Lecture 1/2 - Diagnostics Flashcards
What is red light/filter used for?
travels the furthest - pigmentary disturbances, choroidal ruptures, choroidal nevi, choroidal melanomas
What is blue light/filter used for?
NFL, ILM, ERM, retinal folds, cysts
What is green light/filter used for?
retinal vasculature, hemorrhages, drusen, exudates
what are the 4 parts to the early phase in FA?
choroidal flush, arterial phase, arteriovenous phase, and venous phase
when is the choroidal flush?
10-15 seconds after injection, dye in choriocapillaries
when is the arterial phase?
1-2 seconds after choroid - about 12 seconds
a delay may indicate injection or circulatory problems = heart or peripheral disease
when is the venous phase?
about 30 seconds after injection - maximum vessel filing
what are the 3 main phases of FA?
early phase, mid phase (recirculation phase) and late phase
when does the mid phase occur?
2-4 minutes - veins and arteries remain roughly equal in brightness
when does the late phase occur?
7-15 minutes - gradual elimination of dye from retinal and choroidal vasculature (late staining of optic disc is normal)
what are the 2 main causes of hypofluorescence?
vascular filling defect or blockage
if you use a red-free filter to view a dark spot on the retina and it disappears, what was it?
choroidal nevus (CHRPE will remain with red-free)
what 2 conditions can cause autofluorescence (or preinjection fluorescence)?
optic nerve drusen and optic nerve hemartoma
what causes pseudofluorescence?
poorly matched filters
what can cause early hyperflorescence in the retina?
abnormal vessels = tortuosity, dilation, anastomosis, neo, aneurysms, telangiectasia, tumor vessels
what can cause early hyperflorescence in the choroid?
PE window defect = atrophy or congenital
Abnormal vessels = subretinal neo, inflammation, tumor vessels
what can cause late hyperflorescence in the vitreous?
neo, inflammation, tumors
what can cause late hyperflorescence in the retina?
cystoid edema or non-cystic edema
what can cause late hyperflorescence in the choroid?
pooling or staining
what is leakage hyperfluorescence?
seepage of NaFl, increases in intensity and margins blur in late phase (Ex: CNVM, DME, Neo)
what is staining hyperfluorescence?
dye enters tissue and it retains it - intensity increases during transit but then stays the same, margins are distinct (Ex: scar, drusen, optic nerve tissue or sclera)
what is pooling hyperfluorescence?
accumulation of dye in a fluid-filled space in the retina or choroid, margins are distinct (Ex: RPE detachment in CSR)
what is transmission/window defect hyperfluorescence?
increased normal choroidal fluorescence through RPE defects or loss of pigment - dye stays in choroid, does not enter retina (Ex: macular hole or RPE loss)
how is ICG different than NaFl?
higher molecular weight, remains in larger blood vessels (cannot pass through choriocapillaris fenestrations) and is not blocked by melanin/xanthophyll
what are the contraindications for ICG?
caution with history of iodine or shellfish allergy and contraindicated in liver disease or DM on Metformin
what is OCT used for?
lamellar vs. pseudo/full thickness macular holes, VMT, DME, CSR, AMD
what structures in the eye normally autofluoresce?
corneal epithelium/endothelium, lens, macular and RPE pigments
why is autofluorescence useful in Bests Disease?
RPE cells are eating up dye and appear hyper (lipofuscin) and RPE cells are dead are hypo
what is near infrared reflectance imaging used for?
better resolution of outer retina - RPE, bruch’s, and choroidal vessels are more detectable (uses melanin)
what is adaptive optics?
uses very high transverse resolution (2um) and capable of visualizing rod photoreceptors
what frequency B-scan do we normally use in clinic?
7-10 MHZ (medium) = retina, vitreous, optic nerve
when do you use increase gain on a B-scan?
increased tissue penetration and sensitivity but decreased resolution = hemorrhage, syneresis, posterior hyaloid, inflammatory cells
when do you use low gain on a B-scan?
good resolution but poor sensitivity = layers or membranes, hyaloid, retina, choroid, retinal break/tear, tumor, macular edema, holes
what is an electroretinogram (ERG) and what are the 3 waves?
mass response evoked from the entire retina = A wave is late receptor potential, B wave is on-bipolar potential and C wave is inner retinal potentials
when are the inner retinal potentials/C wave (oscillatory potentials) reduced in an ERG?
retinal ischemic states and in some forms of congenital stationary night blindness
what do focal and multifocal ERG test?
foveal or parafoveal cones (topographic ERG map of the retina is produced) = plaquenil toxicity
what does a bright flash ERG test?
performed pre-op for severely traumatized globes with a brighter than usual stimulus - un-recordable response is a poor prognosis (moderate signal suggests some salvageable retina)
what is a pattern ERG?
alternating checkerboard presented to central retina - integrity of optic nerve, ganglion cells and their retinal interactions (early recognition of glaucoma)
what conditions have an abnormal ERG?
foveal disease, RP, CRAO
what is an elector-oculogram (EOG)?
measures a response from the RPE (+ corneal end and - retinal end)
what disease is the EOG severely reduced?
Best disease
what is a visually evoked cortical potential (VEP)?
electrical signals generated by occipital visual cortex in response to stimulation of the retina
what does the VEP response look like?
2 (N) negative and 2 (P) positive peaks
when is VEP used?
assessing misprojection, estimating VA, detecting/localizing VF defects, visual potential, amblyopia/optic neuritis prognosis
what is a sub-normal, severely abnormal and nearly extinguished Arden ratio in EOG?
less than 1.86 and less than 1.30
