
<ul>
  <li>
    Fluorescence: the property of emitting a longer wavelength light when stimulated by a shorter
    wavelength
  </li>
</ul>
<ul>
  <li>White light from the camera passes through a blue excitation filter</li>
  <li>
    Blue light (wavelength of <span className="font-semibold">490nm</span>) is transmitted to the fundus and is absorbed
    by the fluorescein molecules in the retinal and choroidal vasculature
  </li>
  <li>
    They are stimulated to emit yellow-green light (<span className="font-semibold">530nm</span>)
  </li>
</ul>
<HotTopic>
  <p>
    Both the excitation and fluorescence of fluorescein angiography are absorbed and scattered by
    retinal pigments meaning that structures deep to these tissues are poorly visualised
  </p>
</HotTopic>
<ul>
  <li>
    Macular xanthophyll may have a physiological role in limiting damage to the photoreceptors by
    protecting them from high energy short-wavelength light
  </li>
</ul>
<ul>
  <li>A yellow-green filter is placed to block blue light reflected from the eye</li>
  <li>The yellow-green light therefore reached the camera</li>
  <li>Fluorescein has a low molecular weight</li>
  <ul>
    <li>
      Can pass between endothelial cells in the choriocapillaris and other capillary beds in the
      body (therefore, in other tissues it does not stay intravascular)
    </li>
    <li>
      The RPE tight junctions normally prevent this leak into the neural retina (outer barrier)
    </li>
    <li>
      The tight junctions between retinal vascular endothelial cells also prevent leak normally
      (inner barrier)
    </li>
    <li>Fluorescein is 80-85% bound to serum protein (it is primarily hydrophilic)</li>
    <li>Leaks readily from fenestrated choriocapillaris</li>
    <li>10% concentration fluorescein is used</li>
  </ul>
</ul>
<ul>
  <li>Anaphylactic shock: &lt;1 in 100,000 (&lt;0.001%)</li>
  <li>More common side effects</li>
  <ul>
    <li>Discolouration of skin and urine</li>
    <li>Nausea and vomiting</li>
    <li>Urticarial rash</li>
    <li>Flushing</li>
    <li>Photosensitivity&nbsp;</li>
    <li>Itch</li>
    <li>Discomfort at injection site</li>
  </ul>
  <li>The diameter of retinal vessels on FFA is larger than that of a fundus photograph</li>
  <ul>
    <li>
      A photo only visualises the axial blood column whereas fluorescein reaches the peripheral
      blood in the vessel
    </li>
  </ul>
</ul>

## Uses
<ul>
  <li>Diagnosis</li>
  <ul>
    <li>AMD</li>
    <li>CSR</li>
    <li>CMO</li>
    <li>Diabetic retinopathy</li>
    <li>Retinal vein occlusion</li>
    <li>Posterior uveitis</li>
    <li>Disc drusen</li>
    <li>Choroidal haemangiomas</li>
  </ul>
  <li>Management</li>
  <ul>
    <li>To guide laser in CNV, CSR, diabetic maculopathy and vein occlusion</li>
  </ul>
</ul>

## Normal phases
<ul>
  <li>Choroidal: 10-12 seconds after injection in young patients but depends on vascular health</li>
</ul>
<HotTopic>
  <p>
    A cilioretinal artery, if present, is a branch of the short posterior ciliary artery so fills
    during the choroidal phase
  </p>
</HotTopic>
<ul>
  <li>Arterial: 1-3 seconds after the choroidal phase</li>
  <ul>
    <li>
      Neovascularisation of the disc (part of the retinal circulation) is visible during the early
      arterial phase
    </li>
    <li>
      The central retinal artery provides a circuitous route for the dye so it appears 1 or 2
      seconds later than in the choroidal circulation
    </li>
  </ul>
  <li>Arteriovenous</li>
  <ul>
    <li>
      Demonstrates laminar flow: the veins are fluorescent near their walls and darker centrally
    </li>
    <li>Lasts for 1-2 seconds</li>
  </ul>
  <li>Venous</li>
  <li>Late phase</li>
  <ul>
    <li>Highlights cystoid macular oedema, CSR, or occult subretinal neovascular membranes</li>
  </ul>
  <li>Late staining of the optic disc is normal</li>
</ul>

