Cornea Flashcards
In come people the corneal dendritic scar (with bulbous ends) heals, but what are some of the complications that could arise for those who dont heal?
if the infection is confined to the epithelium, healing occurs without scarring.
Sometimes stromal inflammation may occur and so this can lead to some level of scarring.
anterior uveitis can occur
what can happen if you put a topical steroid on a herpetic corneal ulcer?
results in an amboeid ulcer and is slow to heal and very hard to treat.
what are some complications of herpes zoster virus?
conjuctivitis
keratitis
anterior uveitis
scleritis and episcleritis
What are three viruses that can affect the cornea?
herpes simplex
herpes zoster
adenovirus
WHat are predisposing factors that make bacterial infection likely to happen in the cornea?
corneal trauma
contact lens wear
chronically compromised ocular surface such as dry eye, blepharitis and keritopathy
hepatitis keratitis
corneal exposure (facial nerve palsy (cant close eyes) and proptosis)
immunosupression, including topical steroid use
what is the management for bacterial keratitis?
urgent investigation and admission!
conjuctival and corneal samples sent for microscopy and culture
broad-spectrum topical antibiotics such as quinilone, are administered frequently 24 hrs per day, intially until a favourable response is seen.
sometimes subconjuctival and systemic antibotics are given
despite the liklihood of permanent scarring topical steroids are only used when resolution of the infection element.
what is marginal keratitis?
blepharitis is a common cause of marginal corneal ulceration which is a hypersensitivy reaction to bacterial toxins - NOT an infection
what are the three types of corneal transplantation one can do?
penetrating keratoplasty - full thickness
deep anterior lamellar keratoplasty - partial thickness leaving endothelium in place
endothelial keratoplasty - just the endothelium is transplanted
what causes corneal melting?
infection
reduction of tear flow
autoimmune process
sx of adenovirus keratitis?
blurring and photophobia after viral conjuctivits
What is recurrent corneal erosion syndrome?
caused by epithelial or stromal dystrophy or by previous trauma
what are some systemic associations with cataract?
diabetes
corticosteroid therapy
hypocalcemia and other metabolic disorders
what are the three types of cataracts that can develop?
nuclear scelrosis - central opacity
posterior subscapular - back of capsule
cortical - spoke like opacities of the cortex
What are some caused of leukocoria? (white pupil)
cataract retinoblastoma retinopathy of prematurity corneal opacity coat's disease
what is ectopia lentis?
a disolcated lens - causes include trauma, marfans, cataract
WHat is the difference between open and close angle glaucoma?
Open-angle is when there is an open and wide angle between iris and cornea, develops over a very long time and symptoms are not always known.
Angle-closure is when there is a closed and sharp angle, happens quickly and symptoms are very obvious.
When the block is at the entrance it is called Closed Angle Glaucoma. When the blockage is not at the entrance, but beyond, somewhere inside, we call it Open Angle Glaucoma. Closed angle is assosciated with a pupillary block.
WHat are the sx of close angle vs open angle glaucoma?
open angle:
not much
closed angle: pain, nausea and vomiting loss of vision red eye (usually unilateral) cloudy cornea a hx of a previous attack
what is the surgical procedure for open vs closed angle glaucoma?
open-angle: trabeculectomy
closed-angle: iridotomy
How can you test if there is a pupil sympatehtic problem?
cocaine test - 4% cocaine solution into eye and if pupi does not dilate (which a normal one would) then this indicates a loss of sympathetic innervation.
What is denervation hypersensitivity?
This is when postganglionic fibers are damaged and so the iris creates more receptors and therefore reacts to a smaller concentration of neurotransmitters than it normally should
How can you test for denervation hypersensitivity?
postganglionic parasympathetic lesions - pilocarpine 0.1% - affected pupils will constrict while normal pupils will not
postganglionic sympathetic lesions - 0.1% adrenaline - affected pupils will dilate while normal won’t.
how are the pupils affected in third nerve palsy?
dilated pupil that fails to react to light.
also has ptosis and down and out eye.
What is Adie’s pupil?
damaged postganglionic parasympathetic fibers causes a semi dilated pupil that reacts poorly to direct light and to accommodation. redilation is slow.
cause unknown - likely viral???
diagnosed with hypersensitivity to 0.1% pilocarpine.
What is Horner’s syndrome?
miosis, ptosis and anhydrosis
most obvious in a dim room when the horner’s eye fails to dilate.
cocaine 4% dilates the normal pupil but not the horner’s one. whereas adrenaline 0.1% dilates the horner’s pupil but not the normal one. (since cocaine only prevents reuptake of adrenaline)
investigate for a pancoast tumour in the lung.
what is RAPD good for testing which conditions?
test is positive in unilateral disease in the optic nerve,
retinal detachment
severe wet macular degeneration
negative in
cataracts
corneal opacity
vitreous hemmorhage
What is scintillating scotoma? and what are the causes?
a kaleidoscope pattern (shattered glass), water running down a window kind of distortion of vision.
This is often seen when the retina or cerebral cortex is being underperfused such as in:
migraine
emboli
giant cell arteritis
what are floaters and what are the causes?
floaters are objects seen in vision such as cobwebs, a hair, tadpoles in vision.
causes include anything occurring in the vitreous:
vitreous degeneration or posterior vitreous detachment
vitreous hemorrhage
posterior uveitis.
what is happening when someone sees a flickering light?
when a vitreous detachment occurs the posterior vitreous gel may exert traction on the retina, stimulating the retina to see a flickering light.
the traction may tear the retina.
what questions should you ask when someone has flashes of light that come and go in the past 5 years?
how long do these episodes last? - 5-20mins suggests a migraine
do you have any assosciated headache that comes after these visual sx? - migraine is usually unilateral throbbing nature.
do you have any hx of diabetes, heart disease, hyperlipideamia, previous stroke/tia, peripheral vascular disease, do you smoke?, arteritis?
do you have a family hx of migraines?
are you on the COC pill?
other neuroligical sx?
What is the treatment for corneal abrasion (severe)?
chloramphenicol ointment
dilating drops for comfort
occlusive dressing pad
what is corneal abrasion syndrome?
recurrent corneal abrasion syndrome is caused when the attachment of the epithelium to the basement membrane is weak.
it causes episodic sx of:
pain and watering especially in the morning
between attacks, nothing is usually seen on pentorch other than punctate fluorescein staining
what is the management of corneal abrasion syndrome?
regular lubrication using artificial tears during day and ointment at night
what is someone at risk of developing if they had been kicked in face?
corneal abrasion acute and chronic glaucoma pressure on optic nerve and other cranial nerves due to swelling and face frcatures vitreous hemmorhage retinal damage orbital blow out fracture
what are the clinical features of an orbital blow out fracture?
enophthalmos - initially can be masked by orbital hemmorhage
altered face sensation of the infraorbital nerve (cheek)
reduced vertical ocular movement - causes vertical double vision.
