All causes such as aging, genetics, local nutritional disorders, immune and metabolic abnormalities, trauma, poisoning, radiation, etc. can cause disorders of lens metabolism, resulting in clouding of the lens proteins, called cataracts. It is most common over the age of 40 and its incidence increases with age.
The onset of cataract can be unilateral or bilateral, with progressive vision loss in both eyes. Due to clouding of the crystal cortex, the refractive power of different parts of the lens varies, and there can be glare, or monocular diplopia and increased nearsightedness.
Cortical cataract is characterized by grayish-white clouding of the crystal cortex, and its development process can be divided into four stages: incipient stage, immature stage, mature stage, and over-ripe stage.
2.Nuclear cataract Crystal clouding starts from the central part of the lens, i.e. the embryonic nucleus, and gradually increases in density and slowly expands to the periphery, with a light yellow color in the early stage, and as the clouding increases, the color deepens such as dark yellow and dark brownish yellow, the density of the nucleus increases, the refractive index increases, and the patient often complains of reduced presbyopia or increased myopia. The peripheral cortex is still transparent in the early stage, therefore, the pupil is dilated in the dark and the vision is diminished in the bright light.
3.Posterior subcapsular cataract The clouding is located in the subcapsular cortex of the lens, and if it is located in the visual axis area, it will affect the vision at an early stage.