A Scan

An A-scan ultrasound is a technology used to measure the axial length of the eye, which is crucial for monitoring eye growth and managing myopia. The procedure works by measuring the time it takes for sound waves to travel from the front of the eye to the back. It is a non-invasive process where the patient rests their chin and forehead on the machine and is instructed to look at a green light. Results are obtained and interpreted immediately.

The A-scan is typically performed every six months to ensure that eye growth is within the expected range. Normal eye growth is approximately 0.1 mm to 0.2 mm per year, and an increase of 0.33 mm in eye length corresponds to a 1.00 diopter increase in myopia. An emmetropic eye, which requires no corrective lenses, has an axial length of about 23.8 mm, while an eye measuring 26.00 mm or more is considered to have high myopia. Close monitoring is especially recommended for patients with a family history of myopia or those exhibiting rapid progression based on exam results.