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Ocular Physiology Test 1
Eyelid structure and function Part 1
65
Physiology
Professional
09/22/2007

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Term
The eyelids function to do what?
Definition
Maintain the integrity and clarity of the ocular surface
Term
Many corneal and conjunctival diseases are the result of abnormalities and or malfunctioning of what?
Definition
The eyelids
Term
The three principal fxns of the eyelids in humans are what?
Definition
To protect, lubricate, and maintain the ocular surface
Term
What is the outermost barrier of the ocular surface?
Definition
The cilia - eyelashes
Term
The cilia of the eyelids are extremely sensitive and when stimulated elicit what?
Definition
A blink reflex
Term
Do the cilia of the eyebrow grow in the same direction
Definition
NO
Term
The position of the eyebrow is dependent upon the relationship between the elevator and depressor muscles. What is the principal elevator of the eyebrow and forehead? What are the depresso muscles?
Definition
The frontalis muscle
The corrugator supercilius, the obicularis oculi, and the procerus
Term
The elevation of the eyebrows helps do what?
Definition
Clear the visual axis
Term
The elevation of the eyebrows also compensates for sagging of the forehead and dermatochalasis that comes with aging. What is dermatochalasis?
Definition
Sagging of the eyelids
Term
The superior and inferior eyelids develop embryologically from what?
Definition
Mesenchymal condensations located inferior and superior to the optic cup, referred to as the frontonasal (paranasal) and maxillary (visceral) processes
Term
The normal vertical palpebral fissure in adults is what?
Definition
10-12 mm
Term
The horizontal dimension of the eyelids is approximately what?
Definition
30 mm
Term
The horizontal fissure length increases by 10% between the ages of 12 and 25 years and then does what?
Definition
decreases by the same amount after middle age
Term
The inferior eyelid margin rests at approx where in normal adults?
Definition
The inferior limbus
Term
Is it uncommon to see the inferior lid margin below the limbus in older adults? Why?
Definition
NO - The loss of lid elasticity
Term
The eyelid margin is divided into what 2 divisions?
Definition
The anterior and posterior lamellae
Term
The anterior lamellae is made up of what?
Definition
Skin, muscle, and associated glands
Term
The posterior lamellae comprises what?
Definition
Tarsal plate, conjunctiva, and associated glands
Term
Contraction of what muscle helps in the lacrimal pump mechanism?
Definition
Orbicularis Oculi
Term
What two glands are located in the anterior lamellae of the eyelid and give rise to the oils that coat the lashes?
Definition
Glands of Zeiss and Glands of Moll
Term
The Glands of Zeiss are modified _____ glands and the Glands of Moll are _____.
Definition
Sebaceous
Eccrine or modified sweat glands
Term
Which muscles are the thin horizontal muscles that travel between the pretarsal orbicularis muscle and the tarsal plates in the superior and inferior eyelids?
Definition
The muscles of Riolan
Term
Contraction of the muscles of Riolan may help do what during eye closure?
Definition
Rotate the eyelashes and help the glands secrete their contents during blinking
Term
The muscles of Riolan can be seen as a what that is obvious in youth but less apparent with aging?
Definition
A thin gray line
Term
The tarsal plates contain what in the superior and inferior eyelids?
Definition
The Meibomian glands
Term
There are about ____ Meibomian glands in the superior eyelid and ____ in the inferior eyelid.
Definition
25
20
Term
The Meibomian glands are what type of gland and produce what?
Definition
Holocrine sebaceous glands that produce the lipid layer of the tear film
Term
Distichiasis is what? Is it congenital or acquired?
Definition
The accessory row of eyelashes, either partial or complete, emerges adjacent to or from the opening of the Meibomian glands. It can be congenital or acquired
Term
What happens in ocular cictrial pemphigoid?
Definition
It affects the mucousal glands and thus its surfaces. It causes the lids to stick to the eye and ocular scarring.
Term
What is Stevens-Johnson syndrome?
Definition
It is a bacterial infection caused by an over-reaction to some entity like drugs
Term
Does acquired or congenital distichiasis casue a significant ocular irritation?
Definition
Acquired
Term
What occurs when the Meibomian glands of the posterior lamellae become impacted with lipid or cellular debris?
Definition
Hordeolum or chalazion
Term
What is the difference between a chalazion and a hordeolum?
