VisionVision

Anatomy of the EyeAnatomy of the Eye

Fibrous tunic– Sclera – Cornea

Anatomy of the EyeAnatomy of the Eye

Vascular tunic = Uvea– Choroid– Ciliary body– Iris– Pupil

Anatomy of the EyeAnatomy of the Eye

Nervous tunic = Retina & optic nerve– Outer pigmented layer– Nervous layer

PhotoreceptorsPhotoreceptors

RodsConesMaculaFovea centralis

Optic NerveOptic discBlind Spot

Anatomy of the Eye – Anatomy of the Eye – Miscellaneous structuresMiscellaneous structures

LensAnterior cavity

– Aqueous humor

Posterior cavity– Vitreous humor

Anatomy – Accessory Anatomy – Accessory structuresstructures

Eyelids = Palpebrae– Tarsal plate– Meibomian glands– Palpebral fissure– Lateral commissure– Medial commissure– Caruncle– Sebaceous ciliary glands

Anatomy – Accessory Anatomy – Accessory structuresstructures

Conjunctiva– Palpebral– Bulbar

Anatomy – Accessory Anatomy – Accessory structuresstructures

Lacrimal apparatus– Function– Lacrimal gland– Lacrimal puncta– Lacrimal canal– Nasolacrimal duct

VisionVision

LightRefractionEmmetropia = Normal vision, light rays

focus on a single point called the Focal Point

Focal Point

Retina

VisionVision

Accommodation– For close vision– Pupils constrict– Eyeballs converge– Near point of vision

VisionVision

Eye movement controlsVoluntary fixation (premotor area)Involuntary fixation (visual area)

VisionVision

Binocular visionDiplopiaStrabismus

Photoreceptors of VisionPhotoreceptors of Vision

Rods– Rhodopsin is photopigment– Numerous – about 120 million– Sensitive to light– Relative lack of color discrimination– Peripheral retina in location– Good for night vision, but poor detail– Convergence

Photoreceptors of VisionPhotoreceptors of Vision

ConesFew – about 6 millionPhotopigments sensitive to differing

wavelengths of light– 400 nm blue– 500 nm green– 600 nm red

Photoreceptors of VisionPhotoreceptors of Vision

ConesHigh level of illuminationNot very sensitive to lightSee in colorPrecise detailLittle convergenceMostly in center of retina, esp. fovea

Neural Components of VisionNeural Components of Vision

Bipolar neuronsGanglion neuronsLateral inhibition

– Horizontal cells– Amacrine cells

Visual AcuityVisual Acuity

Snellen Eye Chart20/20

Light/Dark AdaptationLight/Dark Adaptation

Photopigment concentrationPupillary light reflex

– PNS constricts pupil– Direct – ipsilateral– Indirect = Consensual - contralateral

Cones inhibit rods in bright light

Visual PathwayVisual Pathway

Optic NerveOptic ChiasmaOptic tractsThalamus – lateral geniculate bodyOccipital lobe of cerebral cortex