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Chapter 15 Notes Eyes ⭐..

Simple Anatomy:

Conjunctiva: Clear or pale pink structure that covers the white part of the eye and lines the inside of the eyelids.

Cornea: The transparent “crystal” at the very front of the eye. Covers and protects the iris (colored part of the eye, this is actually a muscle that constrict the pupil).

Lacrimal Apparatus: Tear system, if lachrymal sac is obstructed, pt. will present with constant tearing.

Pupil:

  • PERRLA:
    • Pupils are Equal, Round and Reactive to Light and Accommodation.
    • Controlled by parasympathetic and sympathetic nervous system.
      • Condition
      Pupil Reaction
      Light
      Constricts (small)
      Dark
      Dilates (big)
      Close object
      Constricts (small)
      Far object
      Dilates (big)

      👉 Parasympathetic = constrict (small).

      👉 Sympathetic = dilate (big).

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Internal Structure:

The eyes have three layers:

  • Sclera (Outer, fibrous)
  • Choroid (Middle, vascular)
  • Retina (Inner, Nerves)
    • Vitreous body: The water inside the eyes. gel-like substance.
  • Intraocular pressure (IOP) = controlled by aqueous humor circulation, not the vitreous.
    • Aqueous humor: water in the anterior part of the eyes (Lens, cornea).
      • To much aqueous humor→ Glaucoma→ blurred vision or blindness.

Cranial Nerves & Muscles

Conjugate Movement: Both eyes move together in the same direction.

  • CN VI (Abducens): lateral rectus muscle.
  • CN IV (Trochlear): superior oblique muscle.
  • CN III (Oculomotor): most eye movements.
  • 6 muscles attach to eyeball (4 straight, 2 oblique).
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Examination
  • Reflexes:
    • Corneal reflex → mental status.
    • Pupillary light reflex → light on retina.
    • Accommodation → pupils constrict, eyes converge. To see close objects.
    • Fixation: Eyes automatically focus on an object that catches attention.
  • Record as PERRLA: Pupils Equal, Round, Reactive to Light & Accommodation.
  • Note: The left vision field signal goes to the right side of the brain. The right vision field goes to the left.

Vision Testing

  • Snellen Chart:
    • Normal result: 20/20
    • 20/20 = sees at 20 ft what average person sees at 20 ft.
    • 20/30 = sees at 20 ft what average person sees at 30 ft. worst than normal.
    • 20/15 = better than normal.
  • Jaeger card: Measures short distance vision. Held at 14 inches.
    • Normal result: 14/14
    • Personal key to remember: Eren Jaeger, moved closer to the enemy.
  • Confrontation Test → compares peripheral vision.
  • Corneal light reflex → symmetry of reflection.
  • Six cardinal positions of gaze → diagnostic positive.
  • General Inspection:
    • Eyelids/lashes → should close completely (incomplete closure = weakness).
    • Lacrimal apparatus → no discharge; obstruction = tearing.

Aging

  • Pupil size decrease.
  • Presbyopia: Lens loses elasticity → becomes hard and glasslike.
  • Cataracts: a clouding of the eye's natural lens, which causes blurry or distorted vision.
    • Cataracts are a leading cause of blindness worldwide.
  • Visual Acuity Decline: start to diminish after age 50, more noticeable after 70.
  • Age-Related Macular Degeneration: Loss of central vision (can’t see straight ahead clearly, but side vision is okay). Age-related macular degeneration (AMD): common >75 yrs.
  • Glaucoma: A group of eye diseases that damage the optic nerve. More common with age. Loss of peripheral (side) vision.

Disorders

  • Stroke: peripheral vision loss.
  • Diabetic retinopathy: Damage to retinal blood vessels from diabetes. Leading cause of blindness in adults ages 25 to 74.
  • Diplopia: double vision. Di means 2.
  • Nystagmus: Rapid involuntary eye movement.

Class Recap

  • Cranial nerves to check: II, III, IV, VI → eye movement and vision.
    • III, IV, VI are motor
    • II is sensation.
  • Bell’s Palsy → cannot close eyes properly.
  • Prevention: Eye protection, regular screenings, annual eye check-up.