A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light. Early in the development of age-related cataract the power of the lens may be increased, causing near-sightedness (myopia), and the gradual yellowing and opacification of the lens may reduce the perception of blue colours. Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated. The condition usually affects both eyes, but almost always one eye is affected earlier than the other.
Glaucoma is a GROUP of disorders. What they all have in common is an increase in the pressure inside the eye. When the pressure is too high, damage occurs to the optic nerve. The optic nerve is made up of a bundle of nerve fibers which sends signals to the brain. Damage to the optic nerve can initially cause blind spots at the outer edges of the field of vision called peripheral or side vision. This is the main sign of glaucoma. As damage to the optic nerve gets worse, the visual field can shrink leading to tunnel vision or even loss of central vision affecting a patients ability to read.