Flashcards in Disorders of the Retina Deck (53)
What does a slit lamp examine?
Anterior of the eye
-everything is reversed
What does an ophthalmoscope examine?
Posterior of the eye
-Everything right way up and round
-Bit like looking through a keyhole through
What does biometry do?
Measures shape and size of eye.
Commonly used to calculate power of the intraocular lens implants for cataract and refractive surgery
What does perimetry do?
Systematic measurement of visual field
What does a fundus camera do?
Takes a photo of the back of the eye (retina).
Like a large ophthalmoscope with a camera attached
What is optical coherence tomography?
Optical Coherence Tomography, or ‘OCT’, is a technique for obtaining sub-surface images of translucent or opaque materials at a resolution equivalent to a low-power microscope. It is effectively ‘optical ultrasound’, imaging reflections from within tissue to provide cross-sectional images.
Allows you to look at the fovea as a cross section
What is Fluorescein Angiography?
Medical procedure where a fluorescent dye is injected into the bloodstream. The dye highlights blood vessels in the back of the eye so that they can be photographed.
Describe Fleurescin and its reaction with the Blood-Retinal barrier
85% bound to serum proteins
15% unbound "free"
Inner + Outer Blood-retinal barrer
(retinal capillaries + zonula occludens respectively)
-Impermeable to fleuroscein
-Permeable only to "free" fluorescein
What light do you shine on the eye in Fluorescein angiography and what shines back?
Shine blue at the eye and green light given off
How do cones and rods differ?
Just cones at fovea
Cones more to do with central vision and colour
Rods more black and white and periphery of visual field
What does electrophysiology do?
Series of investigations recording electrical signals from the eye, optic nerve and brain in response to visual stimuli
What is an electroretinogram (ERG)?
Measures retinal function
Records action potentials within the retina.
Different waves measure different cells.
Can test both rods and cones
What is an electro-oculogram (EOG)?
Measures function of RPE and photoreceptors
Measures resting potential difference between the RPE and photoreceptors
-Max PD in light adapted eye
-Max PD in dark adapted eye
What is visually evoked potentials (VEP)?
Records optic nerve function
Measures electrical activity in the visual cortex in response to either a flashing light or a checker board pattern
What does reduced amplitude and latency in VEP indicate?
-Reduced cell number
-Ischaemic/traumatic optic neuropathy
-Reduced cell function
-Optic neuritis (demyelination)
What methods can you use to detect retinal pathology?
Visual acuity, visual fields, colour vision, RAPD
Optical coherence tomography (OCT)
What is RAPD?
Relative Afferent Pupillary Defect
In optic nerve pathology what is usually the first aspect of eyesight to go?
(before visual acuity and visual fields)
What causes sudden painless loss of vision?
-Central retinal vein occlusion
-Central retinal artery occlusion
-Ischaemic optic neuropathy
-Sudden discovery of pre-existing unilateral LoV
What can cause Central Retinal Vein Occlusion (CVAO)?
What can cause Central Artery Occlusion (CRAO)?
What are the two types of Ischaemic Optic Neuropathy?
What are the symptoms of Giant cell arteritis?
Loss of vision
What is the cardinal feature of giant cell arteritis?
Raised inflammatory markers
What is the gold standard in diagnosis of giant cell arteritis?
Temporal artery biopsy
What are the symptoms and signs of optic neuritis?
-Pain on eye movements
(nerve becomes inflamed)
(loss of colour first, esp red)
-Relative afferent pupil defect
-Swollen optic disc
What conditions cause gradual painless loss of vision?
-Age-related macular degeneration
-Open angle glaucoma
-Inherited retinal dystrophies
What is age-related macular degeneration?
Progressve loss of central vision
What are the two types of age-related macular degeneration?
Dry type (80-90%)
Wet type (10-20%)
-Neurovascular membrane (blood and fluid)