Common Conditions of The Eye Flashcards
What is the risk associated with the thin walls of the orbit?
Easily fractures leading to herniation of contents into the surrounding sinuses.
What is meant by a blow out fracture?
Bony orbit rim is strong, impact of a ball will transmit to the walls of the orbit and blow out – called a blow out fracture – contents of orbit leak out into adjacent sinus (maxillary sinus) - eye can’t move because there is a tethering effect
Why does a blow out fracture sometimes result in reduced feeling in the lower eyelid, upper lip and part of the nasal vestibule?
Maxillary nerve leaves the infraorbital foramen and is called the infraorbital nerve – fracture often results in palsy of this nerve and so there is reduced feeling in the lower eyelid, upper lip, and part of the nasal vestibule
What is often the cause of orbital fat hypertrophies? (leads to staring appearance)
Occurs in thyroid diseases
A previously well 23 year old woman attended A&E with a two hour history of blurred vision and a red and swollen eye
O/E: red, painful no eye movement. Progressed within an hour to complete loss of vision.
History elicited of having squeezed a pimple near her left nasolabial fold 3 days prior
Infection spread to the cavernous sinus via emissary veins which resulted in cavernous sinus thrombosis - venous drainage from the orbit is compromised since ophthalmic vein drains into the cavernous sinus. There is now compression and paralysis of nerves that pass through the cavernous sinus - nerves 3,4 and 6 pass through cavernous sinus.
Which nerve is responsible for the parasympathetic effect of constricting the pupil?
Third nerve carries parasympathetic effect – constricts pupil
Why does diabetic nerve damage to the oculomotor nerve result in preservation of the parasympathetic function of the pupil reflex?
Parasympathetic fibres run on the surface of the third nerve, diabetic nerve damage is from the inside out. If the pupillary reflex fails it could be as a result of an aneurysm.
Where do the central retinal artery and vein enter the orbit?
Choroidal fissure
What is meant by coloboma?
Normal tissue in or around the eye is missing from birth
Why does a coloboma form?
Failure of fusion of the choroidal fissure before birth?
What parts of the eye can be affected by a coloboma?
Irirs
Retina
Optic disc
Eyelid
Lens
Macula
Optic nerve
Uvea
Why can blunt trauma cause blindness?
The retina next to the ora serrata is very thin and so blunt trauma may result in holes forming here.
Vitreous gel gets liquefied, liquid vetrous pushes through retinal tear and detaches it.
Liquified vitrous should usually separate the 9th and 10th layer of the retina as these layers are not attached
What is the cause of conjunctivitis?
Self-limiting bacterial or viral infection of the conjunctiva
What are the signs and symptoms of conjunctivits?
Red, watering eyes, discharge
No loss of vision so long as the infection doesn’t spread to the cornea, blurry vision may indicate that the infection has spread to the cornea
What is the treatment for conjunctivitis?
Antibiotic eye drops if likely to be bacterial
What can cause the drooping of an eyelid?
LPS elevates the eye
Drooping eyelid means ptosis – think third nerve dystrophy or paralysis
What causes the inability to close an eyelid?
Facial nerve is responsible for the orbicularis occuli muscle - therefore failure to close the eye indicates facial nerve palsy/paralysis
What can happen as a result of dry eyes?
Ulcers form
What are the meibomian glands?
Glands at the rim of the eyelid (within tarsal plate) responsible for the produciton of meibum, an oily substance that prevents evaporation of the eye’s tear film.
What is a hordeolum?
Localised infection or inflammation of the eyelid margin involving hair follicles of the eyelashes or meibomian glands.
The infection of a hordeolum usually is painful, erythematous, and localized
What are the two types of hordeolum / stye?
Internal and exteranl hordeolum
What is the name given to the granuloma of the meibomian glands?
A chalazion
What is the main feature of the chalaizon that makes it distinguishable from the hordeolum?
Chalaizon is painless
What causes external hordeolum?
Arises from a blockage and infection of Zeiss or Moll sebaceous glands
What causes internal hordeolum?
Secondary infection of meibomian glands in the tarsal plate,
What is surgical treatment of hordeolum?
Surgical incision and curettage
What are the two pathologies associated with the cornea?
Inflammatory - e.g corneal ulcers
Non-inflammatory - e.g dystrophies
What is often the result of corneal pathologies?
Frequently lead to opacification of the cornea - might need to be treated with corneal transplant - keratoplasty
What are the causes of inflammatory ulcers?
Viral/ bacterial/ fungal infection of cornea
Needs aggressive management to prevent spread, scarring
What are the causes of non-infectious ulcers?
Trauma, corneal degenerations or dystrophy
What are corneal dystrophies?
They are a group of diseases affecting the cornea which are:
- Bilateral
- Opacifying
- Non – inflammatory
- Mostly genetically determined.
