Changes in protein composition of tear fluid in schoolchildren with high progressing myopia

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Abstract

Purpose

Defining the protein composition of tear fluid (TF) of schoolchildren with high progressive myopia

Methods

We tested TF samples of 35 patients aged 10-17 (ave. 13.1±2.2 yrs) with myopia from 5.0 to 20.5D (ave. 9.5±3.7D) and year progression rate 0.98±0.8D. 19 had various forms of peripheral vitreochoreoretinal dystrophies. No patients used contact lenses to correct myopia. The control group contained TF samples of 9 children aged 10-13 (ave. 12.4±0.5 yrs) with normal eye fundus. Total protein content (TPC) was determined according to M.Bradford. Qualitative determination of protein composition and content in TF was performed by SDS polyacrylamide gel electrophoresis. The proteins were separated by unidirectional gel electrophoresis and stained with coomassie solution. Qualitative determination of major proteins – lactoferrin (Ltf) and lysozyme (Lys) – was conducted using two different primary antibodies (sandwich ELISA). Variation significance of qualitative parameters was assessed by nonparametric methods using Mann-Whitney U-test.

Results

Characteristic distinctions were found for TF of highly myopic children: 1) a significant reduction of TPC against the norm: 5.65 [4.85; 6.33] mg/ml and 7.66 [6.83; 8.16] mg/ml respectively (p=0.000408); 2) a significant increase of Ltf/TPC ratio against the norm: 0.23 [0.2; 0.29] and 0.37 [0.33; 0.43] resp., p=0.000185. The lysozyme share in the total protein content (Lys/TPC) was invariable.

Conclusion

The data confirm the pathogenetic role of the damaged antioxidant protective system of eye media and tissues in the development of myopia. Reduced TPC and increased share of Ltf in TF may be considered as possible diagnostic signs of the progressing character of myopia.

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