| disease | Central Retinal Artery Occlusion |
The central retinal artery is the sole source of nutrition for the inner layer of the retina. As this artery is an end artery with no anastomoses between its branches, any obstruction leads to an interruption of blood supply to the inner retinal layer, causing acute ischemia and a rapid decline in visual function. The onset of this condition is sudden. Most cases involve one eye, though the other eye may be affected days or years later. Patients are typically over 40 years of age, with no significant gender differences.
bubble_chart Etiology
1. Changes in the stirred pulse wall and thrombosis Most cases of this disease involve heart and blood vessel system conditions such as stirred pulse sclerosis, hypertension, systemic or local inflammatory vascular diseases (e.g., temporal stirred pulse arteritis, thrombotic vessel inflammation, periarteritis nodosa, Behcet's disease, Eales' disease, uveitis, etc.), all of which can affect the stirred pulse, leading to intimal hyperplasia or edema, narrowing the lumen and roughening the inner wall. Due to the impact of blood flow, a gap often remains at the narrowed site. When the gap retains one-third of the original lumen, there are no clinical manifestations. However, under certain factors (e.g., thrombosis, vascular spasm, insufficient blood perfusion pressure, or elevated intraocular pressure), this gap may suddenly close.
2. Stirred pulse spasm Acute progressive hypertension, renal hypertension, etc., can cause stirred pulse spasm, as can chronic progressive hypertension with widespread hardening of small stirred pulses throughout the body. These spasms can affect the central stirred pulse of the retina, leading to transient obstruction of its main trunk or branches.
3. Embolism As mentioned earlier, this condition is rarely caused by emboli in the blood circulation. When obstruction occurs due to emboli, they often originate from vegetations detached from the heart valve membrane or the inner walls of nearby large stirred pulses. Examples include vegetations on the aortic or mitral valves in bacterial endocarditis, atherosclerotic plaques, and thrombi within stirred pulse aneurysms. Pathological examination of emboli may reveal calcium, cholesterol, lipids, neutral fats, platelets, etc. Additionally, literature reports cases involving air, fat, tumor fragments, cortisone, pus clots, Chinese Taxillus Herb parasites, and eggs. The central stirred pulse of the retina is prone to embolism at the narrow sections where it enters the optic nerve and eyeball, specifically at the dura mater of the optic nerve and the scleral sieve plate. Smaller emboli may lodge in one of the branches of this stirred pulse.4. Other factors Retrobulbar hemorrhage during orbital anesthesia or prone general anesthesia during surgery can also lead to central retinal stirred pulse obstruction. The cause may be related to pressure on the eyeball and the patient being in a state of blood loss or shock.
bubble_chart Pathological Changes
When the central retinal artery is blocked, blood flow is interrupted, leading to immediate hypoxia, necrosis, and degeneration in the inner layer of the retina. The severity and speed of these changes correspond directly to the completeness of the blockage. Reports indicate that histological examinations conducted three hours after complete blockage reveal ruptured cell membranes in the inner retinal layer, accumulation of nuclear chromatin, cellular autolysis, and fluid loss. Subsequently, the endothelial cells and pericytes of the capillary walls degenerate, leaving large areas of acellular and nonfunctional capillaries. After the necrotic inner retinal cells are absorbed, they are replaced by glial tissue.
Clinical manifestations vary depending on the location of the obstruction (main trunk or branch occlusion) and the degree (complete or incomplete occlusion).
