Applied ocular anatomy, physiology, biochemistry

• Eye

  A paired organ and the terminal receptor end of the optic nerve
• The eye is the portion of the brain exposed to the outside world
• Eye

  Made of two incomplete spheres
• Cornea

  The anterior 1/6th transparent portion of the eye
• Sclera

  The posterior 5/6th non-transparent and fibrous portion of the eye
• Orbit

  The bony case in the skull that houses the eye
• Orbital fat surrounds the eyeball in the orbit
• Each eye has 6 extra-ocular muscles that facilitate its movement
• Conjunctiva

  A thin membrane that covers the exposed portion of the sclera and secretes tears
• Eyelids


  Protect the eyeball from external injury and help spread tears
• Sclera


  Thick, fibrous, and inelastic; ends anteriorly at the limbus
• Choroidal Layer


  Loose layer containing blood vessels, ciliary processes, ciliary muscles; ends anteriorly as the iris
• Retina

  Thin membrane with 9 layers of cells, contains photoreceptors (rods and cones); macula responsible for ~85% of vision; ends anteriorly at the ora serrata
• Cornea


  Transparent due to collagen fibers arranged in parallel lines; avascular; most innervated tissue of the body; deep wounds heal by fibrosis
• Anterior Chamber


  Aqueous humor fluid-filled space between the posterior cornea and the anterior iris; aqueous humor flows out through the drainage angle
• Posterior Chamber

  Aqueous humor fluid-filled space between the posterior iris and the anterior capsule of the lens; aqueous humor produced at its base by the ciliary processes; linked by the pupil
• Aqueous Humour

  Transparent ultrafiltrate of the blood supplying nutrients to the posterior cornea and lens
• Lens

  Biconvex transparent refractive tissue; avascular; grows throughout life; most proteinous tissue in the human body (33% protein); suspended by zonules attached to ciliary muscles
• Vitreous

  Gel-like transparent fluid filling the space between the posterior lens and the retina; liquifies with age
• Vision

  Light within the visible spectrum (340-750nm) enters the eye through the cornea to reach the retina; photons in the light excite the photoreceptors, converting light to electrical energy through transduction
• Photoreceptors


  Rods and cones; rods contain rhodopsin for night vision; cones have opsins for vision in bright lights and color vision
• Visual Pathways

  Electrical energy generated in the retina is transmitted through the optic nerve to the chiasma; decussation of nasal fibers occurs at the chiasma, continuing as the optic tract; at the Lateral Geniculate body, the optic tract synapses to continue as the optic radiation ending in the calcarine area of the brain
• Colour Vision

  • Cones responsible for color vision; three principal forms code for red, green, and blue; defects can occur in any of these; Ishihara plates used for evaluation