I read with great interest the article by Sidath Wijetilleka and Gwyn Williams titled “Are patients with poorer vision more polite? A study examining door closing tendencies in patients with poor vision” [1]. The authors performed a prospective cohort study of clinic room door closing on two groups of patients, with the group inclusion criteria being based on a visual acuity of more or less than 0.3 logMAR. The authors observed that patients with poor vision had higher rates of door closing and therefore concluded that poor vision is a risk factor for politeness.

I have identified a number of potential confounders that the authors did not report matching for. For instance, women have higher levels of politeness, conscientiousness and orderliness on measures of personality traits [2]. Furthermore, women demonstrate higher rates of visual impairment, therefore the low-VA group may have demonstrated a higher rate of door closing because there were more women in this group [3]. Age is another important confounder as it has been shown that there is a positive correlation between levels of empathy and kindness with advanced age [4]. As there is an increased risk of poor vision with advancing age, this could be another potential confounder [4]. I suggest 12 potential confounding variables, which should be appropriately matched for (Table 1).

Table. 1 Table highlighting possible confounding factors in the authors' study

Recruiting a cohort large enough to match for these confounders may be challenging, and so I propose the first UK wide multicentre study of door closing outcomes. Furthermore, sub-group analysis could investigate whether being from the south of England has a beneficial effect on politeness as appears to be the case in studies elsewhere [5]. Being a young man with a visual acuity greater than 0.3 logMAR, I am particularly susceptible to low-levels of politeness, and so I am interested to know if living in London is protective.