Cataract overview

# Overview
A cataract is an opacity that develops in the crystalline lens of the eye or in its envelope. Early on in the development of age-related cataract the power of the crystalline 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. Moreover, with time the cataract cortex liquefies to form a milky white fluid in a Morgagnian Cataract, and can cause severe inflammation if the lens capsule ruptures and leaks. Untreated, the cataract can cause phacomorphic glaucoma. Very advanced cataracts with weak zonules are liable to dislocation anteriorly or posteriorly.  Such spontaneous posterior dislocations (akin to the historical surgical procedure of couching) in ancient times were regarded as a blessing from the heavens, because it restored some perception of light in the bilaterally affected patients.
Cataract derives from the Latin cataracta meaning "waterfall" and the Greek kataraktes and katarrhaktes, from katarassein meaning "to dash down" (kata-, "down"; arassein, "to strike, dash"). As rapidly running water turns white, the term may later have been used metaphorically to describe the similar appearance of mature ocular opacities. In Latin, cataracta had the alternate meaning, "portcullis", so it is also possible that the name came about through the sense of "obstruction".

# Historical Perspective

# Classification

# Pathophysiology

# Causes

# Differentiating Cataract from Other Diseases

# Epidemiology and Demographics
Cataracts are the leading cause of blindness in the world. In the United States, age-related lenticular changes have been reported in 42% of those between the ages of 52 to 64, 60% of those between the ages 65 and 74, and 91% of those between the ages of 75 and 85.

# Risk Factors

# Screening

# Natural History, Complications and Prognosis

## Natural History
Vision may not improve to 20/20 after cataract surgery if other eye diseases, such as macular degeneration, are present. Eye doctors can usually, but not always, determine this in advance.

## Complications

## Prognosis

# Diagnosis

## History and Symptoms

## Physical Examination

## Laboratory Findings

## Imaging Findings

## Other Diagnostic Studies

# Treatment

## Medical Therapy

## Surgery
Cataract surgery is the removal of the lens of the eye (also called "crystalline") that has developed an opacification, which is referred to as a cataract.   Metabolic changes of the crystalline lens fibers over the time lead to the development of the cataract and loss of transparency. Following surgical removal of the natural lens, an artificial intraocular lens implant is inserted (eye surgeons say that the lens is "implanted"). Cataract surgery is generally performed by an ophthalmologist (eye surgeon) at an ambulatory (rather than inpatient) setting, in a surgical center or hospital, using local anesthesia (either topical, peribulbar, or retrobulbar).   Well over 90% of operations are successful in restoring useful vision, with a low complication rate.  Day care, high volume, minimally invasive, small incision phacoemulsification with quick post-op recovery has become the standard of care in cataract surgery all over the world.

## Prevention
Although cataracts have no scientifically proven prevention, it is sometimes said that wearing ultraviolet-protecting sunglasses may slow the development of cataracts. Regular intake of antioxidants (such as vitamin C and E) is theoretically helpful, but this has not been proven.