Intraocular hemorrhage

Ocular Anatomy
The volume of the vitreous in the adult is about 4 cc or 80% of the volume of the eye's globe. Water makes up 99% of the vitreous content. The remaining 1% mostly is composed of collagen and hyaluronic acid which although clear, causes the vitreous to be gelatinous.

The vitreous is attached to the retina in three locations. The vitreous base refers to a 4 mm circular band where the vitreous body attaches to the anterior retina (ora serrata). This is the strongest of the three attachments. The vitreous also attaches in a circular zone around the optic nerve head. This is the second strongest attachment of the vitreous. This attachment becomes progressively weaker with advanced age, and it is this attachment that may become separated in posterior vitreous detachment.

The vitreous is itself avascular and therefore the blood in vitreous hemorrhage comes from organs outside the vitreous. When hemorrhage occurs into the vitreous, it accumulates in potential spaces within and around the vitreous body. These potential spaces for blood to accumulate include the following:
 * 1) The retrolental space of Erggelet
 * 2) The canal of Petit
 * 3) The Cloquet canal
 * 4) The bursa premacularis
 * 5) The canal of Hannover (between the orbiculoanterocapsular and posterocapsular portions of the zonular fibers)

The borders of the vitreous body are as follows:

Posterior: The internal limiting membrane of the retina

Anterior: The nonpigmented epithelium of the ciliary body, and anteriorly by the lens zonular fibers and posterior lens capsule.

Pathophysiology
The two most common overarching pathophysiologic mechanisms of vitreous hemorrhage involve hemorrhage into the vitreous from a diseased retina or trauma. Specific pathophysiologic mechanisms are discussed below:

Extraocular Causes of Vitreal Hemorrhage
Diabetes and sickle cell disease are obvious extraocular diseases that are associated with retinopathy. Retinopathy is characterized by neovascular vessels, fragile vessels, occluded vessels and ischemic vessels, all of which increase the risk of vitreous hemorrhage. The disorders are associated with retinal ischemia which in turn causes the release of angiogenic growth factors including vascular endothelial growth factor (VEGF), basic fibroblast growth factors (bFGF), and insulin-like growth factor (IGF).

Trauma is another major pathophysiologic mechanism of intraocular hemorrhage.

Conditions that may increase the risk of vitreal hemorrhage also include coagulation disorders (e.g. leukemia and thrombocytopenia). While coagulation disorders may not themselves be primarily associated with bleeding, in the presence of trauma or retinopathy they may secondarily increase the risk of bleeding. Autoimmune / collagen vascular disorders such as Behcets disease and sarcoid have also been associated with an increased risk of intraocular hemorrhage. Thus a careful history should be obtained regarding all these systemic / extraocular causes.

Subretinal Bleeeding with Breakthrough Bleeding into the Vitreous
Other less common pathological mechanisms of vitreous hemorrhage include subretinal bleeding with secondary extension into the vitreous cavity.

Age-related macular degeneration and choroidal melanoma are the two leading causes of vitreous hemorrhage secondary to breakthrough bleeding. Terson syndrome is subarachnoid hemorrhage associated with vitreous bleeding caused by rupture of retinal venules and/or capillaries as a result of a sudden increase in intracranial pressure (which is transmitted to the retinal vasculature via the optic nerve).

Subarachnoid Hemorrhage and Associated Intraocular Hemorhhage
Approximately one of three patients with subarachnoid hemorrhage will sustain an intraocular hemorrhage, and approximately 6% of patients have vitreous hemorrhage.

Terson Syndrome
In this condition, the branches of the central retinal vein or the central retinal vein itself are generally the source of intraocular bleeding. This syndrome occurs predominantly patients aged 30 to 50 years.

Differential Diagnosis of Causes of Intraocular Hemorrhage
In general, vitreous hemorrhage results from tears of the retina or neovascularization of the retina

Common causes in descending order of frequency

Proliferative diabetic retinopathy

Posterior vitreous detachment

Trauma (blunt or penetrating, including shaken baby syndrome/child abuse)

Retinal tear

Central retinal vein occlusion

Hypertensive retinopathy

Subarachnoid hemorrhage (Terson syndrome)

Avulsed retinal vessels

Age-related macular degeneration

Radiation retinopathy

Macroaneurysms

Others rare causes of vitreous hemorrhage include the following:

Complications of surgical procedures
Retinal laser photocoagulation

Intruding (scleral erosion) scleral buckle

Trabeculectomy

Globe perforation during retrobulbar or peribulbar surgery/anesthesia

Intraocular lens implantation or removal

Neovascularization from cataract wound

Tumors
Malignant choroidal melanoma

Melanocytoma of optic nerve disc

Astrocytic hamartoma of the retina

Retinoblastoma

Cavernous hemangioma of optic nerve disc

Vascular/neovascular
Coats disease / retinal telangiectasia

Retinopathy of prematurity (ROP)

Ocular ischemic syndrome

Branch retinal artery occlusion

Central retinal artery occlusion

Retinal angiomatosis

Retinal vasculitis

Hyperviscosity syndrome

Sarcoid posterior uveitis

Persistent hyaloid artery

Congenital prepapillary

Vascular loop venous stasis retinopathy

Dominant (familial) exudative vitreoretinopathy

Incontinentia pigmenti

Norrie disease

Inflammation
Behçet disease

Presumed ocular histoplasmosis syndrome

Eales disease (also known as also known as angiopathia retinae juvenilis, periphlebitis retinae, primary perivasculitis of the retina)

Uveitis (including pars planitis)

Syphilitic retinitis

Dermatomyositis

Systemic lupus erythematosus (SLE)

Toxocara

Hematologic disorders
Thrombocytopenia

Idiopathic thrombocytopenia purpura

Thrombotic thrombocytopenic purpura

Leukemia

Hemophilia

Disseminated intravascular coagulation

Protein C deficiency

Antiphospholipid antibodies

Von Willebrand syndrome

Miscellaneous causes

 * Talc retinopathy
 * Retinitis
 * Pigmentosa Valsalva retinopathy