Ancillary testing is not usually necessary to make the diagnosis. Fluorescein angiography reveals an abrupt diminution in dye at the site of the obstruction. Visual field testing can confirm the extent of visual loss.

The diagnosis of BRVO is made clinically by finding retinal hemorrhages in the distribution of an obstructed retinal vein.

- Fluorescein angiography is a helpful adjunct. Findings include delayed venous filling, hypofluorescence caused by hemorrhage and capillary nonperfusion, dilation and tortuosity of veins, leakage due to neovascularization and macular edema.

- Optical coherence tomography is an adjunctive test in BRVO. Macular edema is commonly seen in BRVO in OCT exams. Serial OCT is used as a rapid and noninvasive way of monitoring the macular edema.

No proved treatment exists for branch retinal artery occlusion.

In the rare patient who has branch retinal artery obstruction accompanied by a systemic disorder, systemic anti-coagulation may prevent further events.

In general, BRVO has a good prognosis: after 1 year 50–60% of eyes have been reported to have a final VA of 20/40 or better even without any treatment. With time the dramatic picture of an acute BRVO becomes more subtle, hemorrhages fade so that the retina can look almost normal. Collateral vessels develop to help drain the affected area.

Retinopathy is diagnosed by an ophthalmologist or an optometrist during eye examination. Stereoscopic fundus photography is the gold standard for the diagnosis of retinopathy. Dilated fundoscopy, or direct visualization of the fundus, has been shown to be effective as well.

A retinal haemorrhage is generally diagnosed by using an ophthalmoscope or fundus camera in order to examine the inside of the eye. A fluorescent dye is often injected into the patient's bloodstream beforehand so the administering ophthalmologist can have a more detailed view of the blood vessels in the retina.

The fluorescent dye can have dangerous side effects: see Fluorescein

Treatment consists of Anti-VEGF drugs like Lucentis or intravitreal steroid implant (Ozurdex) and Pan-Retinal Laser Photocoagulation usually. Underlying conditions also require treatment. Non-Ischemic CRVO has better visual prognosis than Ischemic CRVO.

A systematic review studied the effectiveness of the anti-VEGF drugs ranibizumab and pagatanib sodium for patients suffering from non-ischemic CRVO. Though there was a limited sample size, participants in both treatment groups showed improved visual acuity over 6 month periods, with no safety concerns.

Several treatments have been attempted for CRAS; however, none show definitive improvement in outcomes. The Undersea and Hyperbaric Medical Society lists Central Retinal Artery Occlusion (CRAO) as an approved indication for Hyperbaric Oxygen Therapy. This a treatment for CRAO that is covered by medical insurance in North America. Other treatments include ocular massage, anterior chamber paracentesis, and inhalation therapy of a mixture of 5% carbon dioxide and 95% oxygen.

The artery can re-canalize over time and the edema can clear. However, optic atrophy leads to permanent loss of vision. Irreversible damage to neural tissue occurs after only 90 minutes. Two thirds of patients experience 20/400 vision while only one in six will experience 20/40 vision or better.

There are divergent views as to whether everyone with an unprovoked episode of thrombosis should be investigated for thrombophilia. Even those with a form of thrombophilia may not necessarily be at risk of further thrombosis, while recurrent thrombosis is more likely in those who have had previous thrombosis even in those who have no detectable thrombophilic abnormalities. Recurrent thromboembolism, or thrombosis in unusual sites (e.g. the hepatic vein in Budd-Chiari syndrome), is a generally accepted indication for screening. It is more likely to be cost-effective in people with a strong personal or family history of thrombosis. In contrast, the combination of thrombophilia with other risk factors may provide an indication for preventative treatment, which is why thrombophilia testing may be performed even in those who would not meet the strict criteria for these tests. Searching for a coagulation abnormality is not normally undertaken in patients in whom thrombosis has an obvious trigger. For example, if the thrombosis is due to immobilization after recent orthopedic surgery, it is regarded as "provoked" by the immobilization and the surgery and it is less likely that investigations will yield clinically important results.

