Category: 4. Painless Vision Loss

The central retinal artery (CRA) is a branch of the ophthalmic artery that travels within the optic nerve to supply blood to the retina. Occlusion of the central retinal artery is an ophthalmic emergency as the remaining posterior ciliary artery cannot sufficiently supply the retina’s needs. Emergent Opthalmology consult must be placed and hyperbaric oxygen therapy may be required.

CRAO commonly occurs from carotid artery atherosclerosis and plaque embolism. Some contributing risk factors for include diabetes, hypertension, cardiovascular disease, and hyperlipidemia (Varma et al).

Patients with CRAO usually have sudden, painless monocular vision loss. If you suspect CRAO, it is important to measure the blood pressure as there is a strong relationship between CRAO and hypertension (Varma et al). Another important area to assess is the radial pulse rate and rhythm. Atrial fibrillation has a high risk for embolisms and can be detected as an irregularly irregular pulse.

Central Retinal Artery Occlusion (CRAO) Ultrasound Findings

CRAO is a rare finding and requires color Doppler mode to diagnose with ocular ultrasound. On the ocular ultrasound exam, you will find diminished or absent flow of the central retinal artery (see below). You may also only see flow from the central retinal vein (blue on color Doppler) with absent central retinal arterial flow (red on color Doppler)

(Editor’s Note: In some circumstances, you may also still see some arterial flow on color Doppler from the posterior ciliary artery, even though the central retinal artery is occluded)

Vitreous hemorrhage occurs when extravasated blood is inside or around the vitreous humor of the eye. This can occur from damage to normal blood vessels, growth of abnormal blood vessels, or bleeding from other parts of the eye.

Symptoms of vitreous hemorrhage include sudden, painless vision loss, photophobia, and the perception of shadows and cobwebs floating in front of their eyes. Sometimes, patients describe their vision as worse in the morning because blood has settled at the back of their eye during the night.

Vitreous Hemorrhage Ultrasound Findings

On ophthalmic ultrasound, vitreous hemorrhage looks like echogenic material in the posterior chamber. If you ask the patient to move their eye on ophthalmic ultrasound, vitreous hemorrhage is best visualized with normal or high gain settings. Vitreous hemorrhage looks like echogenic material in the posterior chamber. If you ask the patient to move their eye side-to-side, you may see the washing machine sign, where the echogenic material appears to swirl like clothes in a washing machine.

Retinal detachment and posterior vitreous detachment can present with similar symptoms but the management and prognosis between the two conditions are very different.

While retinal detachment is an ocular emergency, posterior vitreous separation is generally not. Ultrasound of the eye can help diagnose and distinguish between Retinal Detachment and Posterior Vitreous Detachment but an urgent/emergent ophthalmology consult should be placed to definitively differentiate between the two.

If you see a hyperechoic membrane tethered to the optic nerve, this is a retinal detachment. However, if the hyperechoic flap is along the posterior wall of the eye and not tethered to the optic nerve, this could be a retinal detachment or a posterior vitreous detachment.

The table below shows the differences between retinal detachment and posterior vitreous detachment:

	Retinal Detachment	Posterior Vitreous Detachment
Emergency Referral Needed	Yes	No
Vision Changes	Constant vision loss	Fluctuating vision blur
Optic Nerve Sheath Attachment	Hyperechoic line most often attached to the optic nerve sheath (unless RD is not right next to optic nerve)	Hyperechoic line is not attached to the optic nerve sheath
Mobility with eye movements	Less mobile: adheres closely to wall	Very mobile; undulates like “seaweed”
Thickness	Thick folded membrane	Thinner, smooth folded membrane

A posterior vitreous detachment (PVD) occurs when the vitreous body separates from the posterior portion of the normal retina, but the retina is still intact.

There is a higher prevalence of PVD in elderly and myopic patients. Patients with posterior vitreous detachment (PVD) often present with fluctuating cloudy vision, acute floaters, and brief flashes (photopsia).

Posterior Vitreous Detachment Ultrasound Findings

On ocular ultrasound, posterior vitreous detachment looks like a thin, hyperechoic membrane lifted off the posterior surface of the globe that is NOT tethered to the optic nerve. The membrane will freely move with ocular movements in an undulating fashion, like “swaying seaweed.”

Retinal Detachment (RD)

A retinal detachment is defined by a separation of the sensory retina from the underlying retinal pigment epithelium. This cuts off the blood supply to the rods and cones in the eye and can cause permanent vision loss. A retinal detachment is an ocular emergency that must be referred immediately to an ophthalmologist (Ghazi & Green).

A patient with a detached retina typically presents with painless, fixed visual field loss, new floaters, or flashes (photopsia) with the perception of a curtain coming down (inferior detachment) or up (superior detachment). Unfortunately, fundoscopy using a direct ophthalmoscope is limited and can miss retinal detachments.

There are three major types of retinal detachment (rhegmatogenous, traction, and exudative):

Ocular ultrasound is both sensitive and specific for diagnosing retinal detachments. While distinguishing between the 3 types of retinal detachment is important from a treatment standpoint, ocular ultrasound should not focus on distinguishing between them. The primary purpose of POCUS is to be able to diagnose a retinal detachment and then allow the ophthalmologist to help definitively diagnose the retinal detachment type and treatment option.

Retinal Detachment Ultrasound Findings

On B scan (B mode), ocular ultrasound retinal detachment is best visualized in normal and often low gain settings. A retinal detachment looks like a thick/hyperechoic membrane lifted off of the posterior surface of the globe that floats and moves with the patient’s eye movement.

If the retinal detachment is large, the hyperechoic membrane will be tethered to the optic nerve. However, if the retinal detachment is small or not near the optic nerve, the hyperechoic membrane will be tethered closely to the back wall of the eye and will not move much with eye movement. It is important to scan the eye in multiple axes (transverse and sagittal) to detect small retinal detachments.

See below for an ocular ultrasound retinal detachment image and video. Notice how the retinal detachment is tethered to the optic nerve as the patient moves their eye.