Amino Acid Levels in Subretinal Fluid of Patients with Retinal Detachment

Abstract

Purpose: : Patients who undergo repair of a retinal detachment (RD) often lose vision despite a good anatomic result. The mechanisms underling this vision loss are not fully understood. Elevated levels of the excitatory amino acid glutamate can lead to excitotoxicity of neurons in the central nervous system and retina. We hypothesize that the outer retinal ischemia associated with RD leads to accumulation of glutamate in the retina and potential excitotoxicity. To test this hypothesis we measured the amino acid levels in subretinal fluid of patient undergoing repair of a RD.

Methods: : We obtained clean subretinal fluid samples from 20 patients undergoing scleral buckle placement for rhegmatogenous RD. Subretinal fluid drainage was performed using a 27G needle on a 3 cc syringe under direct ophthalmologic visualization. Undiluted vitreous specimens from 10 patients undergoing pars plana vitrectomy and membrane peeling were used as controls. All of the specimens were immediately frozen at –80 degrees. The amino acid levels in these fluid specimens were measured using high–pressure liquid chromatography. Multivariate analysis of the amino acid levels and other information regarding the RD was performed.

Results: : We found that the mean glutamate level in the subretinal fluid from patients with RD (8.31 nmoles; SD 19) was significantly elevated compared to the undiluted vitreous specimens (0.17 nmoles; SD=0.08; p=0.0002). Multivariate analysis will be performed in order to identify any associations between amino acid levels and specific characteristics of the RD.

Conclusions: : Glutamate levels in subretinal fluid appear to be elevated in the presence of RD. Elevated levels of glutamate in the retina may be responsible for some of the loss of vision associated with RD. NMDA–antagonists may help improve the visual results after RD repair.

Keywords: retinal detachment