Question

You are caring for a patient who has a visual disturbance. You have already tested their CNII.

Can you explain to this patient the pathway that electromagnetic radiation in the visible spectrum takes through the eye to get to the sensory receptors?

Answer 1

Electromagnetic radiation in the visible spectrum is the portion which is visible to eye. The human eye responds to visible spectrum which ranges from 380 nm to 740 nm. This spectrum is called as light and in this spectrum violet has the highest frequency and red has the lowest frequency. This visible spectrum which is Light, enters from cornea of the eye. The cornea bends the light and then light passes through pupil which is an opening in iris. The iris acts like a camera shutter, depending on the intensity of light it enlarges and shrinks. After iris light enters lens which is a transparent and flexible structure in eye that shortens and lengthens it's width in order to focus the light. After lens light rays passes through vitreous humour which is a clear gel like substance and then light strikes the retina where sensory receptors i.e photoreceptors are present. At retina the image gets formed. The retina then transforms the image into electrical impulses which is carried to the occipital lobe of brain via optic nerve (CN II). The brain then processes the image and the vision happens i.e one is able to see. There are two types of sensory receptors i.e photoreceptors in the retina: Rods and Cones. Rods are responsible for vision in low light and Cones are responsible for vision in bright light and Cones are also responsible for colour vision. Rods are more sensitive to light.