All you need to know about: central retinal vein occlusion

Recent media reports from Pakistan suggest that Imran Khan, the former Prime Minister and World Cup-winning captain, has reportedly lost nearly 85% of vision in his right eye due to central retinal vein occlusion (CRVO). For a cricketer once known for sharp reflexes and precise timing, this is particularly sobering.

Understanding the retina

The retina is a thin, delicate layer of nerve tissue lining the back of the eye. It is the part that “catches” light and converts it into electrical signals, which then travel to the brain through the optic nerve. The retina is not just a screen: it is living neural tissue that is constantly processing light, contrast, colour, and motion, which is why it needs a steady supply of oxygen and nutrients.

Every organ depends on blood flow because blood is the delivery system for oxygen and glucose and the removal system for waste. The retina is no exception. Blood reaches it through the central retinal artery. After delivering oxygen, the deoxygenated blood drains out through the central retinal vein. Both vessels pass through a confined space within the optic nerve head. For vision to remain clear, blood must flow in without obstruction and exit without resistance.

If its blood circulation is disturbed, retinal cells begin to malfunction, and vision can decline rapidly. In retinal vein occlusion, the problem is not that blood cannot enter, but that blood cannot leave efficiently. When drainage fails, pressure builds up inside tiny vessels, fluid leaks into the retinal tissue, and the light-sensing layer becomes swollen and injured.

What is CRVO?

Central retinal vein occlusion, or CRVO, occurs when the main vein draining the retina becomes blocked, usually at or near the optic nerve head, where space is tight. This blockage leads to congestion, retinal haemorrhages, and swelling at the macula, the small central area responsible for sharp reading vision. Retinal vein occlusion can also occur in smaller branches, called branch retinal vein occlusion, where only part of the retina is affected, and the visual loss may be limited to one sector. CRVO itself is commonly divided into non-ischemic and ischemic forms. Non-ischemic CRVO is the more common form (about 75%) and tends to have better vision at presentation and a better chance of stabilising with treatment. Ischemic CRVO is roughly 25% of cases and is the dangerous form, because large areas of retina are deprived of oxygen, raising the risk of fragile new vessel growth, bleeding, and neovascular glaucoma. 

Symptoms and risk factors

The typical story is sudden, painless blurring or loss of vision in one eye. Some people notice a fog, a dark patch in the centre, or distortion while reading. Others notice it on waking up, because swelling and congestion may become more apparent after hours of lying down. Pain is not a usual early feature, because the retina itself does not “ache” the way skin does. Pain can appear later if the ischemic form triggers neovascular glaucoma, in which abnormal vessels block the eye’s fluid drainage, leading to increased eye pressure and a painful, red eye with further vision loss. 

The commonest drivers are the same vascular risks that damage arteries and veins elsewhere: high blood pressure, diabetes, high cholesterol, smoking, older age, and glaucoma. Certain blood-clotting disorders and autoimmune conditions can also contribute, especially in younger patients. In young women, oral contraceptive pills have been reported as a risk factor in such settings, particularly when other risks like smoking or thrombophilia coexist. However, the absolute risk remains low for most healthy users. 

Diagnosis and treatment

Diagnosis begins with a dilated retinal examination to look for venous congestion, haemorrhages, and retinal swelling. Optical coherence tomography, or OCT, is used to measure macular oedema and track response to therapy. Fluorescein angiography, in which a dye is injected, and the retinal circulation is photographed, helps distinguish non-ischemic from ischemic disease by mapping areas of nonperfusion and guiding laser decisions when needed. Doctors also evaluate systemic health by measuring blood pressure, blood sugar, lipid profiles, and, in selected patients, tests for clotting disorders and autoimmune diseases, because CRVO can be the first visible sign that vascular risk is uncontrolled. 

There is no simple way to “unblock” the vein directly. Treatment focuses on preventing swelling-related damage and ischemia-related complications. The mainstay is intravitreal anti-VEGF injections, which reduce macular oedema and often improve vision. Steroids may be used in selected cases, balancing benefits against risks such as raised eye pressure and cataract. If abnormal new vessels develop, laser treatment may be used to reduce the drive for neovascularisation. Alongside eye treatment, aggressive control of blood pressure, diabetes, and lipids is essential, as the retina reveals a systemic vascular problem, not an isolated eye event. 

Prognosis

Prognosis depends largely on whether the CRVO is non-ischemic or ischemic. Many non-ischemic cases can stabilise, and some recover meaningful reading vision with timely therapy. Ischemic CRVO has a higher likelihood of severe, persistent visual loss and complications such as neovascular glaucoma, which is why close follow-up in the first months is critical. 

The reported visual loss of a former sports icon is also a reminder that systems, not just biology, often shape illness. CRVO is, ultimately, a vascular event that exposes how quickly sight can be altered when chronic risks go unchecked and when timely medical monitoring is disrupted.

(Dr. C. Aravinda is an academic and public health physician. The views expressed are personal. aravindaaiimsjr10@hotmail.com)

Published – February 19, 2026 10:31 am IST