Overall, 230 respondents participated in the study. Fifty per cent (50.0%) were outdoor street sweepers while the remaining 50.0% were indoor office cleaners. Female: male ratio was 1:0.03. Over half of the respondents (51.3%) were aged 40 years and below with a mean age of 40 ± 9.6 years.
The mean age of the outside street sweepers was 41.78 ± 10.39 years while that of the office cleaners was 40.26 ± 9.46 years (Table 1). There was no statistically significant difference between the mean ages of the different group of workers (t = 1.187, p = 0.155) Slightly less than one-third (31.7%) of the respondents had been educated up to primary school level.
Prevalence of dry eye disease using OSDI, Schirmer’s Test 1, TBUT
Overall, dry eye disease was found in 64 of the 230 respondents assessed, giving a prevalence of 27.8% using the ocular surface disease index (Fig. 1). Results obtained from the OSDI ranged from 0–78, with a mean score of 26.4 ± 16.0.
Overall, the prevalence of dry eye disease assessed by Schirmer’s test was 31.3% (Fig. 1). Out of 230 respondents, 72 had abnormal Schirmer’s test. Results obtained from Schirmer’s test ranged 1 mm to 35 mm with a mean of 16.44 ± 9.52.
The overall prevalence of dry eye disease assessed using the TBUT among street sweepers and office cleaners was 35.2%. 81 respondents out of 230 had abnormal TBUT. Results obtained from the TBUT ranged between 2seconds to 35seconds, with a mean of 12.12 ± 4.28.
Comparing prevalence of dry eye disease in street sweepers and office cleaners using OSDI
Dry eye disease was found in 41 out of 115 street sweepers giving a prevalence of 35.7% (Fig. 2). On the other hand, dry eye disease was found in 23 out of 115 office cleaners resulting in a prevalence of 20%. This difference was not statistically significant (p value 0.352).
Comparing prevalence of Dry Eye disease in street sweepers and office cleaners using Schirmer’s test
Comparing the prevalence of dry eye disease diagnosed using Schirmer’s test in street sweepers and office cleaners showed that 37(32.2%) out of 115 street sweepers had abnormal Schirmer’s test compared to 35 (30.4%) of 115 office cleaners (Fig. 3). The prevalence was higher in street sweepers compared to office cleaners. However, this difference was not statistically significant (p value = 0.73).
Comparing prevalence of dry eye disease using TBUT in street sweepers and office cleaners
Assessment of dry eye disease using TBUT shows that, out of 115 street sweepers, 44 had abnormal TBUT giving a prevalence of 38.3% (Fig. 4). On the other hand, of the 115 office cleaners, 37 had abnormal TBUT giving a prevalence of 32.2%. This difference was however not statistically significant (p value = 0.48).
Relationship between risk factors and the occurrence of dry eye disease
Logistic regression was performed to assess the impact of statistically significant factors on the likelihood of developing dry eye disease. As shown in the Table 2, the class of workers and ages of respondents had a statistically significant contribution to the occurrence of dry eye disease.
The result demonstrates that street sweepers were more likely to develop a dry eye disease compared to office sweepers with an odds ratio of 2.085 (Table 3). Another predictor observed in this study for developing dry eye disease was the age of respondents in years with a prevalence odds ratio of 1.092. This indicates that increasing age of respondents in years is a weak predictor of the occurrence of dry eye disease.