Role of the vitreous in cystoid macular edema.

Eyes suffering from various conditions, such as aphakia, diabetic retinopathy, peripheral uveitis, branch vein occlusion, or retinitis pigmentosa, are predisposed to vitreous detachment. When vitreous detachment occurs, the vitreous can remain attached to the macula due to a firm vitreomacular adhesion. This partial posterior vitreous detachment associated with continuous vitreous traction to the macular area can lead to the development of cystoid macular edema. Two types of vitreous traction have been observed: traction with narrow vitreous strand and traction with broad vitreoretinal adhesion. It has been postulated that the posterior vitreous can cause cystoid macular edema by vitreous contraction without vitreous detachment, producing tractional forces at sites of firm vitreoretinal adhesions that are located at the optic disc and macula. Cystoid macular edema is often accompanied by leakage from dilated retinal capillaries at the optic disc.