Ophthalmology Flashcards
What is an relevant afferent pupillary defect (RAPD) and how is it tested for?
Comparing the paradoxical pupil dilation, when light is shone in one side, pupil constriction may happen less in both eyes than compared when light is shone in the other eye
Tested using the swinging torch test to compare the level of constriction
If an RAPD is present, what pathology does this suggest?
Pathology in the optic nerve on the side which causes less constriction. This could be due to:
- large retinal detachment
- central retinal artery or vein occlusion
- optic neuritis
When measuring visual acuity, what does 6/6 mean or 6/12?
6/6: they can see at 6 metres what they should be able to see at 6 metres
6/12: they can see at 6 metres what they should be able to see at 12
What is the driving test legal standard for visual acuity?
6/12
If the patient struggles with the visual acuity test using a snellen chart, how can you adapt the test?
Bring the chart closer
Use fingers - get patient to tell you how many fingers you’re holding up
Use hand movement - ask which hand is moving
Use light - can they perceive light
How is using pin holes useful when testing visual acuity?
It allows for refractive errors by only letting light through the centre of the lens so the image should be focused
Means that ophthalmologists can determine if the problem is due to a refractive error (which are resolved at opticians) and an eye problem
Which drugs are used to dilate eyes in opthalmascopy?
Tropicamide (most common)
Cyclopentolate
Phenylephrine
What are the 3 C’s to consider when visualising the optic disc?
Cup - cup to disc ratio (increased ratio is known as cupping)
Contour - check borders are well defined
Colour - pink/orange is healthy, pale/yellow suggest nerve damage
What is a normal cup to disc ratio of the optic disc?
Normal ratio: 0.3
When the cup to disc ratio is greater this can suggest the fibres are lost so the cup in the middle gets greater in size
In myopia, where does the focused image lie in retrospect to the retina?
Anterior to the retina
What type of lens are used to correct myopia?
Concave, diverging lens
This focuses the image back onto the retina
In hyperopia, where does the focused image lie in comparison to the retina?
Behind the retina
How is hyperopia (long-sightedness) managed?
With convex, converging lens
What is the visual acuity standards for lorry and bus drivers?
Must have a visual acuity of 6/7.5 in best eye and at least 6/60 is other eye
Must have horrizontal visual field of at least 160 degrees
What is the most common cause of visual loss in the elderly?
Age-related macular degeneration (AMD)
What is the pathophysiology of AMD?
Undigested lipid products accumulate in the retinal pigment epithelium
These accumulate under the retina in the macula as yellow lesions called drusen, accumulate in bruch’s membrane
Changes in the macula, leads to problems with central vision
What are the two types of drusen?
Hard drusen - small, spread out, people get some as they age, don’t cause visual problems (however the more you have the greater the risk of developing soft drusen)
Soft drusen - small, cluster together, associated with AMD
What type of drusen is associated with AMD?
Soft drusen
As they get larger, they can cause bleeding and scarring in the cells in the macula
How does age related macular degeneration usually present?
Blurring of central vision
Difficulty seeing detail e.g, small print
Increased sensitivity to light
What are the two types of AMD?
Dry (90% of cases) - gradual loss of central vision over time
Wet (10% of cases) - sudden changes to central vision, majority of patients have dry AMD previously
What is the pathophysiology of wet AMD?
Cells of the macula stop working
The eye undergoes angiogenesis to fix problem
New blood vessels growing int eh wrong place causes swelling and bleeding underneath the macula
What are the risk factors for dry AMD?
Increasing age Female gender Smoking Hypertension Previous cataract surgery
How is AMD managed?
No treatment available
Conservative management - some evidence of zinc and anti-oxidant vitamins A, C and E to help slow progression of disease
How is wet AMD managed?
Using anti-vascular endothelial growth factor (Anti-VEGF)
This stops the new blood vessels from forming
What is glaucoma?
Group of eye diseases where you get intraoccular hypertension (increased pressure in the eye)
This can damage the optic nerve and lead to blindness
What is the normal intraoccular pressure of the eye?
