Cornea, Sclera, Conj

What is the purpose and characteristics of the sclera?

• Form a protective shell to protect the internal structures of the eye

• Opaque - prevents light entering and minimises internal light scatter

• Rigid - prevents eyeball from being distorted when rotated

• Resists changes in shape from changes in IOP

What is the sclera innervated by?

• Long and short ciliary nerves 

• Has widespread nervous plexus

What Sx are present if the nervous plexus is inflamed?

• Dull ache 

• Pain on eye movement - EOM attached to sclera

How many layers does the sclera have?

• 1) Tenon’s capsule or Fascia Bulbi 

• 2) Episclera

• 3) Scleral Stroma

• 4) Lamina Fusc

What is Tenon’s capsule?

• Connective tissue layer made up of radial collagen bundles which commence at the limbus

• Avascular structure

What is the Episclera?

• Made up of loosely arranged collagen bundles in a circumferential arrangement

• Highly vascular structure fed by the anterior ciliary arteries

What is Scleral Stroma?

• Consists of dense layers of collagen bundles arranged in an irregular pattern 

• Irregular pattern = opacity of the sclera 

• Viscoelastic structure - can respond to external forces 

Receives a small blood supply from the anterior and posterior ciliary arteries

What is Lamina Fusca?

• Innermost layer e.g forms an interface c Choroid

• Faint brown appearance - melanocytes

Collagen fibres passing from sclera to choroid form a weak attachment

Why may the sclera appear yellow?

• Age - increased fatty deposits

• Liver disease

Why may the sclera have a blue tinge?

• Seen in infants - due to underlying uveal tract showing through

• Seen in Px with connective tissue disorder

What is a scleral hyaline plaque + RF?

• Innocuous condition seen in elderly px, close to the insertion of the medial or lateral muscles

• RF; age, females, moderate to high myopia and degenerative arthritis

What is the corneal epithelium?

• Consists of 5-7 layers of cells - connected by tight junctions which prevent entry of water from TF

• Squamous cell layer - shows microvilli 

• Cell division occurs at limbus - then migrate to centre of cornea - approx 7 days for corneal epithelium to be replaced

What is the function of microvilli?

• Assist in the retention of tears on the eye

• Secrete a glycocalyx substance which connects with the mucin layer of TF

What is Bowman’s layer?

Dense acellular fibrous layer of collagen which terminates at limbus

What is corneal stroma?

• Thickest layer (90% of CT)

• Regular matrix of collagen fibrils embedded in glycosaminoglycans - regular pattern - ensures cornea remains transparent

• Any disruption to the regular spacing = reduction in transparency e.g penetrating injury

What is Descemet’s membrane?

• Basement membrane of the corneal endothelium

• Continuous with the TM  - Schwalbe’s line

• Thickens with age

What is corneal endothelium?

Single cell layer - hexagonal & regular in shape

Where does the cornea receive its nutrients from?

• Avascular structure - receives nutrients via diffusion from the aqueous and vessels of the limbus 

• Central cornea - oxygen from the atmosphere indirectly via TF

Where do the vessels at the limbus arise from?

• Anterior ciliary arteries of the conjunctiva and sclera

Why is the cornea immune privileged and what does it mean?

• Due to an absence of BV

• It means that there is a reduced risk of a corneal graft being rejected

How is the cornea innervated?

• Sensory nerves arising from the long and short ciliary nerves - they arise from the Ophthalmic division of the trigeminal nerve

• Corneal nerves are unmyelinated - don’t interfere with corneal transparency

• Nerves terminate at the corneal epithelium 

Dense nerve endings account for the cornea’s pain response to even a slight touch

What occurs with a loss of corneal innervation?

• Neurotrophic Keratopathy

What is the conjunctiva?

• A thin mucous membrane which covers the outer surface of the eye

What are the two layers of the conjunctiva?