When venous thromboembolism occurs when a patient is experiencing transient major risk factors such as prolonged immobility, surgery, or trauma, testing for thrombophilia is not appropriate because the outcome of the test would not change a patient's indicated treatment. In 2013, the American Society of Hematology, as part of recommendations in the Choosing Wisely campaign, cautioned against overuse of thrombophilia screening; false positive results of testing would lead to people inappropriately being labeled as having thrombophilia, and being treated with anticoagulants without clinical need

In the United Kingdom, professional guidelines give specific indications for thrombophilia testing. It is recommended that testing be done only after appropriate counseling, and hence the investigations are usually not performed at the time when thrombosis is diagnosed but at a later time. In particular situations, such as retinal vein thrombosis, testing is discouraged altogether because thrombophilia is not regarded as a major risk factor. In other rare conditions generally linked with hypercoagulability, such as cerebral venous thrombosis and portal vein thrombosis, there is insufficient data to state for certain whether thrombophilia screening is helpful, and decisions on thrombophilia screening in these conditions are therefore not regarded as evidence-based. If cost-effectiveness (quality-adjusted life years in return for expenditure) is taken as a guide, it is generally unclear whether thrombophilia investigations justify the often high cost, unless the testing is restricted to selected situations.

Recurrent miscarriage is an indication for thrombophilia screening, particularly antiphospholipid antibodies (anti-cardiolipin IgG and IgM, as well as lupus anticoagulant), factor V Leiden and prothrombin mutation, activated protein C resistance and a general assessment of coagulation through an investigation known as thromboelastography.

Women who are planning to use oral contraceptives do not benefit from routine screening for thrombophilias, as the absolute risk of thrombotic events is low. If either the woman or a first-degree relative has suffered from thrombosis, the risk of developing thrombosis is increased. Screening this selected group may be beneficial, but even when negative may still indicate residual risk. Professional guidelines therefore suggest that alternative forms of contraception be used rather than relying on screening.

Thrombophilia screening in people with arterial thrombosis is generally regarded unrewarding and is generally discouraged, except possibly for unusually young patients (especially when precipitated by smoking or use of estrogen-containing hormonal contraceptives) and those in whom revascularization, such as coronary arterial bypass, fails because of rapid occlusion of the graft.

Retinal haemorrhages, especially mild ones not associated with chronic disease, will normally resorb without treatment. Laser surgery is a treatment option which uses a laser beam to seal off damaged blood vessels in the retina. Anti-vascular endothelial growth factor (VEGF) drugs like Avastin and Lucentis have also been shown to repair retinal haemorrhaging in diabetic patients and patients with haemorrhages associated with new vessel growth.

Quick determination of the cause may lead to urgent measures to save the eye and life of the patient. High clinical suspicion should be kept for painless vision loss in patients with atherosclerosis, deep venous thrombosis, atrial fibrillation, pulmonary thromboembolism or other previous embolic episodes. Those caused by a carotid artery embolism or occlusion have the potential for further stroke by detachment of embolus and migration to an end-artery of the brain. Hence, proper steps to prevent such an eventuality need to be taken.

Retinal arterial occlusion is an ophthalmic emergency, and prompt treatment is essential. Completely anoxic retina in animal models causes irreversible damage in about 90 minutes. Nonspecific methods to increase blood flow and dislodge emboli include digital massage, 500 mg IV acetazolamide and 100 mg IV methylprednisolone (for possible arteritis). Additional measures include paracentesis of aqueous humor to decrease IOP acutely. An ESR should be drawn to detect possible giant cell arteritis. Improvement can be determined by visual acuity, visual field testing, and by ophthalmoscopic examination.

At a later stage, pan-retinal photocoagulation (PRP) with an argon laser appears effective in reducing the neovascular components and their sequelae.

The visual prognosis for ocular ischemic syndrome varies from usually poor to fair, depending on speed and effectiveness of the intervention. However, prompt diagnosis is crucial as the condition may be a presenting sign of serious cerebrovascular and ischemic heart diseases.

In 2009, the Undersea and Hyperbaric Medical Society added "central retinal artery occlusion" to their list of approved indications for hyperbaric oxygen (HBO). When used as an adjunctive therapy, the edema reducing properties of HBO, along with down regulation of inflammatory cytokines may contribute to the improvement in vision. Prevention of vision loss requires that certain conditions be met: the treatment be started before irreversible damage has occurred (over 24 hours), the occlusion must not also occur at the ophthalmic artery, and treatment must continue until the inner layers of the retina are again oxygenated by the retinal arteries.

