differemce between FAF and FNIAF
FAF is done using SLO uses 488 nm blue light and a 500 nm filter to isolate fluorescence other than lipofuscin FNIAF (NIA) is the fluorescence of melanin on RPE cells. uses excitation of 787 nm is less commonly used
visible light spectrum?
which is dangerous the short of long wavelength?
the short is sharp and cuts :) gamma, x-rays and UV short is less than 400 nm wavelength
where is the raio, IR and TV waves on the light spectrum?
on the red side >700 nm
what wavelength has more retinal penetration?
the longer the wavelength the better penetration longer is safer so ok to penetrate longer>700 longer on NIA for ex longer gets to the choroid
remember the longer WL the more penetration so the original lfilters were 580/590 then spaide did 580/700 so more penetration but spectralis dies 480/520 so barely starting on the visible light spectrum (that is why is blue) and is more superficial imaging thus letting have infor on RPE only..
its the SLO imagign by NIR (700-1400nm) Reveal info of -outer retina, RPE, bruchs - good to localize SRF
confocal SLO NIR
675 nm diode laser its the one used with OCT
uses principle of low-coherence interferometry uses principle of interferometry axial res
adverse effects of ICG
less than FA nausea and vomiting are super rare adverse events in less than 1% contraindicated if allergy to iodine and shellfish ICG contains 5% of iodine relative contrainidcation is metformin use an dliver disease
is water soluble low molecular weight 775 protein bound 98% does not leak the small choriocapillaris fenestrations Good to look at choroidal vessels. uses NIR 790-895 nm barrier filters of 500-810nm can be injected before or after FA metabolized in liver and excreted in bile videos of 30 fps good for feeder vessels that disappear super fast on FA good for occult lesions, polypoidal and RAP, tumors and white dot syndromes
Fa comes in 10% or 25% presentations bottles of 2 or 5 ml eliminated through liver and kidneys in 24-36 hours FA is molecular weight 376 DA 80% protein bound BLUE exitation (465-490) returns green (520-530) blue light enters green light exits yellow-green filter used so we capture only the green light from the fluorescein. injected and enters the ophthalmic artery in 8-12 seconds -choroidal phase 10-15 secs (PATCHY) -arterial phase fills the arteries - AV phase ends with laminar flow of veins (1 minute after injection). This is the PEAK of the study, the most beautiful image of vessels. -recirculation phase
FA side effects
yellow skin and yellow eyes x 12 hours yellow urine for 24-36 hours -nausea, vomit and allergic
what % of the eye is occupied by vitreous?
what is the vitreous composition?
water, collagen and Hyaloronan (WCH)collagen fibrils separated by hyaluran molecules
division of the vitreous?
core and cortex
what is the name of the potential space between the posterior lens capsule and the anterior vitrteous?an space that no surgeon wants to visit...
The Berger spacethe anterior vitreous has a pit called the patellar fossa
the vitreous attaches in a ring to the posterior lens capsule forming a ligament called?
extension of vitreopus base in respect to ora serrata?
2 mm anterior and 3 posterior so the magic 23
name the vitreous attachment sites?
the vitreous has some areas that are liquified and called?
Pre-cortical vitreous pocket (in front of macula) and area of martegiani around the optic nerve
which is the Ganglion cell richest area of the retina?
the macula (has 2 layers of GC) that is 50% of GC of the entire retina
why is the macula yellow?
because it has lutein and zeaxanthin
tell me the size ofmaculafoveafoveolaumbo
what is the most common place for peripheral retinal tears?
the vitreous base
what is white without pressure?
white-opalescent color of the retina wo indentationsharp demarkated marginsunknown reasonnormal findingcommonly mistaken with RD or retinoschisishttp://www.eyerounds.org/atlas/pages/white-without-pressure/index.htm
what is an ora bay?
posterior extension of pars plana
what is a meridional fold?
is a thickened radial extension of the retina in the pars plana
ora bay and meridional folds kid of the same but oposite because
ora bay is PP that goes in to retinameridional is retina that fold goes in to pars plana
what is the cone density at the fovea?
does the fovea contain rods?
no, only cones and muller cells
what % of fones are outside the fovea?
where is the highest density of RODS?
