Loss of vision Flashcards
What is the first most important question to ask in loss of vision?
Is it painless or painful
Why is it important to ask about pain in loss of vision?
important for localisation; painful means affecting structures with rich sensory innervation (iris, cornea, sclera) but painless suggests lens structures further back in eye e.g. retina, such as macular degeneration and retinal detachment, glaucoma
What type of cause of loss of vision is the exception to the anterior=painful, posterior=painless rule?
Optic nerve pathology: can and often does cause pain, but associated with ocular movements
What are 7 important questions to ask in a loss of vision history?
- painful or painless?
- Duration
- Degree of vision loss
- Permanent or transient
- Central or peripheral loss
- One or both eyes
- Associated symptoms
Why is it important to ask about duration in los of vision?
sudden reduction tends to be vascular or rarely neurological; chronic diseases of the retina tend to have slow course, gradual impairment of vision
Why is important to ask about the degree of vision loss?
if sudden and complete –> neurological or vascular insult, blurring or loss of ability to read fine print implies difficulty focusing light on retina, tends to be caused by media opacity and varies with ambient lighting levels. Unusual to get complete visual los - NPL (no perception of light)
What are usually the causes of NPL (no perception of light)?
Significant neurological or vascular problems
What are 2 common causes of transient visual loss?
- Amaurosis fugax in transient ischaemic attacks (TIAs): black curtain over vision in one eye at a time resolving within 24 hours
- Optic nerve pathology - transient visual obscurations, or complete NPL for second or two
What does permanent visual loss suggest?
Significant structural damage to other structures of the eye e.g. macular degeneration or glaucoma
Why is it important to ask about central or peripheral loss of vision?
Localising pathology: central implies macular disease, peripheral suggests retinal detachment or glaucoma, or could be problem with neurological pathways to occipital cortex
What does both eyes simultaneously experiencing loss of vision suggest?
Neurological pathway problem, or macular degeneration/ diabetic eye disease/ glaucoma occurring at different rates
What does it tell you if just one eye experiences visual loss?
Localised pathology to eyeball or section of optic nerve connecting eye to chiasm
What are 3 key systemic diseases that affect the eye, meaning associated symptoms are important?
HTN, DM, vasculitis (e.g. co-existent kidney disease)
What are 2 key important parts of examination in patients with visual loss and why?
- visual acuity: need to know baseline acuity
2. Swinging light for RAPD: to detect early damage to optic nerve by comparing pupils
When performing the swinging light test for RAPD, which part of the eye’s response are you looking for?
Dilation rather than constriction: comparing constriction between the two eyes; consensual constriction will be normal but direct will be reduced, so what you see is diminished constriction as affected eye can’t constrict quick enough when light is shone directly. Affected eye continues to dilate for a few seconds when moving back to it before impulses travel back to the brain to overcome dilation
Where is the cause of painless loss of vision usually?
Back of the eye i.e. lens backwards: lens, vitreous, retina, some causes of optic nerve damage (glaucoma, optic neuropathy)
What are 9 causes of SUDDEN, painless loss of vision?
- Branch retinal vein occlusion
- Central retinal vein occlusion
- Branch retinal arteriolar occlusion
- Central retinal arteriolar occlusion
- Anterior ischaemic optic neuropathy
- Proliferative diabetic retinopathy
- Vitreous haemorrhage
- Retinal detachment
- WET age-related macular degeneration
What is the fovea and where is it located?
Centre of macula and part of eye with highest density of cone photoreceptors, 2.5 disc diameters temporal to the optic disc
What is the macula?
part of the eye we use for most visual tasks, 2 disc diameters in radius from the centre of the fovea
On a photograph of the back of the eye, how is the fovea identified?
Using a fixation marker: patient asked to look at a point while photo is taken, marker casts black shadow that points to fovea
What are the 4 arcades that retinal vasculature is split into?
Superotemporal
Superonasal
Inferotemporal
Inferonasal
What does each arcade of the retinal vasculature consist of?
Vein (thicker, darker vessel) and arterial (thinner, lighter coloured)
How will the retina appear in branch retinal vein occlusion?
