Certified Ophthalmic Technician (COT) Practice Test 2025 - Free COT Practice Questions and Study Guide

The immersion A-scan method is recognized for its ability to eliminate corneal distortion during measurement. This technique involves placing an ultrasound probe in a saline solution, allowing it to directly contact the eye without the additional layer of tear film that can cause inaccuracies in measurements when using other methods, like contact A-scan. By immersing the probe, the A-scan can accurately measure the axial length of the eye while minimizing any effects that the cornea may impose, resulting in more reliable data.

In contrast, methods such as the contact A-scan might not provide the same level of accuracy due to potential variances caused by the corneal surface and the tear film. B-scan ultrasound is primarily used for imaging structures within the eye but does not focus on axial length measurements. Optical coherence tomography (OCT) provides a different type of imaging that is valuable for detailed retinal and optic nerve analysis but does not specifically address corneal distortion in axial length measurements. Therefore, immersion A-scan stands out as the method that effectively reduces distortion for accurate measurements.