Normal fundus 2 Flashcards
are myelinated nerve fibres (feature of the optic disc) physiological or pathological
physiological, but not present on most people
it i non-progressive and benign
when are nerve fibres usually myelinated until
not myelinated until the lamina cribrosa
where can nerve fibres sometimes retina their myelin sheaths
on the disc or the retina
why are retinal ganglion axons usually unmyelinated as they cross the retina
because even though myelin sheaths speed up nerve transmission, if the RGC axons were myelinated across the retina, we won’t be able to see anything as they’re opaque, so it will block the light hitting the retina
what symptoms will a person have if they have myelin sheaths on their retina
visual field defect corresponding to there the myelin sheaths are on the retina
what is the appearance of the nerve fibres as a result of myelin sheaths on the retina
normally transparent nerve fibres now appear a brilliant white against the fundus background
describe the two layers of capillaries that are over most of the fundus
- a superficial network in the nerve fibre layer close to the vitreous
- a deep network at the junction on the inner nuclear & outer plexiform layers
where in the retina are no capillaries found
central macula
what are the outer layers of the retina e.g. photoreceptors supplied by
the underlying choroidal circulation which is not directly visible with the direct ophthalmoscope
what circulation is seen when doing ophthalmoscopy and what does it consist of
the inner retinal circulation only, consisting of central retinal arteries & veins which branch out to supply the inner retinal layers & those two capillary networks are found in the retina
what is the appearance of a normal blood vessel wall and what is visible when seen with the direct ophthalmoscope
normal walls of bv’s are transparent and only the blood column of the vessels is seen
what is a notable feature of arterioles seen as a reflex in the ophthalmoscope light
linear light reflex which is a light following the arterioles
what 2 things is the linear light reflex seen in the arterioles formed by
- reflection from convex, cylindrical blood column
- reflection from convex vessel wall
- both surfaces act as convex mirrors
linear light reflex is more obvious in arteries than veins
what is the purpose of the retinal vessels
to supply oxygen and other nutrients from the blood to the 6 inner layers of the retina & take away waste materials
what does the health of the retinal vessels reflect upon
the health of the circulation throughout the body
what does examination of the retinal blood vessels assist in
detection and monitoring of systemic diseases e.g. hypertension, arteriosclerosis, diabetes
what do arterioles not cross
other arterioles
what do venules not cross
other venules
what is the normal positions of the arterioles and venules in the retina
usually
arterioles remain at normal level in the nerve fibre layer and venule dips to avoid the arteriole, called a/v crossing (artery crossing over vein)
what is the normal appearance of the route of the arterioles and venules at the a/v and v/a crossings in the retina
retinal vessels normally curve very gently with no deflections at the a/v and v/a crossings = carry on in their normal directions & don’t look like they’re being squashed
what 2 things does hypersensitive retinopathy cause to the retinal blood vessels
- a/v nipping
- tortuosity (BV’s become wiggly)
how does a/v nipping occur
a/v crossing changes are caused, where the underlying venule is compressed by the sclerosed/hardened artery as it crosses over and causes pressure on the vein which gets pinched by the artery
what can a further hardening of the arteriole in the retina cause to the course of the venule
may cause deflection of the venule which means it changes directions in right angle
what is a normal cause of tortuous arterioles
congenital which should then be uniform across the fundus
what does isolated regions of arteriolar tortuosity suggest
sclerosis of arteriole due to high blood pressure
what do pathological changes to the arterioles cause to their appearance
causes arteriole narrowing
what do pathological changes to the venules cause to their appearance
an increase in width
what does pathological changes in vessel calibre (thickness) cause to the a/v ratio
it gets altered to e.g. 1/4 or 1/5
what is a normal a/v ratio considered to be
2/3
how are you supposed to check the a/v ratio in order to detect change in vessel calibre
- chose vessels of comparable order of branching i.e. vessels that branch by the same amount
e. g. if artery we’re looking at has branched twice since the optic disc, then compare that with a vein thats branched twice since the optic disc
what naturally happens to the vessel calibre of all the vessels the further away they get from the disc
get narrower the further away from the optic disc
what two things must you look for when detecting abnormal changes e.g. from hypertension in vessel calibre (thickness)
- focal narrowing
- generalised narrowing to arterioles (severe narrowing in the case of hypertension)
when is mild generalised narrowing of the arteriole normal
found in a healthy elderly fundus
what does focal narrowing of the vessels look like
a patch of narrowing of changes of vessel thickness as you go along
what is leakage of a vessel a sign of
pathology
what 3 things are shown in a fundus when a blood vessel leaks
- hard exudates (lipids)
- haemorrhages (blood)
- oedema (fluid e.g. plasma or serum)
what is oedema fluid e.g. plasma or serum viewed in a OCT scan as
dark patches within the reflective layers
which imaging technique is oedema hard to view
in fundus photography, may see a bit of swelling
in a healthy eye, what is the only non visible part of the vessel
the part of the vessel (e.g. of a venule) that is obscured by an arteriole at an a/v crossing
