The Ultimate Eye Anatomy Quiz

Structure and Function of the Eyeball

• The eyeball consists of three main layers: the fibrous layer, the vascular layer, and the inner layer (retina).
• The fibrous layer includes the sclera, which protects and shapes the eyeball, and the cornea, which forms a clear window that lets light enter and bends light as it enters the eye.
• The vascular layer includes the choroid, ciliary body, and iris. The choroid supplies blood to all layers of the eyeball and contains brown pigment to absorb light and prevent visual confusion.
• The iris, the colored part of the eye, contains the pupil, which regulates the amount of light entering the eye.
• The inner layer, or retina, contains millions of photoreceptor cells, neurons, and glial cells. It also has a pigmented layer and a neural layer.
• The retina has a quarter-billion photoreceptors, including rods for dim light and cones for bright light and color vision.
• Retinal detachment, where the pigmented and neural layers separate, can lead to permanent blindness and is often caused by traumatic blows to the head.
• The eye is separated into two segments by the lens and ciliary zonule: the posterior segment and the anterior segment.
• The lens is biconvex, transparent, flexible, and avascular, and it changes shape to focus light on the retina.
• Clouding of the lens, a consequence of aging and other factors, can be treated by surgically replacing the lens with an artificial one.
• Visible light is broken up into bands of colors, and the color perceived by the eye is a reflection of the wavelength, with different colors having different energy levels.
• Refraction, the bending of light rays, occurs when light passes from one transparent medium to another, and the lenses of the eye also refract light due to their curved shape.