Certified Ophthalmic Medical Technologist (COMT) Practice Exam

What type of eye structure measurement does an A-scan primarily assess?

1. Visual acuity

2. Corneal curvature

3. Axial length

4. Intraocular pressure

The correct answer is: Axial length

An A-scan primarily assesses the axial length of the eye, which is crucial for determining the dimensions of the eye for various applications, particularly in ophthalmology. The axial length is a key measurement for diagnosing and managing refractive errors, as well as for calculating the correct power of intraocular lenses used in cataract surgery. During an A-scan ultrasound, sound waves are emitted and then reflected back from the different structures within the eye, producing a reading that represents the distances between these structures, specifically measuring from the anterior surface of the cornea to the retina. Visual acuity refers to the sharpness of vision and is assessed using different tests that evaluate how well one can see. Corneal curvature measurement typically involves techniques like keratometry, which focuses on the front surface of the eye, while intraocular pressure is measured using tonometry methods. These concepts are distinct from what an A-scan ultrasound directly measures. Thus, the emphasis of the A-scan on axial length makes it an essential tool in ocular assessments and surgical planning.