Retinal Disorders Flashcards
How does fundus fluorescein angiography (FFA) show a defect/damage in the retina?
Inner and outer blood-retinal barriers are impermeable to fluorescein, and choriocapillaris is only permeable to free fluorescein (15%), therefore the majority is kept within the retina, so a leak is indicative of retinal defect/damage
How does optical coherence tomography (OCT) work?
Uses light waves to take cross-section pictures of the retina, allowing each layer to be mapped and measured
How does electroretinogram (ERG) work?
Measures retinal function by recording action potentials within the retina
How does electro-oculogram (EOG) work?
Measures function of RPE and photoreceptors by measuring resting potential difference between RPE and photoreceptors
How are visually evoked potentials (VEP) measures?
Records optic nerve function by measuring electrical activity in the visual cortex in response to a flashing light or a checker board patter
What does reduced amplitude of VEP indicate?
Reduced cell number - ischamic/traumatic optic neuropathy
What does latency in VEP indicate?
Reduced cell function - optic neuritis
Causes of central retinal vein occlusion
Hypertension
Glaucoma
Hyperviscosity
Inflammation
Presentation of central retinal vein occlusion
Macular oedema
Causes of central retinal artery occlusion
Emboli
Inflamamtion
Presentation of central retinal artery occlusion
Pale retina with cherry-red spots
Types of ischaemic optic neuropathy
Arteritic (AION)
Non-arteritic (NAION)
Cause and presentation of arteritic ischaemic optic neuropathy
Giant cell arteritis
Headaches, weight loss, lethargy
Sudden painless vision loss in one and then both eyes
How do you differentiate between arteritic and non-arteritic ischaemic optic neuropathy?
Using blood tests for inflammatory markers, particularly ESR and CRP, as non-arteritic is not related to inflammation
Sign of ischaemic optic neuropathy seen on examination of the eye
Swollen nerve
Indistinct margins
Pale if atrophy has occurred