QS Study

Light reflex: When the eye exposed to bright light, it causes constriction of pupils is called light reflex. It is a reflex that controls the diameter of the pupil, in response to the intensity of light. Its functions to consent to the size of the pupil to react to light conditions by contracting and dilating and also allows both pupils to react jointly or consensually.

It is of two types:

(i) Papillary light reflex: When light directed to the one eye, it causes constriction of the pupil is called papillary light reflex. Thus, the papillary light reflex regulates the intensity of light entering the eye.

(ii) Consensual light reflex: When light directed to the one eye, it also causes constriction of the pupil of another eye is called consensual light reflex. For example, if an individual’s right eye is shielded and light shines into the left eye, constriction of the right pupil will occur, as well as the left.

Pathway of light reflex

Fig: pathway of the light reflex

  • Fall of light on cornea →
  • refractive media →
  • retina →
  • received by rods and cones →
  • optic nerve optic chiasma →
  • optic tract → pretectal nucleus →
  • Edinger – Westphal nucleus →
  • oculomotor nerve →
  • ciliary ganglion →
  • short ciliary nerve →
  • sphincter pupillae →
  • constriction of the pupil.