Normal fundus 2 Flashcards
When do nerve fibres get myelinated?
Level of lamina cribrosa
Where do nerve fibres sometimes retain their myelin?
On the disc or the retina
What are myelinated nerve fibres?
Non progressive
non pathogenic condition
What are the two layers of capillaries of the fundus?
A superficial network in nerve fibre layer
A deep network at junction of INL and the OPL
What do you find in the central macula?
No capillaries
What is the outer layer of the retina supplied with?
By underlying choroidal circulation
What do the Blood vessels walls look like
Transparent
How is the light reflex formed by>?
Reflection at convex cylinder blood column
Reflection from the convex vessel walls
Both surfaces act as convex mirrors
What is the purpose of retinal vessels?
Supply oxygen and other nutrients from the blood to first six layers of the retina
What can you detect by assessing the blood vessels of retina?
Systemic diseases such as hypertension, diabetes, arteriosclerosis
What is the general rule for A/V and V/A crossing?
Arterioles dont cross arterioles
Venules dont cross venules
Where does the artery remain?
Arteriole remains at normal level of the nerve fibre layer and the venule dips to avoid the arteriole
What happens to A/V crossing in hypertension?
A/V crossing changes as venule is compresses by sclerosed arteriole may cause deflection of venule
What is the name for changes in course of the vessels?
Tortuosity
What are tortuosity of arterioles?
May be congenital - should be uniform across the fundus
isolated regions of arteriole tortuosity suggests sclerosis
What can pathology show?
Narrowing of arteries
increase in width of vein
What do arteries do ?
Arteries get narrower
What do veins do?
Veins get wider
What is the normal A/V ratio?
2/3
When do you find generalised narrowing of the arteries?
Healthy elderly px
How is severe narrowing of arteries caused?
Systemic hypertension
What does focal narrowing indicate?
Hypertension
what other signs can you see ?
Leakage of blood vessels
What does leakage of blood vessels show?
Haemorrhages (blood)
hard Exudates (lipids)
oedema (fluid)
How are vessels obscured?
Myelinated Nerve fibres
Pre retinal haemorrhages
What is type of Hyperplasia of fundus are there?
Choroidal neavus
Malignant Choroidal melanoma
Congenital hypertrophy of RPE (CHRPE)
Coloboma of retino choroid
What is a Choroidal neavus?
- round or oval shaped
- uniform slate grey or brown colour
- less than 3 disc diameter
- flat or min elevated
- underlying drusen
- benign
How are Choridal neavus caused?
Accumulation of melanocytes in choroid
What is a malignant choroidal melanoma?
- -Often mottled
- -Range in colour from white to greenish grey
- -larger than neavi
- -may present with serious retinal detachment
- -significantly elevated
- -overlying orange pigmentation (lipofuscin)
- -asymptomatic but may present with metamorphopsia, photopsia, visual field defect, hypermetropic shift
What is a congenital Hypertophy of RPE (CHRPE)?
- —-Congenital flat black lesion with sharp dramatic outline
- —-Ring of hypo pigmentation is frequently seen
- —-benign
What is a coloboma of retino (choroid)?
>Large white oval lesion in fundus >usually inferior nasal region >effect iris and lens as well as fundus >unilateral and bilateral >visual field defect >amblyopic px >non progressive
How is coloboma caused?
Failure of embryonic fissure to close
what does the macula look like?
Centre of macula is 1.5 to 2 DD temporal to disc and usually just below the centre of the disc
Shape usually oval with long axis horizontal
bit bigger than optic disc
centred on the fovea
What is the foveal reflex ?
Bright spot of light at the centre of the macula
Image of ophthalmoscope beam formed by the concave surface of the fovea acting as a concave mirror
What is the major cause of blindness and partial sight?
Diabetic retinopathy
ARMD
Taxoplasmosis
