Dopamine Levels in the Vitreous of Diabetic and Non-Diabetic Humans

Abstract

Purpose : Human clinical observations and animal laboratory analysis have shown retinal neuronal dysfunction in diabetic subjects that precedes vasculopathy. Dopamine (DA) levels in the retinas of diabetic animals are significantly lower than in wild type animals. Supplementation with L-DOPA results in a reversal of visual dysfunction in diabetic animals, and DA antagonism alters visual function in humans treated with anti-psychotic medications that target DA receptors. We sought to analyze levels of DA and its metabolites in the vitreous of diabetic and non-diabetic human subjects.

Methods : We collected undiluted vitreous samples at the beginning of routine vitrectomy for epiretinal membrane, macular hole, and vitreous opacities in both diabetic and non-diabetic human subjects. Patients with vitreous hemorrhage, retinal detachment, Parkinson disease, schizophrenia, or systemic DA-modulating medications were excluded. High performance liquid chromatography was used to measure levels of 3,4-Dihydroxyphenylacetic acid (DOPAC) and DA in the vitreous specimens.

Results : 30 samples were analyzed, 9 from diabetic eyes and 21 from non-diabetic eyes. The average sample was 0.52 grams of undiluted vitreous. Mean DA concentration in diabetic vitreous was 8.83 pg/mL vs. 11.25 pg/mL in non-diabetic vitreous (p=0.2877). DOPAC concentration was 0.69 pg/mL in diabetic vitreous vs. 0.76 pg/mL in non-diabetic vitreous (p=0.6714).

Conclusions : There was no significant difference in the concentration of DA and its metabolites in the vitreous of diabetics versus non-diabetics. A trend toward lower DA levels in diabetic vitreous existed, but did not reach statistical significance. Additional study is needed to determine the reasons for clinically observed visual function changes in diabetics without vasculopathy as well as patients who are treated with DA-modulating medications.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.