Common Conditions of the Eye Flashcards
What is the conjunctiva?
Thin vascular membrane that covers inner surface of eyelids and loops back over sclera.
Does not cover the cornea
What is conjunctivitis?
Self-limiting bacterial or viral infection of the conjunctiva
What are the symptoms of conjunctivitis?
Red, watering eyes, discharge
No loss of vision as long as infection does not spread to cornea
What is the treatment of conjunctivitis?
Antibiotic eye drops if it is likely to be bacterial
Name a condition of the conjunctiva
Conjunctivitis
Name a condition of the eyelids
Style or hordeolum
What is the difference between a style or hordeolum?
External – affecting the sebaceous glands of an eyelash
Internal – affecting the meibomian glands
What is the epithelium of the cornea?
Stratified squamous nonkeratinsed
What is the nam for the basement membrane of the cornea?
Bowman’s membrane
Name the 5 layers of the cornea
- Epithelium
- Bowman’s membrane
- Stroma
- Descemet’s layer
- Endothelium
What is the stroma of the cornea?
3rd layer of the cornea: regularly arranged collagen, no blood vessels
What two pathologies can affect the cornea?
- Inflammatory - i.e. corneal ulcers
2. Non-inflammatory - i.e. dystrophies
What do corneal pathologies often lead to?
Opacification of the cornea
Might need to be treated by corneal transplant - Keratoplasty
What are two causes of corneal ulcers?
- Infectious - viral/bacterial/ fungal infection of cornea, needs aggressive management to prevent spread, scarring
- Non-infectious ulcers due to trauma, corneal degenerations or dystrophy
What are the dystrophies and degenerations of the cornea?
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 do dystrophies and degenerations present as?
- First to fourth decade
- Decreased vision
- Start in one of the layers of the cornea and spread to others
Why do researchers refer to the cornea as the “immune-privileged” site?
The avascularity of the cornea means there is a lesser chance of foreign antigens from a corneal graft being recognised by the recipient, so lesser chance of a graft rejection
What happens in cataracts?
The lens become opacified
Why does cataracts develop?
- Older fibres are never shed, compacted in the middle - loss of elasticity and become opaque
- 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 causing opacity
What types of fibres causes dilation of pupil?
Sympathetic
What is used to treat cataracts?
Surgery:
(Day case) small incision -> lens capsule opened -> cataracts lens removed by emulsification (phacoemulisification) -> plastic lens placed in capsular bag
Cant use eyedrops
What is glaucoma?
Raised Intraocular pressure (IOP)
How does glaucoma arise?
Damage to the AH drainage pathway causing raid intraocular pressure (rare for it to be caused by over-production
What is the most common form of primary glaucoma?
Primary Open Angle Glaucoma (POAG) - bilateral
What is the consequence of raised intraocular pressure?
Pressure on nerve fibres on surface of retina -> fibres die -> visual field defects
Pressure on optic nerve head as nerve fibres die out. When seen by ophthalmoscopy – optic disc appears unhealthy, pale and cupped.
This results in altered field of vision as all nerve fibres are lost, which will eventually result in blindness.
What is the triad of signs for the diagnosis of glaucoma?
- Raised IOP
- Visual field defects
- Optic disc changes on ophthalmoscopy
What is the management of glaucoma (POAG)?
- Eye drops to decrease IOP (prostaglandin analogues, beta-blockers, carbonic anhydrase inhibitors)
- Laser trabeculoplasty (unclog trabecular meshwork)
- Trabeculectomy surgery
What is an angle closure glaucoma?
Sudden onset, painful, vision lost/ blurred; headaches (often confused with migraine)
What are the symptoms of angle closure glaucoma?
- O/E – Red eye, cornea often opaque as raised IOP drives fluid into cornea
- AC shallow, and angle is closed.
- Pupil mid-dilated
- IOP severely raised
Why does the angle close in angle closure glaucoma?
- 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 are the two management strategies for angle closure glaucoma?
- Decrease IOP
2. Iridotomy (laser) - drainage in iris to decrease pressure
How do you decrease IOP in angle closure glaucoma?
- IV infusion +/- oral therapy - carbonic anhydrase inhibitors (Acetazolamide)
- Analgesic, antiemetic
- If no contraindication beta-blocker drops such a timolol
Why carry out an iridotomy for angle closure glaucoma?
To bypass blockage to prevent another episode, so the AH has short circuit to the trabecular meshwork
Burns a small hole in the iris
What is uveitis?
Inflammation of the uvea
What are the three different types of uveitis?
- Anterior - iris with or without ciliary body inflamed
- Intermediate uveitis - ciliary body inflamed
- Posterior - choroid inflamed
What are the causes of uveitis?
- Isolated illness
- Non-infectious autoimmune causes – eg: presence of HLA-B27
- Infectious causes – chronic diseases such as TB
- Associated with systemic diseases – eg: ankylosing spondylosis
What happens in anterior uveitis?
Inflamed anterior uvea (iris) leaks plasma ad white blood cells into the aqueous humor
What is the clinical presentation of anterior uveitis?
- Seen in slit lamp examination as a hazy anterior chamber and cells deposited at the back of the cornea
- The eye is red, painful, with visual loss
- Cells in the AC may settle inferiorly – “hypopyon”
What happens in intermediate uveitis?
Ciliary body is inflamed and leaks proteins -> hazy vitreous
What happens in posterior uveitis?
Choroid is inflamed and because the choroid sits under the retina, the inflammation frequently spread to the retina causing blurred vision
What is the uvea?
The pigmented layer of the eye, lying beneath the sclera and cornea, and comprising the iris, choroid, and ciliary body
