EKC is one of the most common eye infections worldwide [10,11,12,13]. The clinical presentation of EKC is rather similar to the different adenovirus-type infections [11]. Most characteristic manifestation at the acute stage was the intense conjunctival hyperemia and edema, pseudomembranes, subconjunctival hemorrhages, superficial punctate keratitis (SPK) [14,15,16,17]. The involvement of the preauricular lymph node was found at this time [18,19,20,21]. After the acute phase, patients may develop multifocal, subepithelial, leukocytic infiltrates of the corneal stroma, which is called multiple subepithelial corneal infiltrates (MSI). These opacities may persist for months and even years with symptoms of visual impairment [22, 23].
EKC can cause large outbreaks worldwide reported by many researchers. For example, Muller et al. reported adenovirus-related EKC outbreak at a hospital-affiliated ophthalmology clinic [24]. Uemura et al. collected a consecutive series of 55 cases diagnosed clinically as EKC confirmed by HAdV-54 detection by polymerase chain reaction (PCR) method. The clinical findings were recorded and summarized [5]. Lei et al. reported the outbreaks of EKC caused by human adenovirus type 8 in the Tibet of China in 2016 [15]. However, EKC can also occur sporadically. There are considerable number of scattered cases in every season. Most of the patients attend the clinic without a clear history of infection or a contact history of red-eye patients. In our study, all 272 patients were sporadic cases over 8 years (2011–2019). To the best of our knowledge, there have been few studies describing the clinical features of sporadic cases in such large scale.
Akiyoshi et al. [6] and Koçluk et al. [7] described the clinical findings which were graded as 0, 1, 2, and 3. The scores of every sign were calculated and used for the statistics. However, this grading method makes a poor guide to the clinical work. There have been no clinical grading criteria so far that have an important guiding value for clinical diagnosis and treatment. In our study, the severity of EKC was classified into three grades according to the course of the disease and the corneal involvement. The grading criteria are useful because they can be performed easily and rapidly in clinical practice. Therapies can be differentiated from different grade.
According to the analysis of the 272 cases, there was no significant difference among the 4 different age groups, in terms of the proportion of mild, moderate and severe cases. According to the analyses of the 192 cases who attended the eye clinic in acute phase, there was also no significant difference among the 4 groups in terms of the proportion of mild, moderate, and severe cases. Which means that the proportion of the degree of EKC is the same in different age groups. According to the analysis of all the patients including acute and non-acute phase, the proportion of severe cases was the highest within the adults group, which is 50.7%. However, according to the analyses of the 192 cases in acute phase, the proportion of moderate cases was the highest within the adults group, which is 44.0%. Within the aged group, the severe cases contributed the largest proportion (62.5%) in the all-patient analysis, whereas the severe cases (40.0%) showed the same proportion as the moderate cases (40.0%) in the acute-phase-patient analysis. It was found that the severe cases accounted for was the highest among all patients. That means adults patients and aged patients should be paid appropriate attention, because of the considerable proportion of severe cases. They should be treated actively and timely. There was no severe case in children group, which may be related to the small amount of children patients to a certain extent. However, it does not mean that the children are less possible to turn to severer degree. Further study is needed in the future work.
The incidence of every typical sign during the acute phase was evaluated. The incidence of eyelid swelling is higher in the children group than that in the adults group and in the adolescents group. That means when a child manifested as eyelid swelling with acute-onset, efforts should be done to distinguish from EKC. In the adults group, the incidence of corneal involvement was significantly higher than that of other signs, suggesting that the adult patient be treated actively and timely because of the high incidence of corneal lesion, which can cause blurred vision temporarily or permanently. Among the incidence of all typical signs, corneal involvement was the most common accounting for 69.8%, followed by preauricular lymphadenopathy (29.2%), conjunctival edema (17.2%), subconjunctival hemorrhage (16.7%), pseudomembrane (15.1%), and eyelid swelling (15.1%). However, as for the relationship between the serotype of the virus and the clnical manifestation, further research is needed.
The results indicated that the MSI were distributed mostly in the central region of cornea, then in the pericentral region. The central region (0 mm to 3.0 mm diameter) is almost pupillary zone, which is near the visual axis closely linked with the visual quality. The multiple subepithelial corneal infiltrates consist of immune complexes deposited beneath the epithelium in the superficial stroma. They can persist months to years, continuing to impair visual acuity by scattering light, causing irregular astigmatism [25,26,27,28,29,30]. Because of the impairment of visual function closely correlated with life satisfaction, mental health and daily active ability, more attention should be paid on MSI caused by EKC. That also means, if the disease involved cornea, efficient measure in the treatment should be taken as quickly as possible.
