Fluoresce In in Ophthalmology Ppt

8/3/2019 Fluoresce In in Ophthalmology Ppt

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Fluorescein is a synthetic organic compound available as a

dark orange/red powder soluble in water and alcohol. It iswidely used as a fluorescent tracer for many applications.

Uses of f luorescein in ophthalmology

1. Fluorescein angiography

2. Applanation tonometry3. Corneal staining


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Fluorescein angiography

Fluorescein angiography is a technique which is basedon the detection of fluorescent light emitted by a dyein circulation.

Mechanism

y It involves injection of sodium fluorescein into thesystemic circulation, and then an angiogram is

obtained by photographing the fluorescence emittedafter illumination of the retina with blue light ata wavelength of 490 nanometers.


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Equipment

1. Exciter filter: Allows only blue light to illuminate the

retina, depending on the filter the excitationwavelength hitting the retina will be between 465-490 nm

2. Barrier filter: Allows only yellow-green light (fromthe fluorescence) to reach the camera, depending onthe filter it can be between 520-530 nm.

3. Fundus Camera


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Technique

y 2-5cc fluorescein dye is injected intravenously

y White light from a flash is passed through a blue excitationfilter.

y Blue light is then absorbed by unbound fluorescein

molecules, emitting light with a longer wavelength in theyellow-green spectrum (520-530nm).

y Barrier filter blocks any reflected light so that the imagescapture only light emitted from the fluorescein

y

Images are acquired immediately after injection and continuefor ten minutes depending on the pathology being imaged.

y These images are recorded digitally or on 35mm film.


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Normal circulatory filling

y 0 seconds injection of fluorescein

y 9.5 sec posterior cilliary arteries

y 10 sec choroidal flush

y 10-12 sec retinal arterial stagey 13 sec capillary transition stage

y 14-15 sec early venous stage or lamellar stage

y 16-17 sec venous stage

y 18-20 sec late venous stage

y 5 minutes late staining


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Uses:-

1. Exposing depth pathological involvement in diabeticretinopathy and reveal neovascularisatio0n occurring inany area of fundus

2. Assessment of disorder of fundus including neoplasia,disorder of optic nerve head such as papilloedema

3. Interpretation of neovascularisation of the iris when

leakage from vessels of the iris

4. Vitreous fluorophotometry - allow measurement offludescein concentration in all parts of vitreous chambervisible through eyepiece of the slitlamp


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Pathological findings

Causes of hyper fluorescence :

1. leaking defects(choroidal or diabetic neovascularization )

2. pooling defects

3. staining

4. abnormal vasculature


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Causes of hypo fluorescence :

1. blocking defect (corneal scar, cataract, vitreoushemorrhage,

2. filling defect (retinal or choroidal vascular occlusion )


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Complication:-

1. Nausea

2. Vomiting

3. Pruritis

4. Pyrexia

5. Thrombophlebitis6. Local tissue necrosis can occur with extravasation of dye


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Applanation Tonometry

Applanation tonometry is technique which is use to measuresintraocular pressure either by the force required to flatten aconstant area of the cornea (e.g. Goldmann tonometry) or bythe area flattened by a constant force.

Equipment

y Tonometer, either Goldmann (used on slit

lamps) or Perkins (hand-held)

y Applanation prismy Local anaesthetic drops

y Fluorescein strips

y Clean cotton wool or gauze swabs.


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Methody Instil the local anaesthetic drops and then the fluorescein

y For measuring the IOP in the right eye , the slit beam which isshining onto the tonometer head should be from the patientsright side

y Move the filters so that the blue filter is used to produce a bluebeam

y

The beam of light should be as wide as possible and bright aspossible.

y This makes visualising the fluorescein rings easier (with the slitdiaphragm fully open)

y Ask the patient to look straight ahead, open both eyes wide, fix his

or her gaze and keep perfectly stilly With the thumb, gently hold up the patients top eyelid, taking

care not to put any pressure on the eye

y Direct the blue light from the slit lamp onto the prism head ,Make

sure that the tonometer head is perpendicular to the eye


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y Move the tonometer forward slowly until the prism restsgently on the centre of the patients cornea

y With the other hand, turn the calibrated dial on the

tonometer clockwise until the two fluorescein semi-circles inthe prism head are seen to meet and form a horizontal Sshape

Finding:


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Purpose

y To help diagnose glaucoma or high eye pressure.

y

The test is often part of a routine eye exam.

Factors affecting results

yAn irregularly shaped cornea

Interpretation

y Pressure readings are in millimetres (mm) of mercury

(Hg).A normal reading is about 20 mm Hg or lower. Higherreadings may indicate either glaucoma or ocularhypertension.


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Advantages

y It's a quick, easy test for glaucoma.

y It's non-invasive.

Disadvantages

y Other tests may be necessary to diagnose glaucoma; theseinclude visual field tests and ophathalmoscopy to evaluate the

optic nerve.


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Corneal staining

This is a test that uses fluorescein and a blue light to detectforeign bodies in the eye. This test can also detect damage tothe cornea, the outer surface of the eye.

Technique:-

A piece of blotting paper containing the dye will be touched to thesurface of patient eye and asked to blink.

A blue light is then directed to eye. Any problems on the surface ofthe cornea will be stained by the dye and appear green under the

blue light.

Depending on the size, location, and shape of the staining it candetermine cause cornea problem


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Normal Resultsy If the test result is normal, the dye remains in the tear film

on the surface of the eye and does not adhere to the eyeitself.

Abnormal Resultsy Abnormal tear production (dry eye)y Corneal abrasion(a scratch on the surface of the cornea)

y Foreign bodies, such as eyelashes or dust (see eye - foreignobject in)

y Infection

y Injury or trauma

y Severe dry eye associated with arthritis

(keratoconjunctivitis sicca)


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Disease cornea withstain


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Fluoresce In in Ophthalmology Ppt

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