Review Article The Human Lens: Inception to Excision

The Human Lens

Abstract

Abstract:

According to World Health Organization (WHO) definition of 20/400 vision approximately 38 million people are blind worldwide. Cataract represents more than 50% of all blindness. About 50% of the general population between the ages of 65 and 75 years has cataracts and that number increases to 70% after age of 75. At least 5-10 million new cataracts occur yearly, throughout the world. It is estimated that more than 1.3 million cataract extractions are performed each year. In India, four million new cataract cases are diagnosed annually. The number of people becoming blind from cataracts each year exceeds the number of surgeries performed for cataracts each year. Cataract surgery is the most common operation performed on patients over 65 years of age.

The human lens is transparent. With advancement of age, there is gradual loss of transparency which may lead to cataract formation. Every aging person develops morphological lens changes. However, it is remarkable that only in some patients these circumscribed opacities progress to mature cataracts. The time of occurrence of these opacities also varies widely. There may be huge variations in the morphological manifestations of these age-related lens changes. It is difficult to understand why opacification in some patients is more intense within the anterior cortex, whereas in the others, within the nucleus or within the posterior subcapsular region. These variations of senile cataracts are not inevitably caused due to aging alone but are caused by some other superimposed influences. Despite intensive research going on throughout the world for the factors which determine cataractogenesis; we know little about it. Knowledge about the development and microstructure of the lens is essential for studying the various biochemical and pathological changes occurring in the human lens leading to loss of its transparency. This article reviews the normal architecture of the human lens, the factors responsible for cataractogenesis and also the evolution of cataract surgery.