An eye disorder in which the optic nerve suffers damage, permanently impacting vision in the affected eye(s) starting with peripheral vision loss and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye. Glaucoma can be divided roughly into two main categories, “open angle” and “closed angle” glaucoma. Closed angle glaucoma can appear suddenly and is often painful; visual loss can progress quickly but the discomfort often leads patients to seek medical attention before permanent damage occurs. Open angle, chronic glaucoma tends to progress at a slower rate and the patient may not notice that they have lost vision until the disease has progressed significantly.