What are the causes of a pre‑retinal hemorrhage?

Causes of Pre-Retinal Hemorrhage

Pre-retinal hemorrhages occur when blood collects between the posterior vitreous hyaloid and the internal limiting membrane (ILM), or less commonly beneath the ILM itself, and result from several distinct mechanisms including posterior vitreous detachment with retinal tears, proliferative diabetic retinopathy, retinal vascular abnormalities, Valsalva maneuver, trauma, and blood dyscrasias. 1

Primary Etiologies

Posterior Vitreous Detachment (PVD) with Retinal Tears

• PVD is the most common cause in middle-aged and older adults, typically occurring between ages 45-65 years, with vitreous traction at sites of vitreoretinal adhesion causing retinal vessel rupture 2, 3
• 8-22% of patients with acute PVD symptoms have a retinal tear at initial examination, and two-thirds of those presenting with vitreous hemorrhage have at least one retinal break 2, 3, 4
• 88% of retinal breaks associated with hemorrhage occur in the superior quadrants 2, 4
• Direct correlation exists between the amount of vitreous hemorrhage and likelihood of retinal tear 2, 3

Proliferative Diabetic Retinopathy

• Neovascularization develops at the inner retinal surface and extends into the vitreous due to global retinal ischemia, creating fragile new vessels prone to spontaneous rupture 4
• These abnormal vessels on or near the optic disc are inherently fragile and bleed easily, causing dense premacular hemorrhages 4, 5
• Affects 28.5-40.3% of diabetic patients over age 40, with higher rates (46.9%) in Hispanic populations 6

Retinal Vascular Abnormalities

• Retinal arterial macroaneurysms are a common source, particularly in hypertensive patients, causing sudden dense premacular hemorrhage when they rupture 5, 7
• Retinal venous macroaneurysms are rare but can cause premacular hemorrhage 7
• Retinal vein occlusions (both BRVO and CRVO) cause intraretinal hemorrhages due to increased intravenous pressure and vascular leakage 2

Valsalva Retinopathy

• Sudden increase in intrathoracic or intra-abdominal pressure (from vomiting, heavy lifting, straining, coughing) causes retinal vessel rupture 1, 5, 8
• Results in hemorrhagic detachment of the ILM or sub-hyaloid hemorrhage in the macular region 7, 8
• Typically occurs in younger, otherwise healthy patients 1

Trauma

• Both blunt and penetrating ocular trauma can cause immediate pre-retinal hemorrhage 4, 1
• Trauma-induced PVD can occur at younger ages than typical age-related PVD 6, 4
• Blunt facial trauma specifically can cause sub-ILM hemorrhages 1

Blood Dyscrasias and Systemic Conditions

• Hematologic abnormalities including coagulopathies, thrombocytopenia, and leukemia can cause spontaneous pre-retinal hemorrhage 1
• Terson's syndrome (subarachnoid hemorrhage with associated intraocular hemorrhage) causes sub-ILM hemorrhages 1
• Systemic lupus erythematosus increases CRVO risk 3.5-fold, which can lead to hemorrhage 2

Anatomical Distinction

Sub-Hyaloid vs. Sub-ILM Location

• Sub-hyaloid hemorrhages collect between the posterior vitreous hyaloid and ILM 1, 9
• Sub-ILM hemorrhages are located between the ILM and retinal nerve fiber layer, often requiring biostaining during surgery to confirm 1, 9
• This anatomical distinction is clinically important for treatment planning but both are termed "pre-retinal" 9

Risk Factors Accelerating Onset

Patient-Specific Factors

• Myopia causes earlier PVD onset regardless of age due to increased axial length 3, 6
• Male gender associated with earlier PVD occurrence across all age groups 3, 6
• Prior RVO increases risk: 1% per year for fellow eye CRVO, 10% over 3 years for any RVO type after BRVO 2

Iatrogenic Triggers

• Cataract surgery precipitates PVD in approximately 34% of cases 3
• Intravitreal injections can trigger PVD and subsequent hemorrhage 6

Critical Clinical Pitfalls

• Never assume isolated floaters are benign without examination, as no symptoms reliably distinguish benign PVD from one with retinal breaks 3
• Patients with initially normal exams still have 2-5% risk of developing breaks within 6 weeks, requiring follow-up even when initial examination shows no pathology 2, 3
• 80% of patients who later develop breaks had pigmented cells, hemorrhage, or new symptoms at some point, emphasizing the importance of patient education about warning signs 2, 3
• Sub-ILM hemorrhages are often misidentified as sub-hyaloid, which can affect surgical planning 9