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which part of the orbit gets fractured the most and why?
- inferior orbital wall - maxillary bone
- blow out fracture
which is the thinnest part of orbit, what clinical significance?
- ethmoid bone
- infection in paranasal sinus can get through tiny holes in ethmoid and to orbit
what does the optic canal carry?
- optic nerve
- ophthalmic artery with its sympathetic nerves
what are the 3 layers to the external layer of the eyeball?
what does the intermediate layer of the eyeball consist of? and what is its other name and why?
- anterior: iris, ciliary body
- posterior: choroid
- other name: uveal layer - black grape - choroid is very vascular
what does the internal layer of the eyeball consist of?
what are the 3 chambers in the eyeball?
- anterior chamber
- posterior chamber
- vitreous chamber
what are the 2 muscles in the iris? and nerve supply?
- dilator pupillae: radial configuration - sympathetic
- sphincter pupillage: on the papillary margin - circular motion contracts
where is the choroid and what is its function?
- choroid is between retina and sclera
- function: provide O2 and nutrients to outer layers of retina (RPE)
what colour is the cornea?
what are the 5 layers of the cornea?
- 1. epithelium
- 2. Bowman's
- 3. stroma
- 4. Descemet's membrane
- 5. endothelium
what happens if the endothelial layer of the cornea fails? and why?
- get corneal oedema
- endothelium is an active layer - function is to pump WATER OUT OF CORNEA
- so if waters stays - lose its transparency
what is a dendritic lesion of the cornea? and cause and treatment
- HSV1 and 2 lesion to epithelium of cornea
- treat: antiviral eg aciclovir topical/systemic
what are the symptoms and signs of keratitis?
- reduced VA
- circumcorneal injection
which type of bacterial keratitis do we have to be aware of in contact lens users?
- pseudomonas (anaerobic)
- rapidly destructive
which treatment should NEVER be used in dendritic keratitis?
what investigation needs to be done to detect dendritic ulcer?
fluorescine dye - goes into epithelium
what are the 2 functions of ciliary body?
- 1. aqueous humour production: 2ul/min
- 2. accommodation: from CB - suspensory ligaments hold the lens to fit its position. if ligaments fail, get a dislocated lens
when the ciliary muscle contracts what happens to lens?
becomes more round and fat - looking near
what is presbyopia? what type of glasses?
- with ageing the CB loses its ability to contract so cant look near (accommodate) as well
- so need reading glasses
what are the 2 main layers of the retina?
- inner neurosensory layer
- outer retinal pigmented epithelium
how far is the fovea to the OD?
3 OD diameters temporal to the OD and a bit inferior
what is an OCT and its use?
- optical coherence tomography
- use to detect detachment - fluid between the RPE and NS retina ie intraretinal fluid
what are 2 main symptoms of posterior vitreous detachment and why? and how does PVD happen?
- floaters and flashes
- with age the vitreous gel liquefies - vitreous syneresis
- floaters: collagen fibres in vitreous stick together to make cobweb shapes - black FLOATERS - where vitreous collapses and casts shadow on retina
- these forcibly detach the posterior virtual surface from the retina
- the traction forces applied to the retina create FLASHES
What type of eyes are more susceptible to PVD?
what are the natural history of floaters in PVD?
- most are self limiting, become less noticeable
- only few develop retinal tear
what should patients with PVD be warned of?
risk of retinal tear and detachment if notice sudden shower of floaters or new flashing lights
what causes retinal tear?
where is the most common place to see a retinal tear and what does it look like on fundoscopy?
- upper temporal part
- u shaped
why is retinal tear dangerous?
- vitreous can enter the space between the retina (NS) and RPE
- causing a rhegmatogenous retinal detachment
- myopes are at high risk of this type of RD
what are the symptoms of RD?
- flashing light (photopsia)
- then gradual blurring or LOSS OF VISION -
what are the 2 treatment options of retinal tear without RD?
- 1. argon laser retinopexy in the area around the tear - to make strong adhesions between the retina and RPE
- 2. cryotherapy - if tear in extreme periphery and difficult to approach with laser
what are the 3 main types of RD?
