Sample Qs 3 Flashcards
What is ERG
What is the method?
ERF records mass electrical activity from retina stimulated by flash of light
Full field simulation
Electrodes corneal contact/bulbar conj
Rod response in DA eyes (after 30 mins in dark) with dim white flash below cone sensitvity and b wave only
Maximal ERG - DA eyes using bright white flash - mixed rod and cone repsonse
Photopic response - background that surpresses rod acctivity and single flash cone response in light adapted eyes (after 10 mins in light(
Cone derived flicker using 30Hz white light flicker
Where to ERG a waves come from? b waves? Oscillatory potentials
a - photoreceptors
b - bipolar and Mullar cells
OP - amacrine cells
How do ischaemic and non-ischaemic CRVO differentiated on ERG
b wave affected by large areas of ischaemia
Reduced b amplitude
Reduced b:a wave ratio
Prolonged b wave implicit time
What is the ERG change in achromatopsia
Abnormal photopic and normal scotopic ERG
Absent flicker
What is the ERG change in CSNB
Normal a wave, reduced scotopic b wave
What conditions have reduced a and b waves on ERG
Rod/cone dystrophy
Total RD
Metallosis
Drug toxicity
Autoimmune retinoapthy
CAR
Ophtahlmic artery occlusion
What conditions have normal a and reduced scotpic b waves on ERG
CSNB
XL retinoschiasis
CRAO CRVO
Myotonic dystrophy
Melanoma associated retinopathy
Quinine tox
What gives reduced oscillatory potentials on ERG
Drug tox - vigabatrin
What is achromatopsia
Rod monochromatism
Autosomal recessive
Lack of cone function of all 3 subtypes
Poor VA and CV from birth
Pendular nystagmus
Photophobia
Normal fundus
ERG: reduced photopic, normal scotopis -
What is CSNB
Early non progressive nyctalopia
Associated with reduced VA, refractive error (myopia commonly), nystagmus, strabismus
Normal fundus vs abnomral fundus
Mutations in NYX GRM6 TPRM1
What ERG abnormalities in CSNB
Complete CSNB - no dtectable rod ERG, electronegative bright flash response - reduced b wave to a wave ratio - inner retinal dysfunction
incomplete CSNB - detectable rod specifc ERG and negative bright flash response
cones more abnormal than in cCSNB
What are risk factors for ROP
Low gestational age (<32 weeks)
Low birth weight (<1500g)
High or variable oxygen tension
What are ROP Stages ICROP
Stage 1 - demarcation line - flat white line separating vascular from avascular zones
Stage 2 - ridge - line becomes elevated and thickened, may become pinkish with neovascular tufts posterior to ridge
Stage 3 - ridge with extraretinal fibrovascular proliferation - vascular tissue grows from posterior margin on to retina or into vitreous
Stage 4 subtotal retinal deteachment - extrafoveal 4A or foveal 4B
Stage 5 - total RD
What is plus disease
Significant venous dilatation and arteriolar tortuosity
(compared with standard photo)
of the posterior retinal vessels in two or more quadrants
What is pre-plus disease
There is more venous dilatation and arteriolar tortuosity than normal but insufficient to be plus disease
What are zones of ROP
Zone I - circle centered on disc with radius twice the distance from the centre of the disc to the fovea
Zone II - ring centered on the disc, extending from zone 1 to the ora nasally and the equator temporally
Zone III - remaining temporal crescent
What is threshold disease?
Stage 3 ROP WITH
Plus disease in zone I or II
AND OF
5 continuous or 8 non-continuous hours of disease
What babies must be screened for ROP
<31 week gestational age
<1251g birthweight
When is the first screening examination
Babies born <27wks - 30-31 wk post-menstrual age
Babies born between 27 and 32 weeks
4-5 week postnatal age
> > 32 wk gestational age but < 1501g weight
4-5 wk postnatal age
How frequently to screen if vessels end in zone 1 or posterior zone 2
Weekly
How frequent to screen plus or pre-plus or stage 3 disease
Weekly
When can you terminate screening in babies with no ROP
Vascularization has extended into zone III - 36 completed weeks post-menstrual age
When can you terminate screening in babies with ROP no requiring treatment
2 successive exams showing:
Lack of increase in severity
Partial resolution
Change in colour in ridge from salmon pink to white
Transgression of vessels through the demarcation line
Commencement of the process of replacement of active ROP lesions by scar tissue
What ROP to treat
Zone 1 , any ROP with plus disease
zone 1, stage 3 without plus disease
zone 2 stage 3 with plus disease
Consider treateing zone II stage 2 with plus disease
