
<ul>
  <li>Circular structure</li>
  <li>6mm wide</li>
  <li>Numerous functions</li>
  <ul>
    <li>Accommodation</li>
    <li>Production of aqueous</li>
    <li>Production of zonules</li>
    <li>
      Production of extracellular vitreous components: collagen and hyaluronic acid (main GAG in
      vitreous)
    </li>
  </ul>
  <li>Age related changes:</li>
  <ul>
    <li>
      Atrophy of the CB affects the longitudinal and reticular muscle fibres, less so the circular
      fibres
    </li>
    <li>Migrates anteriorly</li>
  </ul>
</ul>
## Embryology
<ul>
  <li>Derived from a combination of neuroectoderm and mesenchyme</li>
  <ul>
    <li>
      Neuroectoderm bilayer forms the ciliary epithelium which also has two layers and is continuous
      with the neural retina and RPE (also formed from neuroectoderm)
    </li>
    <li>Mesenchyme provides the stroma and ciliary muscle</li>
  </ul>
  <li>Develops at 11-12 weeks</li>
  <ul>
    <li>1. Outer pigmented layer of neuroectoderm is invaded by capillaries</li>
    <li>
      2. The vessels enlarge and push towards inner non-pigmented layer creating folds (future
      ciliary processes)
    </li>
    <li>3. Folds become more numerous and complex</li>
    <li>4. Flat area forms posteriorly (pars plana)</li>
    <li>5. Aqueous production commences at 20 weeks (earliest)</li>
  </ul>
  <li>Scleral spur and CB muscle fibres are not fully developed at term.</li>
</ul>
## Macroscopic structure
<ul>
  <li>Scleral spur anteriorly</li>
  <li>Pars plicata is 2mm wide, sits anteriorly. Comprises about 70 ciliary processes</li>
  <li>Pars plana is 4mm wide, sits posteriorly</li>
  <li>Ora serrata further posteriorly (contains non-pigmented ciliary epithelium)</li>
  <li>Wider temporally than nasally</li>
</ul>
## Epithelium
<ul>
  <li>Bilayer</li>
  <li>Two layers of cells lie apex to apex, hence:</li>
  <ul>
    <li>
      Inner basal lamina facing the posterior chamber: continuous with the ILM of the neural retina
    </li>
    <li>Outer basal lamina against the stroma/muscle: continuous with Bruch&rsquo;s membrane</li>
  </ul>
  <li>The inner non-pigmented layer is rich in Golgi and mitochondria and secretes aqueous.</li>
  <ul>
    <li>Contains carbonic anhydrase</li>
    <li>Contributes to production of zonules and vitreous components</li>
  </ul>
  <li>Tight junctions between the non-pigmented epithelial cells form a blood-aqueous barrier</li>
  <ul>
    <li>The main protein present in tight junctions is occludin</li>
  </ul>
  <li>
    The outer pigmented layer is rich in melanocytes. Permeable zonula adherens and macula adherens
    connect cells
  </li>
  <ul>
    <li>The pigmented epithelial cells are therefore more leaky</li>
    <li>Continuous with the RPE</li>
  </ul>
</ul>
## Aqueous production
<ul>
  <li>
    Relatively constant rate of 1-3 microlitres per minute (the entire volume is replaced every 1-2
    hours)
  </li>
  <li>Produced by the non-pigmented ciliary epithelium</li>
  <li>Produced by a combination of:</li>
  <ul>
    <li>Passive diffusion of electrolytes down a concentration gradient</li>
    <li>
      Ultrafiltration of plasma dependent on BP, IOP and blood osmotic pressure across the leaky
      fenestrated capillaries in the ciliary body
    </li>
    <li>
      Active transport across the epithelial plasma membrane including carbonic anhydrase II and
      Na/K ATPase activity
    </li>
  </ul>
  <li>
    Note: the oncotic pressure of the ciliary stroma is greater than the hydrostatic pressure across
    the epithelium so active transport is the main mechanism of production.
  </li>
  <li>Also under adrenergic control (see below)</li>
</ul>
<p>The composition of aqueous</p>
<ul>
  <li>Electrolytes and low molecular weight compounds</li>
  <ul>
    <li>Slightly higher chloride than plasma</li>
    <li>Similar potassium as plasma</li>
    <li>
      Slightly lower sodium, bicarbonate and glucose than plasma (glucose levels increase in
