What ocular structures are represented between A-scan spikes A and B?

The correct answer is the lens, which is situated between the spikes labeled A and B on an A-scan ultrasound. An A-scan ultrasound provides a graphical representation of the different ocular structures based on their reflective properties, which produce distinct spikes corresponding to the structures within the eye.

In this scenario, the lens is located posterior to the cornea and anterior to the vitreous humor. The A-scan measures the distance to these structures by recording the time it takes for sound waves to travel through the eye, reflect off the different layers, and return to the transducer. The spike associated with the lens appears between the corneal spike and other structures such as the retina and vitreous.

The cornea, being the most anterior structure of the eye, would generate a spike prior to the lens spike. The retina is located at the back of the eye and would produce a spike after the lens spike, and the vitreous is present behind the lens but does not create a variable spike because it is less reflective compared to the lens.

In conclusion, the positioning of the spikes on the A-scan correlates directly to the anatomical arrangement of these structures, confirming that the lens is accurately represented between the specified A-scan spikes.