Eye

Bony orbit

Protects the eye, muscles, vessels, and nerves

Orbital fat

Cushions and protects eye from friction

Eyelids

Close to protect eye surface

Lacrimal apparatus

Lubricates the eye with tears

• Cornea

• Sclera

• Corneoscleral junction

Components of the fibrous layer of the eyeball

• Choroid

• Ciliary body

• Iris

Components of the vascular layer (uveal tract) of the eyeball

• Optic part of retina

• Non-visual part of retina

Components of inner layer of the eyeball

Facial nerve

Motor response to the orbicularis oculi upon stimulus is sent via which nerve?

Ophthalmic nerve

Sensory information upon stimulus is carried by which nerve?

Cornea

• Transparent, anterior portion, allows light entry; involved in the corneal reflex

• Provides constant light refraction

Lens

• Elastic & biconvex

  • Stretched or buldged to modify curvature

• Provides adjustable refraction (accommodation)

Sclera

Opaque, posterior portion, provides structural support and muscle attachment (extrinsic muscles)

Corneoscleral junction

Boundary between cornea and sclera

Choroid

Vascular layer providing nutrients to sclera and retina

Ciliary body

• Contains ciliary muscles and processes

• Produces aqueous humor

• Attaches lens via suspensory ligaments

Iris

• Regulates amount of light via the pupil

• Eye color

• Contains sphincter and dilator pupillae muscles

Sphincter (circular) and dilator pupillae (radial)

Muscles of the iris

Optic part of retina

Contains photoreceptors (rods and cones)

Non-visual part of retina

Lines the ciliary body and iris

Optic disc

• Blind spot, exit for optic nerve & central retinal vein

• Entrance of central retinal artery

• No photoreceptors

Optic nerve and central retinal vein

What exits from the optic disc?

Central retinal artery

What enters the optic disc?

Macula

• High visual acuity area

• Contains only cones

Fovea centralis

• Central area of macula

• Most acute vision

Anterior chamber

Cornea to iris

Posterior chamber

Iris to lens

Posterior segment (vitreous chamber)

Lens to retina

Aqueous humor

• Provides nutrients for cornea & lens

• Produced by ciliary processes → posterior chamber → pupil → anterior chamber → reabsorbed by scleral venous sinus (canal of Schlemm)

Scleral venous sinus (Canal of Schlemm)

Reabsorbs aqueous humor

Vitreous humor

• Provides support to lens & holds the retina in place

• Gel-like substance in the posterior segment

Ciliary muscle

• Controlled by ANS

• Parasympathetic (CN III): Contraction → lens bulges (near vision)

• Sympathetic: Relaxation → lens flattens (far vision)

Contraction; lens bulges (near vision)

Parasympathetic stimulation of ciliary muscle

Relaxation; lens flattens (far vision)

Sympathetic stimulation of ciliary muscle

Miosis (pupil constriction)

Parasympathetic stimulation of sphincter pupillae

Mydriasis (pupil dilation)

Sympathetic stimulation of dilator pupillae

Ophthalmoscope

Retina is analyzed through _____

Orbicularis oculi

• Parts

  • Orbital part: thicker, encircles eye

  • Palpebral part: thinner, near eyelid margin

• Function: Closes eyelids

• Innervation: CN VII

• Clinical note:

  • Facial nerve lesion → muscle dysfunction

  • Impaired blinking → corneal drying, foreign body risk, ulceration

Facial nerve

Innervation of orbicularis oculi

Impaired blinking

Caused by corneal drying, foreign body risk, ulceration

External hordeolum (stye)

• Origin: Gland of Zeis or Moll

• Localized, red, swollen eyelid

• Location: Eyelid margin

• With pain

Zeis or Moll Gland

Origin of external hordeolum

Eyelid margin

Location of external hordeolum

Internal hordeolum

• Origin: Meibomian gland

• Swelling under conjunctiva

• Location: Inner eyelid

• With pain

Meibomian gland

Origin of internal hordeolum

Inner eyelid

Location of internal hordeolum

Chalazion

• Origin: Blocked Meibomian or Zeis gland

• Firm nodule, painless

• Location: Inner eyelid

Blocked Meibomian/Zeis gland

Origin of chalazion

Inner eyelid

Location of chalazion

Conjunctivitis

Affects the conjunctiva — “pink eye” (sore eye)

Keratitis

Inflammatory eye condition affecting the cornea

Keratoconjunctivitis

Inflammatory eye condition affecting the conjunctiva & cornea

Uveitis

Inflammatory eye condition affecting the uveal tract (iris, ciliary body, choroid)

Anterior uveitis

(Uveitis subtype) Affects iris

Posterior uveitis

(Uveitis subtype) Affects choroid ± retina (chorioretinitis)

Glaucoma

• Optic nerve damage from increased intraocular pressure (IOP)

• Aqueous humor flow: Ciliary body → trabecular meshwork at anterior chamber angle

Open-angle glaucoma

(Type of glaucoma)

• Caused by clogged trabecular meshwork

• Chronic

• Painless, slow

Closed-angle glaucoma

(Type of glaucoma)

• Caused by iris bulging, angle closure

• Acute

• Painful, emergency

Horner’s syndrome

Result of blockage/damage to the sympathetic nerves to the eyes

1st-Order Horner syndrome

• Damage to the nerves from hypothalamus → spinal cord (C8-T2)

• Stroke, tumor, syringomyelia, spinal trauma

2nd-Order Horner syndrome

• Damage to nerves from cervical/thoracic spinal cord → superior cervical ganglion

• Pancoast tumor, neck trauma, thoracic surgery

3rd-Order Horner syndrome

• Damage to nerves from internal carotid → orbit

• Carotid dissection, stenting, cavernous sinus aneurysm

Ptosis

• Damaged/weak Müller’s muscle

• Eyelid drooping

Anhidrosis

Loss of sweating

Miosis

Small pupil (excessive constriction)

Central retinal artery occlusion (CRAO)

• Caused by embolus that blocks central retinal artery

• Result: sudden, painless, monocular vision loss

• Common in: Carotid artery atherosclerosis

Orbicularis oculi

Primary structure affected by facial nerve lesion