Haemorrhages confined to area drained by that retinal vein branch; haemorrhages, lipid exudate, fluid leaks into retina
What may be the symptoms of branch retinal vein occlusion?
may pass unnoticed by patient and seen as incidental finding, or patient may be aware of blurring in peripheral part of vision
When to patients with branch retinal vein occlusion tend to present?
When a section of the retina involved overlaps the macula region –> causes profound reduction in vision
How does central retinal vein occlusion compare with branch retinal vein occlusion?
much more dramatic - widespread haemorrhages for central, 360 degrees all the way to the periphery, as well as fluid leakage, exudate into the retina
What causes central retinal vein occlusion?
Blockage of vein beyond the optic disc causing increased back pressure through the entire venous drainage of the eye
What are key risk factors for central retain vein occlusion? What are 3 key management steps?
Cardiovascular risk factors; therefore need to (1) optimise blood pressure and (2) blood sugar, and in (3) rarer cases think about clotting screens (e.g. younger patient)
Look at a picture of central retinal vein occlusion. What are 2 key features?
swollen disc, haemorrhages throughout retina
Look at a picture of central retinal vein occlusion. What are 2 key features?
swollen disc, haemorrhages throughout retina
What may cause arteriolar retinal branch occlusion and how might this be spotted?
Fibrin embolus, may appear as area of whitening within the blood vessel
What is an example of a blood vessel that could contain an embolus leading to branch retinal arteriole occlusion?
Branch of superotemporal retinal arteriole (could also be inferotemporal, superonasal and inferonasal)
What is the appearance of a retina with branch retinal arteriole occlusion?
Distal to blockage is area of infarcted retina, appears very white - has lost transparency; in contrast, normal retina is transparent (for light to reach photoreceptors in deepest parts) so has orange-pink glow from underlying choroidal circulation
Within what time frame after onset of BRANCH retinal arteriole occlusion can good function be restored?
within 4 hours of onset
What is the risk of patients with prolonged branch retinal arteriole occlusion?
Blockage in arterial supply to retina can cause profound reduction in function of photoreceptors in that area
What is the key principle of treatment of branch retinal arteriole occlusion?
drop pressure in eye as much as you can
Within what time frame might it be worth trying to restore normal circulation in the eye in branch retinal arteriole occlusion?
up to 24 hours (but within 4 hours higher chance of getting vision back)
What are 3 options to treat branch retinal arteriole occlusion?
- medically drop pressure: acetazolamide, beta blockers, mannitol, apraclonidine
- remove fluid from anterior chamber via paracentesis to shift clot along and restore blood supply
- rebreathe into brown paper bag, increasing CO2 concentration to cause vessels to dilate and increase blood supply
What are the symptoms of branch retinal arteriole occlusion?
acute onset painless, monocular vision disturbance; focal loss of vision due to only one branch being affected
What is commonly the cause of branch retinal arteriole occlusion?
arteriolar emboli, commonly originating from carotid arteries or AF
What 2 things should be examined in branch retinal arteriole occlusion, due to arterial emboli being a common cause?
auscultate for carotid bruit, feel radial pulse for arrhythmia
What 2 things should be examined in branch retinal arteriole occlusion, due to arterial emboli being a common cause? What 2 types of treatment may be needed if certain underlying causes are present?
auscultate for carotid bruit, feel radial pulse for arrhythmia. carotid endarterectomy or anticoagulation may be needed
What should be investigated for in BRAO if not embolic cause is found?
Coagulopathies - screen with blood tests
What is most likely the cause of central retinal arteriolar occlusion and how does this contrast with BRAO?
more commonly associated with inflammation, unlike BRAO which is often embolic
What could central retinal arteriolar occlusion be a presenting feature of?
