Bleeding in the back of the eye is called a retinal hemorrhage. Retinal hemorrhages occur within the retina, the part of the eye responsible for vision production. The retina has many blood vessels, which are necessary for its functions. Retinal hemorrhages occur when these vessels break or leak. These hemorrhages are classified based on their location within the retina and the specific blood vessels affected.
Types of Retinal Hemorrhages
Five types of retinal hemorrhages are pre-retinal, flame-shaped, dot-blot, sub-retinal, and vitreous. These are each identified by the location of the broken blood vessels that lead to the hemorrhage.
Preretinal Hemorrhages
Pre-retinal hemorrhages occur within the top two layers of the retina. The outer layers of the retina have capillaries prone to bleeding due to diseases affecting other blood vessels in the body, such as high blood pressure. The Valsalva maneuver can also cause pre-retinal hemorrhages during vomiting, coughing, or straining. Pre-retinal hemorrhages typically resolve on their own without any lasting effects.
Flame Shaped Hemorrhages
Flame-shaped hemorrhages occur within the nerve fiber layer of the retina, near the top, and just below the pre-retinal layer. Flame-shaped hemorrhages are usually caused by underlying conditions such as high blood pressure, diabetes, or leukemia. If the hemorrhages are isolated, they can resolve within a few weeks. However, they can also indicate a more severe condition such as hypertensive retinopathy.
Dot blot Hemorrhages
Dot-blot hemorrhages occur within the inner nuclear layer of the retina, which is deeper than the layers affected by pre-retinal and flame-shaped hemorrhages. These hemorrhages affect veins more than arteries within the retina. Conditions such as diabetes, vein occlusion, and choroidal neovascular membrane can cause dot-blot hemorrhages. Isolated dot-blot hemorrhages are not threatening to vision and will usually resolve on their own. However, if there are many or recurrent hemorrhages, a more serious underlying condition, such as diabetic retinopathy, could be the cause.
Sub-retinal Hemorrhages
Sub-retinal hemorrhages occur in the retinal pigmented epithelium, which is below the bottom layer of the retina. This type of hemorrhage is usually associated with a choroidal neovascular membrane or age-related macular degeneration. Sub-retinal hemorrhages heal slowly, causing a lot of scar tissue, which can significantly reduce vision. While outcomes are often poor, treatments can help manage these hemorrhages and reduce vision loss.
Vitreous Hemorrhages
Vitreous hemorrhages occur between the back of the vitreous and the front of the retina. This type of hemorrhage can cause significant vision loss, as blood leaks into the space. Although vision may be initially decreased, it normally returns to its prior state as the blood is cleared from the eye. Vitreous hemorrhages can be caused by a posterior vitreous detachment, diabetes, or a retinal tear.
Importance of Diagnosing and Treating Retinal Hemorrhages
Retinal hemorrhages are a clinical finding that should not be ignored. They can be among the first signs of a more serious condition. Hemorrhages can be caused by many conditions, some of which are exclusive to the eyes, but can also be a symptom of systemic diseases such as high blood pressure or diabetes. Physicians who suspect a retinal hemorrhage will perform a thorough physical examination to identify the cause of the hemorrhage and to determine the appropriate course of treatment.