00:00 / 00:00
Okay now, let’s go over some physiology. Normally, the lens is a transparent biconvex structure that lies behind the iris, dividing the anterior and posterior segments of the eye. The lens is held in place by the ciliary processes, which are tiny projections from a structure called the ciliary body. The ciliary body also controls the degree to which the lens becomes flatter or rounder. And this in turn bends the light entering the eye to focus images onto the retina. If we zoom into the lens, we’ll see that it’s composed of three layers: the capsule, cortex, and nucleus. The nucleus is made up of concentric layers of transparent proteins called crystallins.
Now, cataracts are caused by the opacification or clouding of the lens. When this occurs at birth, it's called congenital cataracts. So, risk factors for congenital cataracts include congenital infections, such as toxoplasmosis and rubella, as well as genetic conditions, such as trisomy 13, which causes Down syndrome, Wilson’s disease, in which extra copper is stored in the body tissues, and myotonic dystrophy, which is characterized by progressive muscle weakness and loss. Other risk factors for congenital cataracts include inborn errors of metabolism, like galactosemia, which is a hereditary condition that impairs the conversion of galactose to glucose in newborns.
Now, cataracts can also develop later in life, in which case it's acquired. Acquired cataracts are often associated with advanced age, usually above 60, smoking, excessive alcohol use, penetrating eye trauma, and infections. Other risk factors for acquired cataracts include exposure to UV light, prolonged use of medications like glucocorticoids, and diabetes mellitus.
Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.