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?
4. Descemet's membrane
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?
which type of bacterial keratitis do we have to be aware of in contact lens users?
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
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?
previous eye surgery
what is the different in axial length between myopia and hypermetropia?
what is a cataract?
opacity of lens
when fluid gathers between lens fibres
what are the symptoms of cataract?
glare in sunshine - due to scattering of light rays
difficulty reading and watching tv
cant recognise faces
gradual PAINLESS loss of vision
diplopia in one eye
what are the RF for cataract formation?
what are the 4 types of cataract?
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