Purpose
To investigate, in pediatric patients, the rate and clinical features of unspecific conjunctivitis of unknown origin (UCUO) and to evaluate their relationship with air pollution.
Methods
Over the period January 2013 - December 2013, we consecutively screened all the patients referred for symptomatic ocular surface inflammation to the Unit of Pediatric Ophthalmology, University Eye Clinic of San Giuseppe Hospital in Milan. Inclusion criteria for this study were age<18, diagnosis of conjunctivitis, residence in the region Lombardia. Exclusion criteria were previous ocular surgery, ocular diseases (other than ocular surface diseases), keratitis (other than punctate keratopathy), contact lens wearing, systemic conditions or therapies with well-known effect on the ocular surface, topical treatments in the 3 months before screening. All included patients underwent a full eye exam. UCUO was defined as conjunctivitis of unknown etiology, not clearly due to infection or allergy. Based on addresses of residence and sites of 73 automatic air pollution monitoring stations (location and mean annual particulate matter, PM10 and PM2.5, concentrations were provided by the Regional Environmental Protection Agency - ARPA Lombardia), each patient was paired with a value of exposure to PM. Relationship between UCUO and PM exposure was investigated.
Results
132 of 251screened children were included in this study (72 females and 60 males, mean age 5.9±3.4, range 1-12). Figure 1 reports diagnosis’ rate in included children. UCUO was diagnosed in 48 (36%) patients. The most common symptoms and signs in UCUO children were foreign body sensation (37/48), photophobia (28/48), conjunctival hyperemia (45/48), and limbal corneal vascularization (22/48). PM10 exposure value was significantly higher in UCUO (33.5±5.4µg/m3) compared to each other group (25.2±5.9, 28.9±6.9, 27.5±5.7, respectively; P<0.001, ANOVA). UCUO/total conjunctivitis ratio was significantly higher in residents in areas with more than 75 (Q3) days/year exceeding 50µg/m3 (EU legal limit) compared to areas with less than 45 (Q1) exceedances/year: 24/39: 61% vs 8/35: 23%; P>0.001, Chi-square test.
Conclusions
Our data suggest a relationship between UCUO and air pollution. This form of conjunctivitis is not rare in pediatric patients and may be the most frequent in most polluted areas.