Eye

• How many muscles in the eye?

  6

  Recti muscles (sup, inf, lat, med)

  Oblique muscles (Sup and inf)

  
• Borders of Bony Orbit?

  Roof = Frontal bone and lesser wing of sphenoid

  Floor = Maxilla, palatine and zygomatic

  Medial = Lacrimal, maxilla and ethmoid

  Lateral = Zygomatic and greater wing of sphenoid

  
• Contents of Bony orbit?

  Eyeball, extra-occular muscles (6), Eyelids, Nerves and opthalamic artery and veins
• Nerves in the Bony Orbit?


  Optic, oculomotor, trochlear, abducens, ophthalmic branch of trigeminal.
• Contents of Optic Canal?

  Optic nerve, ophthalmic artery
• Contents of Superior Orbital Fissure?

   lacrimal, frontal, trochlear (CN IV), oculomotor (CN III), nasociliary and abducens (CN VI) nerves. It also carries the superior ophthalmic vein.
• Inferior orbital fissure contents?

  Infraorbital nerve, zygomatic nerve, infraorbital artery.
• What is an Orbital Rim fracture?

  Facial bone fracture.

  occurs at the sutures of the maxilla, zygomatic and frontal
• What is a Blowout Fracture?

  Facial fracture

  Herniation of orbital contents into one of its walls (medial and inferior weakest). Any injury which increases infraorbital pressure results in exophthalmos (protrusion of the eye).

  
• Levator Palpebrae Superioris's attachments, innervations and action?

  function: lift the eyelid up

  innervation: oculomotor nerve (CN III)

  Origin: lesser wing of sphenoid (above optic foramen)

  attaches to superior tarsal plate

  
• Which recti muscle is innervated by Abducens Nerve (CN VI)?

  Lateral rectus
• What happens in Oculomotor nerve palsy?

  Eye is "Down and out", displaced laterally by the lateral rectus and inferior by inferior oblique.

  Diplopia (double vision), ptosis (drooping eyelid), and eye movement abnormalities.

  
• If a patient is experiencing diplopia with no obvious affect on eye, what nerve is damaged?

  Trochlear nerve CN IV
• What is Horner's Syndrome?

  damage to the sympathetic trunk in the neck

  • Partial ptosis (drooping of the upper eyelid) – Due to denervation of the superior tarsal muscle.
  • Miosis (pupillary constriction) – Due to denervation of the dilator pupillae muscle.
  • Anhidrosis (absence of sweating) on the ipsilateral side of the face – Due to denervation of the sweat glands.

  can represent serious pathology, such as a tumour of the apex of the lung (Pancoast tumour), aortic aneurysm or thryoid carcinoma.

  
• Where do all the Recti muscles originate from?

  Different parts of the Common tendinous ring
• Innervation of Oblique muscles?

  Sup = Trochlear nerve (CN IV)

  Inf = Oculomotor nerve (CN III)
• How many layers does the eyeball have and what are they?

  Three layers: Fibrous, Vascular and inner

  
• Fibrous layer and its contents?

  outermost layer of the eye, contains:

  sclera: majority of the fibrous layer. It provides attachment to the extraocular muscles, it is visible as the white part of the eye.

  cornea: is transparent and positioned centrally at the front of the eye. Light entering the eye is refracted by the cornea.

  
• Choroid


  A layer of connective tissue and blood vessels that supplies the outer layers of the retina with oxygen and nutrients.
• Ciliary Body


  A structure consisting of the ciliary muscle and ciliary processes, which control the shape of the lens and contribute to the formation of aqueous humor.
• Ciliary Muscle


  A ring-shaped muscle that changes the shape of the lens, allowing for focus on objects at different distances.
• Aqueous Humor Flow Importance

  Regulates IOP, delivers nutrients, removes waste products, maintains lens shape, and prevents corneal ulcers and ocular diseases
• Ciliary body


  • Contains the ciliary muscle and ciliary processes
  • The ciliary muscle consists of a collection of smooth muscles fibres
  • The ciliary processes are attached to the lens of the eye
  • The ciliary body controls the shape of the lens, and contributes to the formation of aqueous humor
• Iris


  • Circular structure, with an aperture in the center (the pupil)
  • The diameter of the pupil is altered by smooth muscle fibers within the iris, which are innervated by the autonomic nervous system
  • Situated between the lens and the cornea
• Vascular layer and its contents?

  • Choroid
  • Ciliary body
  • Iris

  
• Retina of eye (inner layer) and its contents?

  Light detecting component

  • Pigmented (outer) layer – formed by a single layer of cells. It is attached to the choroid and supports the choroid in absorbing light (preventing scattering of light within the eyeball). It continues around the whole inner surface of the eye.
  • Neural (inner) layer – consists of photoreceptors, the light detecting cells of the retina. It is located posteriorly and laterally in the eye.

  
• What is Vitreous Body?


  transparent gel which fills the posterior segment of the eyeball.

  functions:

  • Contributes to the magnifying power of the eye
  • Supports the lens
  • Holds the layers of the retina in place

  
• Lens of the eye?

  The lens of the eye is located anteriorly, between vitreous humor and pupil. The shape of the lens is altered by the ciliary body, altering its refractive power.

  In old age, the lens can become opaque – a condition known as a cataract.

  
• What is Aqueous Humor?


  clear plasma-like fluid that nourishes and protects the cornea and lens, also maintains intraocular pressure.

  The aqueous humor is produced constantly, and drains via the trabecular meshwork, an area of tissue at the base of the cornea, near the anterior chamber.

  If the drainage of aqueous humor is obstructed, a condition known as glaucoma can result.

  
• Occlusion of what artery will quickly result in blindness?

  Central retinal artery
• Which artery supplies blood to the eye?

  Ophthalmic artery
• Venous drainage of the eye is carried by?

  Ophthalmic veins (sup. and inf.)
• What is Glaucoma?


  Eye disease which result on damage to the optic nerve

  • Open angle – where the outflow of aqueous humor through the trabecular meshwork is reduced. It causes a gradual reduction of the peripheral vision, until the end stages of the disease.
  • Closed angle – where the iris is forced against the trabecular meshwork, preventing any drainage of aqueous humor. It is an ophthalmic emergency, which can rapidly lead to blindness.

  
• What is Papilloedema?


  Swelling of the optic disc (occurs second to raise in intercranial pressure)

  Common causes include:

  • Intracerebral mass lesions
  • Cerebral haemorrhage
  • Meningitis
  • Hydrocephalus

  
• What is the most superficial layer of the eyelid?

  Skin and subcutaneous tissue
• Which glands are attached to the eyelid?

  Ciliary glands of moll - modified sweat glands

  Glands of Zeis - sebaceous glands
• What is Orbicularis Oculi?

  • Actions:
  • Palpebral part – gently closes the eyelids.
  • Lacrimal part – involved in the drainage of tears.
  • Orbital part – tightly closes the eyelids.
  • Innervation – Facial nerve (CN VII, temporal and zygomatic branches)

  
• Layers of eyelid?

  5 layers (superficial to deep)

  • Skin and subcutaneous tissue
  • Orbicularis oculi
  • Tarsal plates
  • Levator apparatus
  • Conjunctiva