A cataract is clouding and opacification of the lens inside the eye. Opacification of the eye decreases the vision. The light and images from outside need to be refracted first by cornea, the outmost transparent layer of the eye, then by the lens layer inside eye to reach to the visual cortex. After entering into the eye, the light passes through the cornea, aqueous humor (transparent fluid in the anterior chamber of the eye), pupil, and lens, and creates an upside down image on the retina. The image of the object created here is transmitted to the visual cortex in the brain through optical nerves to produce a straight image.
A cataract makes the lens opaque because some protein is produced in the lens, obstructing the light to pass through the transparent lens and resulting in a decrease in vision.
Congenital cataract: A congenital cataract is sometimes caused by an infection, trauma, and growth deficiency and may occur without any causes. Symptoms of a congenital cataract may include one pupil’s color being different (white) from the other pupil’s color or cross-eye (strabismus). If a congenital cataract obstructs the vision and is unilateral in particular, it must be operated as soon as diagnosed. If un-operated, an amblyopia may occur.
Secondary cataract: A type of cataract that occurs associated with certain diseases. For example, diabetes, some medicines (corticosteroids, diuretics) ultraviolet light, and radiation.
Traumatic cataract: develops associated with an eye trauma.
The opacified lens is removed and an artificial lens is implanted inside the resulting cavity to correct the vision of the patient. This artificial lens is called intraocular lens.