Certified Ophthalmic Assistant Practice Exam

Which tool is a series of red cylinders used to assess phoria?

1. Gunn's net

2. Maddox rod

3. Duochrome test

4. Stereo Fly test

The correct answer is: Maddox rod

The Maddox rod is usually a glass rod with a series of red cylinders running parallel to each other. When one eye sees a red horizontal line and the other eye sees a vertical white light, the brain can produce inaccurate depth perception. The other options, Gunn's net, duochrome test, and Stereo Fly test are all used to assess other aspects of vision and are not specifically designed to evaluate phoria. Gunn's net is used for visual acuity, duochrome test is used for determining refractive errors, and Stereo Fly test is used for evaluating stereopsis (depth perception). Therefore, these options are incorrect in the context of evaluating phoria.