OPHTHALM Flashcards
What structures are contained in the bony orbits?
- The eyeballs
- Extra-ocular muscles
- Nerves
=> Optic, oculomotor, trochlear, trigeminal and abducens - Blood vessels
- (Most of) the Lacrimal apparatus.
- Orbital fat
What is the purpose of orbital fat?
Fills any space that is not occupied by other structures
Cushions the eye and stabilises the extraocular muscles.
What are the three main pathways by which structures can enter and leave the orbit?
- Optic canal
- Superior orbital fissure
- Inferior orbital fissure
(There are other minor openings into the orbital cavity.)
What goes through the optic canal?
transmits the optic nerve and ophthalmic artery.
What goes through the superior orbital fissure?
transmits the lacrimal, frontal, trochlear (CN IV), oculomotor (CN III), nasociliary and abducens (CN VI) nerves.
It also carries the superior ophthalmic vein.
What goes through the inferior orbital fissure?
transmits the:
Zygomatic branch of the maxillary nerve,
Inferior ophthalmic vein,
Sympathetic nerves.
How can the layers of the eyeball be divided?
Fibrous
Vascular
Inner
What makes up the Fibrous layer of the eyeball?
What is the main function?
The outermost layer.
Consists of the sclera and cornea
Their main functions are to provide shape to the eye and support the deeper structures
What is the main function of the sclera?
The sclera provides attachment to the extraocular muscles; it is visible as the white part of the eye.
What is the main function of the cornea?
The cornea is transparent and positioned centrally at the front of the eye; it refracts the light entering the eye
What does the vascular layer of the eyeball consist of?
the choroid, ciliary body and iris
What is the Choroid ?
= layer of connective tissue and blood vessels.
provides nourishment to the outer layers of the retina.
What is the ciliary body?
= comprised of two parts – the ciliary muscle and ciliary processes.
=> The ciliary muscle = a collection of smooth muscles fibres.
=> These are attached to the lens of the eye by the ciliary processes.
The ciliary body controls the shape of the lens, and contributes to the formation of aqueous humour.
What is the iris?
= circular structure, with an aperture in the centre (the pupil).
The diameter of the pupil is altered by smooth muscle fibres within the iris, which are innervated by the autonomic nervous system.
It is situated between the lens and the cornea.
What is the inner layer of the eyeball?
= the retina
What are the 2 layers of the retina?
- Pigmented (outer) layer
2. Neural (inner) layer
Neural/inner layer of retina
Consists of photoreceptors, the light detecting cells of the retina.
It is located posteriorly and laterally in the eye.
Pigmented/outer layer of retina
Formed by a single layer of cells.
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.
Where is the non-visual retina?
Anterior of the retina
the pigmented layer continues but the neural layer does not
Where is the optic part of the retina?
Posteriorly and laterally
Both layers of the retina are present.
What is the macula?
The centre of the retina is marked by an area known as the macula.
It is yellowish in colour, and highly pigmented.
What is the fovea?
The macula contains the fovea, which has a high concentration of light detecting cells.
It is the area responsible for high acuity vision.
What is the optic disc?
= the area where the optic nerve enters the retina
it contains no light detecting cells.
What is the vitreous humour?
= a transparent gel which fills the posterior segment of the eyeball.
has three main functions:
• Contributes to the magnifying power of the eye
• Supports the lens
• Holds the layers of the retina in place
What is the hyaloid canal ?
a narrow canal on the vitreous humour, which runs from the optic disc to the lens
this is a foetal remnant which was involved in oxygenation of the lens
Lens of the eye
The lens of the eye is located anteriorly, between the vitreous humour and the pupil.
The shape of the lens is altered by the ciliary body, altering its refractive power.
What fills the anterior and posterior chambers of the eye?
What does this do?
Aqueous humour
=> Nourishes and protects the eye.
It is produced constantly, and drains via the trabecular meshwork, an area of tissue at the base of the cornea, near the anterior chamber.
Where is the anterior chamber of the eye?
The anterior chamber is located between the cornea and the iris
Where is the posterior chamber of the eye?
The posterior chamber between the iris and ciliary processes
Arterial supply of the eyeball
receives arterial blood primarily via the ophthalmic artery (branch of internal carotid a.)
The ophthalmic artery gives rise to many branches
The central artery of the retina is the most important branch - supplying the internal surface of the retina
What is the venous drainage of the eyeball?
the superior and inferior ophthalmic veins.
These drain into the cavernous sinus.
What are the 7 extra-ocular muscles?
What are their general functions?
