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					                          Leicester scrubs- head and neck revision

                           Farhaan Moosa & Mohammad Afzal

                                  The eye and orbital region
Aims and objectives:

    •   Anatomy of the bony skeleton around the eye
    •   Macroscopic structure of the eye
    •   Microscopic structure of the eye
    •   Muscles controlling the eye
    •   Vasculature of eye
    •   Clinical cases of common conditions
    •   Cross modular

Anatomy of orbit

                                 Label the anatomy of the bones that make up the orbital region.
                                 Label the fossa/fissures that are part of the orbit?
                                 Which structures run through these?
                                 There are two fissures above and below the orbital margins.
                                  Name these and which vessels run through these?
                                 What are the functions of these vessels?
                                 Which is the weakest part of the orbit?
                                 What is the fracture called when the wall of the orbit is compromised?

Boundaries of the orbit                                   Label the different structures of the cross
                                                          section view of the eye
       Apex-
       Base-
       Roof-
       Medial wall-
       Lateral wall-
       Floor-

External view of eye




                                                   Muscle                         Action              Innervations
                                                   Inferior rectus
                                                   Lateral rectus
                                                   Superior oblique
                                                   Inferior oblique
           1.    Explain the process of lacrimation
Lacrimal gland in the lacrimal fossa of the frontal bone. Continuously secretes the fluid.
When you blink fluid is pushed across the the eye.
Eye closes lateral to medial
Fluid is moved medially to lacrimal duct
Canaliculi
Nasolacrimal duct → inferior meatus
           2.    Which nerves are involved in the process of lacrimation

innervation of lachrymal gland is parasympathetic and sympathetic.
Large petrosal: Lacrimation & Salivation; Parasympathetic
The trigeminal V1 (fifth cranial) nerve bears the sensory pathway of the tear reflexes.
presynaptic parasympathetic fibres fromCN VII travel in the facial nerve, and then in the greater petrosal nerve to the
pterygopalatineganglion. Postsynaptic fibres from here innervate the lacrimal glands. Postsynaptic sympathetic fibres arise from the
superior cervical ganglion, traverse the pterygopalatine ganglion with the parasympathetic fibres to innervate the lacrimal gland


           3.    What is a sty. What is the clinical appearance and the pathophysiology behind this?
           This is a common infection of the glands (sebaceous) of the eyelids causing an abscess, most frequently, due to staphylococcus
           aureus (1).

usually a self limiting condition
can be multiple or bilateral
commonly seen in association with chronic blepharitis (1)
Episodes of hordeolum is more commonly observed in patients with chronic skin conditions decreased immunity due to certain systemic
diseases e.g. - diabetes (1)Vision is not affected (2).
There are two types:
an external hordeolum (commonly known as a stye) - more common, external stye is an acute infection of a lash follicle (in the skin) and
always associated with glands of Zeis or Moll
an internal hordeolum - the internal stye is an acute infection of a meibomian gland situated within the tarsal plate (1).


           4.    What colour is the conjunctiva. What is hyperaemia of the conjunctiva?

           5.    What is conjunctivitis? What can cause this? what are the principles of treatment?

           6.    What is reiter’s syndrome?

Reiters disease comprises a triad of symptoms:
urethritis
conjunctivitis
a seronegative arthritis
Two broad subtypes are recognised:
a genital form related to sexual activity
an enteric form related to gastrointestinal infection.


           7.    What is the puplillary light reflex? Why is it consensual?

Cranial Nerve III - Oculomotor Nerve
Visceral motor component, pupillary light reflex
Light entering the eye causes signals to be sent to the pretectal region of the midbrain via the optic nerve (CN II).
The pretectal nucleus in turn projects bilaterally to the Edinger-Westphal nucleus.
Preganglionic parasympathetic fibers from each half of the Edinger-Westphal nucleus then project to the ciliary ganglion of the ipsilateral
orbit.
Post-ganglionic parasympathetic fibers exit the ciliary ganglion to innervate the constrictor pupillae muscle of the ipsilateral eye.
Due to the bilateral projections from the pretectal nuclei to the Edinger-Westphal nuclei, light shined into one eye produces pupillary
constriction in both eyes.
Direct pupillary light reflex - response in the stimulated eye. Consensual pupillary light reflex - response in the opposite eye.

           8.    What is Uveitis?
           the part of the eye that contains the iris and ciliary body and choroid
           9.    What is the basis of the embryological development of the retina? How does this explain the
                 pathology of retinal detachment?
Clinical note: Although cells of the pigmented epithelium are intimately associated with outer segments (rods and cones) of receptor cells,
this surface where the neural retina contacts the pigmented epithelium is inherently extremely fragile and is the site where retinal
detachment can occur.


           10. What is an end artery? Why are end arteries problematic? Where else do you find end arteries?

           11. What is the canal of Schlemm?
           (see diagram)
           12. What is closed angle glaucoma? Which class of drugs can be used to treat this condition?

in closed angle, there is contact of the peripheral iris with the trabecular meshwork (iridotrabecular
contact) at the entrance to Schlemm's canal (1).
impairment of the aqueous outflow may be caused by obstruction or by irreversible degeneration and
damage of trabecular meshwork
the closure of the anterior chamber angle may result in increase intraocular pressure (IOP).
When these changes results in glaucomatous optic neuropathy it is termed as primary angle closure
glaucoma (1).
The condition is frequently bilateral and its incidence increases with age. 90% of acute attacks are
unilateral (2).
Often, closed angle glaucoma presents acutely as a painful red eye.


           13. What is papilloedema? What causes it? How can it be detected?
The subarachnoid space of the brain is continuous with the optic nerve sheath. Hence, as the
cerebrospinal fluid (CSF) pressure increases, the pressure is transmitted to the optic nerve, and the
optic nerve sheath acts as a tourniquet to impede axoplasmic transport. This leads to a buildup of material at the level of the lamina
cribrosa


           14. What are cataracts? What causes the condition in
                  a. Elderly
          Trauma (sometimes years later)
          Smoking
          Alcohol use
          Exposure to x-rays
          Heat from infrared exposure
          Systemic disease (eg, diabetes)
          Uveitis
          Systemic drugs (eg, corticosteroids)
          Undernutrition
          Dark eyes
          Possibly chronic ultraviolet exposure

                      b.    Children/neonates
                                  i. Removal of a cataract within 17 wk after birth
                                       permits the development of vision and cortical
                                       visual pathways.

           15. What is hyphema? - blood in the front (anterior) chamber of the eye.
           16. What are the signs and symptoms of horners syndrome? Explain
               each of these symptoms?

           17. What is diploplia?

           18. What are the medical terms for

                      a.    Long sightedness

                  b. Short sightedness
           19. What shape lenses can be used to correct vision in each of the above
         20. What structure run through the cavernous sinus?

A large channel of venous blood creating a "sinus" cavity bordered by the sphenoid bone and the temporal bone
of the skull. The cavernous sinus is an important structure because of its location and its contents which include
the third cranial (oculomotor) nerve, the fourth cranial (trochlear) nerve, parts 1 (the ophthalmic nerve) and 2 (the
maxillary nerve) of the fifth cranial (trigeminal) nerve, and the sixth cranial (abducens) nerve.

A cavernous sinus thrombosis is a blood clot within the cavernous sinus.

         21. A tumour of the pituitary gland will affect the vision? Can you explain how it will cause visual
             problems and for browny points what the abnormality is?



(See diagram)

				
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posted:2/16/2013
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