Uvea and Sclera Flashcards
What are the 3 components of the uvea
The choroid, iris and ciliary body
Considered together as the uveal tract
What is the sclera?
The sclera is the white part at the front of the eye, wrapping all the way to the back and terminating at the optic nerve.
Revise
Anatomy of the choroid
The choroid is a highly vascular, pigmented structure extending from the ora Serrata to the optic disc.
It provides vascular supply and absorbs reflecting light. The choroid gets thinner as you move anteriorly.
Layers of the Choroid
(external to internal)
- Haller’s layer (large vessels)
- Sattler’s layer (medium vessels)
- Choriocapillaris (capillaries)
- Bruch’s membrane (basement membrane)
What is the suprachoroidal space
A potential space that sits on top of Haller’s layer. It separates the sclera from the choroid.
Anatomy of the Iris
The iris is the anterior part of the uveal tract. It extends from the anterior chamber angle to the pupil. Its muscles are responsible for changing the size of the pupil. The iris is the coloured part of the eye when you’re looking at someone directly.
Dimensions of the iris
- 12mm diameter
- 37mm circumference
- 2mm thickness
- The anterior chamber volume is 200uL compared to the posterior chamber at 60uL
Iris Zones
When looking at someone’s iris head-on, the visible anterior border is described in 3 zones
- The inner pupillary zone contains the sphincter pupillae muscle
- The outer ciliary zone contains the dilator pupillae muscle
- The collarette is the middle zone used for anatomical division
Muscles of the iris
The sphincter pupillae is responsible for pupil constriction and is innervated by postganglionic parasympathetic short ciliary fibres of CN3
The dilator pupillae is responsible for pupil dilations and is innervated by sympathetic branches of the ciliary nerves
Blood Supply to the iris
- Major circle comprised of 2 long posterior and 7 anterior ciliary arteries
- Minor circle is formed at the level of the collarette
- Iris vessels are not fenestrated, they do not leak during FFA
Layers of the Iris
- Anterior border
- Stroma
- Dilator pupillae
- Posterior pigment epithelium
Structure of the iris
- The anterior border is composed of modified stromal cells with crypts
- Koganei are clumps of pigmented macrophages found in the iris stroma
- The sphincter pupillae muscle lies within the stroma
- The posterior pigmented epithelium is cuboidal
Anatomy of the Ciliary Body
A muscular secretory structure involved in accommodation, aqueous production, and the blood-aqueous barrier.
Divisions of the Ciliary Body
Anterior functional part → pars plicata
Posterior non-functional part → pars plana
There are around 70 major ciliary processes in the pars plicata which are involved in aqueous secretion
What is ‘snow banking’
Snow banking is deposition on the pars plana of the ciliary body, a characteristic clinical sign of uveitis
Layers of the Ciliary Body
Epithelium, stroma and muscles:
The epithelium is bilaminar (arranged apex to apex) and cuboidal.
* The outer layer is pigmented.
* The inner layer in non-pigmented and produces aqueous.
There are 3 muscles: longitudinal (outermost), oblique, circular (innermost)
Nerve Supply to the choroid
PNS: Edinger Westphal nucleus of CN III → ciliary ganglion → short ciliary nerves → contract ciliary body and laxes zonular fibres
SNS: Hypothalamus → spinal cord → superior cervical ganglion → ICA plexus or by joining V1 → long ciliary nerves → relax the ciliary body and tenses zonular fibres
Anatomy of the Sclera
The sclera stretches from the iris at the front of the eye, to the optic nerve at the back. It is a tough outer coat of connective tissue.
The episclera is another layer of connective tissue which sits on top of the sclera. It is highly vascular and supplies the sclera with nutrients.
Where is the scelera thickest vs thinnest
- Thickest at the optic nerve
- Thinnest posterior to rectus muscle insertions
What type of collegen makes up the sclera
Contains mainly type 1 and 3 collagen
What ratio of the globe is formed by the sclera vs cornea
Sclera forms 5/6ths of the outer layer of the globe.
The cornea forms the remainder
What separates the sclera from the uvea
The suprachoroidal space
Innervation to the sclera
Innervated by long and short ciliary nerves
Anatomy of the Episclera
Heavily vascularised
The episclera is in between the sclera and the conjunctiva
Clinically differentiating Scleritis vs Episcleritis using phenylephrine
Scleritis results in inflammation of the deep vascular plexus of the sclera. This is too deep to be affected by topical phenylephrine (vasoconstrictor).
Contrastingly, episcleritis leads to the inflammation of the superficial vascular plexus and is affected by topical phenylephrine.
This means that the reddened vessels in episcleritis blanch with the administration of topical phenylephrine, compared to in scleritis where they don’t.
Compare scleritis vs episcleritis
Episcleritis is benign and self-limiting, compared to scleritis, which can be severe and sight-threatening.
Episcleritis
A benign inflammatory condition which typically re-occurs but is often self-limiting.
Pathology of Episcleritis
- Not classically associated with systemic disease
- Inflammation of the episclera is relatively benign
Presentation of episcleritis
- Sudden onset eye ache, tearing and photophobia.
- The eye is sectorally red and non-tender
Investigation for episcleritis
The red parts of the eye blanch with the administration of topical vasoconstrictors such as phenylephrine 10%
Sectoral red-eye in a patient with episcleritis
Management of episcleritis
Conservative management with topical lubricants and NSAIDs for symptom control is sufficient.
