Tear Lactate Levels as a Surrogate Marker of Oxidative Stress in Myopia: A Case-control Study

Abstract

Introduction: Myopia is most common refractive error leading to visual dysfunctions worldwide. Oxygen deficit due to environmental stress leads to increase in anaerobic glycolysis which results in lactate production. Increase in Reactive Oxygen Species (ROS) and inability of defense system to eliminate them is also responsible for alteration of regulatory pathways. The patient with elevated lactate levels are at significant risk of morbidity and hence, require a prompt treatment. Aim: To estimate and study the lactate levels in tear in various degree of myopia. Materials and Methods: This case-control study was conducted in tertiary care center, Pt. B.D. Sharma PGIMS, Rohtak, Haryana, India. Twenty five patients each with low, medium, high myopia, age and sex matched healthy controls (i.e, Group 1-4). Diagnosis was established with help of detailed history, clinical and ocular examination. Lactate levels were estimated in tear samples by enzymatic method on autoanalyzer within 30 minutes of collection. Independent Student’s t-test was used to determine the significance between myopia and controls. Results: Out of total 100 subjects, 68% were males and 32% were females. The mean±SD age was 24.56±6.35, 24.12±5.45, and 23.24±5.17, 21.69±3.95 in the Group 1, Group 2, Group 3 and Group 4 respectively in the control group, group with low, medium and high myopia respectively which was statistically not significant. The results of this study showed that lactate levels in tears were significantly higher (p-value=0.013) in myopia patients as compared to controls (1.34±0.46 versus 1.06±0.50). Additionally, the lactate levels increased with the progression of degree of myopia. Conclusion: Increase in the level of lactate in tear was directly proportional to the degree of myopia. Tear lactate levels can be used as a non invasive method to study oxidative stress in individuals. Further studies with more oxidative markers in tears can also be compared with blood values in larger groups of patients with long-term follow-up to validate the finding.