Glaucoma overview

# Overview
Glaucoma is not a single disease but a group of disorders characterized by a progressive optic neuropathy, leading to a characteristic appearance of the optic disc and a specific pattern of irreversible visual field defects that are associated frequently but not invariably with raised intraocular pressure. The normal range of eye pressure in general population is usually between 10-22 mmHg. Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness.

# Historical Perspective

# Classification

# Pathophysiology

# Causes

# Differentiating Glaucoma from Other Diseases

# Epidemiology and Demographics

# Risk Factors

# Screening
Due to an insidious beginning of the disease, slow progression which is usually not noticed by the patient, screening is essential for glaucoma.The purpose of glaucoma screening tests is to diagnose the disease in the pre-perimetric stage disease, so that these patients can be treated to reduce the risk of subsequent visual field loss. The screening tests in the pre-perimetric glaucoma, screening tests are limited to the evaluation of the optic nerve and the nerve fiber layer.
To evaluate the optic nerve and retinal nerve fiber layer imaging is used to find anatomic alterations using the  OCT of the optic nerve; the new spectral domain OCT is used to screen for loss of the retinal fiber layer in glaucoma. High clinical suspicion is paramount, the increase in vertical cup/disc ratio, the appearance of cup notching or hemorrhages in the disc are considered as a positive screening for glaucoma.A decreased visual acuity, high or borderline intraocular pressure, or a characteristic glaucomatous vertical optic nerve excavation or disc hemorrhages studies point towards an early stage of pre-perimetric glaucoma. To assess the patient further corneal pachymetry, optic nerve head OCT and a 24:2 visual field are required.

# Natural History, Complications and Prognosis

# Diagnosis

## Diagnostic study of choice

## History and symptoms

## Physical examination

## Laboratory findings

## Electrocardiogram

## X-ray

## CT scan

## MRI

## Other imaging findings

## Other diagnostic studies

# Treatment

## Medical Therapy
Although intraocular pressure is only one major risk factors of glaucoma, lowering it via pharmaceuticals or surgery is currently the mainstay of glaucoma treatment. In Europe, Japan, and Canada laser treatment is often the first line of therapy. In the U.S., adoption of early laser has lagged, even though prospective, multi-centered, peer-reviewed studies, since the early '90s, have shown laser to be at least as effective as topical medications in controlling intraocular pressure and preserving visual field. Some studies suggest that acupuncture can be very helpful in the treatment of glaucoma.

## Surgery
Glaucoma is a group of diseases affecting the optic nerve that results in vision loss and is frequently characterized by raised intraocular pressure (IOP). There are many glaucoma surgeries, and variations or combinations of those surgeries, that facilitate the escape of excess aqueous humor from the eye to lower intraocular pressure, and a few that lower IOP by decreasing the production of aqueous.

## Primary Prevention
There is no way to prevent open-angle glaucoma, but one can prevent vision loss from the condition. Early diagnosis and careful management are the keys to preventing vision loss. Most people with open-angle glaucoma have no symptoms. Everyone over age 40 should have an eye examination at least once every 5 years, and more often if in a high-risk group. Those in high-risk groups include people with a family history of open-angle glaucoma and people of African heritage. Such high-risk groups should have a comprehensive dilated eye exam at least once every two years. People at high risk for acute glaucoma may opt to undergo iridotomy before having an attack.

## Secondary Prevention
Patients who have had an acute episode in the past may have iridotomy to prevent a recurrence.