Giant cell arteritis
What tests should always be performed in patients with CRAO?
inflammatory markers due to possibility of GCA
Look at a photograph of a retina showing central retinal arteriolar occlusion
white retina, cherry red spot at macula
What is the classical appearance of a retina with central retinal arteriolar occlusion?
ischaemic retina across a wider area than RAO with a cherry red macula temporally if soon after onset
What is a cherry red macula in CRAO a sign of?
early sign of central retinal artery occlusion
Why might a cherry red spot not be visible in CRAO?
it disappears soon after onset, as the retina tends to reperfuse and loses its whitish colour (however, no recovery of function if reperfuses)
if the retina is reperfused shortly after the onset of CRAO, does this mean there is recovery of function?
often not - can be cause of profound retinal pathology, e.g. causing NPL and RAPD
What is anterior ischaemic optic neuropathy?
blood supply to the optic nerve is lost
What are the two types of anterior ischaemic optic neuropathy?
- arteritic i.e. GCA
2. non-arteritic
What 2 types of risk factors can non-arteritic anterior ischaemic optic neuropathy be associated with?
- cardiovascular risk factors (like branch retinal vein occlusions)
- also sometimes seen in people with a small optic disc, where there isn’t much space for blood vessels so leads to mechanical obstruction of blood supply
What happens in vitreous haemorrhage?
blood pouring into vitreous cavity
What is the range of presentations like in retinal detachment?
Wide spectrum of presentation; can be innocuous flashers and floaters or quadrantanopic or hemianopic visual field loss in one eye (depends on extent of detachment)
What pathology occurs in anterior ischaemic optic neuropathy?
front part of the optic nerve loses its blood supply
What is the clinical appearance of the optic disc in AION?
instead of pink healthy appearance get pale, white, swollen optic disc with indistinct margins, blood vessels obscured as they pass through the edge of the nerve
What causes pallor of the optic disc in AION?
loss of blood supply
What key disease MUST be ruled out in AION?
Giant cell arteritis
What is usually the cause of AION if GCA can be ruled out?
same risk factors as other forms of stroke/vein occlusions - high blood pressure, high blood glucose
What are the symptoms of AION?
reduction or loss of vision
What occurs in proliferative diabetic retinopathy?
New vessels at the disc, lacy appearance over the disc
Look at an image of what anterior ischaemic optic neuropathy looks like in a retina.
pale, swollen optic disc, indisctinct margins, blood vessels obscured as passing through edge of nerve
Why does proliferative diabetic retinopathy occur?
response to hypoxia due to impaired blood supply –> compensation by upregulating pro-angiogenic signals to grow new blood vessels
What do the new blood vessels formed in proliferative diabetic retinopathy have a tendency to do?
often grow where they’re not wanted, can be leaky and result in haemorrhage. can also burst
What happens if blood vessels burst in proliferative diabetic retinopathy?
eye fills with blood, obscures path of light to the retina, causing a reduction in vision
What may be the consequence of a burst vessel in proliferative diabetic retinopathy?
can clear on its own but may take a long time; if actively bleeding, as blood starts to clear can bleed again
What may need to be done as treatment for a burst blood vessel in proliferative diabetic retinopathy if it doesn’t clear on its own/takes too long?
wash out back of eye to view what is causing the bleed and treat it
How common are vitreous floaters and what are they?
very common: areas of vitreous gel becoming solidified, casting shadow on retina as they move around
What is the most common cause of vitreous floaters and how serious is this?
posterior vitreous detachment; this is a normal age-related process as the vitreous jelly degenerates i the back of the eye, shrinks, collapses in on itself, forms black lines and dots
Why can vitreous floaters be more significant in a diabetic patient?
may be vessels bleeding in the back of the eye
What should be done if a diabetic patient notices a sudden increase in floaters in the eye?
could be vitreous haemorrhage due to vessels bleeding, must get it checked straight away as may be leaky blood vessels –> needs to be treated before progresses to full vitreous haemorrhage
What can posterior vitreous detachment occasionally be associated with?
retinal tears and detachments
What causes retinal detachment to occur?
posterior vitreous detachment; in areas where the jelly is firmly adherent - in the most peripheral anterior portion and around nerve and fovea - can lift retina in rare cases during posterior vitreous detachment, and with it may causes a retinal tear