SPECIAL SESNES

• Eyes


  • Transmit visual stimuli to the brain for interpretation
  • The organ of vision

  
• Eye orbit

  • The cavity wherein the eyeball, along with the different eye muscles can be seen
  • Brings the eyeballs its white pigment (sclera)
  • Has cushion of fat that surrounds and protects the eyes

  
• Eyelids


  • Serve as protection of the eyes
  • Two movable structures composed of skin and two (2) types of muscles: smooth muscles and striated muscles
  • Upper eyelids are larger, more mobile, and contains tarsal plates made up of connective tissue that contain meibomian glands which secrete an oily substance that lubricates the eyelids
  • Excessive blinking distributes and balances the tears or secretions from the lacrimal gland and makes eyes moist and well-lubricated
  • Join at two (2) points: lateral (outer) canthus and medial (inner) canthus
  • Medial (inner) canthus contains the puncta and caruncle where the entry point of the lacrimal ducts is connected
  • Functions: protect the eye from foreign bodies, limit the amount of light entering the eye, distribute tears to lubricate the surface of the eyes
• Eyelashes


  Hair-like projections at the tip of the eyelids that filter dust and dirt from entering the eyes
• Conjunctiva


  • Thin, transparent continuous membrane that allows for inspection of underlying tissue and protects the eyes from foreign bodies
  • Divided into two portions: palpebral conjunctiva that lines the inside of the eyelids and bulbar conjunctiva that covers most of the anterior eye, merging with the cornea at the limbus

  
• Eye muscles


  • Six muscles attached to the outer surface of the eyeball responsible for the six directions of eye movements
  • Four (4) rectus muscles: superior, inferior, lateral, medial
  • Two (2) oblique muscles: superior and inferior
  • Each muscle coordinates with a muscle in the opposite eye, allowing for parallel movement of the eyes and binocular vision in humans
  • Cranial nerves that supply the innervation of the eye muscles: CN III (oculomotor) for lifting eyelids and eye movement, CN IV (trochlear) for vertical/medial gaze, and CN VI (abducens) for lateral gaze

  
• Rectus muscles


  • Superior rectus allows the eyes to move upward
  • Inferior rectus allows the eyes to move downward
  • Lateral rectus allows the eyes to move laterally and abducts the eyes
  • Medial rectus allows the eyes to move medially and adducts the eyes

  
• Oblique muscles


  Inferior and superior oblique allow circular motion of the eyes

  
• Six cardinal gazes


  • Up right
  • Up left
  • Right
  • Left
  • Down right
  • Down left
• Lacrimal system


  • Enables body to absorb and distribute tears that serve as protection
  • Act as responsive organs in times of foreign body entries affecting the eyes
  • Consists of glands and ducts that lubricate the eyes
  • Lacrimal glands located in the upper outer corner of the orbital cavity above the eye produce tears
• Flow of tears


  Lacrimal gland → produces tears → tears are washed across the eyes → drained in the puncta → emptied in the lacrimal canals → channeled into the nasolacrimal sac (through nasolacrimal ducts) → drained in the nasal meatus
• Eyeball


  • Located in the eye orbit
  • Round, bony hollow formed by the different bones of the skull
  • Composed of three layers: external (sclera and cornea), middle (iris, ciliary body, lens, choroid), and innermost (retina, optic disc, vessels)

  
• Sclera


  • White part of the eyeball
  • Outermost layer of the eye
  • Hardest part of the eye

  
• Cornea


  • Outermost layer of the sclera
  • Translucent film that is over the sclera, iris, and pupil
  • Permits the entrance of light that passes through the lens to the retina
  • Supplied with nerve endings, making it responsive to touch and pain
• Corneal reflex


  • Stimulation of the blinking of the eyes
  • Controlled by the CN V (trigeminal) and facial (CN VII) nerves
  • CN V carries afferent (towards) sensation to the brain
  • CN VII carries efferent (away) message that stimulates the blinking of the eyes

  
• Anterior chamber


  • Found underneath the cornea
  • Where the aqueous humor is distributed (anterior and posterior chamber)
  • Aqueous humor is a clear, liquid substance produced by the ciliary body that helps cleanse and nourish the cornea and lens, and maintains intraocular pressure (IOP)
• Glaucoma


  • There is accumulation and increase in aqueous humor in the posterior and anterior chambers of the eyes
  • Sometimes causes irreversible blindness if IOP is way too high
• Ciliary body


  Controls the thickness of the lens
• Iris


  • Circular disc of muscle containing pigments that determine or projects the eye color
  • Iris muscles stretch the iris together with the ciliary muscles

  
• Pupil


  • Center aperture of the iris
  • The opening of the internal aspect of the eyes
  • Accommodates (constricts / dilates) depending on the amount of light needed by the eyes
  • Constriction happens if there is too much light, accommodating near vision
  • Dilation happens in times of darkness, accommodating far vision
• Lens


  • A biconvex, transparent, avascular, encapsulated structure seen inside the pupils
  • Functions to refract (bend) light rays onto the retina
  • Adjustments (shape of the lens) depend on the distance of the object being viewed: bulges to focus on close objects, flattens to focus on far objects

  
• Near/farsightedness


  Accommodation disorders of the eyes

  
• Cataracts


  Disorder of the lens wherein an opaque material (hardened protein and glucose content) sticks and blocks the lenses
• Choroid


  • A vascular layer after the sclera with many blood vessels for delivering of oxygen, nutrients, and provide perfusion in the eyes
  • Prevents light from reflecting internally
• Retina


  • Neural layer (after choroid) where nerves can be found
  • Receives visual stimuli and sends it to the brain
  • Contains rods and cones which are photoreceptors sensitive to light
  • Rods regulate black and white vision and function in dim light, cones function in bright light and are sensitive to colors

  
• Optic nerve (CN II)


  Connected to the retina and the occipital lobe to be able to interpret vision

  
• Optic disc


  • Cream-colored, circular area where the optic nerve (CN II) is connected and enters the eyeball
  • Physiologic cup is a smaller, circular area that appears to be slightly depressed and appears somewhat whiter than the disc borders

  
• Fovea centralis


  • Retinal depression with a paler color than macula, surrounded by macula which appears darker than the rest of the fundus
  • Highly concentrated with cones and forms the area of the highest visual resolution and color vision
• Neural pathway of the eyes

  • Right visual cortex controls the right side of both eyes, left visual cortex controls the left side of both eyes
  • Optic chiasm - if damaged, temporal field of both eyes are affected

  
• If there is a problem in the right visual cortex, a person can have loss of vision on the right side of their eyes (kalahati lang). Right side of the brain controls the right vision / side of both eyes, while the left side of the brain controls the left vision / side of both eyes.

  
• Astigmatism


  When light scatters as you focus on an object
• Signs of glaucoma


  • Spots, floaters, blind spots (scotoma), halo
• Cataract


  White, hazy vision

  
• Eye pain


  Use COLDSPA / PQRST
• Tearing, eye discharges


  Yellowish discoloration is a sign of infection
• Past health history


  • Eye / vision problems
  • Eye surgery, treatments and medications
  • Last eye examination
  • Corrective lenses
  • Specific test: glaucoma & macular degeneration

  
• Amsler grid


  Test for macular degeneration
• Tonometry


  Test for glaucoma
• Amsler test


  • Test / screening for macular degeneration
  • If client sees a distortion, they have macular degeneration
• Macular degeneration


  • Degenerative condition associated with the macula
  • As a person ages, the macula disintegrates / decreases its function