Central Retinal Vein Occlusion (CRVO) is an eye condition where the main vein responsible for draining blood from the retina becomes blocked, typically due to a blood clot. This blockage can cause blood and fluid to leak into the retina, leading to swelling and impaired vision. Fundoscopy, also known as ophthalmoscopy, is a medical procedure used to examine the back of the eye, providing a view of the retina, optic disc, macula, and blood vessels. This examination helps eye care professionals identify various eye conditions, including CRVO, by observing specific changes in the eye’s internal structures.
Understanding Central Retinal Vein Occlusion
CRVO involves an obstruction of the central retinal vein, which carries deoxygenated blood away from the retina. This blockage prevents proper drainage, causing blood and fluid to back up and spill into the retina. The accumulation of fluid can lead to swelling, particularly in the macula, the part of the retina responsible for sharp, central vision.
Individuals with CRVO often experience sudden, painless blurry vision or vision loss in one eye. This vision impairment can appear abruptly or worsen gradually over several hours or days. Some people may also notice floaters, which are dark spots or lines caused by tiny clumps of blood leaking into the vitreous humor. In more severe instances, pain and pressure in the affected eye can occur.
Several factors can increase the risk of developing CRVO, with age over 50 being a common risk factor. Underlying health conditions like high blood pressure, diabetes, high cholesterol, and glaucoma are frequently associated with CRVO. These conditions can contribute to narrowed or hardened blood vessels, which may lead to blood clot formation or compression of the central retinal vein.
What is Fundoscopy?
Fundoscopy, also called ophthalmoscopy, is a medical examination that allows a healthcare provider to look inside the back of the eye. The “fundus” refers to the inner back wall of the eye, including the retina, optic disc, choroid, and blood vessels. This procedure assesses the health of these structures and detects various eye diseases.
During a fundoscopic examination, the healthcare provider uses an ophthalmoscope, a magnifying tool with a light source. Two main types exist: direct ophthalmoscopy, a handheld device, and indirect ophthalmoscopy, which uses a head-mounted light and a handheld lens. Patients are usually seated in a dimly lit room, and their pupils may be dilated with eye drops for a clearer view. The provider shines a light into the eye and looks through the ophthalmoscope’s viewing window to observe internal structures.
How Central Retinal Vein Occlusion Appears on Fundoscopy
During a fundoscopic examination, central retinal vein occlusion presents with distinct visual signs. A classic presentation is the “blood and thunder” appearance, reflecting widespread retinal hemorrhages and engorged, tortuous veins. These hemorrhages vary in size and shape, appearing as dot-and-blot or flame-shaped hemorrhages across all four quadrants of the retina.
The retinal veins become dilated and tortuous, appearing swollen and winding due to impeded blood flow. Retinal edema, or swelling of the retina, is common, particularly in the macula, which can significantly impact central vision. Cotton wool spots, small, white patches on the retina, may also be observed, indicating nerve fiber layer damage from restricted blood supply.
Optic disc swelling, where the optic nerve head appears elevated and blurred, is a frequent finding in CRVO. This swelling can occur due to increased pressure from fluid buildup. While fundoscopy provides substantial information, distinguishing between ischemic and non-ischemic CRVO based solely on these signs can be challenging. Ischemic CRVO, which is more severe and involves greater capillary non-perfusion, presents with more extensive retinal hemorrhages, pronounced venous engorgement, and widespread macular edema compared to the milder non-ischemic form.
Next Steps After a Central Retinal Vein Occlusion Diagnosis
Once central retinal vein occlusion is diagnosed through fundoscopy, further evaluations assess the condition’s extent and guide management. Optical Coherence Tomography (OCT) measures retinal swelling, particularly macular edema, a frequent complication causing vision loss. OCT provides detailed cross-sectional images of the retina, allowing precise monitoring of fluid accumulation and treatment response.
Fluorescein angiography is a diagnostic test involving the injection of a yellow dye into the bloodstream. As the dye travels through retinal blood vessels, a special camera captures images, revealing blocked vessels, leakage, and capillary non-perfusion. This helps differentiate between ischemic and non-ischemic CRVO and provides insight into blood flow dynamics and areas of oxygen deprivation within the retina.
Management focuses on addressing underlying systemic conditions and treating ocular complications, with patients working with their primary care physicians to optimize control of conditions like high blood pressure, diabetes, and high cholesterol. Ocular treatments include anti-VEGF (vascular endothelial growth factor) injections directly into the eye, such as ranibizumab, aflibercept, or bevacizumab, which reduce macular edema and inhibit abnormal blood vessel growth. Steroid injections can also decrease swelling. In severe ischemic CRVO cases where abnormal new blood vessels grow, laser photocoagulation may be performed to prevent bleeding and high eye pressure. Regular follow-up appointments, initially monthly, monitor vision and assess treatment effectiveness.