Despite the temporary nature of the vision loss, those experiencing amaurosis fugax are usually advised to consult a physician immediately as it is a symptom that may herald serious vascular events, including stroke. Restated, “because of the brief interval between the transient event and a stroke or blindness from temporal arteritis, the workup for transient monocular blindness should be undertaken without delay.” If the patient has no history of giant cell arteritis, the probability of vision preservation is high; however, the chance of a stroke reaches that for a hemispheric TIA. Therefore, investigation of cardiac disease is justified.

A diagnostic evaluation should begin with the patient's history, followed by a physical exam, with particular importance being paid to the ophthalmic examination with regards to signs of ocular ischemia. When investigating amaurosis fugax, an ophthalmologic consult is absolutely warranted if available. Several concomitant laboratory tests should also be ordered to investigate some of the more common, systemic causes listed above, including a complete blood count, erythrocyte sedimentation rate, lipid panel, and blood glucose level. If a particular cause is suspected based on the history and physical, additional relevant labs should be ordered.

If laboratory tests are abnormal, a systemic disease process is likely, and, if the ophthalmologic examination is abnormal, ocular disease is likely. However, in the event that both of these routes of investigation yield normal findings or an inadequate explanation, noninvasive duplex ultrasound studies are recommended to identify carotid artery disease. Most episodes of amaurosis fugax are the result of stenosis of the ipsilateral carotid artery. With that being the case, researchers investigated how best to evaluate these episodes of vision loss, and concluded that for patients ranging from 36–74 years old, "...carotid artery duplex scanning should be performed...as this investigation is more likely to provide useful information than an extensive cardiac screening (ECG, Holter 24-hour monitoring, and precordial echocardiography)." Additionally, concomitant head CT or MRI imaging is also recommended to investigate the presence of a “clinically silent cerebral embolism.”

If the results of the ultrasound and intracranial imaging are normal, “renewed diagnostic efforts may be made,” during which fluorescein angiography is an appropriate consideration. However, carotid angiography is not advisable in the presence of a normal ultrasound and CT.

If caught early, the neovascularization can be reversed with prompt pan retinal photocoagulation (PRP), or injection of anti-VEGF medications with subsequent PRP. The injection blocks the direct effect of VEGF and acts more quickly but will wear off in about 6 weeks. PRP has a slower onset of action but can last permanently. Once the neovascularization has been longstanding, the new vessels recruit fibrous tissue, and as this forms and contracts, the angle can be permanently damaged, and will not respond to treatment. If this occurs, then surgical intervention is required to reduce the pressure (such as a glaucoma drainage implant)

Several other diseases can result in retinopathy that can be confused with hypertensive retinopathy. These include diabetic retinopathy, retinopathy due to autoimmune disease, anemia, radiation retinopathy, and central retinal vein occlusion.

Telemedicine programs are available that allow primary care clinics to take images using specially designed retinal imaging equipment which can then be shared electronically with specialists at other locations for review. In 2009, Community Health Center, Inc. implemented a telemedicine retinal screening program for low-income patients with diabetes as part of those patients annual visits at the Federally Qualified Health Center.

This condition is often associated with diabetes in advanced proliferative diabetic retinopathy. Other conditions causing rubeosis iridis include central retinal vein occlusion, ocular ischemic syndrome, and chronic retinal detachment.

A major aim of treatment is to prevent, limit, or reverse target organ damage by lowering the person's high blood pressure to reduce the risk of cardiovascular disease and death. Treatment with antihypertensive medications may be required to control the high blood pressure.

If the diagnostic workup reveals a systemic disease process, directed therapies to treat that underlying cause should be initiated. If the amaurosis fugax is caused by an atherosclerotic lesion, aspirin is indicated, and a carotid endarterectomy considered based on the location and grade of the stenosis. Generally, if the carotid artery is still patent, the greater the stenosis, the greater the indication for endarterectomy. "Amaurosis fugax appears to be a particularly favorable indication for carotid endarterectomy. Left untreated, this event carries a high risk of stroke; after carotid endarterectomy, which has a low operative risk, there is a very low postoperative stroke rate." However, the rate of subsequent stroke after amaurosis is significantly less than after a hemispheric TIA, therefore there remains debate as to the precise indications for which a carotid endarterectomy should be performed. If the full diagnostic workup is completely normal, patient observation is recommended.

