Certified Ophthalmic Medical Technologist (COMT) Practice Exam

What is produced in spectacle lenses by improper decentration?

1. Induced prism

2. Image distortion

3. Increased glare

4. Reduced clarity

The correct answer is: Induced prism

Improper decentration of spectacle lenses can lead to the production of induced prism. This occurs when the optical center of the lens is not properly aligned with the pupil of the eye. A shift in the lens position creates a situation where the light entering the lens is not directly aligned with the visual axis of the eye, causing the light to bend in an unintended manner. This results in the perception of a prism effect, where objects may appear to be displaced from their original positions. The amount of induced prism can be quantified and is typically based on the amount of decentration. Induced prism can affect the visual performance of the lens wearer, potentially leading to discomfort or visual disturbances such as double vision or blurred vision if significant enough. Understanding this principle is crucial in the fitting of prescription eyewear to ensure optimal alignment and visual acuity.