• Outer stratified epithelium - contains goblet cells - responsible for producing the mucus content of TF

• Inner connective tissue layer - BV of conjunctiva are located alongside nerves 

  • Conjunctiva also contains accessory lacrimal glands

How does the conjunctiva receive its blood supply?

• Palpebral arcades of the eyelids OR anterior ciliary arteries

What is the conjunctiva’s nerve supply?

• From the trigeminal nerve via Ophthalmic division - as with cornea

What is episcleritis?

• An inflammatory condition affecting the episclera 

• Can be recurrent 

• Many cases idiopathic but association possible in bilateral cases with rheumatoid arthritis and IBS

• More frequent in Females

• No tarsal conj, AC/Corneal involvement 

• Peaks at 12 hours and typically lasts 2-3 days

• May lead to dry eyes due to association with RA

• Mostly Unilateral

What is Simple Episcleritis?

• 80% of cases 

• Sectoral or diffuse redness - dilated episcleral vessels WITH areas of WHITE unlike Scleritis 

• Px reports mild ache or burning sensation of acute onset

• Eye will be tender to touch + watery, painful

• No affect on VA, rarely photophobia

What is Nodular Episcleritis?

• 20% of cases

• Less acute onset with redness increasing over a couple of a days

• Elevated nodule is seen 

• Can be more persistent

• No affect on VA, rarely photophobia

Simple v Nodular Appearance

What can be useful in the diagnosis of Episcleritis?

• Use 2.5% Phenylephrine - check if vessels blanch - e.g area of redness to now quiet 

• Use cotton bud to see if redness/vessels move

What is the management for either case of Episcleritis?

• Nothing as usually self resolves within 7-10 days if mild 

• Advise cold compress, ocular lubricants + NSAIDs e.g ibuprofen to ease sx

• In severe cases/nodular - refer for mild topical steroids + systemic NSAIDs 

In recurrent cases - refer to secondary care for investigation for any underlying systemic disease

What is scleritis?

• Inflammation of the sclera - scleral + episcleral tissues - can also involve cornea and uveal tissues

• Rare but sight threatening 

• More frequent in females - aged 40-60

• 30-40% of cases are associated with autoimmune conditions 

• Small proportion due to infectious origin from organisms - Herpes Zoster Ophthalmicus

• Can affect both anterior and posterior sclera

• Vessels would not blanch with phenylephrine

• May see uveitis alongside

• Bilateral in 30-50% of cases

• Sx worse at night

What is anterior scleritis?

• Usually in 50s and over - females

• Redness can be diffuse or nodular due to dilated scleral vessels 

• Diffuse - generalised or sectoral redness - in top and lower fornix 

• Nodular - raised areas about 3-4mm from the limbus - becomes translucent as scleritis resolves

Diffuse

Nodular

What are the sx of anterior scleritis?

• Intense, Severe and deep pain, may radiate to face and brow area - may wake them up from sleep

• Eye is tender on eye movement 

• Reduced Vision

• Photophobia

What is Necrotizing anterior scleritis?

• 15% of cases - more aggressive form

• Px generally older ~ 60yrs 

• 60% cases are bilateral 

• Can suffer severe ocular damage if treatment is delayed

What is posterior scleritis + sx?

• 10% of scleritis cases

• Sight loss can be rapid

• 35% cases bilateral 

• Can present in healthy px under 40 yrs 

• When it occurs in older px, they generally have systemic disease e.g rheumatoid arthritis

• Associated inflammation of EOM (myositis) = px may experience pain on eye movement + painful to touch 

• NO PHOTOPHOBIA

What is posterior scleritis associated with?

• May lead to;

  • exudative RD

  • Choroidal folds

  • Disc Oedema

Management for different types of scleritis?

• Necrotizing Anterior Scleritis + posterior scleritis = emergency same day referral

• Non-necrotizing Anterior Scleritis - seen within a week - semi-urgent referral

• Advise analgesia 

• Advise Sun Rx to minimise photophobia

What does Chemosis mean?

• Oedema of the Conjunctiva

What are follicles?