- Levator palpebrae superioris
- Superior rectus,
- Inferior rectus,
- Medial rectus,
- Lateral rectus,
- Inferior oblique
- Superior oblique.
LPS = superior eyelid movement
All others = eye movement
Levator Palpebrae Superioris - attachments
Originates from the lesser wing of the sphenoid bone, immediately above the optic foramen.
It attaches to the superior tarsal plate of the upper eyelid
Levator Palpebrae Superioris - innervation
oculomotor nerve (CN III)
What is the superior tarsal muscle ?
= a small portion of the LPS muscle, which contains a collection of smooth muscle fibres
HAS SYMPATHETIC INNERVATION
Superior Rectus - attachments
Originates from the superior part of the common tendinous ring.
Attaches to the superior and anterior aspect of the sclera.
Superior Rectus - innervation
Oculomotor nerve (CN III)
Superior Rectus - actions
Mainly elevation of eye.
Also contributes to adduction and medial rotation.
Inferior rectus - attachments
Originates from the inferior part of the common tendinous ring
Attaches to the inferior and anterior aspect of the sclera.
Inferior rectus - innervation
Oculomotor nerve (CN III)
Inferior rectus - actions
Mainly depression of the eye
Also contributes to adduction and lateral rotation.
Medial Rectus - attachments
Originates from the medial part of the common tendinous ring
Attaches to the anteromedial aspect of the sclera.
Medial Rectus - innervation
Oculomotor nerve (CN III)
Medial Rectus - actions
Adduction
Lateral rectus - attachments
Originates from the lateral part of the common tendinous ring
Attaches to the anterolateral aspect of the sclera.
Lateral rectus - innervation
Abducens nerve (CN VI).
Lateral rectus - actions
Abduction
Superior Oblique - attachments
Originates from the body of the sphenoid bone.
Its tendon passes through a trochlea and then attaches to the sclera of the eye, posterior to the superior rectus.
Superior Oblique - innervation
Trochlear nerve (CN IV).
Superior Oblique - actions
Depresses, abducts and medially rotates the eyeball.
Inferior Oblique - attachments
Originates from the anterior aspect of the orbital floor.
Attaches to the sclera of the eye, posterior to the lateral rectus
Inferior Oblique - actions
Elevates, abducts and laterally rotates the eyeball.
Inferior Oblique - innervation
Oculomotor nerve (CN III)
Monocular Causes of Acute Painless Vision Loss
Acute corneal disease Acute cataract Optic neuritis Vitreous haemorrhage Ischaemic optic neuropathy Retinal vein/artery occlusion Retinal detachment
Binocular Causes of Acute Painless Vision Loss
Pituitary tumour Optic neuritis Severe papilloedema CVA Migraine
What is retinal detachment?
= the retina at peels away from its underlying layer of support tissue.
Initial detachment may be localised, but without rapid treatment the entire retina may detach, leading to vision loss and blindness.
It is a surgical emergency.
Causes of retinal detachment
- Age
- Post-op/trauma
- Diabetic retinopathy
Symptoms of retinal detachment
- Floaters
- Flashes
- Field Loss
- Fall in acuity
+ absent red reflex
Treatment of retinal detachment
Refer for urgent surgery (vitrectomy and reattachment)
What is vitreous haemorrhage?
= the extravasation of blood into the areas in and around the vitreous humour of the eye
Causes of vitreous haemorrhage
- Proliferative diabetic retinopathy
- Retinal tear
- Retinal detachment
Symptoms of vitreous haemorrhage
- Floaters = small black dots in vision
- Absent red reflex (if large bleed)
Treatment of vitreous haemorrhage
Vitrectomy and reattachment if necessary
What is a vitrectomy?
= removal of the vitreous and replacement it with saline
Central Retinal Artery Occlusion - symptoms
Sudden, profound, entire vision loss
Central Retinal Artery Occlusion - signs
Relative Afferent Pupillary Defect (RAPD)
Retinal Oedema
Pale retina (ischaemic)
Cherry red spots
+/- carotid bruits
Central/Branch Retinal Artery Occlusion - Investigations
To r/o causes of: HTN, DM, Heart problems, GCA
- BP
- FBC, ESR, glucose
- Carotid USS
- Cardiac Echo
Central Retinal Artery Occlusion - management
REFER to eye casualty (&TIA clinic)
Rebreathe into paper bag (CO2 dilates vessels)
Ocular massage
Acetazolamide (to decrease IOP)
Paracentesis (to decrease IOP)
in which class of drugs is Acetazolamide?
