Myopia is not only the most common type of refractive error, but is also ranked first in the general structure of ocular pathology [1]. The prevalence of myopia is growing. According to available data, myopia of varying degrees affected approximately 1.6 billion people worldwide in 2000. This figure is expected to in crease to 2.5 billion by 2020 [2]. It is important to note that prevalence of the disease among children [3, 4] is growing, and progression of the disease is often observed in school children [5, 6].

Myopia is considered a polyetiological disease, but some of its causes are not yet fully studied. Studying the role of immune disorders in the development of myopia is a promising research area [5, 6, 7, 8, 9]. Children with myopia have clinical signs of secondary immunodeficiency more often than their peers with other types of clinical refractive errors [5, 7, 8, 9].

Our study aims at investigating the surface phenotype of blood lymphocytes in children with emmetropia and medium axial myopia, with or without clinical signs of secondary immunodeficiency.

METHODS

The study was conducted in 2013–2015 and featured 24 school children in Moscow aged between 10 and 18 years (mean age of 16 ± 0.25 years): 16 boys and 8 girls. The control group included 8 children (16 eyes) with emmetropia without chronic diseases but with incidence of acute respiratory infections (ARIs) for less than five times a year. The experimental group consisted of 16 children (32 eyes) and was divided into two subgroups. The first subgroup (Group I) included 8 children diagnosed with medium axial myopia and clinical signs of secondary immune deficiency (SID). These children were observed with increased incidence of ARIs (more than 7 times a year). The exclusion criterion was the presence of autoimmune diseases. The second subgroup (Group II) included 8 children with medium axial myopia, but without clinical signs of SID and with incidence of ARIs for less than five times a year and absence of ARIs for two months prior to the study. The diagnosis was verified at the Diagnostic and Consultative Unit, Children’s Medical Centre of the Administrative Directorate of the President of the Russian Federation, Moscow, Russia. The presence or absence of SID was determined based on dispensary data.

All the children examined underwent standard ophthalmic examination, including visometry, (digital chart OAP-250, Carl Zeiss, Germany), autorefractometry (auto kerato-refractometer KR-8900, Topcon, Japan), biomicroscopy (SL 120 slit lamp, Carl Zeiss, Germany), identification of relative accommodation reserves by Avetisova method [10], and ophthalmoscopy and echo biometry (HiScan scanner, OPTICON, Italy).

Lymphocytes were separated from peripheral blood using a one-step Boyum density gradient technique [11]. The expression of CD3, CD4, CD8, CD16, CD56, CD20, CD72, CD38, CD25, CD71, HLA-DR, CD95, CD54, mIgM, mIgG, ICAM-1 antigens was studied using monoclonal antibodies ICO and LT by indirect immunofluorescence under the Luman I-3 microscope (LOMO, Russia).

The results were statistically processed using software package Statistica. The statistical significance was estimated using Student’s test.

RESULTS

The research results are presented in the table. Group I children (with SID signs) showed reduced expression of CD3, CD4 and CD8 antigens in comparison with the control group. However, the difference was significant only for lymphocytes with surface phenotype CD4⁺ (p < 0.05). In Group II children (with no SID signs), on the contrary, the number of lymphocytes expressing CD3, CD4 and CD8 antigens was higher than that of the control group.

But for all of them, the difference was insignificant. Differences in expression of CD16 and CD56 antigens identified for both groups in comparison with the control group was also not statistically confirmed.

The content of lymphocytes with surface phenotype CD20⁺ in Group I children was 14.54 ± 2.36 %, which is lower than similar indicator in the group of healthy children (19.87 ± 2.15 %). However, the difference was insignificant. A significant increase in the expression of this antigen in Group II children was observed. The identified differences on lymphocytes with surface phenotypes CD72, CD38, CD25, CD71, HLA-DR, CD95, mIgM and mIgC were not statistically confirmed.