Intravitreal Vascular Endothelial Growth Factor Concentration and Axial Length

Background: To examine the intravitreal concentration of vascular endothelial growth factor (VEGF) in dependence of the axial length in eyes without intraocular neovascularization.

Methods: The concentrations of VEGF in vitreous samples and blood samples of patients undergoing pars plana vitrectomy for treatment of idiopathic macular holes or epiretinal membranes were examined using enzyme-linked immunosorbent assay. Axial length was determined by biometry.

Results: The study included 34 patients with macular holes (n = 21) or epiretinal membranes (n = 13) with a mean age of 62.4 ± 10.5 years (range: 35-76 years) and a mean axial length of 24.1 ± 1.8 mm (range: 21.0-29.1 mm). The intravitreal VEGF concentration (mean: 71.0 ± 63.2 pg/mL) was significantly (P < 0.001) lower than the VEGF concentration in the blood (830 ± 585 pg/mL). Both parameters were significantly associated with each other (P = 0.04; correlation coefficient r = 0.35). The intravitreal VEGF concentration was not significantly associated with gender (P = 0.25) or age (P = 0.48). A higher intravitreal VEGF concentration was significantly associated with a shorter axial length (P = 0.025; r = -0.39) or a higher hyperopic refractive error (P = 0.04; r = 0.35). Neither plasma concentration of VEGF nor the ratio of plasma VEGF concentrations to intravitreal VEGF concentration was significantly associated with axial length (P = 0.89 and P = 0.22, respectively) or with refractive error (P = 0.89 and P = 0.26, respectively).

Conclusion: Intravitreal VEGF concentration decreased with increasing axial length. It suggests a diluting effect in eyes with larger intraocular volume and/or a faster turnover rate of VEGF in axially myopic eyes with vitreous liquefaction.