In cases of complete occlusion of the main trunk, in most patients, visual function is completely lost immediately or within minutes, the pupil dilates, and the direct light reflex disappears. However, some patients retain a narrow area of light perception in the temporal periphery of the visual field. The reason for this may be related to the fact that the nasal retina extends further forward than the temporal side, and the peripheral full-thickness retina is nourished by both the choroid and the retinal arterial circulation. In some cases, a small island of vision may also remain near the physiological blind spot. This is likely due to the retinal blood supply around the optic disc being maintained through small branches of the Zinn-Haller ring or anastomoses between the posterior ciliary artery and the retinal circulation. On fundoscopy, immediately after the occlusion, the optic disc retains its original color, the retinal arteries are severely narrowed, the blood column appears dark, the central reflex of the vessel wall becomes very thin or even disappears, and the distal small branches are no longer visible. The veins are also significantly narrowed, sometimes with segmented blood columns moving slowly. The entire retina, especially the posterior pole, appears milky white and opaque. The fovea, which lacks the inner retinal layers and is unaffected by the central retinal artery's blood supply, retains its normal red color, appearing as a strikingly contrasting round or oval dark red or brown-red spot against the surrounding milky-white opacity, known as the "cherry red spot." However, in a few cases, due to particularly severe edema forming folds that obscure the fovea, the cherry red spot may not be visible. One to two weeks after the occlusion, the retinal opacity gradually recedes from the periphery toward the posterior pole, and the retina regains transparency, approaching its original fundus color. However, the inner retinal layers have already undergone necrosis and atrophy, and visual function cannot recover. The retinal arteries remain severely narrowed, with degenerative thickening of the vessel walls, and may develop white sheathing or become thread-like. The veins also become thinner, sometimes with parallel white sheathing. The posterior pole often shows pigmentary disturbances, such as small pigment spots and depigmented spots, giving a rough, granular appearance. The optic disc becomes pale and clearly demarcated, a condition known as vascular optic atrophy.
In cases of incomplete occlusion of the main trunk, changes in visual function and fundoscopic findings also vary depending on the severity. In mild cases, the retinal artery diameter shows no significant change, retinal opacity is slight, and visual impairment is relatively minor. In severe cases, the presentation is similar to complete occlusion. Occasionally, segmented blood columns may be seen moving slowly centrifugally within the arteries.
In branch occlusions, any of the retinal artery branches may be affected, with the superior temporal branch being the most commonly involved. When a branch is completely occluded, the affected branch becomes narrowed, the corresponding retinal area becomes edematous and opaque, and the corresponding visual field is suddenly lost. If the macula is involved, a cherry red spot appears, and central vision declines sharply. In incomplete branch occlusions, the degree of fundus changes and visual impairment varies depending on the severity of the occlusion.
In cases of central retinal artery occlusion, occasional small retinal hemorrhages may be seen, mostly near the optic disc. These small hemorrhages typically occur weeks after the occlusion and may result from the rupture of newly formed anastomotic vessels or capillary damage due to hypoxia, leading to leakage. If the fundus shows more extensive and dense patchy or flame-shaped retinal hemorrhages, this indicates combined venous occlusion.
Approximately 15% of the Chinese population has a cilioretinal artery (Zhang Meixin, 1979). When the main trunk of the central retinal artery is occluded, if the patient has this anomalous artery, a small area of normally colored retina (usually including the macula) on the temporal side of the optic disc may be preserved due to the blood supply from this artery, allowing some residual central vision. Conversely, this anomalous artery may also suddenly become occluded, causing the optic disc and macular retina to become pale and edematously opaque, with a sharp decline in central vision and the appearance of a central scotoma.
bubble_chart Auxiliary Examination
Due to variations in the time interval between angiography and occlusion, the location and severity of the occlusion, as well as the compensatory and reconstructive status of blood circulation post-occlusion, the angiographic findings can differ significantly. Observations range from complete absence of perfusion in the stirred pulse, delayed filling, non-perfusion of small branches, to entirely normal filling. In general, the manifestations include the following:
**Findings in the early stage of the disease course**: Clinically, it is virtually impossible to perform fluorescein angiography immediately at the onset of occlusion. The so-called early-stage findings actually refer to angiographic changes observed hours or days after the onset.
**Complete occlusion of the main trunk**: In such cases, the retinal stirred pulse shows no perfusion of fluorescent dye. However, the capillaries of the optic disc, supplied by the ciliary stirred pulse, quickly exhibit dye filling with marked dilation, forming collateral anastomoses. The dye rapidly refluxes into the root of the central vein on the optic disc, accumulating in the proximal segment of the main venous trunk. A distinctive retrograde flow phenomenon is also observed, where the dye fills the venous branches outside the optic disc in a reverse manner from the main venous trunk.
**Sudden partial relief of complete occlusion or incomplete occlusion of the main trunk**: The angiographic findings vary depending on the degree of occlusion at the time of angiography. In cases of severe occlusion, delayed fluorescence filling is observed. The retinal stirred pulse completes its circulation in approximately 1–2 seconds in normal eyes, but this can extend to 30–40 seconds in occluded stirred pulses. The appearance of fluorescence in the veins is also significantly delayed. Normally, the interval between the stirred pulse phase and the early venous phase is only 1–2 seconds, but it can extend to 30–40 seconds in such cases. Dim or granular venous fluorescence indicates severely compromised blood flow. In milder cases of occlusion, the filling times of arteries and veins may be slightly prolonged or entirely normal.
