MRCP UK EXAMINATIONS

Detailed explanation-1: -A greater intensity of light causes the pupil to constrict (miosis/myosis; thereby allowing less light in), whereas a lower intensity of light causes the pupil to dilate (mydriasis, expansion; thereby allowing more light in). Thus, the pupillary light reflex regulates the intensity of light entering the eye.

Detailed explanation-2: -Pupil dilation is controlled by the iris dilator muscle. The dilator muscle consists of fibers that are oriented radially, and connect the exterior of the iris with the interior. When the dilator muscle contracts, it pulls the interior of the iris outward, thus increasing the size of the pupil (Figure 2b).

Detailed explanation-3: -The pupillary light reflex constricts the pupil in response to light, and pupillary constriction is achieved through the innervation of the iris sphincter muscle.

Detailed explanation-4: -In general, the pupil constricted with accommodation and started dilating while accommodation was still maintained, resulting in reduced pupil dilation with disaccommodation. The magnitude of the pupil response increased linearly with that of accommodation and disaccommodation.

Detailed explanation-5: -The pupils are generally equal in size. They constrict to direct illumination (direct response) and to illumination of the opposite eye (consensual response). The pupil dilates in the dark. Both pupils constrict when the eye is focused on a near object (accommodative response).