Opthalomology Flashcards
Small depression in centre of macula
Fovea
Where is the highest concentration of cones
Macula, highest visual acuity area. 3mm temporal from optic disc.
In the centre is the fovea with the highest concentration of cones
What are cones
Found in central retina
Colour vision and acuity
What are rods
Found in outer retina
Night vision
How can you test visual acuity
Snellen chart at 6 metres away.
20/80 = the pt can read at 20 feet what a person can normally read at 80 feet.
Name some risk factors for cataracts and causes
Ageing High-dose corticosteroids Smoking Exposure to UV B light. FHx Co-morbidities = Diabetes mellitus, Atopic dermatitis/eczema, Neurofibromatosis type 2.
Causes:
Complication of secondary eye disease - anterior uveitis acute angle-closure glaucoma.
Trauma to eye - electric shock, radiation, blunt or penetrating trauma to eye, from surgical procedures to eye.
What are cataracts
Opacity that forms within the eye lens.
Presentation of cataracts
- Gradual, PAINLESS, reduced viral acuity. Pt will find difficulty in reading, watching TV, recognising faces.
- Visual difficulty in bright light/glare.
- Radial reduction in colour intensity perception.
- Monocular diplopia.
- Poor sight despite glasses/frequent change of lens prescription.
O/E
- With ophthalmoscope = opacity of lens, reduced red reflex.
- Slit lamp shows opacity.
- Reduced acuity with Snellen Chart.
Mx of cataract (including risks and benefits)
- Decision for surgery based on impact not on clinical extent of disease.
- Phacoemulsification surgery + intraocular lens implant. This involves removing the nucleus of the lens and inserting an implant to prevent the patient having a high refractive error.
- Benefits = improved visual acuity, colour vision and clarity of vision.
- Risks = capsular opacification, intraocular infection (endophthalmitis) and some other.
- Fitness to drive a car = contact DVLA and can’t drive if they can’t read a number plate and must be at least Snellen 6/12.
Presentation of congenital cataract or severe age-related cataract
Leukocoria - white pupillary reflex.
Types of age-related macular degeneration
Dry
- Geographic atrophy
- Drusen = waste products build up in and below retinal pigment epithelium and are seen as yellow spots on retina. Also get pigmentary changes on retina (hypo or hyper).
Wet
- Exudative
- Neovascular age related macular degeneration = new blood vessels in retina which can easily bleed and leak serum causing scarring of retina. More rapid loss of vision.
Can get a change from dry macular degeneration to wet!
Modifiable and non-modifiable risk factors for macular degeneration
Modifiable = smoking, HTN. Non-modifiable = age, FHx, blue iris.
Mx of age-related macular degeneration
Lifestyle advice = increase vitamin A–> eat more dark green leafy veg + oily fish. Weight loss to control BP and stop smoking.
If advanced wet AMD = can use anti-VEGF
Register as blind.
Presentation of macula degenreation
Dry - central scotoma, good peripheral vision, straight lines appear wavy. O/E - Drusen can become confluent, geographic atrophy and pigmentary changes
Wet - more rapid vision loss. Central distortion and central scotoma. O/E - Drusen, choroidal neovascularisation and exudate.
Complain of = difficulty reading, need larger prints, straight lines are wavy (metamorphopsia), central grey patch (scotoma), poor adaptation to dark.
Ix for age related macula degeneration and Management
Amsler grid = metamorphopsia, scotoma. Advise those with dry AMD who may develop wet AMD to test often.
Fundscopy, Slit-lamp biomicroscopy, ∆ = ocular coherence tomography.
Vitamin supplementation, lifestyle advice, register as visually impaired.
Rx is limited. Wet AMD can be helped with anti-vascular endothelial growth factor e.g. Ranibizumab.
Normal intra-ocular pressure
11-21mmHg
What is this angle they speak of in glaucomas and how does it cause the disease?
- Space between posterior surface of cornea and anterior surface of iris. Where trabecular meshwork is to drain aqueous humour.
- Can get closed or open glaucoma depending on whether there is clogging of meshwork (open) or lens pushed onto iris occluding flow of aqueous humour (closed).
- Increase in intra-ocular pressure damages optic nerve.
Main drainage aqueous humour
Trabecular meshwork. At apex of anterior chamber angle. From trabecular meshwork it drains to Canal of Schlemm and to episceral veins.
Ways to classify glaucoma
Open or closed anterior chamber angle
Acute or chronic
Cause - primary or secondary
Age of onset - infantile, adult etc.
Risk factors and secondary causes of open angle glaucoma.
- Open more common than closed + less likely acutely presentation.
