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

The Maddox rod is indeed the correct tool used to assess phorias, which are misalignments of the eyes that can occur when a person is not focusing on an object. This instrument consists of a series of red cylinders that create a series of vertical and horizontal lines when placed in front of one eye. The patient is asked to identify the direction of the lines which helps the examiner to determine the presence and type of phoria the patient may have.

Using the Maddox rod allows the examiner to measure the deviation of the eyes under binocular or monocular conditions, providing a clear and quantifiable assessment of phoria. Its design is specifically tailored for this purpose, making it an essential tool in optometric practice for diagnosing and treating binocular vision problems.

Other tools mentioned, such as the phoropter, are used to determine refractive errors and prescriptions for glasses, while the retinoscope is employed to evaluate the refractive state of the eye by measuring how light reflects off the retina. The Snellen chart is a visual acuity test to measure sharpness of vision but does not assess eye alignment or phorias. Each of these tools serves a different purpose and is not suited for assessing phorias like the Maddox rod is.