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Irina Kuryleva, Irina A. Kostanyan, Elena N. Iomdina, Julia M. Volkova; Study of the Lactoferrin Level in Tear Fluid as a Possible Marker of Progressive Myopia. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4456.
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The development of degenerative processes in the retina associated with progressive myopia is known to correlate with the decreasing level of antioxidant protection. Our purpose was to evaluate lactoferrin concentration changes in the tear fluid (TF) as an indicator of myopia progression, since this multi-glycoprotein has an antioxidant effect.
Comparative analysis of concentration ratios of two major TF proteins produced by the lacrimal gland - lactoferrin and lysozyme - in normal and myopic eyes was performed. TF samples were obtained from 26 teenagers aged 10-17: 12 of them had emmetropia, 9 - moderate progressive myopia and 5 - high progressive myopia. One-dimensional SDS-polyacrylamide gel electrophoresis was used to separate TF proteins and then was stained with Coomassie blue. Concentration ratio of lactoferrin and lysozyme in TF ([Ltf]/[Lys]) was evaluated as the ratio of protein band intensities. ImageJ software was used to measure the bands’ intensities (densitometry). Protein composition of lactoferrin bands was examined by Matrix Assisted Laser Desorption/Ionization. Statistical analysis was performed using nonparametric Mann-Whitney U-test for two independent groups, with Bonferroni correction for subsequent paired comparison.
[Ltf]/[Lys] ratio was greater in moderate myopia than in high myopia: 0.88 [0.75; 1.01] and 0.6723 [0.60; 0.78], respectively. Emmetropes demonstrated the highest [Ltf]/[Lys] ratio - 1.59 [1.43; 1.98] (p<0,001 and p=0,005, respectively). Ratio [Ltf]/[Lys] correlated moderately with clinical refraction values, r=0.55, p<0.05. Emmetropic patients’ TF contained three isoforms of lactoferrin with molecular weight of 76703.960, 77930.740 78318.020 kDa; whereas the TF of the patients with progressive myopia only contained one isoform with a molecular weight of 76703.960 kDa.
Our results suggest the existence of previously unknown features of changes in TF protein composition that identify the progression of myopia. [Ltf]/[Lys] index is likely to be considered a marker of progressive myopia.
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