• Discrete raised translucent lesions with blood vessels running around them

• Indicate prolonged inflammation has been present

What are Papillae?

• Discrete raised lesions with a central vascular core 

• Macro papillae <1mm diameter

• Giant papillae >1mm diameter

• Indicate prolonged inflammation has been present

Img of Follicle vs Papillae

What is a pseudo membrane?

• Coagulated exudative material which can be peeled away from the conjunctiva

Conjunctivitis - monocular/binocular

• B - starts mono, bino within 1-2 days

• V - starts mono, bino within 1-2 days

• A - acute onset mono/bino - depends on allergen type

Conjunctivitis - redness

• B - towards fornixes

• V - generalised redness - more severe than others - poten. haemorrhage

• A - generalised redness

Conjunctivitis - VA

• B - normal

• V - mildly affected

• A - Fluctuates

Conjunctivitis - chemosis

• B - No

• V - No

• A - YES

Conjunctivitis - Papillae/Follicles

• B - P

• V - F

• A - P

Conjunctivitis - Discharge

• B - muco-purulent

• V - watery, sticky

• A - watery with increase in mucous

Conjunctivitis - irritation

• B - mild, burning, gritty

• V - mild, burning, gritty

• A - itchy

Conjunctivitis - photophobia

• B - NO

• V - MILD

• A - NO

Conjunctivitis - cornea

• B - superficial punctate stains

• V - Microcysts, punctate epithelial stains within 7-10 days, corneal infiltrates if severe

• A - generally clear

Conjunctivitis - Eyelids

• B - Stuck together in the morning

• V - Oedema

• A - Oedema

Conjunctivitis - Lymph node signs

• B - absent unless very severe

• V - enlarged preauricular nodes - in front of the ear

• A - absent

Conjunctivitis - GH

• B - possible compromised immune system e.g Diabetes 

• V - YES - sore throat, flu-like sx

• A - history of allergies

What is the treatment for Bacterial Conjunctivitis?

• Usually resolves itself within 5-7 days s Tx

• FUSIDIC ACID + CHLORAMPHENICOL

• Return if persists longer than 7 days

What is the treatment for Viral Conjunctivitis?

• Ocular Lubricants + Cold compress

• May last 7-21 days

What is the treatment for Allergic Conjunctivitis?

• Avoid Allergen

• Cold compress + Ocular lubricants 

• Topical antihistamines + mast cell stabilisers may be used

• Avoid eye rubbing

Bacterial Conjunctivitis summary

• Contagious

• Eyes stuck together in the morning - yellow/green muco-purulent discharge

• Young Children + Elderly more at risk

• Onset - over 24hrs

• 2nd eye involvement after 1-2 days

• Papillae present 

• Vision is normal

• Mild, burning, gritty

• NO photophobia

• Superficial punctate stains

•  In very severe cases - lymph node signs

• Resolves without Tx - usually within 5-7 days

Viral Conjunctivitis Summary - adenovirus

• Highly contagious

• Sticky discharge in morning, watery discharge during day

• Onset - 12 hours - 2/52

• Severe redness compared to others

• Vision affected - mildly 

• Mild, burning, gritty

• Follicles

• Mild Photophobia 

• Swollen eyelids

• Microcysts, punctate epithelial stains, corneal infiltrates

• Conjunctival Haemorrhages

• Lymph node signs

• PRESENCE OF PSEUDOMEMBRANE

• Recent flu sx/sore throat

• Ocular lubricants + cold compress 

• Lasts 7-21 days

Allergic Conjunctivitis Summary - Seasonal/Perennial

• Not Contagious

• Vision fluctuates 

• Common in young px - LESS COMMON with increasing age

• Oedema of conjunctiva - chemosis!

• Papillae

• Watery discharge

• No photophobia

• Swollen eyelids

• Itchy

• NO lymph nodes

• Cornea clear 

• Cold compress + Lubricants

• Oral Antihistamine + Mast Cell Stabiliser e.g Sodium Cromoglicate

Can you continue wearing CL with Conjunctivitis?

