Flashcards in Anatomy of the Eye Deck (33):
Which bones make up the medial surface of the orbit?
Ethmoid, lacrimal and maxilla
Which bones make up the floor of the orbit?
Maxilla and zygomatic
Which bones make up the lateral surface of the orbit?
Zygomatic and sphenoid
Which structures pass through the supra-orbital fissure of the orbit?
Trochlear nerve (CN4)
Superior branch of the oculomotor nerve (CN3)
Inferior branch of the oculomotor nerve (CN3)
Abducens nerve (CN6)
What are the coverings of the optic nerve?
What is the importance of this?
It has coverings of pia, arachnoid, and dura mater of the meninges so infections can spread from the eye to the brain
What is meant by the lacrimal apparatus?
Lacrimal glands, ducts and canaliculi
How do the lacrimal secretions drain in to the nasal cavity?
Superior and inferior puncta, superior and inferior canaliculi, through the lacrimal duct, lacrimal sac, passes through the nasolacrimal duct, which opens into the inferior meatus
What is meant by the optical axis?
The axis where the eyes point forward
What is meant by the orbital axis?
Halfway between the medial and lateral walls of the orbit
What vessels are found within the optic nerve?
Central artery and vein
In a fundoscopy, what can we see if there is an increase in ICP?
Venous engorgement and papilloedema (optic disc swelling)
What muscles are responsible for the opening of the eyelid?
Levator palpebrae superioris
And the superior tarsal muscle
What muscles are responsible for the closing of the eyelid?
What nerves produce the corneal (blink) reflex?
CN V1 (sensory)
CN VII (motor)
What is the venous drainage of the orbit?
Superior and inferior ophthalmic veins, which drain in to the cavernous sinus
What is meant by the danger space?
Communication between facial vein to cavernous sinus via ophthalmic veins
Cavernous sinus thrombosis, meningitis, brain abscess
The facial vein has no valves so blood may pass in the opposite direction and may enter the cavernous sinus
During examination of the eye, which side of the fundus would you find the "blind spot" in a normal eye?
It lies on the nasal side of the fundus
Why might a lesion of the ophthalmic division of the trigeminal nerve be dangerous to the eye?
It supplies the sensory component to the cornea, the cornea becomes insensitive to touch and specks of dust or grit will not be felt in the eye. This quickly leads to corneal ulceration and scarring
What is the arterial supply to the orbit?
Internal carotid artery gives rise to the central artery to the retina and the ophthalmic artery via the optic canal (lacrimal artery, muscular branches, posterior ciliary arteries)
Also, minor source: intra-orbital artery off the maxillary artery off the external carotid
What happens if there is paralysis of levator palpebrae superioris?
Ptosis - compromising vision
Residual opening - due to the superior tarsal muscle
What happens if there is paralysis of orbicularis oculi?
Loss of blink and corneal reflex
Dry eyes and a risk of infection
Damage to the muscle causes the eyelid to fall away from the eye
What is meant by a blow-out fracture?
What are some of the consequences?
Fracture of medial or inferior walls of the orbit
The ethmoid, sphenoid and maxillary sinuses can become full of flood
The contents of the sinuses can spread, causing infection
Muscles in the inferior part of the orbit can become trapped, diplopia
What is meant by enopthalmos?
The eye sits further back than usual (this mp an be due to the impact of an force)
What is meant by ptosis?
Dropping of the upper eyelid
Which bones make up the roof of the orbit?
Frontal and sphenoid
What is meant by the ciliary body? What does it do?
Ciliary muscles and suspensory ligaments It secretes aqueous humour that fills the chambers The contraction of the ciliary body changes the shape of the lens
What are the different chambers of the eye?
Anterior chamber: space between the cornea and iris
Posterior chamber: space between the lens, ciliary body and iris
Vitreous chamber behind the lens, containing vitreous humour
What is the optic disc?
Aka blind spot The point of contact between the optic nerve and the retina There are no photoreceptors
What is meant by the macula?
Area lateral to the optic disc with lots of photoreceptors specialised for visual acuity
What is meant by the fovea?
Depression in the macula, area of most acute vision
What is meant by the strength of the lens?
Its dioptic strength
defined as the reciprocal of its focal length in m
What is meant by myopic?
the strength of the lens is too strong or the axial length of the eye is too long so that the focus lies in front of the retina
It can be corrected with concave lenses (subtract diopters)
It can correct itself as the lens become weaker with time