## Principles
<ul>
 <li>A piezoelectric crystal transducer produces high-frequency (8-100 MHz) sound waves</li>
 <ul>
 <li>Ultrasound waves have a frequency &gt;20,000Hz</li>
 <li>Higher frequencies provide greater resolution but poorer tissue penetration</li>
 <li>Most ocular ultrasound is performed around 10 MHz</li>
 </ul>
 <li>
 The sound waves travel through tissues and echos are generated from changes in the impedance of
 a tissue (therefore a homogenous tissue does not produce echoes)
 </li>
 <li>
 The reflected echo signal is converted into an electrical signal and the amplitude is measured
 </li>
</ul>

## A-scan
<ul>
 <li>Plots the intensity of the echo versus time delay: converted to distance</li>
 <li>5 peaks in a normal A-scan</li>
 <ul>
 <li>Corneal surface</li>
 <li>Anterior lens</li>
 <li>Posterior lens</li>
 <li>ILM of retina</li>
 <li>Sclera</li>
 </ul>
</ul>

## B-scan
<ul>
 <li>2-dimensional images created from multiple A-scans.</li>
</ul>
<HotTopic>
 Malignant melanoma on ultrasound
 <ul>
 <li>Mushroom, dome-shaped</li>
 <li>&gt;2mm thickness</li>
 <li>High surface reflectivity</li>
 <li>Low internal reflectivity</li>
 <li>Choroidal excavation&nbsp;</li>
 </ul>
</HotTopic>

## Posterior segment tumours on ultrasound
<ul>
 <li>Choroidal haemangioma:</li>
 <ul>
 <li>Dome-shaped</li>
 <li>Acoustic solidity</li>
 <li>
 High, regular internal reflectivity (due to tightly packed blood vessels)
 </li>
 </ul>
 <li>Choroidal melanoma:</li>
 <ul>
 <li>Smooth, dome-shaped</li>
 <li>Mushroom/collar button shape is pathognomonic</li>
 <li>
 Low to medium, regular internal reflectivity
 </li>
 </ul>
 <li>Retinoblastoma:&nbsp;</li>
 <ul>
 <li>
 High, irregular internal reflectivity (due to focal calcification, necrosis
 and haemorrahge all within the tumour)
 </li>
 </ul>
 <li>Choroidal metastases:</li>
 <ul>
 <li>Irregular, lumpy</li>
 </ul>
</ul>

 Medium-to-high internal reflectivity

Principles A piezoelectric crystal transducer produces high-frequency (8-100 MHz) sound waves Ultrasound waves have a frequency >20,000Hz Higher…

Clinical Techniques

Ultrasound

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