- Sometimes due to accumulation of substances such as lipids within the cornea
What is the clinical presentation of corneal dystrophy?
- First to fourth decade
- Most commonly - decreased vision
- Start in one of the layers of the cornea and spread to the others.
What are some of the common conditions of the eye?
Why do cataracts develop?
- Older (embryological, foetal) fibres are never shed – compacted in the middle
- No blood supply to lens, which depends entirely on diffusion for nutrition
- Absorbs harmful UV rays preventing them from damaging retina but in the process, get damaged themselves
- Damaged lens fibresà opaqueà CATARACT
What is the management of cataracts?
Surgery - (day case) small incision - lens capsule opened - cataractous lens removed by emulsification (phacoemulsification) - plastic lens placed in capsular bag
What is responsible for removing the aqeous humour?
The endothelium
What is the lens implant after the cataract surgery?
PICOL - posterior chamber intraocular lens
What is the most commonly seen form of primary glaucoma?
Primary open angle glaucoma (POAG)
What does glaucoma mean?
Raised intraoccular pressure
What is the effect of raised pressure on nerve fibres on the surface of the retina?
Die out and causes visual field defects
What is the effect of the nerve fibres dying out?
Means there is now pressure on optic nerve head - when seen by ohthalmoscopy - the optic disk appears unhealthy, pale and cupped
Results in altered field of vision - ultimately all nerve fibres are lost which results in blindness
What is the triad of glaucoma?
What is the management of POAG - primary open angle glaucoma?
Eye drops to decrease IOP
- Prostaglandin analogues
- Beta-blockers
- Carbonic anhydrase inhibitors
Laser trabeculoplasty - laser burns part of the trabecular meshwork apart - increase drainage
Trabeculectomy - Trabeculectomy is a surgical procedure used in the treatment of glaucoma to relieve intraocular pressure by removing part of the eye’s trabecular meshwork and adjacent structures. It is the most common glaucoma surgery performed and allows drainage of aqueous humor from within the eye to underneath the conjunctiva where it is absorbed.
What is the onset of angle closure glaucoma?
Sudden onset, painful, vision lost/ blurred; headaches (often confused with migraine)
What are the findings on examination of angle closure glaucoma?
O/E – Red eye, cornea often opaque as raised IOP drives fluid into cornea
Why are long sighted eyes more susceptible to angle closure glaucoma?
Lens is big – congested. When the pupil dilates it causes the iris to make the trabecular network congested, depth of the anterior chamber becomes really shallow.
Describe the anterior chamber in the case of angle closure glaucoma
Anterior chamber is shallow, angle is closed
IOP is severley raised
What are the three mechanisms involved that cause angle closure?
- Functional block in a small eye – large lens
- Mid-dilated pupil - periphery of iris crowds around angle and outflow is obstructed
- Iris sticks to pupillary border (synechia) which prevents reaching AC. Leads to iris balooning anteriorly and obstructing angle.
What is the management of acute episode of angle closure glaucoma?
1.Decrease IOP
- IV infusion with or without oral therapy – carbonic anhydrase inhibitors (acetazolamide)
- Analgesics, antiemetics (effective against vomitting and diarrhoea)
- Constrictor eye drops – pilocarpine
- If no contraindication beta-blocker drops such as timolol
- Steroid eye drops (dexamethasone)
2.Iridotomy (laser) - both eyes - to bypass blockage
In POAG what is the cause of increase in intraoccular pressure?
Trabecular meshwork is blocked
Which is an emergency, POAG or angle closure glaucoma
Angle closure glaucoma
What are the types of uveitis?
Anterior uveitis – iris with or without ciliary body inflammed
Intermediate uveitis – ciliary body inflammed
Posterior uveitis – choroid inflammed
What are the causes of uveitis?
Isolated illness
Non-infectious autoimmune causes – eg: presence of HLA-B27 predisposes to anterior uveitis
Infectious causes – chronic diseases such as TB
Associated with systemic diseases – eg: ankylosing spondylosis
What is the pathophysiology of anterior eveitis?
Uvea leaks plasma and white blood cells into the aqueous humour
What is the result of slit lamp examinations on anterior uveitis?
Hazy anterior chamber, cells are deposited at the back of the cornea
What does the eye look like in anterior uveitis?
The eye is red, painful with visual loss
Hypopyon - cells in the aqueous humour may settle inferiorly
What is the pathophysiology of intermediate uveitis?
In intermediate uveitis the ciliary body is inflammed and leaks cells and proteins.
This leads to a hazy vitreous
Patient complains of “floaters” or hazy vision
What is the pathophysiology of posterior uveitis?
Choroid is inflamed
Since the choroid sits under the retina, the inflammation frequently spreads to the retina causing blurred vision
