Causes of vision loss

Human beings suffer many kinds of vision problems, and vision loss is the most serious one with the absence of vision which is existed before. This kind of vision problems can happen either acutely or chronically. So vision loss can be divided into two parts: one is acute vision loss, which means the pitient can’t see anything suddenly, it maybe tempoarly or devastating; and the other is chronic vision loss, in which patient’s visual acuity is becoming lower and lower.

There are many causes for acute vision loss. The most common one is media opacity. Vision problems caused by opacities of the refractive media of the eyes, such as the cornea, anterior chamber, lens, or vitreous humor can cause these vision problems, for example, cataract, glaucoma, corneal edema, hyphema and vitreous hemorrhage. Among which, cataracts and glaucoma cause more than 50% of the vision loss, according to WHO estimates. Retinal diseases such as retinal detachment, macular disease, retinal vascular occlusions and central retinal artery occlusion may cause sudden visual loss. Besides, the optic nerve disease, functional disorder and visual pathway disorders may also cause vision problems. Sometimes, low oxygen supply for the eyes may cause a temporarily vision loss, for example, standing up suddenly, shock or infirm.

People with chronic vision problems may suffer vision loss day by day. Usually if the patient can’t tell light from dark or just can tell the general direction of a light source they are described as blind. In medicine, vision problems of central visual acuity of 20/200 or less in the better eye with corrective glasses, or central visual acuity of more than 20/200 but the widest diameter of the visual field is less than 20 degrees in the better eye is defined as blindness.