Cataract

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Cataract
Cataract in human eye.png
Magnified view of cataract in human eye, seen on examination with a slit lamp using diffuse illumination

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Pathophysiology

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Differentiating Cataract from other Diseases

Epidemiology and Demographics

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Case #1

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Kenneth J. Hoffer, M.D. [2], Clinical Professor of Ophthalmology, UCLA, St. Mary's Eye Center Associate Editor(s)-in-Chief: Rohan Bir Singh, M.B.B.S.[3]

Overview

A cataract is an opacification of the natural intraocular crystalline lens that transmits the light entering the eye onto the retina in the posterior part of the eye. The opacification leads to a decrease in vision and may lead to complete vision loss if left untreated for long. Cataracts are the leading cause of preventable blindness in the world . At present, there is no preventive intervention for the progression of cataracts. The modern cataract surgery, which is the removal of the opacified lens and implantation of a clear intraocular lens (IOL), is the only known and approved treatment for cataract. The cataract surgery involving removal of natural lens and implantation of IOL is the most effective procedure performed in ophthalmology with 3 million Americans choosing to have cataract surgery each year, and with a success rate of 97 percent or higher.

Historical Perspective

The earliest references to cataract surgery are found in Sanskrit manuscripts dating from the 5th century BC, which show that Sushruta developed specialised instruments and performed the earliest eye surgery in India. In the Western world, bronze instruments that could have been used for cataract surgery, have been found in excavations in Babylonia, Greece and Egypt. The first references to cataract and its treatment in the West are found in 29 AD in De Medicinae, the work of the Latin encyclopedist Aulus Cornelius Celsus.

The first extracapsular cataract surgery using a sharply pointed instrument with a handle fashioned into a trough was described in Susrutasamhita. This technique is known to have existed in India as described and performed by Susruta sometime in early BC. Another early technique to remove cataracts was couching, which involved using a thin needle or stick to remove the clouding. This technique is known to have existed in ancient times and continued to be used throughout the Middle Ages - However, it has now been replaced by extracapsular cataract surgery and, specially, phacoemulsification.

The word cataract, is derived from the Greek word υπόχυσις (kataráktēs) meaning the fall of water. The Latins have known it as "suffusio", which translates to an extravasation and coagulation of humors behind the iris; and the Arabs, call it white water . There is no mention of cataract in ancient Egyptian medical literature, except a similar disease, mentioned in the Ebers Papyrus.

The ancient Greeks believed that the lens was a part of the eye responsible for vision. It led to development of the "Emanation Theory" of vision. They believed that the optic nerves were hollow channels through which “visual spirits” were from the brain to meet visual rays from the outside world at the lens, in the center of the globe. The visual information would then flow back to the brain.

Around 30 AD, the Greek philosopher, Celsus drew the lens in the center of the globe, with an empty space called the locus vacuus anterior to it. This model about lens position and function persisted through the Middle Ages and into the Renaissance, as shown by the drawing of the Belgian anatomist Andreas Vesalius in 1543. The first accurate position of the crystalline lens was illustrated by the Italian anatomist Fabricius ab Aquapendente in 1600.

Swiss physician Felix Plater was the first to the challenge the emanation theory, and suggested that retina was the part of the eye responsible for sight.

In 1748, Jacques Daviel started with modern cataract surgery, in which the cataract is actually extracted from the eye. In the 1940s Harold Ridley introduced the concept of implantation of the intraocular lens which permitted more efficient and comfortable visual rehabilitation possible after cataract surgery. The implantation of foldable intraocular lens is the procedure considered the state-of-the-art.

In 1967, Charles Kelman introduced phacoemulsification, a technique that uses ultrasonic waves to emulsify the nucleus of the crystalline lens in order to remove the cataracts without a large incision. This new method of surgery decreased the need for an extended hospital stay and made the surgery ambulatorial.

Classification

Pathophysiology

Causes

Differentiating Cataract from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms | Physical Examination | Laboratory Findings | X Ray | CT | MRI | Other Imaging Findings | Other Diagnostic Studies

Treatment

Medical Therapy | Surgery | Primary Prevention | Secondary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies

Case Studies

Case #1

Related Chapters

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