- 1. rhegmatogenous RD: from PVD - lqd between retina and RPE
- 2. tractional RD: in proliferative diabetic retinopathy - fibrous or vascular membranes growing abnormally in the vitreous can contract and pull retina away from RPE
- 3. exudative RD: inflammatory or neoplastic condition can lead to serous exudate form leaky bld vessels beneath retina
in PVD when do pts see more floaters?
when look at white background (snow / ceiling)
what is the treatment for retinal detachment? think about 2 different approaches
- 1. external approach: scleral buckle - silicone band presses the etina and enforces the RPE to attach to the retina
- 2. internal approach: laparoscopic vitrectomy - mainly used nowadays. remove vitreous and source of traction that caused RD then inject gas into eyeball to make retina stick to RPE (or silicone oil - but very heavy and need to remove)
which type of retinal detachment requires urgent treatment?
- macula on - as able to repair
- macula off - too late :(
what are risk factors for retinal detachment?
- acute PVD
- previous eye surgery
what is the different in axial length between myopia and hypermetropia?
- myopia: longer
- hypermetropia: shorter
what is a cataract?
- opacity of lens
- when fluid gathers between lens fibres
what are the symptoms of cataract?
- reduced VA
- glare in sunshine - due to scattering of light rays
- blurred vision
- difficulty reading and watching tv
- cant recognise faces
- gradual PAINLESS loss of vision
- diplopia in one eye
what are the RF for cataract formation?
- UV light
- myotonic dystrophy
- atopic dermatitis
what are the 4 types of cataract?
- anterior subcapsular
- posterior subcapsular
- cortical - see in periphery of eye
what is a complication of mature cataract?
dislocated lens: suspensory ligaments degenerate so lens falls down
what is the lens problem in marinas?
superior subluxation of the lens
what is the lens problem in homocystinuria?
inferior subluxations of the lens
what type of lens is needed to correct myopic eyes?
- negative lens to weaken the high power of the eyeball
what type of lens is needed to correct hypermetropic eyes?
- positive lens to weaken the high power of the eyeball
what is the advantage of being myopic?
wont need reading glasses over 40yo as they wont get presbyopia
what is the operation called for cataract?
phaecoemulsification: use US to emulsify nucleus and take out of the capsule, without breaking the capsule and suspensory lieges
what are the 6 steps of cataract surgery?
- local anaesthetic drops - awake but feel nothing in eye
- 1. corneal incision
- 2. capsulorrhexis: make incision into anterior capsule (5-6mm)
- 3. hydrodissection: blunt needle between the capsule and cortex - inject water and detach the cortex from capsule so easy to suck out cortex
- 4. phaecoemulsification: US to nucleus - it is very hard so need to break it into 4 pieces
- 5. remove remaining cortex
- 6. implant IOL - artifical lens. haptics stabilise lens into capsule
- 7. put pad/shield over eye to protect it from accidental rubbing after op
when do you decide to operate on cataract?
- no threshold of VA
- depends upon impact of cataract on QOL
what are the 2 benefits of cataract surgery?
- 1. improve vision
- 2. prevent glaucoma. the natural lens grows in life with age which increases pressure on anterior chamber, may get glaucoma
what are the risks of cataract surgery?
- 1. worse vision: 1%
- 2. blind 0.1%
- 3. inflammation
- 4. bleeding
- 5. endophthalmitis
- 6. PC rupture or dropped nucleus or IOL into vitreous
- 7. retinal detachment
- 8. posterior capsule opacification - long term complication - individual cells remain, multiply and migrate to the posterior capsule. treat with YAG laser capsulotomy
- 9. crystoid macular oedema: esp in DM or uveitis
what is the main contraindication to cataract surgery?
unable to lie flat
what are the usual causes of endophthalmitis?
gram positive strep or staph
what are the symptoms of endophthalmitis?
- reduced VA
- vision gets progressively worse
- red eye
- hazy cornea
what is the treatment of endophthalmitis?
- vitreous aqueous tap
- intravitreal antibiotics
what is the definition of glaucoma?
optic neuropathy which may result in progressive visual field loss
what is normal IOP?
what is used to measure IOP?
what os the definition of ocular hypertension?
what is the pathway of aqueous humour?
- produced: CB
- goes through pupil
- drainage: to iridocorneal angle of anterior chamber - trabecular meshwork - canal of schlemm - episcleral veins
what is normal cup:disc ratio?
what is the problem in open angle glaucoma?
- aqueous humour has access to the angle
- BUT there is RESISTANCE in the trabecular meshwork
what is the problem in angle closure glaucoma?