## Abnormalities
<ul>
  <li>
    Pooling: hyperfluorescence that increases in size and intensity as dye enters a closed space eg
    a pigment epithelial detachment
  </li>
  <ul>
    <li>Once the space is filled, the hyperfluorescence remains stable (cp leakage)</li>
  </ul>
  <li>
    Leakage: increases in size and intensity of hyperfluorescence over time (due to extravasation of
    dye)
  </li>
  <ul>
    <li>Incompetence of the inner or outer blood-retinal barriers</li>
    <li>Neovascularisation: defective inner barrier</li>
    <li>Defective choroidal circulation eg. AMD</li>
  </ul>
  <li>Window defect: unmasking of the normal choroidal fluorescence</li>
  <ul>
    <li>RPE atrophy</li>
    <li>Window defects are seen early</li>
  </ul>
  <li>Staining: hyperfluorescence appears late. Uptake of dye into structures</li>
  <ul>
    <li>Drusen</li>
    <li>Disciform scars</li>
    <li>Optic disc</li>
  </ul>
  <li>
    Pseudo-autofluorescence: overlap in the spectral transmission of the excitation and barrier
    filters
  </li>
</ul>

## ICG
<ul>
  <li>Provides more information about the choroidal circulation</li>
</ul>
<HotTopic>
  <p>
    ICG peak absorption (790-805nm)&nbsp; and fluorescence (770-880nm) are within the infrared range
    of wavelengths (&gt;800nm) and thus can penetrate the overlying RPE, pigments and any overlying
    haemorrhages
  </p>
</HotTopic>
<ul>
  <li>
    ICG circulates 98% bound to plasma protein (it is amphiphilic, ie. both hydro- and lipophilic
    therefore binds lipproteins and phospholipids) so less leakage&nbsp;
  </li>
  <li>
    Therefore provides information about the choroid that would be invisible to FFA due to
    extravasation of fluorescein from the choroid
  </li>
  <li>Takes longer than FFA</li>
  <li>Excreted by the hepatobiliary system: discoloured stool for several days</li>
  <li>Useful for</li>
  <ul>
    <li>Occult/poorly defined CNVM: can be more easily measured</li>
    <li>Polypoidal CNV</li>
    <li>Fibrovascular PEDs</li>
    <li>Medial opacities/vitreous haemorrhages</li>
    <li>Photophobic patients (they cannot see the infrared lights)</li>
    <li>
      Inflammatory disease: to identify possibly occult choroidal disease (crucial investigation for
      inflammatory disease)
    </li>
  </ul>
</ul>
<p>
  <span className="font-semibold">Summary Table</span>: FFA findings of important pathologies table
</p>
<div className="bg-blue-200 px-4 rounded-md shadow-lg dark:text-gray-700">
  <table>
    <tbody>
      <tr>
        <td>Classic CNV</td>
        <td>
          Well-delineated &lsquo;lacy&rsquo; hyperfluorescence in early phasesAggressive/progressive
          leaking leads to dye pooling in subretinal space
        </td>
      </tr>
      <tr>
        <td>Occult CNV</td>
        <td>
          <ol>
            <li>
              &lsquo;Stippled&rsquo; hyperfluorescence early with increasing pooling in the sub-RPE
              space (fibrovascular PED)&nbsp;
            </li>
            <li>
              Diffuse hyperfluorescence late with poorly defined boundaries (late leakage of
              indeterminate origin)
            </li>
          </ol>
        </td>
      </tr>
      <tr>
        <td>RAP</td>
        <td>Early hyperfluorescence with progressive leakage</td>
      </tr>
      <tr>
        <td>PCV</td>
        <td>ICG better: shows early subretinal hyperfluorescence &lt;5 minutes</td>
      </tr>
      <tr>
        <td>CSR</td>
        <td>Expansile dot (/ink-blot)Smoke-stack pattern</td>
      </tr>
      <tr>
        <td>CMO</td>
        <td>Parafoveal leakage into petaloid pattern (cystoid spaces)</td>
      </tr>
      <tr>
        <td>Myopic CNV</td>
        <td>Smaller than ARMD CNV with less subretinal/intraretinal fluid&nbsp;</td>
      </tr>
      <tr>
        <td>Angioid streaks</td>
        <td>Hyperfluorescence due to window defect</td>
      </tr>
      <tr>
        <td>OIS</td>
        <td>
          delayed/patchy choroidal filling, prolonged AV transit time, macular leakage/oedema, optic
          disc hyperfluorescence, retinal vascular staining (due to endothelial damage). Peripheral
          capillary non-perfusion
        </td>
      </tr>
      <tr>
        <td>Coats</td>
        <td>Highlights abnormal vessels with leakage and areas of capillary dropout</td>
      </tr>
      <tr>
        <td>MacTel type 2</td>
        <td>
          Telangiectatic capillaries temporal to the fovea with early leakage. Signs of CNV if
          present
        </td>
      </tr>
      <tr>
        <td>Macroaneurysm&nbsp;</td>
        <td>Immediate complete filling with late leakage</td>
      </tr>
      <tr>
        <td>Stargardt&rsquo;s&nbsp;</td>
        <td>
          Dark choroid due to blockage of choroidal fluorescence by abnormal deposits in RPE (of
          lipofuscin and A2E)
        </td>
      </tr>
      <tr>
        <td>Hydroxychloroquine toxicity</td>
        <td>Windows defects due to RPE loss</td>
      </tr>
      <tr>
        <td>Capillary haemangioma</td>
        <td>
          Rapid filling of a feeding artery followed by complete hyperfluorescence of the lesion,
          then filling of the vein and diffuse late leakage
        </td>
      </tr>
      <tr>
        <td>Cavernous haemangioma</td>
        <td>Slow incomplete filling of lesion with fluid meniscus and no leakage</td>
      </tr>
      <tr>
        <td>Racemose haemangioma</td>
        <td>Rapid filling with no leak</td>
      </tr>
    </tbody>
  </table>
</div>