Definition
Hordeolum - aka "sty" - It is red, irritated and hurts patient
Chalazion - cupped cyst knot found under the skin that doesn't hurt the patient
Term
What is xerosis?
Definition
Drying out of the eye
Term
The movements of the eyelids can be divided into what 2 movements?
Definition
Opening and closing
Term
What muscles are responsible for opening the eyelid?
Definition
The levator palpebrae superioris muscle, the retractors of the lower lids, and the smooth muscle of Muller
Term
What muscle is responsible for eyelid closure?
Definition
Orbicularis Oculi
Term
What muscle is referred to as the chief retractor of the superior eyelid?
Definition
The levator palpebrae superioris
Term
The _______ of the levator palpebrae superioris inserts into the anterior tarsal, passes through the orbicularis muscle and inserts into the dermis to form the upper eyelid skin crease.
Definition
Aponeurosis
Term
Sometimes the levator aponeurosis disinserts from its tarsal insertion with age, resulting in what?
Definition
Ptosis
Term
One can quantify the strength of the levator by measuring the amount of displacement in mm of the upper eyelid from down gaze to upgaze after fixing the frontalis muscle and the brow. What is the normal displacement and what is poor?
Definition
Normal - 14-17 mm
Poor - less than 4 mm
Term
The most common type of acquired ptosis, where the aponeurosis disinserts, is called what?
Definition
Aponeurogenic Ptosis
Term
What type of ptosis occurs when, rather than normal muscle fibers being present in the muscle belly, fibrous and adipose tissues are present, thus diminishing the ability of the levator to contract and relax?
Definition
Myogenic ptosis
Term
Is myogenic ptosis congenital or acquired?
Definition
Congenital
Term
Is neurogenic ptosis congential or acquired? What causes the acquired form?
Definition
Both
Horners, 3rd nerve problems, Myasthenia Gravis
Term
What are the four most common etiologies of ptosis?
Definition
Dermatochalasis, IOL surgery, trauma, congenital
Term
Is dermatochalsis a true ptosis or a psuedotosis?
Definition
Psuedotosis
Term
What is phthisis bulbi?
Definition
Eyelid shrinks because of advance glaucoma
Term
A lid elevation of 1 cm corresponds to a decrease in the length of the levator muscle by how much?
Definition
1.4 cm
Term
Since the levator muscle and the superior rectus share a common relationship in their anatomical development, the upper eyelid follows what in its movement?
Definition
The globe
Term
In upgaze both muscles ______ and in down gaze both muscles ______ allowing the lid to track the globe.
Definition
Contract
Relax
Term
Hering's Law applies to the innervation to the levator superioris muscle. What does that mean?
Definition
Synergistic muscles equal and simultaneous innervation
Term
What is the minor retractor of the upper eyelid? How much upper lid elevation does it produce?
Definition
Muller Muscle - it produces 2mm of elevation
Term
Is the Muller muscle innervated by the sympathetic or parasympathetic nervous system?
Definition
Sympathetic
Term
In downgaze, the lower lid retractors do what to the eyelids?
Definition
Depress
Term
It has been corroborated that depression of the lid in downgaze moves together with what muscle?
Definition
Inferior Oblique
Term
Attenuation or disinsertion of the lower lid retractors cause instability of the lower lid and results in what?
Definition
Entropion or ectropion
Term
What muscle is primarily responsible for eyelid closure and blinking? What cranial nerve is it innervated by?
Definition
Orbicularis Oculi
CN 7
Term
The orbicularis oculi muscle can be divided anatomically into what 3 parts?
Definition
Pretarsal, preseptal, orbital
Term
What parts of the pretarsal orbicularis muscle contribute to the lacrimal pump mechanism?
Definition
The deep and superficial heads
Term
Does the orbicularis muscle have fibers of differing lengths? Why?
Definition
YES - They may contribute to the variety of facial expressions and lid fxns
Term
Closure of the eyelid can be divided into what 3 actions?
Definition
Blinking, winking, spasm
Term
The eyelids do not close all at once. Instead, the eyelids close how?
Definition
In a zipper-fashion
Term
Which portions of the orbicularis muscle are responsible for blink reflex and unforced eyelid closure?
Definition
Pretarsal and preseptal portions
Term
The orbital portion of the orbicularis is responsible for what?
Definition
Forced closure
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