What is a cataract and what are its hazards? The human eye is like a sophisticated camera, and behind the pupil there is a biconvex lens shaped transparent body called the lens of the camera, which is collectively called cataract when the lens becomes cloudy for various reasons. Once the lens becomes cloudy, it will affect the light entering the eye, causing blurred vision and varying degrees of vision loss, which is harmful because of progressive vision loss or even blindness. The most common type of cataract is senile (age-related) cataract. During the aging process, various factors such as environmental, nutritional, and metabolic factors can cause oxidative damage to the lens and decrease transparency, resulting in vision loss. In addition, cataract types include concurrent cataracts, traumatic cataracts and congenital cataracts. What are the symptoms of senile cataract? Depending on the degree of lens clouding, patients will experience different degrees of vision loss. Both eyes often develop at the same time, or they may develop sequentially, and the degree of progression in both eyes is not synchronized. In brightly lit areas, the pupil narrows, the pathway for light to enter the eye becomes narrower, or blurred vision becomes more pronounced when reading, or halos, iridescence and glare appear around light. Some patients may also develop monocular diplopia or hyperopia. For myopic patients there will be an increase in nearsightedness, looking at close objects or books appears clearer, and presbyopia improves, suggesting the occurrence of a cataract. In some patients, although the decrease in vision is not obvious, the contrast sensitivity of visual objects has significantly decreased, which is manifested by seeing objects in darker colors or yellow, etc. The ability to discriminate the outside environment is reduced especially when there is not enough light or driving at night. Note: Although senile cataracts are generally painless with slow vision loss, a few patients have high-risk anatomical factors for acute angle-closure glaucoma, such as short eye axis, shallow anterior chamber, anterior displacement of iris or bulging, which can aggravate the shallow anterior chamber and block the flow of atrial water due to the accumulation of lens water during the expansion phase of cataract development, leading to the accumulation of intraocular pressure to induce acute glaucoma major The patient presents with redness and eye pain. Patients show red eyes, eye pain and even headache and nausea, and their visual acuity decreases sharply or even they lose their sense of light.