Sclera Flashcards
anatomy of sclera
The sclera forms 5/6 of the outer coat of the globe. It starts at the limbus anteriorly and terminates at the optic nerve posteriorly. The sclera is thinnest posterior to the rectus muscle insertion and thickest surrounding the optic nerve.
what are the three parts of the sclera
- Episclera (outermost): Thin vascularized connective tissue anterior to the sclera and posterior to the Tenon capsule.
- Substantia propria: Made of irregularly arranged type I collagen fibrils.
- Lamina fusca (innermost): Made of loosely arranged connective tissue and
separated from the choroid by the suprachoroidal space.
bloody supply of the sclera
● Anterior sclera: Long posterior ciliary nerves.
● Posterior sclera: Short posterior ciliary nerves.
what is episcleritis
who does it affect the most
(inflammation of the episclera) is a common self-limiting condition which typically affects middle-aged females. It is usually idiopathic.
what is simple episcleritis
● Most common.
● Acute onset, peaking at 12–24 hours and then slowly fades after a few days.
● Localized triangular redness and discomfort.
what is nodular episcleritis
● Insidious onset and longer recovery time.
● Red eye and discomfort are the most common symptoms.
● Tender vascular nodule seen most commonly at the interpalpebral fissure.
on slit lamp the anterior scleral surface is flat - shows absence of scleral involvement
Ix for episcleritis
Instillation of 10% phenylephrine blanches the redness in episcleritis.
Mx for episcleritis
Cool compresses and oral nonsteroidal anti-inflammatory drugs (NSAIDs).
what is scleritis
Full-thickness inflammation of the sclera, most commonly associated with autoimmune diseases.
deep vascular plexus is affected
systemic associations of scleritis
● Rheumatoid arthritis (RA): The most common systemic association of scleritis. (Note: The most common ocular manifestation of RA is keratoconjunctivitis sicca.)
● Granulomatosis with polyangiitis.
● Polyarteritis nodosa.
● Relapsing polychondritis.
● Infection: Herpes zoster, Lyme disease, syphilis, etc.
what is diffuse anterios scleritis
Sx
Signs
● Most common.
● Dull pain that may radiate to the forehead or jaw.
- pain imporves over the day
● Gradual onset of localized or diffuse redness of the eye.
● Oedematous sclera that often resolves leaving a bluish hue (due to scleral
translucency).
what is nodular anterior non-necrotising scleritis
● Gradual onset of insidious pain followed by red eye.
● Single or multiple erythematous, tender nodules.
- slit lamp - displacement of the beam by the scleral nodule
what is necrotising scleritis with inflammation
Sx
Signs
● Most severe form, can result in visual loss.
● Subacute severe ocular pain that radiates to the forehead or jaw.
- interrupt sleep and responds poorly to analgesia
● Redness and lacrimation.
● White patches of scleral oedema that block overlying episclera and conjunctiva vasculature, leading to low perfusion and necrosis to scleral tissue.
what is scleromalacia perforans
Sx
Signs
● Also known as necrotizing scleritis without inflammation.
● Bilateral involvement, typically seen in elderly patients with advanced RA.
Sx
- keratoconjunctivits sicca (dry eyes)
SIGNS
● Characterized by an asymptomatic, gradual onset of necrotic patches leading to scleral thinning exposing the underlying uvea.
Mx for Scleritis
● Instillation of 10% phenylephrine does not blanch vessels in scleritis.
● Oral NSAIDs for mild-moderate scleritis.
● Systemic steroids and/or other immunomodulatory therapy for severe or
necrotizing scleritis.
what is posterior scleritis
Posterior scleritis is a rare inflammatory condition affecting the posterior sclera.
features of posterior scleritis
● Severe pain (not correlating with severity of inflammation)
- tenderness to palpate
SIGNS
● Choroidal folds - anterior displacement of the choroid
● Retinal detachment
● myositis -> Diplopia and mild proptosis
● Optic disc swelling and vision loss
Ix for posterior scleritis
B-scan ultrasound shows increased thickness of the sclera and fluid accumulation in the sub-Tenon space giving rise to a characteristic ‘T’ sign.
Mx for posterior scleritis
Oral NSAIDs ± corticosteroids.
what is blue sclera
A blue sclera is a result of exposure of underlying uvea due to scleral thinning.
what is OI
characteristics
ocular features
● Osteogenesis imperfecta
AD inherited disease as a result of type I collagen defects.
Characterized by fragility fractures, short stature, hearing loss and easy bruising.
Ocular features: Blue sclera, megalocornea and shallow orbits.
EDS and blue sclera
● Ehlers-Danlos syndrome VI
- AR inherited condition characterized by joint laxity, cardiovascular problems and easy bruising.
- Ocular features: Blue sclera, keratoconus, lens subluxation and strabismus.
pathophysiology of episcleritis
maximal congestion occurs within the vascular plexus
inflammatory infiltrates the episclera and tendons capsule
sclera in itself is not swollen
classification of immune mediated scleritis
non necrotising
- diffuse
- nodular
necrotising w inflammation
- vaso-occlusive
- granulomatous
- surgically induced
scleromalacia perforans
posterior
signs of vaso-occlusive necrotising scleritis
ass w RA
scleral oedema isolated patches
if unchecked rapidly progress to scleral necrosis
signs of granulmoatous necrotising scleritis
ass w polyarteritis nodosa and wegners
within 24 hours the sclera and above structures become raised and irregular
signs of surgery induced necrotising scleritis
within 3 weeks of procedure
necrotising
most common cause of infective scleritis
herpes zoster
causes of scleral discolouration and their colours
alkaptonuria - bluish grey or black discolouration
haemachromatosis - dry eye, rusty brown sclera
what is scleral hyaline plaque
dark grey close to insertion of horizontal muscles
elderly
types of anterior scleritis
diffuse
nodular
necrotising scleritis w inflammation
scleromalacia perforans