carbonic anhydrase inhibitors
Branch Retinal Artery Occlusion - symptoms
Sudden central or sectoral vision loss
Branch Retinal Artery Occlusion - signs
RAPD
Field Defect
Signs of hypertensive retinopathy
+/- carotid bruits
Branch Retinal Artery Occlusion - management
Refer to eye casualty & TIA clinic
Central Retinal Venous Occlusion - symptoms
Blurred, widespread vision loss
Central Retinal Venous Occlusion - signs
Widespread retinal haemorrhages
Oedema
Disc swelling
Tortuous veins
+/- cotton wool spots
Central/Branch Retinal Venous Occlusion - investigations
To r/o causes of: HTN, DM, Glaucoma, Blood problems
- BP
- FBC, ESR, glucose
- Intraocular Pressure
Central/Branch Retinal Venous Occlusion - management
Refer to eye casualty
Branch Retinal Venous Occlusion - symptoms
Blurred, central vision loss
Branch Retinal Venous Occlusion - signs
Focal retinal haemorrhages
Branch Retinal Venous Occlusion - management
Refer to eye casualty
What are Mydriatic eye drops?
Dilate the pupil
Short-acting, relatively weak mydriatics, such as TROPICAMIDE (action lasts for up to 6 hours), facilitate the examination of the fundus of the eye.
What causes the fundal/red reflex?
caused by light reflecting back from the vascularised retina
When might the fundal/red reflex be absent?
ADULTS - cataracts, vitreous haemorrhage, retinal detachment.
CHILDREN - congenital cataracts, retinal detachment, vitreous haemorrhage, retinoblastoma.
Haemorrhages causing red eye
- Sub-conjunctival = blood pools behind the conjunctiva
2. Retrobulbar = blood pools behind the eyeball
Risk factors for sub-conjunctival haemorrhage
post-surgery,
anticoagulants,
trauma,
URTI
Risk factors for retrobulbar haemorrhage
anaesthetic injection,
trauma/perforation => ask if have been using hammer/chisel
sub-conjunctival haemorrhage - symptoms
= asymptomatic and harmless
POSTERIOR BORDER VISIBLE
sub-conjunctival haemorrhage - management
reassure, resolution in 2 weeks
retrobulbar haemorrhage - symptoms
proptosis, decreased eye movement, increased IOP
POSTERIOR BORDER NOT VISIBLE
retrobulbar haemorrhage - management
= CT scan needed
What are the causes of red eye?
Haemorrhages - subconjunctival/retrobulbar
Vascular congestion - localised/generalised
Acute glaucoma
Trauma
Conjunctivitis
= inflamed conjunctiva with bacterial/viral/allergic cause
- Redness in conjunctival fornixes
- Discharge
- Photophobia
- Blanches
• Normal vision, normal pupil, no pain
Keratitis
= inflammation of the cornea
- Ciliary redness
- Does not blanche
- Vision blurry/impaired
- Constricted pupil
- Discharge
- Moderate/severe pain
- Photophobia
Keratitis - Management
- Steroids (PO/topical) +/- ABX
- Analgesia
UNLESS HSV KERATITIS - DO NOT GIVE STEROIDS (topical acyclovir)
Uveitis
= inflamed iris, ciliary body, choroid
- Ciliary redness
- Does not blanche
- Vision blurry/impaired
- Constricted pupil
- No discharge
- Moderate/achy pain
- Photophobia
Uveitis - Management
- Steroids (PO/topical) +/- ABX
- Analgesia
Viral causes of conjunctivitis
= Adenovirus, HSV, molluscum
“Gritty” sensation
Watery discharge
Lymphadenopathy
How is viral/bacterial conjunctivitis managed?
Chloramphenicol/fusidic acid drops and eye hygiene
Bacterial causes of conjunctivitis?
= S. aureus, S. pneumoniae
“Gritty” sensation
Purulent discharge
Lymphadenopathy
Allergic conjunctivitis
= hay fever, pollen, dust
Itchy/stingy eyes
Tx = antihistamines
When would you consider chlamydial conjunctivitis?
consider if prolonged in young adults
=> STI history
Neonatal conjunctivitis
gonococcal/chlamydial infection
can cause permanent scarring and vision loss
What can cause keratitis?
Infection – pseudomonas, HSV*
Trauma – foreign body, post-op, perforation
Inflammation – RA/SLE/Wegner’s
Risk factors for developing keratitis
contact lenses, dry eyes
How is HSV keratitis different from other keratitis?
Causes Dendritic ulcers
DO NOT GIVE STEROIDS (Tx = acyclovir)
Complications of keratitis
= corneal ulcer
Can perforate, so needs URGENT REFERRAL and STEROIDS