What is a consequence of the walls of the bony orbit being very thin?
They can fracture easily which can lead to the contents herniating into surrounding sinuses
What is the bright yellow circle on the retina?
The optic disc and start of the optic nerve
Through what does the orbit drain?
The inferior orbital fissure into the cavernous sinus
If a person has CN III palsy, what has to be checked and why?
The pupillary response because if it is compromised they could have a brain aneurysm
What is a coloboma?
A hole in one of the structures of the eye
How does a coloboma occur embryologically?
When the choroidal fissure does not fuse you get a coloboma in the area that it doesn’t fuse.
What is the conjunctiva?
A thin vascular membrane that covers the inner surface of the eyelid and loops back over the sclera
How can trauma cause retinal detachment?
Peripheral retina tears
Vitreous gel gets liquefied
Liquid vitreous pushes through the retinal tear and detaches it
Which layer of the retina is most vulnerable to being detached from the other layers?
The 10th layer
What is conjunctivitis?
A self-limiting bacterial or viral infection of the conjunctiva.
What are the symptoms of conjunctivitis?
Red, watery eyes with discharge and no loss of vision
How can blindness occur as a result of conjunctivitis?
If the infection spreads to the cornea
How is conjunctivitis treated?
Antibiotic eye drops if it seems to be bacterial
What is the nerve effected in ptosis?
CN III palsy
Why would a person not be able to close their eyelid?
The facial nerve on that side of the face is paralysed so the orbicularis oculi is effected.
What is the effect of not being able to close your eyes?
Dry eye which can lead to ulceration
What are the two types of stye?
External stye (hordeolum externum) Internal stye (hordeolum internum)
What glands are involved in an external stye and how is it dealt with?
The sebaceous glands that sit above the eyelashes get blocked so usually removing the eyelash involved will allow all the pus to drain out.
What glands are involved in an internal stye?
Meibomian glands inside the eyelids that secrete oil get blocked which hurts a lot as they are within the connective tissue.
How are styes treated?
Warm compression
Eyelid hygiene
May need surgical incision and curettage
What are some possible pathologies in the cornea?
Inflammatory conditions such as corneal ulcers
No-inflammatory conditions such as dystrophies
What is the common outcome of corneal pathologies?
Corneal opacifacation
How can corneal opacification be treated?
By corneal transplant (Keratoplasty)
What can cause corneal ulcers?
They can be viral, bacterial or fungal but they can also be due to trauma, degeneration or dystrophy.
What are the common characteristics of non-inflammatory conditions of the cornea?
Bilateral
Opacifying
Mostly genetically determined
Can be due to accumulation of substances such as lipids within the cornea
What is the clinical presentation of non-inflammatory corneal conditions?
First to fourth decade
Decreased vision
Starts in one layer of the cornea and spreads
What is the response for infectious corneal ulcers?
They need aggressive management to prevent spread and scarring
What makes corneal transplantation easier than other transplants?
The vascularity of the cornea which makes it less likely that the body will reject it.
What is cataracts?
Lens opacification
Why do cataracts develop?
Because the new fibres surround the older ones so that they are never shed. This means that when the fibres are damaged by things such as UV rays they are kept in the lens turning it opaque
Why do people with cataracts struggle to see at night?
At night the pupils enlarge and so the opacities are revealed and reflect light making the image of the retina hazy
What is Glaucoma?
Raised intraocular pressure and is the 2nd most common global cause of blindness
What is the most common form of primary glaucoma?
Primary Open Angle Glaucoma (POAG)
What are the consequences of raised intraocular pressure?
There is pressure put of the nerve fibres on the surface of the retina which then die out causing visual field defects. There can also be pressure on the optic nerve head resulting in altered field of visions and eventually all the nerve fibres are lost which results in blindness
What is the appearance of the optic disc in glaucoma?
It looks unhealthy, pale and cupped
What is the triad of signs for glaucoma diagnosis?
- Raised IOP
- Visual field defects
- Optic disc changes on ophthalmoscopy
How is a primary open angle glaucoma managed?
Eye drops to decrease IOP
Laser trabeculoplast
Trabeculectomy surgery
What is used in the eye drops to decrease IOP?
Prostaglandin analogues
Beta-blockers
Carbonic anhydrase inhibitors
What is angle closure glaucoma?
A very sudden condition in which the angle of the anterior chamber is closed causing a massive increase in IOP
Why does angle closure glaucoma normally happen?
Usually it is because a person is hyperopic and so they have a shorter eye ball and miss sized lens that crowds the anterior chamber pushing on the trabecular meshwork so the aqueous humor cannot drain out of the eye, increasing the IOP.
What are the symptoms of angle closure glaucoma?
Pain Vision loss/blurred Headaches Red and inflamed eye Cornea opaque Pupil mid-dilated IOP severely raised
What are some other reasons for angle closure glaucoma?
- With a mid dilated pupil the periphery of the iris crowds the angle and outflow is obstructed
- Iris sticks to the pupillary border leading to iris ballooning and obstructing the angle.
How is acute angle closure glaucoma managed?
Carbonic anhydrase inhibitors (acetazolamide) Analgesics Antiemetics Constrictor eye drops (pilocarpine) Beta blockers (timolol) Iridotomy
What is iridotomy?
Laser therapy used on both eyes to bypass the blockage in angle closure glaucoma
What is the cause of open angle glaucoma?
The drainage through the trabecular meshwork is blocked in most cases, leading to a gradual, painless build up of intraocular pressure.
What is Uveitis?
Inflammation of the urea
What are the different types of uveitis?
Anterior
Intermediate
Posterior
In anterior uveitis what is inflamed?
The iris with or without ciliary body
In intermediate uveitis what is inflamed?
Ciliary body
In posterior uveitis, what is inflamed?
Choroid
What are the causes of uveitis?
Isolated illness
Autoimmune condition
Infection (TB)
Systemic disease (ankylosing spondylosis)