Episcleritis typically self-resolves within 2 weeks
Scleritis
Scleritis is uncommon and potentially blinding. It is typically classified as anterior or posterior scleritis, depending on which part of the sclera is affected. Unlike episcleritis, scleritis is often associated with systemic diseases.
Most common type of scleritis
There are a few different classifications of scleritis, based on location, nodularity, necrosis and inflammation.
Anterior diffuse scleritis is the most common type.
Most common systemic association with scleritis
Rheumatoid arthritis
Presentation of scleritis
- Severe deep boring eye pain that keeps the patient awake
- Tender globe
- Diffusely red eye
Investigation for scleritis
Red-eye does not blanch with topical administration of phenylephrine
Management of scleritis
Strength of treatment is determined by clinical severity.
- Oral NSAIDs
- Oral steroids
- IV steroids
General approach is based on initial high dose rescue therapy followed by tapering treatment.
Uveitis
The term uveitis describes the inflammation of the uveal tract, involving or not involving its neighbouring ocular structures such as the retina and vitreous.
Can be caused by a wide array of diseases
Classification of uveitis
- Anterior uveitis - Iritis + AC inflammation
- Intermediate uveitis - Pars planitis + vitritis
- Posterior uveitis - Chorioretinitis
- Pan uveitis - iritis + pars planitis + chorioretinitis (+ inflammation of associated structures)
A patient with anterior uveitis.
Anterior Uveitis
- Anterior uveitis is the inflammation of the iris (including pars plicata)
- Most commonly idiopathic, but can be HLA-B27 associated, infectious or systemic
- Anterior uveitis can predispose to posterior synechiae and angle-closure
What are keratic precipitates in anterior uveitis
White blood cells can accumulate in the corneal endothelium and are known as keratic precipitates (KPs).
The nature of these can be further classified based on appearance:
* Mutton fat KPs indicate granulomatous inflammation
* Stellate KPs indicate non-granulomatous inflammation
Presentation of anterior uveitis
- Inflammation of the iris and anterior ciliary body leads to AC flare.
- Inflammation of the iris sphincter can lead to irregular meiosis.
- Typically presents with a painful red-eye, AC flare, photophobia and blurred vision
Intermediate Uveitis
- Intermediate uveitis is the inflammation of the posterior ciliary body (pars planitis) and can also involve the vitreous
- Inflammatory accumulations in the vitreous are described as snowballs
- Characteristic white inflammatory exudation on the pars plana and ora Serrata is described as snow-banking (can be seen on indirect ophthalmoscopy with scleral depression)
Presentation of Intermediate Uveitis
- Painless blurry vision and floaters, without red-eye
- Pars planitis and vitritis leads to floaters and blurring of vision.
Causes of Infective Uveitis
Important cause of childhood leukocoria
Toxocariasis
How can toxocariasis be differentied from retinoblastoma?
Both present with leukocoria in childhood
The absence of calcification on CT scan differentiates it from retinoblastoma
Sarcoidosis
A multisystem inflammatory granulomatous disorder characterised by noncaseating granulomata
Presentation of sarcoidosis
- Bilateral: hilar lymphadenopathy, CN7 palsy and parotid enlargement
- More common in black women
- Can cause any type of uveitis.
- Pre-retinal granuloma (Lander sign)
Investigation of sarcoidosis
Associated bloods: high ACE and hypercalcemia
Tuberculosis
Multisystem Infective granulomatous disease caused by Mycobacterium tuberculosis
Tuberculosis presentation
- Can cause any type of uveitis
- More common in Indians
- Night sweats, weight-loss, hemoptysis and dacryoadenitis
Investigation for TB
Mantoux and antigen tests
Reactive arthritis
- HLA-B27 associated reaction caused by non-gonococcal infections, most typically chlamydia.
- A triad of: conjunctivitis, urethritis and arthritis
- Keratoderma blennorrhagica
Behcet’s Disease
HLA-B51 associated multisystem vasculitis
Anterior uveitis with a characteristic mobile hypopyon
Investigation for Bechcet’s disease
- Positive skin pathergy test (lots of skin lesions erupt in response to minor traumatic insult)
- Pulmonary artery aneurysm is pathognomonic
Kawasaki Disease
A medium vessel vasculitis of childhood
Kawasaki Disease presentation
- Bilateral anterior uveitis and conjunctivitis
- Characteristic >5day fever which does not respond to antipyretics
- Red palms and soles and a strawberry tongue
Investigation for Kawasaki Disease
All patients require an echocardiogram to rule out coronary artery aneurysm
Vogt-Koyanagi-Harada disease
Multisystem granulomatous inflammation due to melanocyte Tcell hypersensitivity (commoner people with darker skin)
- Bilateral panuveitis
- Prodrome of fever, meningism and tinnitus followed by vision loss and vitiligo.
- Can effect the auditory, neurological, and dermatological systems
Tubulointerstitial nephritis and uveitis
Non-granulomatous inflammation of the kidneys and the eye
- Bilateral chronic anterior uveitis
- Female adolescent with renal symptoms followed by ocular symptoms
Investigation for Tubulointerstitial nephritis and uveitis
Elevated urinary beta-2 microglobinuria
Juvenile Idiopathic Arthritis
The most common cause of anterior uveitis in children.
Also the most common rheumatological disease in children
Non-granulomatous inflammation
Presentation of Juvenile Idiopathic Arthritis
- Chronic anterior uveitis
- Arthritis, fevers and rashes
- Associated with cataracts and band keratopathy
Limited Ocular Uveitis
Important causes of uveitis which are limited to the eye without systemic involvement
HLA associations with various ophthalmic diseases
