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).
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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- 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.