Comprehensive Osteopathic Medical Licensing Examination (COMLEX USA) Practice

What is the term for the SNS effect on the eye that results in dilation of the pupil?

1. Miosis

2. Myosis

3. Mydriasis

4. Accomodation

The correct answer is: Mydriasis

The term that describes the sympathetic nervous system (SNS) effect causing dilation of the pupil is mydriasis. This process occurs when the dilator muscles of the iris are stimulated, typically in response to stress or low light conditions, allowing more light to enter the eye. The dilation of the pupil enhances vision in dim light and prepares the body for a 'fight or flight' response, as it can help improve awareness of surroundings. Miosis refers to the constriction of the pupil, which is primarily mediated by the parasympathetic nervous system and is opposite to mydriasis. Accommodation is related to the eye's ability to change focus between near and far objects, which also involves the ciliary muscles but does not pertain to pupil size. Myosis is often used incorrectly in this context, as it does not have a widely accepted definition distinct from miosis regarding pupil constriction. Thus, mydriasis is the precise term for pupil dilation resulting from sympathetic stimulation.