Cataracts are the number one blindness-causing eye disease, and it is an eye disease that everyone suffers from, just sooner or later. A cataract is a simple eye disease – a clouding of the lens, which is usually a white clouding, similar to an egg white turning white when cooked.
The lens is an important refractive interstitial of the eye, similar in shape to a convex lens. As the lens is elastic in young people, it thins when stretched, reducing refractive power and making it suitable for seeing far away; when relaxed, it thickens under the effect of elasticity, increasing refractive power and making it suitable for seeing near.
At birth, the lens is the most transparent and clear, and gradually becomes yellow and dull with age, because the lens is also an active tissue, mainly present on the front surface of the lens. However, because there are no blood vessels inside, metabolic products cannot be eliminated and can only accumulate and concentrate in the middle and back part of the lens, and over time, the density of the lens increases and its color becomes yellow. Just as egg white is slightly yellow because it contains a lot of water, if it is concentrated, it will be about the same color as the lens of an older person.
Therefore, in middle age, as the lens becomes denser and harder, it gradually loses its ability to deform, and the eye cannot adjust, which is the reason for presbyopia.
Cataracts occur for many reasons, but their essence is still protein degeneration, whether it is congenital degeneration or acquired due to malnutrition, trauma, poisoning, inflammation or radiation. One of the most relevant to the general public is also senile cataract, also known as age-related cataract, which is divided into three types: cortical, nuclear and posterior subcapsular.
Cortical cataracts are the most common, as the cells on the front surface of the lens cannot metabolize properly after aging, causing degeneration of lens proteins, and water enters the lens to develop fissures and vacuoles, further aggravating the cataract. This type of cataract develops the fastest and vision can be lost in a few months, and it also tends to induce glaucoma.
Nuclear cataracts are also more common. As the cellular metabolites of the lens anterior membrane continue to accumulate and concentrate, they can no longer continue to accumulate at a certain level, or the accumulations are pressed against each other and deformed, and the proteins become degenerated and no longer transmit light well. This type of cataract develops very slowly, usually taking several years before severe vision loss occurs, and is often accompanied by one or both of the other types as it progresses.
The posterior subcapsular type of cataract is relatively rare and is commonly seen in diabetic patients. This type of cataract is gradually increasing due to the prevalence of diabetes in the population. It is mainly the posterior capsule of the lens that develops precipitates under the posterior capsule due to metabolic abnormalities. A typical diagnostic feature of this type of cataract is that in the early stage of its appearance, the vision is good in the dark, decreases immediately in the light, and improves again when it returns to the dark.
This is mainly due to the fact that in the early stage of posterior subcapsular cataracts, the cloudiness in the posterior pole of the lens is small, and in the dark, the pupil of the human eye will be dilated, so that part of the cloudiness in the posterior pole does not completely block the vision and can still see things.