Certified Ophthalmic Medical Technologist (COMT) Practice Exam

Which of the following structures is assessed through A-scan ultrasound?

1. Pupil

2. Vitreous body

3. Cornea

4. Retina

The correct answer is: Vitreous body

A-scan ultrasound is a diagnostic technique primarily used in ophthalmology to measure the dimensions of the eye, particularly the anterior segment structures and the axial length of the eye. This method involves sending ultrasound waves into the eye and measuring the time it takes for them to echo back from different structures. The vitreous body, which is the gel-like substance filling the space between the lens and the retina, is specifically assessed through A-scan ultrasound because it plays a crucial role in determining the overall dimensions of the eye and can be important for diagnosing various conditions, such as retinal detachment or other vitreous abnormalities. The A-scan is particularly beneficial in measuring the axial length since it can assist in calculating intraocular lens power for cataract surgery. The pupil, cornea, and retina are generally assessed using other methods. For example, the cornea is primarily evaluated through techniques like keratometry or topography, while the retina is typically assessed using imaging methods like optical coherence tomography (OCT) or fundus photography. The pupil can be examined with direct observation and will not require ultrasound for standard assessments. Thus, the key focus of A-scan ultrasound is the vitreous body, making this the correct answer.