- RFx = older age, black ethnicity, FHx, use of corticosteroids, T2DM, HTN and CVD, MYOPIA
- 2nd causes = neovascular and ischaemia, angle-recession from trauma.
Risk factors and secondary causes of primary closed angle glaucoma.
- RFx = old age, female, asian ethnicity, FHx.
LESS COMMON IN MYOPIA. - 2nd causes = sublimated lens, chronic anterior uveitis.
Presentation of primary open angle glaucoma
Tunnel vision (arcuate scotoma, join to form ring scotoma) and later total vision loss. Visual acuity is usually alright. O/E with ophthalmoscopy = cupped optic disc as loss of neurones.
Presentation of primary closed angle glaucoma
Acute angle closure = painful, red eye, blurred vision, sees halos around lights, poor visual acuity.
Headache, nausea and vomiting.
Pupil is fixed in a vertically oval shape.
Chronic angle closer glaucoma = tunnel vision, ophthalmoscopy shows cupped optic disc.
Triad for glaucoma
Raised IOP >21mmHg
Abnormal optic disc (cupped, haemorrhage)
Visual field defect.
How to measure intra-ocular pressure
Tonometer
Mx for acute closed angle glaucoma
- Lie flat facing upwards (no pillows).
- Pilocarpoine eye drops (2% if blue eyed, 4% if brown eyed).
- Acetazolamide/Diamox to reduce aqueous humour production.
- Laser iridotomy for acute closed angle glaucoma.
Ix and Mx for non-acute glaucoma
Ix - visual fields, measure pressure with tonometry, view retina with ophthmoscopy = cup-to-disc ratio over 0.6.
Reduce pressure via
- reduced aqueous humour production with topical beta-blockers (timolol ophthalmic).
- increased outflow of aqueous humour with topical prostaglandin analogue (latanoprost).
- achieve both with topical alpha-2 adrenergic agonist (apraclonidine ophthalmic).
Laser treatment
- Laser trabeculoplasty for open angle glaucoma
- Laser iridotomy for closed angle glaucoma.
3 causes of gradual vision loss
Cataract.
Chronic open-angle glaucoma.
Age related macular degeneration.
What genetic condition is associated with cataracts
Down’s syndrome
High intra-ocular pressure but normal disc and visual fields
Ocular hypertension.
Differentials for sudden loss of vision
- Vascular occlusion including: Branch/central retinal artery occlusion. Branch/central retinal vein occlusion. Anterior ischaemic optic neuropathy. - Inflammation with optic neuritis. - Retinal detachment.
Pathology behind a rapid afferent pupillary reflex and some causes
Affected eye has pathology with optic nerve so can not process visual information at all. In normal Leith both pupils are the same size.
- Shine light in affected eye and neither eye react as no information of light is processed.
- Shine light in unaffected eye and both will constrict as pathway in this eye is intact.
- Shine light back on affected eye and the pupil will dilate to the normal ‘resting’ size (appear to dilate to light but actually just re-adjusting).
Causes = retinal detachment, central retinal artery occlusion, optic neuritis, anterior ischaemic optic neuropathy, advanced glaucoma.
Retinal vein occlusion presentation
Branch occlusion will have less severe loss of vision, more blurriness and visual field defects.
Central retinal vein occlusion = painless, sudden, unilateral vision loss. Less acute onset than artery occlusion.
O/E
- Relative afferent pupillary defect.
- Dilated and tortuous retinal veins (neovascularisation), cotton wool spots, retinal and disc oedema, intra-retinal flame haemorrhages. (looks a bit like pizza).
- Ix = fluorescein angiography
Rfx for retinal vein occlusion
Hypertension
Atherosclerosis
Diabetes mellitus
Blood coagulation disorders e.g. Factor V Leiden.
Mx for retinal vein occulsion
Must establish retinal perfusion with Fluorescein angiography.
Laser photocoagulation
Intravitreal steroids
Retinal artery occulsion
- Similar Rfx as for stroke/emboli (atherosclerosis, aortic stenosis, Factor V Leiden)
- Sudden, unilateral, painless vision loss with central artery occlusion. Altitudinal loss with branch occlusion.
- O/E relative afferent pupillary defect. CHERRY RED SPOT (fovea) + RETINAL OEDEMA (pale). Maybe able to visualise emboli. If a branch is occluded only a sector of the retina will be pale.
- Ix could include carotid artery doppler USS.
- Can not cure vision back but can manage risk factors to prevent reoccurence e.g aspirin, clopidogrel.
What is amaurosis fugax
Transient monocular visual loss.
‘Curtain coming over vision.’
Complete resolution usually within 30mins.