      diabetes with consequences for the lens)
    </li>
    <li>Much lower calcium than plasma</li>
    <li>Lactate is the most abundant anion and at higher levels than plasma</li>
    <li>Slightly lower levels of urea: passes quite readily across membranes</li>
  </ul>
  <li>Oxygen: from the blood supply of the CB and iris (oxygen cannot pass through the cornea)</li>
  <ul>
    <li>Supplies the corneal endothelium, TM endothelium and lens</li>
  </ul>
  <li>Steroid sex hormones&nbsp;</li>
  <li>Ascorbic acid:&nbsp;</li>
  <ul>
    <li>
      Unique constituent, much higher levels than plasma. Possibly has a role as an antioxidant
    </li>
    <li>
      Glutathione is also present in aqueous and acts as a stabiliser of ascorbate as well as for
      enzymatic processes involved in cellular detoxification ie. protection of tissue from
      oxidative stress
    </li>
  </ul>
  <li>Lysozyme: provides antibacterial protection</li>
  <li>Carbonic anhydrase</li>
  <li>Plasminogen and plasminogen activator</li>
  <li>Hyaluronidase: may help regulate flow through the TM&nbsp;</li>
  <li>Cytokines and growth factors including VEGF</li>
  <ul>
    <li>
      Growth factors may regulate the endothelium and epithelium of the cornea, hence the
      hyperplastic changes in these tissues in chronic inflammatory conditions
    </li>
    <li>
      Insulin-like growth factor and its binding protein are elevated in patients with diabetes
    </li>
    <li>
      VEGF-A is induced by hypoxia and is a potent regulator of angiogenesis and vascular
      permeability. It is increased in patients with active neovascularisation in PDR and CRVO
    </li>
  </ul>
  <li>Higher molecular weight compounds may be added in the AC</li>
  <li>
    Very low protein content (allows optical clarity): mainly albumin but some immunoglobulin and
    fibronectin, due to exclusion by the blood-aqueous barrier
  </li>
  <ul>
    <li>
      Some proteins do enter, possibly through the iris root but others may have been synthesised
      directly into the aqueous by the CB
    </li>
    <li>Complement C4</li>
    <li>
      Alpha2-macroglobulin: a carrier protein and proteinase inhibitor present in aqueous. Imbalance
      between these may lead to disease eg. glaucoma
    </li>
  </ul>
  <li>Hyaluronic acid</li>
</ul>
<ul>
  <li>AC volume: 0.2ml</li>
  <li>PC volume: 0.06ml</li>
  <li>pH: 7.5-7.6</li>
</ul>
## Stroma/muscle
<ul>
  <li>The ciliary muscle comprises the anterior two-thirds of the CB</li>
  <li>
    It is smooth muscle comprising three groups of fibres in the vascular connective tissue stroma
  </li>
  <ul>
    <li>
      Outer longitudinal fibres (aka Brucke&rsquo;s muscle) are continuous with the choroid (hence
      this also moves with accommodation) and attach to the sclera spur
    </li>
    <li>Middle oblique/radial fibres attach to scleral spur</li>
    <ul>
      <li>Continuous with the corneoscleral trabeculae</li>
    </ul>
    <li>Inner circular fibres: these are the most anterior (aka Muller&rsquo;s muscle)</li>
  </ul>
  <li>
    Contraction produces an inwards and forwards movement of the CB which slackens the zonules and
    allows the lens to adopt a spherical shape, thus increasing its refractive index.
  </li>
</ul>
## Blood supply
<ul>
  <li>
    Long posterior ciliary arteries travel anteriorly in the choroid and then divide in the CB
  </li>
  <li>They anastomose with the anterior ciliary arteries forming the major circle of the iris</li>
  <li>Venous drainage via vortex veins</li>
</ul>
## Nerve supply
<ul>
  <li>
    Parasympathetic supply: preganglionic fibres originate in the Edinger-Westphal nucleus and
    travel in the oculomotor nerve. They synapse in the ciliary ganglion and postganglionic fibres
    travel in the short ciliary nerves to produce a plexus in the CB
  </li>
  <li>Sympathetic innervation via the sympathetic chain and superior cervical ganglion</li>
</ul>