- aqueous humour has NO ACCESS TO THE ANGLE - cannot enter the pupil as the iris is bowed and touching the lens
- so aq hum stuck in posterior chamber
what is the treatment for POAG? and give eg and MOA for each
- 1st: BB monotherapy eg timolol, MOA: reduces production of AH
- 2nd: PG analogue monotherapy eg latanoprost MOA: increase uveoscleral outflow of AH
- 3rd: combination therapy
- 4th: alpha 2 agonist eg brimonide MOA both reduce AH production and increase trabecular outflow
- CAinhibitor eg acetozolamide, MOA: reduces production of AH
- cholinergics eg pilocarpine: contract CB so miosis and so increased outflow
what type of VF defect is found in glaucoma?
peripheral, nasal step
what are the CI of using BB?
- COPD, asthma
- heart block
if medical treatment for POAG doesn't work then what are the 2 next in line?
- laser treatment: selective laser treatment trabeculoplasty - laser spots increase the intratrabecular space and increase outflow of AH
- surgeli: trabeculectomy +/- mitomicin (antimetabolite) to prevent fibroplast prolif and scar tissue closing the hole made! this operation creates an alternative route for AH flow.
what are the symptoms and signs for POAG?
- halos due to corneal oedema
- reduced vision
- peripheral loss of vision: arcuate scotoma
- optic nerve cupping
- disc haemorrhages
what is a typical history of POAG?
what are the 3 secondary causes of open angle glaucoma? and general mechanism of causing glaucoma?
- cavernous sinus thrombosis
- Sturge Weber syndrome - large haemangioma in the face
- all increase the pressure in the episcleral veins
what are the RF for acute angle closure glaucoma?
what are they symptoms and signs of acute angle closure glaucoma?
- acute PAINFUL red eye
- loss of vision
- pupil: fixed, semi dilated - vertical oval
- corneal oedema
what is the immediate treatment for acute angle closure glaucoma?
- 1. iv acetozolamide (diamox) or mannitol
- 2. topical BB, PG, CAI, alpha 2 agonist (brimonidine), cholinergics
- 3. topical steroids to reduce inflammation
what is the definitive treatment of acute angle closure glaucoma?
- bilateral YAG laser peripheral iridotomy
- this makes a hole in the iris to create
what is the commonest cause of blindness in elderly?
what are the symptoms of ARMD?
- loss of central vision
what are the 2 types of ARMD and the difference between the 2?
- dry: drusen deposited on RPE - slow distortion and reduced vision
- wet: new bld vessels - choroidal neovascularisation, vessels leak/bleed get SUDDEN (not slow) distortion of vision
which type of AMD is more common?
what is the treatment for each type of ARMD?
- dry: untreatable but get them to self test using an Amsler grid - if get lines of distortion then go to A&E as may have some wet ARMD which can treat
- wet: anti VEGF
what does wet ARMD look like on fundoscopy?
see haemorhage in retina
what is the cause of BRVO/CRVO?
- same as atherosclerotic disease because happens where the hardened, calcified arteries press on the veins
- Age, BP, DM
- also blood dyscrasias
what is the difference on fundoscopy between ischaemic and non ischaemic retinal vein occlusion?
- non ischaemic: see blot haemorrhage
- ischaemic: more CWS
what are complications of ischaemic retinal vein occlusion?
VEGF secreted so get neovascularisation which are abnormal vessels - they get replaced with fibrous tissue and contract and can cause tractional detachment
what is another complication of ischaemic retinal vein occlusion?
- new vessels forming in the iris
- called rubeotic glaucoma
what are the symptoms of BRVO/CRVO?
- sudden onset
- reduced vision
- VF defect
- blurred vision - whole retina
if there is an inferior BRVO, what kind of VF defect will there be?
superior VF defect
what can be seen on fundoscopy of retinal artery occlusion?
- cherry red spot in fovea - which is the choroidal circulation underneath
- oedema in CRAO - as retina not perfused so becomes oedematous and opaque
why is it important to look for cherry red spot?
- in GCA - may affect ophthalmic artery
- in that case no cherry red spot because the choroidal circulation is also affected (as supplied by ophthalmic artery)
if an embolus is not seen on fundoscopy of BRAO or CRAO, what needs to be excluded?
what are the symptoms of BRAO/CRAO?
sudden painless loss of vision - amourosis fugal
what is a sign of BRAO/CRAO?
- cherry red spot
- if TIA - then contralateral CNS signs
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