• NO - must cease until issue is resolved

What is GPC / CLAPC + Signs?

• Conjunctival reaction due to mechanical action - CL / Ocular Prosthesis

• Reaction is exacerbated by protein deposits on the surface of a CL / Prosthesis

• Mucus discharge and papillae under upper lid

Sx of GPA?

• FB sensation

• Itching 

• Mucous discharge

What is the treatment for GPC?

• Ensure Optimum fit + cleaning process of CL / Prosthetic 

• Mast Cell Stabilizers - to alleviate acute Sx

• Temp. cease lens wear

What is Molluscum Contagiosum?

• Associated with chronic unilateral conjunctivitis - mild redness + irritation

• Usually in children aged 2-4 

• Assessment of eyelid may reveal a small wart lesion on lid margin and a follicular conjunctivitis - follicles under eyelids

• More severe in immunocompromised individuals

• Referral indicated for lesions on eyelid margin

What is Vernal Keratoconjunctivitis?

• Inflammatory condition that affects both conjunctiva + cornea

• Combined IgE and Histamine modulated 

• Mediated due to immune reaction 

• Occurs mainly in boys from 5 to teenage years before resolving

• Recurrent, rare in UK 

• 90% of Px have a history of Atopy - asthma / eczema

• Bilateral 

• More common in Africa + Indian subcontinent

What are the sx of Vernal Keratoconjunctivitis?

• Itchy, watery eyes 

• FB sensation 

• Pain + Photophobia if corneal involvement 

• Blurry vision

What are the signs of Vernal Keratoconjunctivitis?

• Reduced VA - corneal involvement

• Thick, stringy mucous deposit may be seen 

• Papillae on palpebral conjunctiva >1mm in size - cobblestone c large hyperaemia -

• Superior punctate epithelial erosions - can become ulcerative in future - leads to corneal ulcer - photophobia

Management of Vernal Keratoconjunctivitis?

• Referred to Ophthalmologist due to sight threatening nature

• Corneal involvement - emergency

• No corneal involvement - see within 2/52 - semi urgent

What is Atopic Keratoconjunctivitis?

• Similar sx to VKC but occurs in adult population - 30-50 yrs 

• IgE and type 4 hypersensitivity mediated reaction

• Due to overreaction of immune system as with VKC

• Sx are more severe and unremitting than VKC 

• History of Atopy as with VKC - greater link in AKC

• Affects both genders evenly unlike VKC

• May see cracked skin 

• Tarsal papillae

• Typically a year round condition unlike VKC - OFTEN WORSE IN WINTER

Management of Atopic Keratoconjunctivitis

• Referral to Ophthalmologist within 1/52 if active corneal involvement - urgent

• If stable then routine

• Allergen avoidance, cold compress

• Advise seeing GP for oral and topical antihistamine

  • If GP management fails then semi urgent

AKC

What is a Sub-Conjunctival Haemorrhage (SCH)?

• Arise due to bursting of either the episcleral or conjunctival vessels 

• Blood collects in the subconjunctival space due to BV located in inner connective tissue layer of conjunctiva

• Associated with coughing or vomiting - temporary increase in venous pressure = vessel burst 

• Most commonly found on the temporal or inferior conjunctiva - unilateral 

• Seen in over 50s

RF / causes of SCH?

• Hypertension / DM2 / Anticoagulant Meds 

• Ocular Trauma - orbital / skull fractures - blood enters conjunctival space from retrobulbar vessels 

• Eye rubbing

• Surgery

What are the sx of SCH?

• Asymptomatic 

• May report mild irritation

What is the management of SCH?

• If cause is due to Orbital / skull fractures - Emergency referral due to blunt trauma

• Spontaneous SCH - managed in practice as it will resolve over next 1-2 weeks - return if persists longer 

• Recurrent SCH - referral to GP to check bleeding / clotting disorders

What is Pinguecula?

