A cataract is a clouding of the lens in the eye which leads to a decrease or loss in the vision. Cataracts develop slowly and can affect one or both eyes. Cataracts causes half of all cases of blindness and 33% of visual impairment worldwide. Cataracts occurs most due to aging but may also occur due to trauma or radiation exposure. The causes include diabetes, smoking tobacco, prolonged exposure to sunlight, and alcohol. The Symptoms includes such as faded colours, blurry or double vision, trouble with bright lights, and trouble seeing at night. Poor vision is also caused by cataracts and may also result in an increased risk of falling and depression.
Refractive eye surgery is also one type of eye surgery which is used to increase or improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This includes various types of surgical remodelling of the cornea (keratomileusis), lens implantation or lens replacement. The most common methods in advanced uses are excimer lasers to reshape the curvature of the cornea. Proper refractive eye surgery can reduce or cure common vision disorders such as myopia, hyperopia and astigmatism. Paediatric refractive surgery involves other risks than refractive surgery on adults. It may be indicated especially for children whose cognitive or visual development is failing due to refractive error, anisometropia, anisometric amblyopia or accommodative esotropia.