A-scan and B-scan are safe and painless procedures.
During an A-scan, the doctor will put anaesthetic drops in your eyes to make them numb. You will be asked to sit in a chair and place your chin on a chin rest. The doctor will then ask you to look straight ahead. They will place an ultrasound wand (a device that produces ultrasound waves that bounce off eye tissues and make echoes) on the front surface of the eye.
During a B-scan, the doctor will ask you to close your eyes. A gel will be applied to the eyelids before using the probe. The doctor may ask you to move your eyes in multiple directions.
Both the tests are generally quick and cause minimal discomfort.