RETRACTED: Young adults with myopia have lower concentrations of neuromodulators-dopamine and melatonin in serum and tear

Abstract

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the authors, as questions have arisen in the interim regarding the validity of some of the methods and therefore the results. The authors have provided the following statement: "We have addressed a question raised by the reader on the higher levels of dopamine and melatonin in serum and tear levels reported in this study in Myopia along with controls. Serum and tear levels of dopamine and melatonin in Myopia cases were estimated by HPLC (UV detector) is reported by us in a higher order of magnitude (ng/mL) in both specimens compared to most of the reported data (pg/mL) that are reported based on LC/MS/MS or kit based immunoassay(pg/mL). The sample extraction protocol that we followed before estimation of the analytes was based on removing protein by precipitation methods with no further purification by liquid/liquid extraction/use of SPE cartridges as reported in other published reports. This could have possibly extracted related compounds, such as the closely related indoles in the case of melatonin extraction; the other Dopamine related metabolites respectively. The possibility of confounding by other metabolites in our estimation has not been ruled out by any targeted analysis. This we agree is a limitation in the specificity of the protocol we have followed that may have contributed to the nmol range of detection. We have done the HPLC method of analysis and detection (UV) and not LC-MS/MS or immunoassays by kit method whose sensitivity and specificity are reportedly higher based on the range of testing reported in serum. The lower detection limit of our protocol was not in pg/mL but in ng/mL. Parity in the levels reported was discussed in the manuscript attributing to the analytical method adopted and interpretation based on relative changes. Amongst ocular fluids, Aqueous humor by similar HPLC analysis reportedly shows up to 200 ng/ml in literature (Alkozi, H. et al 2017). However, based on our serum data, we feel that further validation studies and method comparisons are required. The method of estimation of the neurotransmitters HPLC (UV detection) seems to have influenced the absolute levels of dopamine and melatonin in the cases and controls studied and therefore casts doubts on the validity of these data. Though further interpretations can be made on relative changes, we decide to withdraw our paper, to work further on the method comparison. We sincerely apologize for the inconvenience to the readers."