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Lecture 16

PHAR 1002 Lecture Notes - Lecture 16: Uveitis, Otosclerosis, Cochlear Nerve

Course Code
PHAR 1002
Lounsbery, Jody

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16.1: Accessory Structures of the Eye
- Eyebrows: keeps sweat from running into eye and function in nonverbal communication
- Eyelids: protects eye from foreign objects, blinks to move tears across eye as well as
remove debris
- Tarsal Glands: flat, fibrous tissue whose ducts open along the edge of the eyelid
-- secrete a fluid that keeps the eyelids from sticking together
- Two corners where the eyelids meet is called the canthi (s. canthus)
- Eyelashes: strong hairs that help keep debris out of the eyes
- Conjunctiva: transparent mucous membrane that lines that inside of both eyelids and
covers all of the front of the eye except the central portion
- Lacrimal Apparatus: consists of 4 structures
- Lacrimal (Tear) Gland: located in upper, lateral corner of the orbit -- secretes
- Lacrimal Ducts: carry tears to the surface of the conjunctiva
- Lacrimal Sac: tears leave the eye at the medial corner of the eye by draining
- Nasolacrimal Duct: flow from here into the nose where they are swallowed
- Function of tears:
- Clean and Lubricate the surface of the eye
- Deliver nutrients and oxygen to the conjunctiva
- Prevent Infection through a bacterial enzyme called lysozyme
Disorders of Accessory Glands:
- Conjunctivitis: inflammation of the conjunctiva
- Eyelid Edema: generalized swelling of the eyelids -- often produced by an allergic
- Stye/Hordeolum: infection of an eyelash follicle producing an abscess with localized
pain, swelling, redness, and pus formation at the edge of the eyelid
- Chalazion: small, painless, localized, whittish swelling inside the lid when a tarsal gland
becomes blocked
- Blepharitis: occurs when multiple eyelash follicles and tarsal glands become infected
- Dacryostenosis: blockage of the drainage of tears, usually due to narrowing of the
nasolacrimal ducts
- Dacryocystitis: infection of the lacrimal sac -- swelling and pus at the medial corner of
the eye
- Ptosis: occurs when the upper eyelid is constantly drooped over the eye due to paresis
(partial paralysis) of the muscle that raises the lid
Extrinsic Muscles of the Eye:
- Stereopsis: 3D perception
- Held in place by 6b extrinsic eye muscles
- When one muscle breaks down -- strabismus -- “squinting”/”cross-eyed”
- Esotropia: eye turned towards the nose
- Congenital and infantile esotropia both eyes look in towards the nose -- requires
surgical intervention
- Accommodative Esotropia: an inward eye turn -- usually noticed around 2 years of age
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- Exotropia: outward turning of one eye, noticed around 2-4 years of age
- Often will respond to visual therapy
- Amblyopia: “lazy eye” occurs when vision in one eye is not as well developed as the
16.2: The Eyeball and Seeing
Eyeball (Globe):
- Functions of the eyeball:
- Adjust continuously the amount of light it lets in to reach the retina
- Focus continuously on near distant objects
- Produce images continuously of those objects and instantly transmit them to the
- Front of eyeball is covered by the conjunctiva (except cornea)
- Thin layer of tissue that covers the inside of the eyelids and curves over the
- Sclera: tough, white outer layer of the eye
- Cornea: center of eye that is transparent, dome-shaped membrane
- No blood supply and obtains nutrients from tears and from fluid in the anterior
chamber behind it
- Light passes through the cornea and into the pupil
- Pupil: controls amount of light entering the eye
- Sphincter Pupillae Muscle: opens and closes the pupil
- After passing through the pupil, the light rays pass through the lens
- Ciliary Body: makes lens thicker or thinner -- enabling them to bend the light rays and
focus them onto the retina at the back of the eye
- Presbyopia: difficulty focusing on objects due to decreased lens flexibility
- PERRLA: pupil equal, round, reactive to light and accommodation
The Retina:
- Final destination of light rays
- Thin lining at the back of the eye
- 130 million rods -- perceive only light (not color)
- 6.5 million cones -- perceive color and light
- Precise visual acuity
- Color Blindness: hereditary lack of responsiveness by one or more of the types of cones
- Photoreceptor Cells: rods and cones
- Convert energy of light into electrical impulses
- Optic Nerve: bundle of more than 1 million nerve fibers transmits impulses to the visual
cortex in the back of the brain
- Optic Disc: spot where the optic nerve leaves the retina -- no rods or cones (blindspot)
- Night Blindness: inability to see in low light -- can be an underlying symptom of:
- Uncorrected nearsightedness
- Cataracts
- Retinitis Pigmentosa
- Vitamin A deficiency
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