• Small lump on the bulbar conjunctiva adjacent to the limbus 

• More common on Nasal side but CAN have on both sides

• Typically Bilateral but Asymmetric

Why does Pinguecula occur and when is treatment necessary?

• Due to the effect of UV on Collagen fibres of the conjunctival stroma

• Tx only required if it becomes inflamed /cosmetically unacceptable

What is the Tx for Pinguecula?

Short course of mild steroids

What is Pterygium and its signs?

• Triangular fibrovascular growth which often commences in the nasal bulbar conjunctiva

• Growth is slow but progresses towards cornea - leading to chronic dryness of cornea 

• Will interfere with CL wear 

• Causes astigmatic changes

• Reduced vision if crosses visual axis / pupil area

• Typically Bilateral but Asymmetric

What causes Pterygium?

• Occurs more often in Px c UV exposure + Hot Dry Climates

• Related to chronic dryness

What is the management of Pterygium?

• Use of Ocular Lubricants 

• Referred for surgery if pterygium is affecting vision, astigmatism / chronically inflamed / cosmetically unacceptable

What is Keratoconus (KC)?

• Corneal shape - conical in profile - due to thinning of corneal stroma - causes a bulge forward

• Bilateral BUT Asymmetric

• Changes initially occur at the posterior corneal surface 

• Topographer used to aid diagnosis

When does KC typically manifest?

• Manifests in 2nd or 3rd decade of life 

  • Stabilises by 4th

What is the sx of Keratoconus?

• Blurred vision 

• Potentially Monocular Dipl - due to irregular astigmatism

What are the signs of KC?

• Myopic shift 

• Irregular Astigmatism - leading to monocular diplopia

• Scissor reflex via retinoscopy

• Vogt Striae

• Fleischer ring

• Munson Sign 

• Increased visibility of corneal nerves

• Corneal scarring if progression

  • more common in younger Px + CL wearers

What is Vogt Striae?

• Fine vertical lines / stretch marks seen in the posterior stroma of Descemet’s membrane 

What is the Fleischer Ring?

Iron Oxide Hemosiderin deposits in the corneal epithelium seen at the base of the cone

What is Munson's sign?

• Bulging of the lower lid on downgaze created by the conical appearance of the cornea

• Creating a V shape of the lower eyelid

RF for KC?

• Atopic conditions - persistent eye rubbing

• Systemic conditions which involve abnormal connective tissue - Marfan Syndrome or Ehlers-Danlos

• Downs syndrome

• Middle Eastern / Asian ethnicity

• FMH

What is the management of KC?

• In mild cases vision may be correctable with specs 

• As it progresses - RGP may be used to correct irregular astigmatism 

  • 90% of px c irregular corneas use CLs to correct vision c majority RGPs 

• Refer for Corneal cross linking using riboflavin - increase biomechanical stability of the cornea - prevent progression - only in younger px

Routine referral in majority of cases

When is Cross linking contraindicated?

• If cornea has <400 micrometres thickness

• Px will still require CL post treatment

What percentage of Keratoconics require corneal transplants?

• 15 - 20%

What are Acute Hydrops + RF?

• Corneal steepening becomes so great that breaks occur in Descemet’s Membrane 

• Aqueous enters corneal stroma + epithelium causing CORNEAL OEDEMA

• MEN 2-3x affected

• Complication of KC

• Eye rubbing

• VKC

What are the sx of Acute Hydrops?

• Reduced vision

• Pain

• Photophobia

• Watery eye

• Intolerable CL wear

What is the management of Acute Hydrops?

• Breaks can repair themselves so condition should subside in approx. 3/12

• No sign of Neovas - then can be managed by Optoms - review weekly

• IF sign of Neo - refer URGENTLY

What is Fuchs endothelial dystrophy + RF?

• Non inflammatory disease of corneal endothelium 

• Progressive dysfunction of endothelial pump mechanism results in corneal oedema and reduced vision

• Most cases develop in 4th decade or later

• Bilateral but ASYMMETRIC

• More common in Females

• Genetic RF 

• Smoking