True sudden vision loss can occur from a variety of reasons and are considered emergencies. Most commonly retinal disease is the culprit. Almost all causes of are painless. While both macular degeneration and diabetic retinopathy can lead to blindness, they both usually do so slowly. There are exceptions.
Vision lost from diabetic retinopathy is usually due to macular edema and is very slowly progressive. Diabetic retinal detachments can also blind, but these, too, occur slowly.
A vitreous hemorrhage can occur in minutes although the sight is only temporarily affected.
Compared to the dry form of the disease, wet macular degeneration is rapid, but does not usually cause abrupt loss of sight. The vision loss can be rapid, say over a period of days or weeks.
Sometimes, the neovascular membrane (the “wet” abnormal blood vessels) can bleed within the retinal tissue and cause sudden loss of vision.
One cause of bleeding into the vitreous is diabetic retinopathy as stated above. Other causes can include a retinal tear. There are a few other causes, but are very uncommon.
By the way, patients on blood thinners generally do NOT develop a vitreous hemorrhage.
Both retinal vein occlusions and retinal artery occlusions can cause instant loss of vision.
Usually rapid loss of vision, but not sudden. A retinal detachment can cause rather quick progressive loss of vision starting with the peripheral vision moving centrally. This can occur over a day or two, but not minutes.
This may be the only exception to the painless statement. The surface of the cornea is responsible for about 2/3 of the focusing power of the (that’s why laser vision correction is performed on the cornea). If you scratch the cornea, you get sudden loss of vision and…pain!
Injury to the optic nerve and stroke can also cause sudden loss of vision. There are certain situations with the optie nerve where pain may be involved. Strokes are usually painless, but other neurologic conditions may be associated.
What Does This Mean? It is impossible to diagnose sudden vision loss over the phone. We treat sudden vision loss as an emergency at our office. Happily, most of the time there really is no emergency because every one’s definition of “sudden” and “vision loss” are different, but how would we know?
In an eye doctor’s office, these unscheduled visits can kill an office schedule. It happens quite often, as you can imagine, to a retinal specialist.