When Light Cannot Pass Through, Ultrasound Helps the Doctor

Sometimes a doctor needs to see the internal structures of the eye, but a standard examination does not provide a complete picture. This may happen in cases of a dense cataract, vitreous hemorrhage, significant corneal opacity, or following an injury.

If the fundus cannot be seen clearly and light-based diagnostic methods are limited, the ophthalmologist may recommend an eye ultrasound, also known as ocular ultrasound.

Ultrasound imaging uses sound waves rather than light. These waves are inaudible to humans, and the device uses the reflected signals to create an image of the eye's internal structures.

Put simply: where light cannot pass through, ultrasound can provide the doctor with important information about what is happening inside the eye.

An eye ultrasound does not replace a consultation with an ophthalmologist. The doctor evaluates the results together with the patient's symptoms, examination findings, and other diagnostic results.

When a Doctor Recommends an Eye Ultrasound

An eye ultrasound is recommended when a standard examination is not sufficient or when the condition of the eye's internal structures needs to be assessed more precisely.

The examination may be necessary:

• in cases of a dense cataract, when the fundus cannot be seen clearly;
• in cases of vitreous hemorrhage;
• in cases of significant opacity of the cornea or other optical media of the eye;
• if retinal detachment is suspected;
• in cases of changes in the vitreous;
• after an eye injury;
• if an intraocular foreign body is suspected, provided that ultrasound can be performed safely given the nature of the injury;
• if an intraocular mass is suspected or to monitor a previously detected mass;
• after certain operations or injuries, if the doctor needs to monitor the condition of the eye's internal structures.

The ophthalmologist determines whether the examination is necessary after evaluating the patient.

What an Eye B-Scan Shows

A B-scan, or B-scan ultrasound, is one of the main types of eye ultrasound. It provides an image of the internal structures even when they cannot be seen clearly through the cornea, lens, or vitreous.

A B-scan can help the doctor:

• detect a retinal detachment and assess its extent;
• detect a vitreous hemorrhage;
• assess opacities and other changes in the vitreous;
• detect a posterior vitreous detachment;
• detect intraocular masses and assess their location and size;
• obtain additional information about a possible intraocular foreign body following an injury;
• assess the structures of the eye and the area around the optic nerve.

This examination is particularly important when the fundus cannot be properly examined because of a dense cataract, vitreous hemorrhage, or significant opacities.

How an Eye Ultrasound Is Performed

The examination usually takes a few minutes and is generally painless.

During a B-scan, the patient sits or lies down with their eyes closed. A small amount of gel is applied to the eyelid, after which the doctor gently moves the ultrasound probe over it.

During the examination, you may be asked to look in a particular direction. This helps the doctor assess the required area of the eye more accurately.

If you wear contact lenses, you should remove them before the examination.

Pupil dilation is generally not required for a standard B-scan.

When to Seek Urgent Ophthalmic Care

Some symptoms require prompt assessment by a specialist.

See an ophthalmologist as soon as possible if:

• a “veil” or “curtain” appears in front of your eye;
• you experience flashes of light;
• you suddenly notice a significant increase in floaters, strands, or spots;
• your vision suddenly deteriorates;
• you sustain an eye injury.

These symptoms may occur with retinal detachment, vitreous hemorrhage, and other conditions for which it is important not to delay examination.

You do not need to decide for yourself whether an ultrasound is specifically required. The doctor will first assess the condition of the eye and choose the appropriate diagnostic method.

Are There Any Contraindications or Risks?

Eye ultrasound does not use ionizing radiation. When medically indicated, the examination can be performed repeatedly, including in children and during pregnancy.

Particular caution is required after an injury.

If an open-globe injury or penetrating wound is suspected, the doctor will determine whether and how the examination can be performed. In such cases, no pressure should be applied to the eye.

When the appropriate technique is used and the necessary precautions are observed, ultrasound is usually well tolerated.

Other Ultrasound Methods Used to Examine the Eye

In ophthalmology, ultrasound is used not only to obtain images of the eye's internal structures. Other ultrasound examinations are available for specific diagnostic purposes.

A-Scan and Ocular Biometry

An A-scan, or A-scan ultrasound, is used to measure the anatomical parameters of the eye, including its length.

These measurements may be used, for example, to calculate the power of an intraocular lens (IOL) before cataract surgery.

Today, optical methods are often used for biometry. Ultrasound biometry is particularly useful when a dense cataract or other opacity makes it difficult to obtain reliable optical measurements.

Learn more: ocular biometry.

Ultrasound Pachymetry

Pachymetry measures the thickness of the cornea. This measurement may be important during an examination before laser vision correction, when a corneal condition is suspected, and in other clinical situations.

Learn more: corneal pachymetry.

Why an Ophthalmologist Should Interpret the Ultrasound Results

An eye ultrasound is more than just an image on a screen. The image alone is not a diagnosis.

The ophthalmologist evaluates the ultrasound results together with:

• the patient's symptoms;
• the examination findings;
• the condition of the cornea and lens;
• the condition of the retina and vitreous;
• intraocular pressure;
• the results of other examinations.

If necessary, ultrasound may be supplemented by other diagnostic methods, such as a fundus examination, OCT, biometry, or a corneal examination.

This gives the doctor a more complete understanding of the condition of the eye and helps determine the next steps in examination or treatment.

Frequently Asked Questions

Is an Eye Ultrasound Painful?

Usually not. During a B-scan, the probe is generally moved over the closed eyelid, so the examination does not cause pain.

How Is an Eye Ultrasound Different from OCT?

OCT uses light to produce highly detailed cross-sectional images of the retina, optic nerve, and other structures.

However, if light cannot pass through properly because of a dense cataract, vitreous hemorrhage, or significant opacities, the capabilities of OCT may be limited.

Ultrasound uses sound waves and can provide information about the internal structures of the eye even through opaque optical media.

Therefore, eye ultrasound and OCT cannot replace each other in every situation. The doctor chooses the examination based on the information that needs to be obtained.

Do I Need to Prepare for an Eye Ultrasound?

No special preparation is usually required.

If you wear contact lenses, you should remove them before the examination.

Can I Drive After an Eye Ultrasound?

After a standard B-scan, generally yes, because pupil dilation is not usually required for the examination itself.

If the doctor also used dilating eye drops as part of the ophthalmic examination, your vision may remain blurred for some time. In this case, it is best not to drive until your vision has returned to normal.

Do I Need a Referral for an Eye Ultrasound?

The ophthalmologist usually determines whether an ultrasound is necessary after examining the patient.

If you are unsure which examination you need, it is best to begin with a consultation with an ophthalmologist and an eye examination. The doctor will determine whether an ultrasound is necessary and which method will provide the most useful information in your case.