Dry eye is a multifactorial ocular surface disease whose prevalence varies according to the operational definition and the characteristics of the population studied. Early detection and timely treatment are of immense importance in managing DED. In different parts of the world, varying prevalence patterns are most likely due to variations in geographic, genetic, sociodemographic and treatment-related factors. This study is intended to evaluate prevalence and associated risk factors in a hospital-based setting, with consequent insights into preventive measures and timely management. Of the 2560 study subjects, 640 (25%) were diagnosed with dry eye. The lower prevalence of 25% in the present study is contrary to 32% and 34.2%, as reported by Titiyal et al. and Shilpy et al. [4,9]. These studies relied only on symptoms to estimate the prevalence of DED, which may have resulted in an overestimation of the prevalence of DED. The prevalence varies with the subject’s geographical location, environmental conditions and lifestyle; hence, places with extreme temperatures and dry weather conditions report a higher prevalence of DED. Factors relating to lifestyle, like sitting in air-conditioned rooms, using digital devices and smoking, increase the likelihood of DED. Past studies suggest that dry eye prevalence ranges from 10.8–57.1% [2]. Such disparity can be attributed to a lack of standardisation of dry eye diagnostic criteria and cut-off values for diagnostic tests.
Association with age
The prevalence of DED in different age groups is important in determining the disease burden in categorised subjects and is known to increase with age. The maximum prevalence of DED (35.8%) was found to be in the 51–70 years age group, which is statistically significant. These results agree with studies which reported that the prevalence of dry eye was higher in increasing age groups [10–12]. This is likely the result of a pathological decrease in tear production and tear stability associated with advancing age and an age-related decrease in meibomian gland secretion due to atrophy of acinar cells [13]. In contrast, the severity of DED had no significant association with different age groups.
The lowest prevalence (7%) was in extreme age group (patients > 70 years). In the more than 70-year age group, the prevalence of DED was paradoxically less as compared to increased prevalence in patients in the younger age group. We also found a significant decrease in associated risk factors comprising visual display terminals (VDT) use, electronic gadgets, and mobile phones in this age group compared to the younger age group, which could be the possible explanation for decreased prevalence in this age group.
Association with Gender
Although the prevalence of DED was higher in females, the difference was not statistically significant. These results are similar to those of the study by Sherry et al. [14]. Contrary to these findings, a significant association between gender and the prevalence of DED have been reported in several studies [10, 15, 16]. A Study by Moss et al. reported a lower prevalence in men, which was explained by the effect of hormonal loss during menopause on ocular dryness in women [15]. Furthermore, the severity of DED was not significantly associated with the gender of the studied population, which indicated a lack of temporal association between disease severity and gender. This could be due to a higher proportion of non-elderly subjects in our study. Elderly females and rural populations living in far areas are less likely to visit hospitals due to sociocultural factors, which could be the potential cause of decreased prevalence.
Association with locality
The association between the prevalence of DED and residential location (rural vs urban) was found to have a non-significant correlation. These results contrast with the findings of studies done by Donthineni et al., Um et al., and Moon et al. [11, 17, 18]. However, our study is similar to Alshamrani et al. [19]. This can be attributed to the use of electronic gadgets and VDTs in equal frequency among both rural and urban populations in India.
Association with occupation
The prevalence of disease was observed to bear a significant association with the occupation of studied subjects. The maximum prevalence of DED was in household workers, followed by students and Govt. employees. Maximum cases of level 4 DED were found in Govt. employees engaged in computer work. Most of the household workers belonged to rural and low socioeconomic backgrounds; hence, elderly females had a history of exposure to smoke and dust while cooking food on “chulha”. Due to their low socioeconomic background, they were deprived of good dietary intake containing essential nutrients. Frequent use of electronic gadgets, VDT use, and air-conditioned atmosphere could be the reason for increased prevalence in urban and higher socioeconomic backgrounds, which also agrees with other studies [4, 11, 20–22].
Association with refractive status
Prevalence of DED was found to be significantly associated with refractive status and was highest in uncorrected refractive error (31.8%), followed by corrected refractive error (22.3%) and emmetropes (20.6%). Sahai et al. have reported a similar high incidence of DED in patients with refractive error [2]. It is postulated that persons with refractive errors have an increased tendency to rub their eyes, which could cause the lodgement of particulate foreign substances, contaminants, sebum and sweat into the eye, predisposing to tear film instability [15]. This result contrasts with Gupta et al., who reported that refractive error does not affect the occurrence of DED [3]. Patients more than 50 years of age group had a coexistent refractive error, accounting for the increased prevalence of DED in the referenced age group. At the same time, the incidence of using electronic gadgets was significantly higher in the younger population. Hence, refractive errors could be confounding to these already-proven risk factors.
Association with systemic illnesses
Dry eye has been associated with systemic conditions, including arthritis, diabetes, and thyroid disease. In the present study, 14.4% of the total 640 DED patients were found to have associated illnesses such as Type 2 DM, thyroid disease, rheumatoid arthritis, and Sjogren’s syndrome. Elevated levels of circulating proinflammatory cytokines and inflammatory cell infiltration of lacrimal glands and associated MGD are responsible for ocular involvement in systemic illness. Many studies reported an association between DED and similar risk factors [15, 23, 24, 25].
Risk factors
DED has a multifactorial etiopathogenesis. Cigarette smoking, ocular allergy, and contact lens usage were identified as significant risk factors for DED. There was no significant association between severe DED and a history of previous ocular surgery, post-menopausal females, alcohol consumption, topical medications, post-viral keratitis, pterygium and systemic illness.
Contact lens usage may cause dry eye or aggravate preexisting DED. Contact lenses cause meibomian gland dysfunction, corneal hypoxia and hyposensitivity, which results in decreased tear production, increased evaporation, and subsequent tear film hyperosmolarity [15,26,27].
Smoking may affect the tear film stability and ocular surface sensitivity and act as a direct irritant to the eyes [15]. A significant association has been reported between smoking and DED in many other studies, too [2, 4, 15, 28].
The Tear Film and Ocular Surface Society Dry Eye Workshop II recently included allergic conjunctivitis among the ‘probable’ risk factors for DED [8, 29]. Recent advances in the DED pathogenic mechanisms provide a strong rationale for considering ocular allergy as a risk factor for DED [30]. Ocular allergy is associated with inflammatory mediators in tears, which can damage surface epithelium and cause tear film instability.
This is the first large sample study from a tertiary eye care centre to ascertain epidemiological patterns and risk factors for DED. It incorporates subjective tools with objective clinical tests to determine dry eye prevalence and risk factors. Most epidemiological studies conducted earlier included the elderly population (> 40 years of age), which falls short of representing the actual disease prevalence in the referenced population. With the increasing use of electronic gadgets by the younger age group, there is a need for more epidemiological studies that widen their inclusion criteria to ascertain precise estimates of the prevalence of DED. This study was designed and conducted to bridge this significant gap in knowledge effectively. As this study is a hospital-based cross-sectional study, there are limitations in extrapolating the results to the general population of this region. Females, the elderly and the rural population living in far areas are less likely to visit hospitals due to the sociocultural environment. This could be a potential cause of decreased prevalence. The study's cross-sectional design precludes us from knowing the antecedent-consequent relationship between risk factors and the endpoint.