What is the name of the instrument that consists of a group of red or colorless parallel rods that function together as a cylinder?

The Maddox rod is a specialized instrument used in ophthalmology, primarily for testing binocular vision and diagnosing various types of strabismus (eye misalignment). It consists of a series of thin, parallel rods that are either red or colorless, arranged in a manner that creates a cylindrical effect when viewed through the instrument.

When a patient looks through the Maddox rod, it creates a visual separation between the images seen by each eye, allowing for the assessment of eye alignment and muscle function. This instrument helps in evaluating conditions such as heterophoria, where the eyes tend to drift when not focusing on a target, and it aids in determining the amount of deviation present. Its unique design and function make it specifically suitable for studying how the eyes work together or diverge under different conditions.

The other options are distinct in their functions: prisms are used to bend light and can assist in vision therapy, a lensometer measures the prescription of lenses, and a retinoscope is employed to evaluate the refractive error of the eyes by projecting light and observing the reflection. Each serves its own purpose in the field of eye care, which differentiates them from the specific function of the Maddox rod.