AC to Lens

Ciliary Body

Intro

FRCOphth Part 2 Study Notes

Tumours, masses and neoplasia

Tumours overview

Uveitis

Uveitis background

Anterior uveitis

Intermediate uveitis

Uveitis in JIA

Uveitis with JIA

Retinal vasculitis

Sarcoidosis

Behcet's disease

Toxoplasmosis

Strabismus

Overview

Viral uveitis

Esotropia

Fungal uveitis

Mycobacterial uveitis

Adnexal masses

Exotropia

Spirochaetal uveitis (including Syphilis)

Melanoma

Nematode uveitis

Retinoblastoma

Retinoblastoma (for Part 2)

Incomitent

Voyt-Koyanagi-Harada syndrome

Conjunctival intraepithelial neoplasia

Vertical deviations

Orbit and ocular adnexae

Orbit

Sympathetic ophthalmia

AV Malformations and hamartomas

Arteriovenous malformations and hamartomas

Restriction syndromes

Paediatrics

Leucocoria

Congenital Cataract

Paediatric Glaucoma

Retinopathy of prematurity

Retinopathy of Prematurity

ROP-like disorders

Congenital nasolacrimal duct obstruction

White dot syndromes

Aniridia: Short Arm 11 Deletion (11p13)

Choristomas

Management Of Amblyopia

Alphabet patterns

Iris Nodules

Scleritis

Meningioma

Strabismus surgery

Optic nerve glioma

Lymphoma

Extraocular Muscles

Rhabdomyosarcoma

Idiopathic orbital inflammation

Orbital neuroblastoma

Anterior Persistent Foetal Vasculature

Lacrimal system

Metastatic lesions

Surgical Retina

Retinal Detachment

Vitreoretinal Interface And Macular Hole

Epiretinal Membrane

Medical Retina

Diabetic Eye Disease

Orbital Blood Vessels

Retinal Vascular Disease

Macular Degeneration

Central Serous Chorioretinopathy (CSCR)

Sickle Cell Retinopathy

Retinitis Pigmentosa

Albinism

Retinal Telangiectasias

Miscellaneous Retinopathies

Atropine And Myopia Progression

Pharmacology

Side Effects Of Systemic Drugs

Foetal Alcohol Syndrome

Neuro-ophthalmology

Optic Neuropathy

Papilloedema

Idiopathic Intracranial Hypertension

Chiasmal Disorders

Retrochiasmal Disorders

Migraine

Paranasal Sinuses

Supranuclear Motility Disorders

Third Nerve Palsies

Fourth Nerve Palsies

Sixth Nerve Palsies

Seventh Nerve Palsies

Anisocoria

Myasthenia Gravis

Myopathies

Blepharospasm

Functional Visual Loss

Lacrimal Glands

Phakomatoses

Developmental diseases

Tear Film

Eyelids

Blinking

Lid Malpositions

Anterior segment - ocular surface

Conjunctiva

Conjunctivitis

Sclera

Pigmented Conjunctival Lesions

Squamous Cell Carcinoma Of The Conjunctiva

Ocular Cicatricial Pemphigoid

Cornea

Corneal Structure And Development