common conditions of the eye Flashcards
where do optic vesicles grow?
outwards from diencephalic part of neural tube towards surface ectoderm.
whaat is conjunctivitis?
Self-limiting bacterial or viral infection of the conjunctiva.
symptoms of conjunctivitis?
Red, watering eyes, discharge +. No loss of vision as long as infection does not spread to cornea
treatment of conjunctivitis?
antibiotic eye drops if likely to be bacterial
what is a stye thats external called?
hordeolum externum
what is a stye that is internal called?
hordeolum internum
what is the treatment of styes?
warm compress, eyelid hygiene, may need surgical incision and curettage
wht is the histology of the cornea?
Epithelium – stratified squamous non-keratinised.
Bowman’s membrane (basement membrane of corneal epithelium)
Stroma – regularly arranged collagen, no blood vessels
Descemet’s layer
Endothelium – single layer (normal - 2500 cells/mm2)
whats the pathology of the cornea?
Inflammatory – eg: corneal ulcers
Non-inflammatory – eg: dystrophies
Corneal pathologies frequently lead to opacification of the cornea. This might need to be treated by corneal transplant - Keratoplasty
psthology of a corneal ulcer
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 corneal dystrophies?
a group of genetic, often progressive, eye disorders in which abnormal material often accumulates in the clear
what are the different types of corneal dystrophies?
Bilateral Opacifying Non – inflammatory Mostly genetically determined. Sometimes due to accumulation of substances such as lipids within the cornea
what is the significance of the avascularity of the cornea?
benefit to surgeons when performing a graft surgery as it 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.
is there any lymphatics draining in the eyes/eyelids?
no
what are some common disease cinditions of the eye?
cataract glaucoma age-related macular degeneration diabetic retinopathy corneal opacities childhood blindness trachoma
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 fibres–> opaque —>CATARACT
what is the management of cataracts?
Eye drops do not treat cataract!
Surgery – (day case) small incision lens capsule opened cataractous lens removed by emulsification (phacoemulsification) plastic lens placed in capsular bag
Lens implant after cataract surgery – PCIOL = Posterior Chamber Intra Ocular Lens
what is the 2nd most common global cause of blindness?
glaucoma
what is the most commonly seen from of primary glaucoma?
primary open angle glaucoma
what is the consequence of raised intraocular pressure
Pressure on nerve fibres on surface of retina–> die out —> visual field defects
what is the triad signs of glaucoma?
raised IOP
visual field defect
optic disc changes on ophthalmoscopy
whats the management of POAG?
Eye drops to decrease IOP
Prostaglandin analogues
Beta-blockers
Carbonic anhydrase inhibitors
Laser trabeculoplasty
Trabeculectomy surgery
what is angle closure glaucoma?
Sudden onset, painful, vision lost/ blurred; headaches (often confused with migraine)
signs of angle closure glaucoma?
Red eye, cornea often opaque as raised IOP drives fluid into cornea
AC shallow, and angle is closed.
Pupil mid-dilated
IOP severely raised
Right eye: red and inflammed, cornea hazy, pupil mid-dilated
what are the mechanisms for the angle closing?
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.
whats the management of an acute episode?
Decrease IOP
IV infusion with or without oral therapy – carbonic anhydrase inhibitors (acetazolamide)
Analgesics, antiemetics
Constrictor eye drops – pilocarpine
If no contraindication beta-blocker drops such as timolol
Steroid eye drops (dexamethasone)
Iridotomy (laser) - both eyes - to bypass blockage
whats the difference between open angle and angle closure glaucoma?
In open angle glaucoma the drainage through the trabecular meshwork is blocked (in most cases)
This leads to a gradual, painless build up of intraocular pressure (IOP).
This type of Glaucoma is called Primary Open Angle Glaucoma (POAG)
In angle closure glaucoma, some event on a predisposed eye leads to the peripheral iris blocking the angle, therefore aqueous can’t drain.
So the increase in IOP is sudden leading to a red eye, and severe pain.
Patient usually presents as an emergency
what is uveitis?
inflammation of uvea
what are the different types of uveitis?
Anterior uveitis – iris with or without ciliary body inflammed
Intermediate uveitis – ciliary body inflammed
Posterior uveitis – choroid inflammed
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
whats the pathophysiology of anterior uveitis?
An inflammed anterior uvea (iris) leaks plasma and white blood cells into the aqueous humor
These are seen during 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”
pathology 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
pathology of posterior uveitis
In posterior uveitis the choroid is inflammed.
Since the choroid sits under the retina, the inflammation frequently spreads to the retina causing blurred vision
