Cataract

 A cataract is a cloudy area in the normally clear lens of the eye. It can occur in one or both eyes, but cannot spread from one eye to the other.

The word “cataract” comes through Latin from a Greek word meaning a waterfall or portcullis. The medical sense probably arose from the idea of something descending across or obstructing the sight.

Most cataracts are related to ageing, although they may also result from eye injuries, certain diseases, some medicines or genetic factors.

The ancient Indian surgeon Sushruta described treating cataracts by “couching” in the Sushruta Samhita, generally dated to around the sixth century BC. The procedure used a needle to push the clouded lens out of the line of sight rather than remove it from the eye in India.

The Code of Hammurabi in ancient Babylonia fixed fees for a successful operation that saved an eye: ten shekels of silver for a high-status patient, five for a freed man and two for a slave. The text refers to opening a growth over the eye, however, so it cannot confidently be described as a cataract operation.

Around AD 1010, Ammar ibn Ali al-Mawsili, an eye surgeon who worked in Egypt, described extracting soft cataracts by suction through a specially designed hollow metal needle.

The French surgeon Jacques Daviel performed the first generally recognised extracapsular cataract extraction in Paris in 1747. Unlike couching, his operation removed the clouded lens from the eye.

Magnified view of a cataract seen during examination with a slit lamp. Rakesh Ahuja, MD/Wikimedia 

The astronomer Galileo Galilei became completely blind in 1637. His loss of sight has often been blamed on observing the Sun, but there is no good evidence that solar damage was responsible; cataract, glaucoma and inflammatory eye disease have all been proposed.

On November 5 and 15, 1850, surgeon William White Cooper operated on two grizzly bears with cataracts at London Zoo. John Snow administered chloroform while several men restrained the animals.

British ophthalmologist Sir Harold Ridley implanted the first artificial intraocular lens in 1949. He used a type of plastic after observing that fragments of aircraft canopies lodged in the eyes of injured Second World War pilots often caused little inflammation.

American ophthalmologist Charles Kelman developed phacoemulsification in 1967 after seeing an ultrasonic instrument at a dentist’s surgery. The technique uses ultrasound to break up the cloudy lens so that it can be removed through a small incision.

Modern cataract surgery removes the clouded lens and usually replaces it with an artificial intraocular lens. About nine out of ten patients see better afterwards.

The World Health Organization estimates that cataracts cause distance-vision impairment or blindness in about 94 million people worldwide. Around half of the people who need cataract surgery still cannot obtain it.