Test 141  (Ocular anatomy)

1. The cornea:

a. has sympathetic innervation by fibres whose cell bodies 
    lie in the superior cervical ganglion

b. exhibits thickened corneal nerve in multiple endocrine 
    neoplasia

c. derives its entire oxygen supply from the anterior 
    chamber

d. is 5% thinner during waking hours than during sleep

e. has a flatter cornea peripherally than centrally, more 
    so nasally than temporally
 

Answer
a.T   b.T   c.F   d.T   e.T
The epithelium derives its oxygen from the tear film.

2. Which of the following are true about tear films:

a. deficiency of the oily layer can be detected with 
    the Schirmer's test

b. the only immunoglobulin present in tears is IgA

c. the pumping action of the orbicularis oculi during 
    blinking is essential for normal tear drainage

d. the mucin provides a hydrophilic surface to the 
    hydrophobic corneal epithelium

e. the mucin is produced mainly by the accessory 
    lacrimal gland

Answer
a.F   b.F   c.T   d.T  e.F
Schirmer's test detects aqueous layer deficiency. 
Ig A is the main immunoglobulin but other immunoglobulins also occur. The mucin is produced mainly by the conjunctiva.

3. Regarding the function of the ciliary body:

a. contraction of its longitudinal muscle opens the canal 
   of Schlemm

b. contraction of its circular muscle relaxes the zonule 
    to increase accommodation

c. carbonic anhydrase enzyme acts on the epithelium 
    of the ciliary body to secrete aqueous humour

d. pilocarpine eye drops cause contraction of the ciliary 
    muscles to produce miosis

e. contraction of the ciliary body decreases with age

Answera.T  b.T  c.T  d.F  e.T
Miosis from pilocarpine is caused by its action on the iris.

4. In the lacrimal system:

a. the lacrimal nerve, a branch of the ophthalmic nerve, is
    the afferent nerve of the lacrimal reflex

b. goblet cells are found in the glands of Moll

c. the mucous layer reduces evaporation of the aqueous 
    layer

d. the accessory lacrimal glands provide the main portion 
    of the normal basal tear flow needed for the general 
    maintenance and proper functioning of the eye

e. a normal Schirmer's test should have a minimal 
    of 15mm of wetting in 5 minutes

Answer
a.F   b.F  c.F  d.T  e.T
The lacrimal nerve is the efferent arm of reflex lacrimation.
Goblet cells are found in the conjunctiva. 
The oily layer reduces evaporation of the aqueous layer.

5. Regarding the blood supply of the eye:

a. retinal blood flow is mainly under the autonomic
    regulation

b. the majority of the blood flow to the eye passes 
    through the retina

c. the ophthalmic artery arises from the internal carotid 
    artery in the cavernous sinus

d. the ophthalmic artery enters the orbit above the optic 
    nerve

e. the retinal artery arises from the ophthalmic artery about
    1 cm behind the eye

 
Answer
a.F   b.F  c.F   d.F   e.T
Retinal blood flow is chiefly under autoregulation.
The majority of the blood flow to the eye passes 
through the choroid. The ophthalmic artery arises
from the internal carotid artery just above the roof
of the cavernous sinus. The ophthalmic artery enters the orbit below the optic nerve.

 

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