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Fixating · saccade · fixating

The eye holds still, then flicks to a new target in under a tenth of a second; the pupil drifts wider and narrower throughout.

  • Cornea: Clear focusing surface
  • Pupil: Not a structure — the hole the iris leaves
  • Iris: Controls light entry
  • Lens: Changes shape to focus near and far
  • Ciliary Body: Muscle that reshapes the lens and makes aqueous fluid
  • Sclera: The tough white shell holding the eye's shape
  • Retina: Light-sensing layer — brain tissue, not eye tissue
  • Macula: Tiny central patch carrying all fine detail vision
  • Optic Nerve: Carries visual signals
  • Zonular Fibres: Suspending threads that hold the lens and keep it pulled flat
  • Choroid: Vascular sheet feeding the outer retina from behind
  • Limbus: Corneoscleral rim — the drainage angle lies just inside it
  • Optic Disc: Where the fibres leave through the sieve in the sclera — the blind spot
  • Lateral Rectus: Turns the eye outward — the abducens nerve's only muscle
  • Medial Rectus: Turns the eye inward — the largest of the four recti
  • Superior Oblique: Runs through a pulley in the orbit's roof — the trochlear nerve's only muscle
Sensory System

Eye

A window made of light · Oculus
Makes thousands of tiny movementsevery single day

A precision sensory organ that converts focused light into neural signals interpreted as vision.

Key facts

Size
About 24 mm across
Weight
Around 7.5 g
Location
Within the bony orbit
Function
Captures and focuses light

Did you knowThe cornea carries no blood vessels at all; it takes oxygen directly from the air.

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Microscopic view

Retinal layers

Compare organs

Eye vs. brain

Function animation

Captures and focuses light

Clinical notes

Red flags

  • Painless loss of vision in one eye over seconds is vascular — a retinal artery occlusion is counted in minutes.
  • Flashes and a shower of new floaters, then a dark curtain across the field — a detaching retina, still fixable if caught.
  • A painful red eye with blurred vision and a fixed mid-size pupil is acute angle-closure glaucoma — sight goes in hours.
  • Myopia
  • Cataract
  • Glaucoma
  • Macular degeneration
  • Retinal detachment
  • Dry eye disease
  • Astigmatism
  • Conjunctivitis
Where it works

Sensory System

Specialised receptors that convert light, sound, pressure, temperature, and chemistry into the one language the brain reads.

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