on the use of preoperative clinical variables for predicting cataract operative time.1 Although improved operating room utilization is a worthwhile endeavor that can improve healthcare productivity and save costs, it seems that several aspects relating to the data analysis preclude any real-world conclusions from being drawn.
The first aspect of concern is the exclusion of cases primarily attended by a resident, which typically take longer regardless of any high-risk preoperative characteristics. The second and more important aspect is the fact that the authors adjusted their results for the surgeon's years of experience or identity, an adjustment that does not occur in real life. As reported by McKay et al., the strongest predictor of operative time was the identity of the surgeon. One might assume that cases with high-risk preoperative characteristics will be assigned to more experienced physicians. In a real-world setting, therefore, high-risk cases operated on by experienced surgeons and low-risk cases operated on by less-experienced surgeons might take similar amounts of time.
To test this hypothesis, after receiving approval from the Institutional Review Board, we used a retrospective real-life registry-based cohort of consecutive cataract surgeries performed between August 2016 and April 2019 at the Department of Ophthalmology, Helsinki University Hospital, Helsinki, Finland. At this institution, all operating surgeons were specialists with varying degrees of experience, and cases were assigned based on the preoperative risk assessment to a surgeon based on the level of expertise.
Included were 4752 cases in which operative time, preoperative clinical variables, and the surgeon’s identity were recorded. The mean age of the patients was 74.1 ± 10.1 years, and 59% were women. The results show that preoperative clinical variables had a minimal impact on operative time. These included the existence of pseudoexfoliation (21.4 ± 10.2 minutes vs 20.8 ± 11.9 minutes, P = .274), poor mydriasis (21.4 ± 9.9 minutes vs 20.7 ± 12.1 minutes, P = .196), and higher than “simple” preoperative grade according to the referral letter (grades 2 or 3 out of 3; 21.2 ± 12.3 vs 19.6 ± 9.4, P < .001). This is presumably due to surgeon selection. Indeed, when incorporating these variables into a linear regression analysis accounting for the surgeon's identity, all these preoperative variables become significantly predictive of operative time (all P < .001), similar to the results of the study by McKay et al.
Predicting cataract operative time is complex. In a real-world setting, social and behavioral aspects come into play, which are challenging to incorporate in a statistical analysis. In our experience, surgeon selection plays an important role, which primarily serves to counteract the effect of high-risk preoperative patient characteristics. Using high-risk preoperative characteristics in a straightforward way to determine operating room utilization might, therefore, not work in clinical practice. We agree with McKay et al. that this is an important and pertinent issue and worthy of further discussion.
1. McKay KM, Borkar DS, Moustafa GA, Haviland MJ, Kloek CE; PCIOL Study Group. Clinical factors affecting operating room utilization in cataract surgery: results from the PCIOL study. J Cataract Refract Surg 2020;46:14–19