Cataracts, one of the primary causes of blindness in older adults, involves a condition of the eyes in which the lens of each begins to thicken over time. In many cases, the cataracts progress to the point where they result in blindness; however, surgery to remove the damaged lens results in an extremely high success rate of near-normal to normal corrected vision. Surgery today is easier and more effective than ever before. Though cataracts can occur at any age, senile cataracts affect people 40 years of age and older, with the risk increasing greatly with age. This type of cataract, when present, generally affects both eyes to one degree or another.

Key points for TCM diagnosis
1. Cortical Cataract
It can be classified, in relation to the stages, into incipient, oncotic, mature and hypermature stages.

(1) Incipient stage: When the pupil is dilated for many times, the lens opacity can be found with the vision almost normal.

(2) Oncotic stage: This is a further stage of lens opacification which is gray-white with water fissure and visual deterioration. Since the crystal cortex is swollen because of water accumulation, the iris bombe appears and the anterior chamber becomes shallow.

(3) Mature stage: The vision deteriorates only to sense hand movement or light perception, and the lens is cloudy in uniform gray-white colour.  The iris bombe disappears gradually and the depth of the anterior chamber returns to normal.

(4) Hypermature stage: This is an overdue state of the mature stage in which the lenticular water keeps on losing, the lens has shrunk, the capsule is wrinkled, the anterior chamber is deepened and the iris vibrates.

2. Nuclear cataract     
The case is not as common as that of cortical cataract and develops slowly. At the initial stage, the opacity starts from the embryonic nucleus or from the adult nucleus with the former to be more often found. Then it spreads gradually to the adult nucleus. The colour of the opacity turns slowly from grayish yellow at the beginning to yellowish brown, then to dark brown or brownish blackfinally. The vision is greatly reduced and the ocular fundus cannot be found at this stage.

3. Capsule cataract
The opacity occurs beneath the anterior or posterior capsule, and the cataract beneath the anterior capsule may gradually develop to a cortical opacity until a complete cataract is formed.