What is the mechanism of papilloedema?
The main mechanism of visual loss in papilledema is likely due to a translaminar elevation of the CSF pressure gradient that is transmitted down the optic nerve sheath from the intracranial cavity and produces axoplasmic flow stasis and resultant intraneuronal ischemia.
What is the principle of FFA in ophthalmology?
FFA is based on the principle of fluorescence. Luminescence is emission of light from any source other than high temperature. Fluorescence is luminescence maintained by continuous excitation. Fluorescent molecules have property to emit light energy of longer wavelength when stimulated by a shorter wavelength.
What is the pathophysiology of papilledema?
Papilledema is caused by transmission of elevated ICP to the subarachnoid space surrounding the optic nerve that hinders axoplasmic transport within ganglion cell axons. There is ongoing controversy as to whether axoplasmic flow stasis is produced by physical compression of axons or microvascular ischemia.
How is Papillitis differentiated from papilloedema of raised intracranial pressure?
Papillitis can be differentiated from papilledema by an afferent pupillary defect (Marcus Gunn pupil), by its greater effect in decreasing visual acuity and color vision, and by the presence of a central scotoma. Papilledema that is not yet chronic will not have as dramatic an effect on vision.
What is the relationship between increased intracranial pressure and papilledema?
Papilledema results from orthograde axoplasmic flow stasis at the optic nerve head leading to edema of the nerve from the increased intracranial pressure pressing on the nerve behind the eye.
What is FFA used for?
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What are the phases of FFA?
Fluorescein angiograms progress through five phases: pre-arterial (choroidal flush), arterial, arteriovenous, venous and late recirculation. The process begins with injection of sodium fluorescein dye into the antecubital vein.
What is the difference between papillitis and papilloedema?
You have 3 more open access pages….comparison of papilloedema and papillitis.
| papilloedema | Papillitis |
|---|---|
| large blind spot | large central scotoma |
| peripheral constriction of visual fields | pain on eye movement |
| usually normal colour vision | partial loss of colour vision |
| increased intracranial pressure | may be associated with multiple sclerosis |
What is Foster Kennedy syndrome?
Foster-Kennedy Syndrome is characterized by unilateral visual loss with a compressive optic atrophy in one eye and contralateral papilledema caused by increased intracranial pressure. The same ophthalmoscopic features however can be seen in the pseudo-Foster-Kennedy Syndrome.
What is the mechanism of increased intracranial pressure?
The three major mechanisms of increased ICP are (1) increased intracranial volume due to an intracerebral mass lesion (e.g., tumor, massive infarction, trauma, hemorrhage, abscess), extracerebral mass lesion (e.g., tumor, hematoma, abscess), or acute brain swelling (e.g., anoxic states, acute hepatic failure.
What is the difference between FFA and acid value?
Acid value (AV) is the milligrams of potassium hydroxide required to neutralize the FFA in one gram of fat. It is independent of molecular weight and, coincidentally, is almost twice the FFA% when the latter is expressed on an oleic-acid basis.
What causes high free fatty acids?
CIRCULATING FREE FATTY acids (FFAs) mainly originate from lipolysis in the adipose tissue; they contribute to insulin resistance and are elevated in obesity and type 2 diabetes (1–4).
How is FFA done?
Fluorescein angiography is a diagnostic test which uses a special camera to take a series of photographs of the retina. A special water-soluble fluorescein dye is injected into a vein in the arm. The dye travels through the veins and into the arteries as it circulates throughout the body.
How do you do the FFA?
FFA is conventionally performed through intravenous injection of 10–20% Sodium Fluorescein dye, following which serial retinal imaging (~490 nm wavelength) is used to dynamically visualise retinal flow, circulation and vascular integrity.
Why does Foster Kennedy have contralateral papilledema?
The lack of colour is more marked in the temporal area (arrows). These findings suggested Foster Kennedy syndrome, in which an anterior intracranial mass directly compresses the ipsilateral optic nerve, causing atrophy, and increases intracranial pressure, which results in contralateral papilledema.
Why is LP contraindicated in raised ICP?
While some patients with CT evidence of increased ICP have undergone LP without herniation, CT findings of increased ICP place patients at a dramatically increased risk for herniation if an LP is performed. Therefore, LP should be avoided when any signs of increased ICP are seen on CT.