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Understanding Eye Anatomy and Function
Aug 6, 2024
Anatomy of Eye
External Structures
Eyelids
Protect the eyeball
Open and close by voluntary or reflex action
Keep the surface of the eye and conjunctiva moist
Eyelashes
Short hair projecting from the border of the eyelid
Trap large airborne particles
Conjunctiva
Thin epithelium covering the surface of the eyeball
Secretes mucus to lubricate, clean, and maintain moisture
Internal Structures
Cornea
Transparent, curved layer
Bends light to converge at the lens
Aqueous Humor
Transparent, watery liquid in the anterior cavity
Medium for diffusion of oxygen and nutrients
Refracts light and maintains the shape of the eyeball
Iris
Pigmented with color
Contains radial and circular muscles to regulate light entering the eye
Pupil
Round hole at the center of the iris through which light enters
Lens
Soft, transparent, and elastic
Focuses light onto the retina
Held in place by suspensory ligaments
Ciliary Body
Muscle that contracts and relaxes
Adjusts the focus strength of the lens for near or distant objects
Vitreous Humor
Transparent, jelly-like substance at the rear of the eye
Refracts light and, along with aqueous humor, maintains the shape of the eyeball
Retina and Associated Structures
Retina
Light-sensitive layer of the eye
Contains photoreceptor cells (rods and cones)
Converts light energy to electrochemical signals
Optic Nerve
Transmits electrochemical signals to the brain
Blind Spot
Area where nerve fibers leave the eye
Lacks photoreceptor cells
Choroid
Middle layer on top of the retina
Contains black pigments to prevent internal refraction of light
Sclera
Tough, opaque, non-elastic outer layer
Helps maintain the shape of the eyeball
Eye Muscles
Hold the eye in place
Lachrymal Gland (Tear Gland)
Secretes tears
Types of Tears
Basal Tears
Always present in the eye
Lubricate and nourish the cornea
Contain natural antibiotics to prevent bacterial infections
Reflex Tears
Produced in response to external stimuli (e.g., dust, onion vapors)
Excess basal tears wash out irritants
Psychic Tears
Produced due to emotions
Contain more proteins and hormones acting as natural painkillers
Vision Process
Cells in the retina absorb light rays from objects
Vision fields of both eyes overlap to form stereoscopic, 3D vision
Brain translates information from both eyes to form an image
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