10-20mmHg
What is the pathophysiology of gluacoma?
Build up of aqueous humor fluid in the eye
This is either due to increased production or decreased drainage
This increase of aqueous humour increases the intraoccular pressure and causes compression of the retinal blood vessels, causing degeneration of the optic nerve
What are the two types of glaucoma?
Primary open angle - where there is a reduction of aqueous outflow through the trabecular meshwork leading to increased pressure (this happens gradually over a long period of time)
Acute angle closure - where the iris is pushed forward against trabecular meshwork, closing the angle so that aqueous fluid cannot drain
What are the risk factors for primary open angle glaucoma?
Increasing age Ethnicity - black Africans at increased risk Family history Diabetes Myopia
How does primary open angle gluacoma present?
Usually painless
Happens over a long period of time
Loss of vision which starts peripherally
What are the risk factors for acute angle closure glaucoma?
Hypertropia (longsightedness)
Sex - women have longer and shallower anterior chambers
How does acute angle closure glaucoma present?
Sudden onset of red and painful eye Blurred vision Nausea and vomiting - due to increased pressure Headache Abdominal pain
How is glaucoma managed?
Eye drops - to reduce intraoccular pressure
Laser trabeculoplasy - used to open up trabecular meshwork in open angle glaucoma
Iridotomy - laser which makes holes in iris, used to treat closed angle glaucoma
What kind of eye drops are used to decreased intraoccular pressure in glaucoma?
Lantanprost (prostaglandin analogue) - increases outflow of aqueous humor
Timolol (beta blocker) - reduces blood supply to cililary body, to reduce production of aqueous humor
Brinxolamide (carbonic anhydrase inhibitor) - inhibition of this enzyme slows production of aqueous humor
Pilocarpine (alpha adrenergic angonist) - contracts cililary muscle, causing trabecular meshwork to open
After someone has had an episode of acute closed angle glaucoma, how would you then manage the other eye?
Need to treat the other eye prophylacticly to prevent condition occurring in the other eye in the future
Done using peripheral iridotomy
Why should tropicamide be carefully used in patients with primary open angle glaucoma?
Dilating the eyes can cause a narrowing of the draining angle
What are the rules surrounding gluacoma and driving?
Patients should inform the DVLA if they have glucoma, which will then conduct their own specific tests to see if their eyes meet the current driving standards
How might glaucoma present on examination?
Normal visual acuity Reduced visual peripheral fields Cupping seen on fundoscopy - increased cup to disc ratio Optic disc pallor on fundoscopy Bayoneting of vessels seen on fundoscopy
Patients recently diagnosed with gluacoma should inform which people?
DVLA - to check if eyes meet standards
Family - as glaucoma has genetic component so relatives should get their eyes screened by local optician
What piece of medial equipment is used to measure intraoccular pressure?
Tonometer
How does central retina artery occlusion present?
Sudden, painless loss of vision to one eye
Vision reduced to light perception only
Pupil barely reactive to light
Cherry red spot on fundoscopy
What is the cherry red spot?
During central retina artery occlusion the retina becomes Ischaemic
However choroidal circulation remains - this can be seen as the cherry red spot
This is present over the central fovea as this is where the retina is present
What are the risk factors for central retinal artery occlusion?
Diabetes Hypertension Hypercholesterolaemia Vascular disease Smoking
What other acute disease do you need to rule out in elderly patients presenting with symptoms of retinal artery occlusion?
Giant cell arteritis
How does retinal detachment present?
Sudden onset of floaters
Associated shadows
Painless
Normal vision
What are the risk factors for retinal detachment
Trauma Myopia (short sightedness) - as patients have larger eyeballs so retina is thinner at the periphery
How does orbital cellulitis present?
Painful eye
Proptosis
Periorbital infalmmation and swelling
Reduction in eye movements
Can have previous conjunctival infection
Patients may have systemic symptoms and fever