What are drugs that dilate the pupil and paralyze the iris sphincter muscle called?

The drugs that dilate the pupil and paralyze the iris sphincter muscle are known as cycloplegics. Cycloplegics are specifically designed to induce paralysis of the ciliary muscle, which in turn affects the ability of the iris sphincter to constrict. This results in pupil dilation, allowing clinicians to better examine the retina and other structures within the eye without the interference of pupil constriction.

Cycloplegics are particularly useful in situations where a thorough examination of the posterior segment of the eye is necessary, as they provide a wider field of view and help eliminate the accommodating effect of the eye during examination.

In contrast, mydriatics, though closely related, primarily refer to drugs that dilate the pupil without necessarily paralyzing the ciliary muscle, hence they may not completely inhibit accommodation. Antihistamines are primarily used to address allergy symptoms and have no significant effect on pupil size. Myotics, on the other hand, are drugs that cause pupil constriction, opposing the action of dilating the pupil. Understanding these differences clarifies the specific role of cycloplegics in ophthalmic practice.