<ul>
 <li>
 Heterotrophic eukaryotes: depend on exogenous food sources (either saprophytes or parasites)
 </li>
 <li>Yeasts: unicellular</li>
 <li>Moulds: branching filaments called mycelium, bear spores and grow as hyphae</li>
 <li>Long-lasting infections that can be difficult to treat</li>
 <li>Fungal infections are more common than bacterial</li>
 <li>Moulds are the most common fungal infection worldwide</li>
 <ul>
 <li>Aspergillus</li>
 <li>Fusarium&nbsp;</li>
 </ul>
</ul>
<ClinicalCorrelate>
 Filamentous fungi are typically implicated in corneal infections associated with trauma
</ClinicalCorrelate>
<ul>
 <li>Candida albicans is the most common yeast infection</li>
 <ul>
 <li>Cataract surgery</li>
 <li>Corneal transplant</li>
 <li>Therapeutic CLs</li>
 <li>Steroids</li>
 <li>Immunosuppression</li>
 </ul>
 <li>Yeasts germinate to form pseudohyphae in the corneal stroma</li>
 <li>CL wear is the main risk factor in industrialised settings</li>
 <li>Fungi can reproduce sexually&nbsp;</li>
 <li>Fungal keratitis presents as a feathery-edged infiltrate with satellite lesions</li>
</ul>

## Candida albicans
<ul>
 <li>Normal commensal yeast</li>
 <li>Cultures on Sabouraud&rsquo;s glucose media in 24-48 hours</li>
 <li>Candidaemia:</li>
 <ul>
 <li>GI surgery</li>
 <li>Prolonged IV antibiotics</li>
 <li>Indwelling catheters</li>
 <li>Diabetes</li>
 <li>Malignancy</li>
 <li>IV drug abuse</li>
 <li>Liver disease</li>
 <li>Alcoholism&nbsp;</li>
 </ul>
 <li>A third of patients with candidaemia develop candidiasis</li>
 <ul>
 <li>80% of patients with candidiasis have candidal chorioretinitis</li>
 <li>Also associated with candidal endophthalmitis (endogenous) in candidaemia</li>
 </ul>
 <li>Candidal infection of the oesophagus, trachea or lung is an AIDS-defining illness</li>
</ul>

## Cryptococcus neoformans
<ul>
 <li>Yeast found in pigeon droppings</li>
 <li>Respiratory infections</li>
 <li>Chronic meningoencephalitis</li>
</ul>

## Aspergillus (and Fusarium) keratitis
<ul>
 <li>Septate fungi</li>
 <li>Saprophytic mould (ie. filamentous)</li>
 <li>
 Spores (&ldquo;conidia&rdquo;) are dispersed in association with plant material or insects
 </li>
 <li>Opportunistic pathogen</li>
 <li>
 Mycelia spark an IgE mediated allergic response in the bronchi (type I hypersensitivity) or
 complement activation and polymorph infiltration (type II hypersensitivity)
 </li>
 <li>Aspergilloma: compact mass of mycelia</li>
 <li>
 If the corneal stroma is exposed (eg. following corneal injury) conidia germinate and hyphae
 penetrate the stroma
 </li>
 <ul>
 <li>
 Hyphae contain proteases eg collagenases that facilitate penetration through the stroma and
 into the AC (hypopyon)
 </li>
 </ul>
 <li>Pathophysiology relates to the inflammatory response causing tissue damage</li>
 <ul>
 <li>
 C-type lectins bind to cell wall components (beta-glucan and alpha-mannose) leading to
 chemotactic/inflammatory cytokine release
 </li>
 </ul>
 <li>Contact lens wear is the main risk factor</li>
 <li>
 Fungal biofilms are complexes of hyphae and extracellular carbohydrates with resistance to
 antimicrobials
 </li>
 <li>The deep penetration of hyphae makes antimycotics less effective.&nbsp;</li>
 <li>Treatment options</li>
 <ul>
 <li>Natamycin</li>
 <li>Voriconazole</li>
 <li>Full thickness keratoplasty</li>
 <li>Enucleation</li>
 <li>
 Steroid use is risky as will cause hyphal growth if given before the infection is controlled
 </li>
 </ul>
</ul>

## Histoplasma capsulatum
<ul>
 <li>Dimorph (may exist as a mould or a yeast)</li>
 <li>Soil yeast fungus, temperature dependent</li>
 <li>Inhaled and spreads haematogenously to the choroid</li>
 <li>Carried on birds feathers and bat droppings</li>
 <li>HLA-DRw2 and HLA-B7 associated.</li>
 <ul>
 <li>Presumed ocular histoplasmosis syndrome (POHS) is not truly an infectious process</li>
 <li>Hence anti-fungal therapy is not beneficial</li>
 </ul>
 <li>Histoplasmin skin antigen test is not sensitive/specific for POHS</li>
 <li>FFA useful</li>
 <li>POHS: immunologically mediated condition in those previously exposed</li>
 <ul>
 <li>Atrophic chorioretinal scars: CNV may form at macula</li>
 <li>PPA</li>
 <li>No vitritis</li>
 </ul>
</ul>

## Mucoraceae
<ul>
 <li>Non-septate fungi: rhizopus, mucor, absidia</li>
 <ul>
 <li>
 Histopathology: non-septate fungi with wide angle branching (cp to Fusaria and Aspergillus
 which are septate fungi)
 </li>
 </ul>
 <li>Ubiquitous saphrophytic fungi in soil, air, ventilation systems, bodily orifices</li>
 <li>Usually phagocytosed by macrophages</li>
 <li>
 In acidic conditions of diabetes, metabolic acidosis or uraemia: spores can
 germinate and hyphae establish infection
 </li>
 <li>
 Causes orbital fungal infection: mucormycosis
 </li>
 <ul>
 <li>Most common route of orbital invasion is from an adjacent sinus</li>
 <li>
 Organisms disrupt blood vessels leading to ischaemia and black eschar
 </li>
 <li>Systemic antifungals are given eg. amphoteracin B</li>
 <li>Surgical debridement may be needed</li>
 </ul>
</ul>

Microbiology

Fungal Infections

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

Viral Infections

Bacterial 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