by what 2 things may a vessel be obscured in a non usual way
- myelinated nerve fibres
or - pre retinal haemorrhages obscures the retina
how does a inner retinal haemorrhage occur
when the inner circulation has bled into the vitreous cavity
name 3 causes of hyperplasia of pigment in the retina
- choroidal naevus
- malignant choroidal melanoma
- congenital hypertrophy of the RPE - CHRPE
what is a choroidal naevus
a harmless area of increased pigment of the choroid
what colour does a choroidal naevus appear
uniform slate grey or brown colour
what shape does a choroidal naevus appear
round or oval
how large are most choroidal naevus
less than 3 disc diameters in diameter
how deep is a choroidal naevus and how can you tell this
flat or minimally elevated, blood vessels passing over will stay in focus & not change course
what can also be spotted on top of a choroidal naevus
overlying drusen speckled on top of it (white spots)
what must you note down when looking at the retina as seen by the ophthalmoscope
any pigment deposition seen in retina
is a choroidal naevus dangerous
no it is benign and won’t cause any problems to the patient at all
what causes a choroidal naevus
accumulation of melanocytes in the choroid
what is the cause of a malignant choroidal melanoma
a cancerous tumour which can metastasise = life threatening
what colour and appearance is a malignant choroidal melanoma
ranges in colour from white to greenish grey and has a mottled appearance
how large is a malignant choroidal melanoma
often larger than a naevus >3 disc diameters
if a malignant choroidal melanoma is larger than 3 disc diameters in size, what 2 things can this cause
- a serous retinal detachment
- disrupts transport between fluid & RPE
how deep is a malignant choroidal melanoma and how can you tell this
significantly elevated
ophthalmoscope will go out of focus as it passes over it and the blood vessels also goes higher as the melanoma acts as a bridge so it looks like the blood vessels are changing direction
what may be found overlying a malignant choroidal melanoma
orange pigment = lipofuscin
what symptoms are presented with a malignant choroidal melanoma
often asymptomatic, but may present with: - metamorphopsia - photopsia - visual field defect - hypermetropic shift all of which disrupt vision
what action must be taken when seeing a malignant choroidal melanoma
urgent referral
what is congenital hypertrophy of the RPE (CHRPE) caused by
congenital hyper pigmentation of the RPE
what appearance of congenital hypertrophy of the RPE (CHRPE)
a flat black lesion with sharply remarked outline, darker than a naevus
what is also frequently seen around congenital hypertrophy of the RPE (CHRPE)
ring of hypo pigmentation
is congenital hypertrophy of the RPE (CHRPE) dangerous
no it is benign
what must you do to monitor a congenital hypertrophy of the RPE (CHRPE)
take a photo to monitor and make sure it doesn’t change size
what is the appearance of a coloboma of (retina) choroid
large, white oval lesion in fundus, benign, non-progressive appearance of retina
what is the appearance of a coloboma of (retina) choroid
large, white oval lesion in fundus, benign, non-progressive appearance of retina, can see right through to sclera underneath
where abouts is a coloboma of (retina) choroid usually found in the retina
usually inferior nasal region
what is a coloboma of (retina) choroid a result of
failure of the embryonic fissure to close = missing part of retina
can a coloboma of (retina) choroid affect one or both eyes
can be unilateral or bilateral
what symptoms may a px with coloboma of (retina) choroid experience
visual field defect corresponding to the missing part of retina e.g. superior temporal VF defect if the coloboma is at the inferior nasal region of fundus
what other visual problem may a px with coloboma of (retina) choroid have
px is often amblyopic
how far away is the centre of the macula from the optic disc
1.5 - 2 disc diameters away
where is the macula located in the fundus
temporal to and slightly lower than the disc
what is the shape of the macula
oval with the long axis horizontal
how large is the macula
a bit larger than the optic disc ~20 degrees diameter
where is the macula entered on
the fovea
where does the colour of the macula come from
accumulation of macula pigment
what component of the fundus does not permeate around the macula
blood vessels
what is the name of a macular reflex
foveal reflex
what is the appearance of a normal foveal reflex
bright spot of light at centre of fovea
what is the only real landmark on a healthy macula
bright foveal reflex
how is a macular/foveal reflex formed
by an image of the ophthalmoscope beam formed by the concave surface of the fovea (foveal pit), acting as a concave mirror
what can someone with early ARMD go on to get
dry or wet stages
what stages can someone with early ARMD go on to get
dry or wet stages
what dos early stages of ARMD show
extensive drusen
what is drusen
pockets of the RPE layer
what characteristic signs on the retina does wet AMD cause
exudates and haemorrhages of the blood vessels
what does dry AMD cause
death/atrophy of the retina & RPE in that area of the macula, causing a complete scotoma corresponding to the atrophy, also called geographic atrophy
what characteristic signs of the retina does dry AMD cause
can see through to underlying choroid where retina & RPE have died away
what is toxoplasmosis caused by
a parasite
what are the symptoms of toxoplasmosis if its in the periphery
none
what is the appearance of an inactive toxoplasmosis
sharply defined edges & pigmented
what are the symptoms of toxoplasmosis if its on the macula
complete scotoma
what is the appearance of an active toxoplasmosis
it means the parasite is still there, and has more of inflammation & pigmentation comes in a later stage
