Explaining What are Cataracts, and the Causes and Types of Cataracts

First, we'll explain "What are Cataracts?", then identify the causes and types of cataracts.

Introduction

A cataract is a clouding of the internal crystalline lens of the eye. This lens is normally a clear tissue that focuses light on the retina so we can see clearly. When the lens turns cloudy it also often turns a greenish-brown color (brunescence). Cataracts are the major cause of impaired vision world-wide.

Location of cataract in the eye	This slit of light shows the brownish coloration of the lens

Causes of Cataracts

The lens of the eye is made of layers of tissues comprised of proteins. These tissues are transparent because of the precise way they are spaced and oriented.

Anything that interferes with this spacing and orientation will reduce the transparency. The process that denatures and cross-links these lens proteins in cataracts is called glycation, and occurs to proteins throughout the body.

Glycation is accelerated by light, especially short-wavelength light like ultra-violet.

Certain occupations like glass-blowers are at high risk for cataracts (glass-blower's cataracts) due to the light given off in glass production. They must wear special glasses to filter out the intense, harmful light.

Cataracts are sometimes caused by trauma to the eye, or occur in conjunction with some systemic diseases such as diabetes.

Cataracts are also known from studies to be influenced by genetics and nutrition.

Most cataract surgery in this country is done on patients in their 60's, 70's and 80's.

Though nearly everyone has clouding changes in their lenses as they age, some patients don't have significant visual impairment until they reach their 90's. On the other hand some patients in their 30's or 40's develop dense cataracts.

Types of Cataracts

At the risk of over-simplification, there are three main types of cataracts we commonly see in clinic.

• Cortical Cataracts. These cataracts have clouding of the outer layers of the lens.
• Nuclear Cataracts. These cataracts have clouding of the central layers of the lens.
• Posterior Sub-capsular Cataracts. These cataracts occur under the rear capsule, or membrane that encloses the lens.