According to the severity of lens clouding and its different effects on vision, cataracts can be divided into the following 4 stages: Initial stage: At first, the part next to the lens becomes chaotic, and then it slowly expands to the center. At this time, if the pupil is dilated with medication and then illuminated with appropriate light, a grayish-white wheel-like clouding of the lens can be seen; at this time, vision is slightly diminished, but the fundus can still be seen clearly.
Immature stage: The lens is swollen and mostly cloudy, but there is still a clear zone. The pupil area appears grayish white. When the flashlight is shone obliquely, the iris shadow can be seen falling on the deeper chaotic aspects of the lens, showing a crescent-shaped projection.
Mature stage: The lens becomes completely chaotic and the swelling subsides. The iris projection disappears when irradiated next to it. At this time, the visual acuity is significantly reduced, mostly to about 0.1, and some can only distinguish the kinetic sensation of the hand, or just the sense of light.
Overripe stage: The lens cortex melts into liquid and appears white. The nucleus sinks and appears brown. Because the capsule membrane is weak, it may also crack under strong fluctuations, and the nucleus of the lens may enter the anterior chamber or inside the vitreous humor, which is a dangerous stage of cataract to be treated surgically.