Certified Ophthalmic Medical Technologist (COMT) Practice Exam

What optical principle is involved when visual acuity improves with a pinhole?

1. The pinhole eliminates light interference

2. The pinhole allows only parallel rays of light to enter

3. The pinhole enhances light dispersion

4. The pinhole corrects refractive error

The correct answer is: The pinhole allows only parallel rays of light to enter

The visual acuity improvement observed when using a pinhole can be attributed to the principle that the pinhole allows only parallel rays of light to enter the eye. This is crucial because parallel rays correspond to light coming from a distance, which helps to reduce the effects of optical aberrations within the eye. When light enters through a small aperture like a pinhole, the depth of field increases, allowing for a clearer image on the retina. This phenomenon effectively minimizes the blurring caused by refractive errors, leading to sharper vision. In contrast, the other options do not accurately describe the role of a pinhole in improving visual acuity. For instance, while some light interference can be reduced, the primary mechanism is not about eliminating interference but rather about controlling the way light enters the eye. Enhancing light dispersion is not relevant in this context because the pinhole does not facilitate dispersion; instead, it focuses light more effectively. Lastly, while the pinhole can provide a clearer image for those with refractive errors, it does not actually correct these errors. It merely offers a temporary solution for improved focus by utilizing the principle of allowing only parallel rays.