Imaging tests of the veins are used in the diagnosis of DVT, most commonly either proximal compression ultrasound or whole-leg ultrasound. Each technique has drawbacks: a single proximal scan may miss a distal DVT, while whole-leg scanning can lead to distal DVT overtreatment. Doppler ultrasound, CT scan venography, MRI venography, or MRI of the thrombus are also possibilities.

The gold standard for judging imaging methods is contrast venography, which involves injecting a peripheral vein of the affected limb with a contrast agent and taking X-rays, to reveal whether the venous supply has been obstructed. Because of its cost, invasiveness, availability, and other limitations, this test is rarely performed.

A fibrinogen uptake test was formerly used to detect deep vein thrombosis.

D-dimers are a fibrin degradation product, and an elevated level can result from plasmin dissolving a clot—or other conditions. Hospitalized patients often have elevated levels for multiple reasons. When individuals are at a high-probability of having DVT, diagnostic imaging is preferred to a D-dimer test. For those with a low or moderate probability of DVT, a D-dimer level might be obtained, which excludes a diagnosis if results are normal. An elevated level requires further investigation with diagnostic imaging to confirm or exclude the diagnosis.

For a suspected first leg DVT in a low-probability situation, the American College of Chest Physicians recommends testing either D-dimer levels with moderate or high sensitivity or compression ultrasound of the proximal veins. These options are suggested over whole-leg ultrasound, and D-dimer testing is the suggested preference overall. The UK National Institute for Health and Care Excellence (NICE) recommends D-dimer testing prior to proximal vein ultrasound.

For a suspected first leg DVT in a moderate-probability scenario, a high-sensitivity D-dimer is suggested as a recommended option over ultrasound imaging, with both whole-leg and compression ultrasound possible. The NICE guideline uses a two-point Wells score and does not refer to a moderate probability group.

Almost all infants with ROP have a gestational age of 31 weeks or less (regardless of birth weight) or a birth weight of 1250 g (2.76 lbs) or less; these indications are generally used to decide whether a baby should be screened for ROP, but some centres, especially in developing countries extend birth weight screening criteria to 1500 g (3.3 lbs).

Any premature baby with severe illness in perinatal period (Respiratory distress syndrome, sepsis, blood transfusion, Intra ventricular haemorrhage, apnoeic episodes, etc.) may also be offered ROP screening.

The treatment method used depends on the cause of the hemorrhage. In most cases, the patient is advised to rest with the head elevated 30–45°, and sometimes to put patches over the eyes to limit movement prior to treatment in order to allow the blood to settle. The patient is also advised to avoid taking medications that cause blood thinning (such as aspirin or similar medications).

The goal of the treatment is to fix the cause of the hemorrhage as quickly as possible. Retinal tears are closed by Laser treatment or cryotherapy, and detached retinas are reattached surgically.

Even after treatment, it can take months for the body to clear all of the blood from the vitreous. In cases of vitreous hemorrhage due to detached retina,long-standing vitreous hemorrhage with a duration of more than 2–3 months, or cases associated with rubeosis iridis or glaucoma, a vitrectomy may be necessary to remove the standing blood in the vitreous.

Tests for thrombophilia include complete blood count (with examination of the blood film), prothrombin time, partial thromboplastin time, thrombodynamics test, thrombin time and reptilase time, lupus anticoagulant, anti-cardiolipin antibody, anti-β2 glycoprotein 1 antibody, activated protein C resistance, fibrinogen tests, factor V Leiden and prothrombin mutation, and basal homocysteine levels. Testing may be more or less extensive depending on clinical judgement and abnormalities detected on initial evaluation.

For hereditary cases, the patient must have at least 2 abnormal tests plus family history.

Retinal examination with scleral depression is generally recommended for patients born before 30–32 weeks gestation, or 4–6 weeks of life, whichever is later. It is then repeated every 1–3 weeks until vascularization is complete (or until disease progression mandates treatment).