20degres from center 160,000/mm2
both cones and rods density decrease towards the peryphery
what is the photoreceptor part that has the Mitochondria?
the ellipsoid zone!!!!ir has the energy!!!that is why that line on OCT is soooo important!!
which retinal cells respond to light INTENSITY?
the amacrine cells (AMA con INTENSIDAD)
how many discs in the rods outer segment?
1000 piled discs
cone - bipolar conections are 1 to 1
cone with midget bipolarsas oposed to many rods with one bipolar
which is the 1st neuron of the visual pathway?
which is the 2nd neuron of visual pathway?
ILM formed by?
muller foot plates
how many layers of capillaries does the retina have?
- superficial (NFL)- capillary plexus superficial and deep (on either side of ONL)
what % of the oxigen to the retiina is supplied by retinal circulation?
only 5% !!!!!!!!!!!!!!!the 95% comes from choroid.
RPE cells characteristics
16 mirons in diamhexagonal and cuboidal
absorbs lightphagocytosis of cone and rod outer segmentsparticipates in fatty acid metabolismforms outer retinal blood barriesmantains subretinal spaceheals and forms scar tissue
cones and rods shed outer segments in a circadian rythm, how so?
rods in dawn (amanecer)cones in dusk (anocheciendo)pretty much the shed when they are done for the day
cis to trans?
thats is the retinal cycle
5 layers of bruchs membrane
basement membrane of RPEinner collagenelastin layerouter collagenchoriocapillarisBruchs is the ELASTIN SANDWICH
vessels that feed the choroid?
posterior cilliary arteries
normal choroidal thickness
max is 220 microns (0.22mm)
what is dark adaptation?
its the process by which, the photoreceptorsrecover sensitivity to light in the darkness after exposed to light.
how do you measure dark adaptation?
1. patient looks at a very bright light for few minutes (to bleach the photopigment ; bleach=lavado)2. patient placed in darkness for 20 mins3. measure time that the patient takes to see a small spot of light.This spot of light is projected 10-20 degrees from the fovea (highest rod concentration)
describe the dark adaptation curve
* after bleaching the photoreceptors and * after darkness for 20 mins * wait until photoreceptors recover sensitivity * the plot on the y axis is the sensitivity being 0 on top and increasing sensitivity going down * the x axis is the time to recover sensitivity * the graph has 2 branches or curves * the cones recover sensitivity first at 5-10 minutes, this represents the first plateau reaching maximal sensitivity at 5 mins * the plateau ends in the rod-cone break the rod-cone break is the point at which RODS become more sensitive than cones!! * then rods continue to increase sensitivity until final threshold or plateau is reached. *
what has been the classic device to measure dark adaptation?
what instruments can be used to measure dark adaptation?
* Goldman-weekers adaptometer * static perimeters (if you turn off the background light) light the HVF. * SST-1 (LKC scotopic sensitivity test) measures global adapted sensitivity
what is better, to measure? * final sensitivity level or * time of adaptation? * and how do you measure?
* its more useful to measure final sensitivity level * patch an eye for 30-45 minutes and then perform dark-adapted static perimetry to determine threshold at different retinal locations. This will tell you how widespread is the disease.
what diagnostic information can you get from doing dark adaptometry?
* gives the degree of involvement of each, the rods and the cones * in CSNB the rod branch or curve is absent so you only see the cone plateau * rod monochromatism (no functioning cones)the cone branch is absent * fundus albinopunctatus shows delayed dark adaptation for BOTH systems. In this case normal sensitivity may be reached at 3 hours other diseases with delayer DA * Stargardts * con-rod dystrophy * RP
* what diseases cause delayed DA?
