Which of the following is the correct spelling of a term commonly associated with vision?

The term "iris" refers to the colored part of the eye surrounding the pupil, which plays a crucial role in controlling the size of the pupil and thus the amount of light that enters the eye. Understanding the anatomy of the eye is fundamental in fields related to vision and health care. The iris adjusts the pupil size based on light conditions and also contributes to eye color. This makes "iris" the correct spelling of the term commonly associated with vision.

The other choices do not accurately represent this anatomical term; "irs," "irrus," and "airis" are not recognized in medical or anatomical contexts and would not be used when discussing aspects of vision related to the eye. Proper spelling is essential in medical terminology to ensure clear communication and understanding among healthcare professionals.