Eye Anatomy: Surface, Key Structures

Surface Anatomy & Key Structures

• Sclera, covered by the bulbar conjunctiva, contains small conjunctival blood vessels
  • Enlarged vessels can indicate conditions like pink eye
• Cornea is continuous with the sclera but not covered by the bulbar conjunctiva
  • The anterior, transparent part of the eye protruding from the palpebral fissure, has greater curvature
  • The corneal limbus is formed at the corneoscleral junction
• Pupil serves as the central aperture of the iris
• Conjunctiva consists of bulbar and palpebral components
  • A clear membrane reflected from the sclera to the eyelid's deep surface, becomes highly vascularized during inflammation
  • Forms a conjunctival sac when the eyes are closed
• Tarsal glands (Meibomian) are distinguished by yellow vertical stripes when upper eyelid is inverted

Medial Angle of the Eye

• The lacrimal lake is a depression filled with tears
• The lacrimal caruncle is an elevated "island" within the lacrimal lake, containing sebaceous and sweat glands to collect Tears
• Lacrimal papilla is a mucosal elevation
• Lacrimal punctum is the opening to the lacrimal canaliculi, leading to the lacrimal sac and nasolacrimal duct

Layers of the Tear Film

• Secretions not limited to the lacrimal gland
• The lipid layer from the meibomian (tarsal) gland limits evaporation and lubricates the conjunctival sac
  • Absence may cause Dry Eye
• The aqueous layer from the lacrimal gland hydrates and nourishes the cornea
• The mucin layer from corneal goblet cells adheres the aqueous solution to the corneal surface

Sequence of Lacrimation

• Tears originate from the lacrimal gland (orbital and palpebral) then drain into lacrimal gland ducts
• Combined with lipid & mucin layers, the fluid flows from lateral to medial side
• Collects around lacrimal caruncle in lacrimal lake, drains to the lacrimal punctum
• Puncta connect to lacrimal canaliculi, converging to the lacrimal sac in the nasolacrimal canal
• Empties to the inferior nasal meatus

Functional Requirements for Vision and Eye Anatomy

• Extra- and intra-ocular muscles change and maintain visual fixation
• The retinal layer varies in color/monochrome light and detail sensitivity
  • Macula is for high-acuity central vision, color vision, fine detail
  • Withing the macula, the fovea is the area with the highest acuity and cone concentration
• Muscles train fovea on scenes with optimal focus and light
• Peripheral vision uses retinal subregions outside the macula, highest rod concentration at the ora serrata
  • External region to eyeball within the orbit: GSE-based movements (striated muscles)
  • Internal region to eyeball: GVE-based movements (SNS & ANS)

Eye Movements and Optical Axis

• Eye movements result from multi-muscle contraction b/c of orbit geometry
• The fovea anchors the optical axis
• Lateral orbital walls 90° apart, anchors the orbital axis
• Eye movements based on a limited sphere

Categories for Extra-Ocular Eye Movements

• Keeping fovea on a stationary target and head still
  • Fixation System: Suppresses gross eye movements towards a point/region
  • Includes saccades for involuntary scanning such as reading
• Keeping fovea on a moving target and head still
  • Smooth pursuit is slower tracking for moving object of interest as when head is still
  • Continuous Binocular Convergence moves eyes in opposite directions simultaneously to position images on both left & right fovea
  • Saccadic eye movements fast, involuntary, pointing fovea to object
• Keeping fovea on a stationary object and head moving
  • VOR reflexes: Hold target on fovea during head movements
  • Prevents image slippage on retina during head movement

Bones of the Orbit

• Base consists of the opening and orbital margin
• The superior wall is the orbital part of the frontal bone includes fossa for the lacrimal gland
• Ethmoid plate walls along with lacrimal bones and sphenoid
• Inferior wall- Maxilla, zygomatic, palatine bones
• Lateral wall- zygomatic (frontal process), greater wing of sphenoid
• Apex - Optic canal (lesser wing), superior fissure
• Periosteum of orbit known as periorbital

Supporting Fascia of the Eye

• Fascial sheath around eyeball: conjunctival fornices to optic nerve forms a socket
  • Pierced by extra-ocular muscles
  • Attaches to conjunctival fornices, fuses with sclera and optic
  • Acts as attachment for extra-ocular muscles

Orbital Septum

• Extension of periosteum from rim to eyelids
  • Attachments: orbital rim, medial and lateral palpebral ligaments, LPS tendon & tarsal plates
  • The anterior boundary stabilizes anatomy and blocks infection
  • Counteracts backward pull of extra-ocular muscle

Suspensory Ligament

• Check ligaments, are extensions of fascia. They blends fascia between certain eye muscles

Levator Palpebrae Superioris

• Elevates by retraction with lamina that connects skin. Contains the superior tarsal muscle. Interrupt sympathetic will stop working. Opposite
• Natural antagonist: orbicularis oculi

Superior Tarsal Muscle

• Keeps lid elevated with sympathetic innervation

Horner's Syndrome

• Sympathetic damage in the region results in partial Ptosis

Extra-Ocular Muscles

• Common Tendinous Ring Splits Fissure Into Superior And Inferior Orbital Fissures
• Venous = drains into ptgergoid plexus

Vasculature of the Orbit

• Ophthalmic artery branches from internal carotid artery
  • Enters the orbit through optic canal beneath optic nerve
  • First branch: _Central Retinal Artery
• A terminal which means no anastomosis, so occlusion leads to blindness
• Pierces dural sheath of optic nerve, runs in the retina, supplies
• Supraorbital Art- Out supraoribital formanem
• Supratrochlear Supply Supra
• Lacrimal Artery has it's own to cunjcaitia + supply
• Dorsal nasal passes to membrane Eth supplies the Chroid then cones
  • Short Posterior Supplies retina layers then goes deepers Shorty anterior ciliary layer:
• Arteris and posterior all Pass into all the area

Venous Drainage

• Each Quadrant With main Veins the
  • Super ophthalmluc passes fissur dralous Zone

Anatomy of the Eye (Outside to Inside)

• Anterior Chamber: Volume btw. Cornea & ivis/ pupil
• Aquoeshumor
• Under Tension

Other Sections Inside

Aqueus-Cilary Musels III, the Ciliary increase for view

Retina/Sclera/Cornea

Maint shape and is mostly avasular and contouns with mingees also touch 1 V.I -reflexs

Choroid

ZONES are controlled by the pupal and color with cilarly

• Short for the supply and cones other long and anti cilary

Non-Optic Part: border which light that contans Ocular optic

Nerves of the Orbit

II for canal III from the ring that contain Trocla Motor Only

4-Ophtham

• Opcic Nerve only s
• III with branches
• Trochlear
• VI with Sensory the Cornea and nasal Canavaty

Sensory Components to Ophthalmic Nerve (CNV₁)

• Frontal: supraorbital and supratrochlear
• Lacrimal: serve lacrimal
• Nasociliary the Cornea

Ciliary Ganglion

Gangal and symapathetics

Reflex arc cILIARY (with with lens) with near view

• CN V can

"H" Test for CN Examination

• Tested with if not working and vision

Clinical Correlations and Exam Notes

• Defect and not visonary Defects will vary

Additional Conditions

• 3 or motor will effict movement also oribital force
• With stimulated by tumor or

The lesions in the the vision from cornea from V, cornea 1 slow Syndrom decrease while 2 others

Clinical correlations and exam notes

If detached retina is present, then a tear in the neural layer will be shown If coloboma is present, then vision impairment may vary If there is oculomotor opthalmoplegia, then a "H" test can be used to diagnose axis.