* other diseases with delayed DA * Stargardts * con-rod dystrophy * RP * fundus albinopunctatus
what is retinal densitometry?
technique used to measure levels of rhodopsin
what is the result in CSNB of * DA * retinal densitometry?
* delayed DA - rod branch absent * normal amount and kinetics of rhodopsin This finding demonstrated that the problem was not at the photoreceptor but in the synapsis
how is the DA sensitivity level and time to reach sensitivity in AMD?
* decreased final sensitivity level * delayed time in dark adaptation These can predict development of advanced AMDAlthough older patients have the same phenomenon, age matched AMD patients phenomenon is more pronounced Histopathology shows that rods die first before cones not only in AMD but in aging patientsDeficits in dark adaptation do not always correlate with scotopic sensitivity
can you do DA sensitivity to colored stimuli?
yes * the rods are more sensitive to blue green than red * cones are equally sensitive to red, blue, green * if the cones are deade outside the fovea (where normaly are more rods than cones), the cones will be the primary cells and if you see that outside the fovea the sensitivity to red, green and blue is similar that means that the rods are gone.
what is ERG?
Its a MASS electrical response evoked from the ENTIRE retina by a brief flash of light
what are the ERG FIVE responses?
* Rod response : scotopic-dark adapted * Maximal combined response (dark adapted) * Oscillatory potentials (dark adapted) * Cone response: Single flash light-adapted * 30-Hz flicker responses (light adapted)
what are the basic standard 5 ERG responses
Dark adapted * Rod response : scotopic-dark adapted (-24 db light) * Maximal combined response (dark adapted) (0 db & 11 db) * Oscillatory potentials (dark adapted) (white 0 db) Light adapted:4. Cone response: Single flash light-adapted (0 db white light)5. 30-Hz flicker responses (light adapted) (0 db flicker)
what does the a and b wave represent?
a wave photoreceptor responseb wave bipolar AND MULLER
what are the scale axis of ERG waves (x and y)
x is in milliseconds (up to 250 ms)y is in MICROvolts (from -500 to 500)
how long does the entire a and b wave retinal response last in time?
150 milliseconds(the y axis goes up to 250 on the graph)
who do you measure a-wave and b wave?
* a-wave from baseline to trough * b wave from a-wave trough to b-wave peak
what is the implicit time?
the time from the stimulus to the trough (awave0 or to the peak (b-wave)
what are the best conditions to do an ERG?
* dilated well pupils * use contact lens method (burian-allen)
describe the ERG rod-response.how is it obtained?what is the significance?
* you have to dark adapt a patient for at least 20 minutes * flash a -24 db white light * this light is below the cone threshold * the response comes from rods only
describe the maximal combined response * how is it done? * what is the significance? what interesting feature you see in the waves?
* flash a 0db and an 11 db white light in the dark * generates a response from rods and cones. produces and a and a b wave * the interesting feature is that on the ascending b-wave you can see oscillatory potentials
what are the Oscillatory potentials?how are they obtained
- how many degrees of the field of view are tested with the following:
- HVF 10-2
- HVF 24-2
- HVF 30-2
- Tangent scree:
- HVF 10-2
- HVF 24-2
- HVF 30-2
- Tangent scree:
- Amsler ----------> central 20
- HVF 10-2 ----------> 20 degrees
- HVF 24-2 ----------> 48 degrees (48 vertical x 54 horizontal)
- HVF 30-2 ----------> 60 degrees
- Tangent scree:----------> 30 degrees sitting at 1m
- GVF----------> 180 degrees
- ON HVF:
- which patient is the trigger happy on HVF?
- sleepy, slow, unmotivated patient
- patient presses button on the blind spot
- marker of retinal sensitivity
- trigger happy is FALSE POSITIVES
- FALSE NEGATIVES
- fixation losses
- the MD is a marker of retinal sensitivity
how can you tell a patient on HVF is a trigger happy?
- due to HIGH FALSE POSITIVES
how can you tell the patient was falling asleep or was desmotivated ot tired during HVF?
due to HIGH FALSE NEGATIVES