Possibilities of using tear fluid for electron microscopic diagnostics of eye diseases

Purpose. To conduct a comparative study of cellular and subcellular components of tear fluid of healthy persons (HP), those suffering from primary open-angle glaucoma (POAG), and patients with diabetic retinopathy (DR). Material and methods. Electron microscopy of ultrathin sections was used to test tear samples of 16 patients with initial POAG, 9 patients with developed POAG, and 6 with an advanced stage of POAG. Besides, 12 patients with proliferative DR (PD) and 6 patients with nonproliferative DR (NPD) were tested. Tear samples of 29 subjects with no ophthalmic pathology served as control. Results. All the examined samples contained cells, cellular fragments and debris, mucous granules and lipid structures. The occurrence of all these structures was found to be different in the tears of diabetic and glaucomatous patients as compared to that of HP. The share of epithelial cells in the tear of patients with the initial stage of POAG was twice as high as in the control group; then it drops gradually so that in the advanced stage, epithelial cells are not detected. The tear of NPD patients shows an increase of the content of mucin and lipids against the control, while in PD it is lower than in HP. Leukocytes were observed in the tear of a quarter of HP, while in diabetic patients leukocytes show a significant increase, which reflect a higher permeability of blood vessels as the disease develops. There were no leukocytes in tear samples of all patients with POAG, which may be associated with damaged functions of the blood vessel wall. We found “hairy” vesicles in the tear which had not been noted previously; the amount of these vesicles was growing at early stages of POAG and DR. Conclusion. Electron microscopy of tear deposits evaluates the state of the cornea and the conjunctiva, as well as goblet cells and the meibomian glands. It reveals signs of permeability change in tissue vessels adjacent to the anterior area of the eye. For the first timechanges in tear components in glaucomatous and diabetic patients, were found: theses changes may in future be used to achieve early diagnosis of these diseases // Russian Ophthalmological Journal, 2017; 1: 56-62. doi: 10.21516/2072-0076-2017-10-1-56-62.