**Complete occlusion of a branch**: During angiography, blood flow is seen to abruptly halt at the occlusion site, with fluorescence leakage observed at the vessel wall. Another hallmark of complete branch occlusion is retrograde filling. Due to the significantly lower pressure at the distal end of the occluded branch, blood reflux from capillaries becomes possible. Thus, in the initial stage of occlusion, the angiogram may show earlier dye perfusion at the distal end of the stirred pulse compared to the proximal end of the occlusion.
**Incomplete occlusion of a branch**: No fluorescence leakage is observed at the vessel wall of the occlusion site. The filling time of the affected stirred pulse branch may be slightly prolonged compared to other normal branches or entirely normal.
**Late stage of the disease course**: This refers to the period weeks or months after the occlusion occurs. In cases of complete occlusion of the main trunk or branches, although collateral circulation may restore the stirred pulse filling time to normal, angiographic findings such as narrowed arterial and venous diameters, vascular sheathing, collateral channels, and non-perfusion areas of capillaries may still be observed. Occasionally, micro stirred pulse aneurysms, neovascularization, abnormal fluorescence, and pseudofluorescence due to retinal proliferative membranes may also be detected.
Whether it is a trunk or branch occlusion, the diagnosis can be made based on the aforementioned clinical manifestations. In cases of central vein occlusion in the trunk, due to extensive retinal hemorrhages and edema, the stirred pulse may be obscured. Relying solely on fundus findings, it can easily be misdiagnosed as an isolated central vein trunk occlusion. However, the sudden loss of visual function can help differentiate the condition.
bubble_chart Treatment Measures
The retinal tissue is extremely sensitive to hypoxia. Once the blood supply is interrupted, it can quickly become necrotic, leading to permanent loss of visual function. Therefore, prompt intervention is crucial to salvage partial vision.
1. Emergency Treatment: Upon diagnosis, immediately administer amyl nitrite (0.2ml per dose) by inhalation every 1–2 hours for 2–3 doses, and sublingual nitroglycerin tablets (0.3–0.6mg per dose) 2–3 times daily. Retrobulbar injection of atropine 1mg or tolazoline 12.5–25mg can dilate the retinal arteries and relieve spasms. Ocular massage or anterior chamber paracentesis can lower intraocular pressure and enhance retinal artery dilation. If the blockage is caused by an embolus, this may help the embolus migrate toward smaller branches.
Concurrently, administer oxygen mixed with 5% carbon dioxide for 10–15 minutes per session, repeated several times.
2. Late-Stage [Third Stage] Treatment: After emergency measures, if visual function shows signs of recovery, continue oral vasodilators such as nicotinic acid (0.1g, 3 times daily) or Salvia tablets (3–5 tablets per dose, 3 times daily). Alternatively, administer Salvia injection (40–60ml, containing 1g of raw herb per ml) mixed with low-molecular-weight dextran or 5% glucose (500ml) via intravenous drip, once daily for 15 sessions as one course.
Traditional Chinese medicine may use the following formula: Pueraria Root 60–150g, Astragalus Root 50g, Salvia 50g, Sichuan Lovage Rhizome 4.5g, Bupleurum 10g, Peach Kernel 10g, Earthworm 10g, decocted in water and taken twice daily as one dose. In the early stages of the condition, add musk 0.5g, divided into two daily doses for infusion.
Additionally, various adjunctive medications such as vitamins B1, B6, B12, E, ATP, and coenzyme A can be used.
This disease causes extremely severe damage to visual function. Whether partial visual function can be preserved depends on the timeliness of medical consultation and emergency treatment, as well as the degree, location, and cause of the obstruction. Patients who receive emergency treatment within hours of onset generally have a better prognosis. Those with vascular spasms or incomplete obstructions also tend to have better outcomes. Branch obstructions have a more favorable prognosis than main trunk obstructions. When the blockage occurs in the central retinal artery after entering the optic nerve's dural sheath but before reaching the optic nerve fiber bundles, collateral circulation can be quickly established, resulting in a better prognosis compared to blockages at the entry point of the dural sheath or within the visual function fiber bundles.
