Damage to the lens in an eye can be from foreign chemicals, from aging, and from trauma. The vitreous has a small affect on the refractive status of the eye, but not enough to be significant compared to the lens and cornea. The vitreous can fill with blood when retinal vessels break. It can also get contaminated with tissue fragments, particularly in some disorders. Blood and debris can be washed from the vitreous as the fluid is refreshed, or surgical replacement can be performed in serious cases.
Congenital abnormalities can affect the structure of the eyes.
If the structure of the eye is affected, the drainage systems for the aqueous and vitreous can get plugged resulting in glaucoma. Glaucoma is the build up of fluid in the eye that results either from a blockage of the drainage system, or from eyes that produce fluid faster than they filter-off old fluid. Structural damage can also affect the operation of the pupil or the lens. Colobomas are birth defects. The developing eye zips shut along the vertical axis in utero.