Common Conditions of the Eye Flashcards
In embryology where do optic vesicles grow outwards from?
Diencephalic part of the neural tube towards the ectoderm
What is the conjunctiva?
Thin vascular membrane that covers inner surface of eyelids and loops back over the sclera
Does he conjunctiva cover the cornea?
No
What causes conjunctivitis?
Bacterial or viral infection
What are the symptoms of conjunctivitis?
Red watering eyes
discharge and no loss of vision
What is the treatment for conjunctivitis?
AB drops if likely to be bacterial cause
If there is visual loss in conjunctivitis what could have happened?
Infection progression to the cornea
What causes an external stye?
Blockage of sebaceous gland that side with the eyelashes
What causes an internal stye?
Blockage and infection of the meibomian glands
What is the treatment for a stye?
Warm compress
What causes ptosis?
Usually due to dystrophy of CN III paralysis
What might cause the inability to close the eyelid?
Paralysis of CN VII which controls orbicularis oculi
Why is closing the eyelid bad?
Cause the cornea will dry out causing lesions
What can you do if your eyelid wont shut?
Tape it
What do corneal pathologies commonly lead to?
Opacification of the cornea
What can cause inflammation of the cornea?
Viral bacterial or fungal infection
What are the features of corneal dystrophies?
- Bilateral
- Opacifying
- Non – inflammatory
- Mostly genetically determined.
What is the clinical presentation of corneal dystrophies?
1st-4th decade
Decreased vision
Why is the avascularity of the cornea a benefit to surgeons when performing a graft?
As there is no blood
No chance of foreign antigens being recognised
less chance of graft rejection
What is the most common cause of blindness?
Cataract
Why does cataract develop?
o Older fibres are never shed – compacted in the middle
o The older fibres are never shed
o No blood supply to lens, which depends entirely on diffusion for nutrition
o Absorbs harmful UV rays preventing them from damaging the retina but in the process gets damaged themselves
- Helpful to the retina
- But damaging to the lens
o Damaged lens fibres
- leading to opacity opaque
- CATARACT
What is the treatment for cataract?
o Eye drops do not treat cataract
o Surgery
o - day case
What causes glaucoma?
Improper drainage of AH through the right path causing increased IOP
What are the 2 types of gluacoma?
Open angle
Angle closure
Describe open angle glaucoma?
- Drainage system is affected
- Develops gradually
- IOP pressure increases gradually
Describe angle closure glaucoma
Rapid or sudden increase in IOP
What is the consequences of increased IOP?
Pressure on nerve fibres on surface of retina
Die out
Visual field defects
How does the optic disc appears in glaucoma?
Unhealthy
Pale
Cupped
What are the triad signs of glaucoma?
Raised IOP
Visual field defects
Optic disc changes on ophthalmoscopy
How is POAG managed?
Eye drops to decrease IOP o Prostaglandin analogues o Beta-blockers o Carbonic anhydrase inhibitors o Laser trabeculoplasty Trabeculetomy surgery
What are the symptoms of Angle closure glaucoma?
o Sudden onset, painful, vision lost/ blurred; headaches (often confused with migraine)
o O/E – Red eye, cornea often opaque as raised IOP drives fluid into cornea
o AC shallow, and angle is closed.
o Pupil mid-dilated
o IOP severely raised
o Long sightedness
Why does the angle close in angle closure glaucoma?
Functional block in a small eye
Mild dilated pupil -> periphery of iris crowds around angle and outflow is obstructed
Iris sticks to pupillary border which prevents reaching AC
Leads to iris ballooning anteriorly and obstructing angle
How is acute angle closure G managed?
- Decrease IOP
o IV infusion with or without oral therapy – carbonic anhydrase inhibitors (acetazolamide)
o Analgesics, antiemetics
o Constrictor eye drops – pilocarpine
o If no contraindication beta-blocker drops such as timolol
o Steroid eye drops (dexamethasone) - Iridotomy (laser) - both eyes - to bypass blockage
What is the difference in blockage mechanism in open angle and angle closure G?
¥ In open angle glaucoma the drainage through the trabecular meshwork is blocked (in most cases)
¥ In angle closure glaucoma, some event on a predisposed eye leads to the peripheral iris blocking the angle, therefore aqueous can’t drain.
Describe IOP changes in angle closure and open angle G?
Open angle -gradual, painless build up of intraocular pressure (IOP).
AC - increase in IOP is sudden leading to a red eye and severe pain
What are the types of uveitis?
Anterior U
Intermediate U
Posterior U
Describe posterior Uveitis?
The choroid is inflamed
Inflammation frequently spreads to the retina causing blurred vision
Describe intermediate uveitis?
Ciliary body is inflamed and leaks cells and proteins
Leads to hazy vitreous
Describe anterior uveitis?
inflamed anterior uvea (iris) leaks plasma and white blood cells into the aqueous humor
Eye is red, painful with vision loss
What an cause uveitis?
Can be an isolated illness
Non-infectious autoimmune causes
Infection
Associated with systemic diseases e.g ankylosing spondylosis
o Previously well 23 year old female
o A&E with 2 hour history of blurred vision and red swollen eye
o O/E: red, painful no eye movement
o Progresses within an hour to complete loss of vision
o History elicited of having squeezed a pimple near her less nasolabial fold 3 days prior
o What might have happened?
- pimple – infection spread through emissary veins – spread to cavernous sinus which has become infected and preventing normal drainage from the orbit
When sclera is seen from above what does this suggegst?
There is a pathology
What is a blow out fracture ?
traumatic deformity of the orbital floor or medial wall, typically resulting from impact of a blunt object larger than the orbital aperture, or eye socket.
The left eye will not abduct what is the problem?
Paralysis of left lateral rectus
CN III
Male
His right eye will only abduct?
CN III palsy
Which CN innervates the SO?
CN IV