Clinical Techniques

Fluorescein Angiography

Intro

FRCOphth Part 1 Study Notes

Orbit and ocular adnexae

Orbit

Extraocular Muscles

Orbital Blood Vessels

Paranasal Sinuses

Lacrimal Glands

Tear Film

Eyelids

Blinking

Anterior segment - ocular surface

Conjunctiva

Conjunctivitis

Sclera

Cornea

Corneal Structure And Development

Corneal Physiology

AC to Lens

Angle

Ciliary Body

Aqueous Humour Dynamics

Iris

Pupil

Lens

Posterior segment

Choroid

Vitreous

Retinal Macrostructure

Neurosensory Retina

Retinal Pigment Epithelium

Neuroanatomy

Venous Sinuses

Cerebral Ventricles

Cerebral Blood Supply

Supranuclear Gaze Pathways

Head And Neck Autonomic Nervous Supply

Head And Neck Glands

Osteology

Nerves

Muscles And Pharyngeal Arches

Extraocular Nerves

Sensory Nerves

Physiology

Physics Of Blood Flow

Neuronal Control Of Blood Vessels

Oxygen-Haemoglobin Dissociation Curve

Cytochrome p450

Pituitary Gland

Thyroid Hormone Production

Insulin

Glucagon

Parathyroid Hormone

Corticosteroids

Catecholamines

Cardiac Cycle

Renal Physiology

Fluid Balance

Acid-Base Balance

Muscle Physiology

Sensory Fibres

Cutaneous Receptors

Endocytosis

Glycosaminoglycans

Condensed Ocular Biochemistry

Eye Movements

Accomodation

Vision

Visual Cycle And Phototransuction

Visual Pathway

Visual Acuity

Colour Vision

Binocular Vision

Pathology

Collagen

Tissue Damage

Inflammation

Disease Entities

Wound Healing

Thrombosis / Atherosclerosis

Cell Growth

Neoplasia

Histopathology

Nystagmus

Free Radicals And Antioxidants

Immunology

Ocular Immunology

Microbiology

Viral Infections

Bacterial Infections

Fungal Infections

Protozoa

Nematodes

Antimicrobials

Genetics

Chromosomes

Mitosis

Meiosis

Genes

Polypeptide Synthesis

Histones

MicroRNA

Hardy-Weinberg Equilibrium

Mutations

Chromosome Defects

Autosomal Inheritance

X-Linked Inheritance

Mitochondrial Inheritance

Multifactorial Inheritance