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A-Scan Ultrasound Biometry

Taking a Deeper Look at A-Scan Ultrasound Biometry

A-scan ultrasound biometry is a relatively routine type of ultrasonic diagnostic testing used to diagnose a range of common sight diseases and disorders. A-scan (Amplitude scan) uses the high-frequency sound wave (ultrasound) to provide information in one dimension, like length.

A-scan ultrasound biometry is also exceptionally beneficial in cataract surgeries because they allow the ophthalmologist to determine the precise power for the intraocular lens of the implant. Similar to how ophthalmologists use the diagnostic test, let's take a deeper look at A-scan ultrasound biometry.

What Is A-Scan Ultrasound Biometry Imaging?

The human eye is primarily a ball of fluid. A-scan ultrasound biometry imaging is a highly efficient way of using ultrasonic waves to gain a unique perspective of the interior of the eye. With A-scan ultrasound biometry imagining, ultrasonic waves are bounced off of tissues from inside of the eye. The dimensional measurements help eye practitioners provide accurate and proper diagnoses.

A-Scan Ultrasound Biometry in Cataract Surgery

A-scan ultrasound biometry is used to determine the eye's axial length as well as the depth of the vitreous cavity, anterior chamber, and lens. The A-scan ultrasound is the most commonly used because as a critical part of the preoperative evaluation of cataract surgery patients.

When cataract surgery is conducted, the patient's natural lens is removed and replaced with an intraocular lens implant(IOL). However, before the IOL is placed, precise measurements of both eyes are needed.  

The A-scan ultrasound biometry is used to measure the length of the eye in conjunction with a series of different algorithms to determine the optimum dioptric intraocular lens power to be implanted at the time of the surgery. Because of its precise measurements and ability to deliver accurate readings on both eyes, the A-scan is always required prior to performing cataract surgery on eyes with dense cataracts.

A-Scan Technology

A-scan technology or amplitude scanning is based on timed echocs. With the A-scan, a one-dimensional sound wave is created at 8 MHz and converted into spikes. This transformation corresponds with the tissue as well as the height of the echo.The results of A-scan technology provide practitioners with vital measurements that help diagnose a vast range of conditions, such as:

  • Choroidal melanoma
  • Retinal detachment
  • And more

When you use A-scan technology, coupling jelly is not required. The single-beam A-Scan produces echoes that assist practitioners explore the densities of tissues determined by the scan's spike height. These readings are highly effective at characterizing the internal structure of tumors and of eye tissues.

A-Scan Ultrasound Biometry Applications

A-scan technology such as the A-Scan Plus Connect is typically used to measure axial length AL, which is important for intraocular lens calculations prior to cataract surgery.

Another application of A-scan is determining the sizes of posterior segment masses of the eye and ascertaining ultrasonic properties. However in many instances, A-scan biometry is used  in conjunction with B-scans to help differentiate lesions.

B-Scan Ocular Technology

B-scan technology — brightness scan — can only be performed on a fully anesthetized eye or a closed lid with coupling gel. B-scan technology produces two-dimensional sound waves at 10 MHz or more. This technology is usually utilized to evaluate orbital pathology and posterior segments — especially in patients when direct viewing isn't an option. Examples of B-scan technology include:

A-Scan Ultrasound Biometry vs B-Scan

While B-scan technology is useful in post-surgery check-ups and in emergency rooms because of it's two-dimensional imaging, A-scan characterizes internal tumors and other composition based on the previously discussed information. The primary differences between A-scan vs B-scan are:

  • With A-scan, diagnoses are made with a one-dimensional beam, and you have to be aiming directly at an object.
  • With B-scan, useful images are produced with a two-dimensional array of single A-scan beams. These beams are generated at a higher MHz frequency and can be used to gauge density.

Contact Keeler Ophthalmic Instruments

In ophthalmology, A-scan ultrasound biometry is utilized to accurately measure the axial length of the eye. It's also critical for cataract surgery as well as other conditions. As a result, it's important for you to have the best and most reliable A-scan ultrasound equipment.

At Keeler Ophthalmic Instruments, we bring more than 100 years of experience manufacturing A-scan ultrasound equipment. Our experienced professionals will listen to your needs and guide you to the most suitable A-scan ultrasound equipment.

Contact Keeler Ophthalmic Instruments today.

About the Author Eugene VanArsdale

Eugene is the Sales & Marketing Manager at Keeler Instruments. He has been with Keeler since 1982 and is co-holder of two patents for the company. Eugene has a true passion for the eye care industry and has dedicated himself to understanding the ins and outs of the optometric and ophthalmic equipment market.