Purpose.To conduct a comparative analysis of the effectiveness of assessing the stability of the tear film using corneotopography and the classic Norn test in patients with myopia and myopic astigmatism before keratorefractive surgery. Material and methods. The study included 26 patients planned for keratorefractive surgery for myopia and myopic astigmatism, aged 18 to 47 years. 7 people there was a mild degree of myopia, in 14 people – medium degree, in 5 people – high degree. The average degree of corneal astigmatism was 2.25 diopters. The stability of the pre-corneal tear film was assessed using computed keratotopography and Norn's test – the tear film rupture time (TFRT) was deter- mined. A standard questionnaire was also used to assess the severity of symptoms of dry eye syndrome. A comparison was made of the indicators of the stability of the tear film obtained by the methods of corneotopography and the Norn's test, with their subsequent comparison with the data of the questionnaire. Results. In 17 patients (65.4%), the TFRT index corresponded to the age norm. In the remaining 9 people (34.6%), indicators of stability of the tear film were reduced both by corneotopography (12±4 sec) and by Norn's test (13.5±4.5 sec), and there were also subjective signs of dry eye syndrome according to data questionnaire. The data turned out to be comparable. Conclusions. 1. Among the total population of patients, 34.6% were persons with impaired tear film stability and subjective manifestations of dry eye syndrome. 2. Assessment of the stability of the tear film, determined using the method of corneal topography, showed a high degree of comparability with the results of Norn's test. A significant advantage of the keratotopography method is its non-invasiveness. 3. It is necessary to pay attention to the condition of the ocular surface and identify risk groups to avoid chronicity or aggravation of existing disorders. Key words: dry eye syndrome, tear film, keratotopography, Norn's test.
Stokes theory of thin-film rupture