Ophthalmology Flashcards
(9 cards)
Acute angle closure glaucoma
Red eye of an acute painful dull nature, with photophobia and reduced vision in a hypermetropic person is highly indicative of acute angle closure glaucoma.
The pupil in this condition is usually mid-dilated oval shaped.
The oval shape is due to the iris sphincter ischaemia from the high intraocular pressure.
Causes of visual field defects
- Central scotoma- optic nerve
- Bitemporal hemianopia- optic chiasma
- Incongruous homonymous hemianopia- optic tract
- Homonymous superior quadrantanopia- Temporal lobe
- Homonymous inferior quadrantanopia- Parietal lobe
- Homonymous hemianopia- posterior occipital lobe
Grave’s Eye Disease
Block replace( high dose carbimazole and thyroxine replacement) is the initial choice for managing thyrotoxicosis in patients with significant thyroid eye disease. This may be continued for up to 18 months until thyroid eye disease is stable.
> > Radioiodine leads to transient worsening of thyroid eye disease.
Proliferative Diabetic Retinopathy
Following panretinal laser photocoagulation up to 50% of patients have a noticeable reduction in their visual field
Pilocarpine
- Pilocarpine is a muscarinic agonist used in glaucoma.
- It stimulates muscarinic cholinergic receptors to increase aqueous humour outflow.
Visual Field Defects
> > Homonymous hemianopia
incongruous defects: lesion of optic tract
congruous defects: lesion of optic radiation or occipital cortex
macula sparing: lesion of occipital cortex
> > Homonymous quadrantanopias*
superior: lesion of the inferior optic radiations in the temporal lobe (Meyer’s loop)
inferior: lesion of the superior optic radiations in the parietal lobe
mnemonic = PITS (Parietal-Inferior, Temporal-Superior)
> .Bitemporal hemianopia
lesion of optic chiasm
upper quadrant defect > lower quadrant defect = inferior chiasmal compression, commonly a pituitary tumour
lower quadrant defect > upper quadrant defect = superior chiasmal compression, commonly a craniopharyngioma
Primary open angle Glaucoma
> > Prostaglandin analogues (e.g. latanoprost) Increases uveoscleral outflow
> > Beta-blockers (e.g. timolol, betaxolol) Reduces aqueous production
> Sympathomimetics (e.g. brimonidine, an alpha2-adrenoceptor agonist) Reduces aqueous production and increases outflow
> > Carbonic anhydrase inhibitors (e.g. Dorzolamide) Reduces aqueous production
> > Miotics (e.g. pilocarpine, a muscarinic receptor agonist) Increases uveoscleral outflow
Proliferative Retinopathy
Proliferative retinopathy
- Panretinal laser photocoagulation
following treatment around 50% of patients develop a noticeable reduction in their visual fields due to the scarring of peripheral retinal tissue
other complications include a decrease in night vision (rods are predominantly responsible for vision in low light conditions, the majority of rod cells are located in the peripheral retina), a generalised decrease in visual acuity and macular oedema
-Intravitreal VEGF inhibitors
often now used in combination with panretinal laser photocoagulation
examples include ranibizumab
strong evidence base suggests they both slow progression of proliferative diabetic retinopathy and improve visual acuity
- If severe or vitreous haemorrhage: vitreoretinal surgery
Relative afferent pupillary defect
Also known as the Marcus-Gunn pupil, a relative afferent pupillary defect is found by the ‘swinging light test’. It is caused by a lesion anterior to the optic chiasm i.e. optic nerve or retina
Finding
the affected and normal eye appears to dilate when light is shone on the affected
Causes
retina: detachment
optic nerve: optic neuritis e.g. multiple sclerosis
Pathway of pupillary light reflex
Afferent: retina → optic nerve → lateral geniculate body → midbrain
Efferent: Edinger-Westphal nucleus (midbrain) → oculomotor nerve
