Diseases of Sclera

Sclera is posterior 5/6th outer opaque fibrous coat of eyeball with 3 layers:

1. vascular CT: episclera
2. avascular collagen: sclera porper
3. innermost brown: lamina fusca

Whole sclera has an outer tenon’s capsule & in addition covered anteriorly by bulbar conjunctiva.
Schlemm’s canal is the furrow near limbus.
It is thinner at extraocular ms insertions & is sieve-like lamina cribrosa at optic.N exit.
Apertures:

1. anterior limbal- anterior ciliary bv
2. middle- vortex veins
3. posterior- long&short ciliary N&bv

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Episcleritis:

benign recurrent inflmm of episclera & tenon+bulbar conjunctiva.
Etiology:

• usually in young adult [female]
• Associated with immune rxns:
  • rosacea, gout, psoriasis
  • TB, strep toxins

Pathogenesis:

1. episclera: localised lymphocytic infiltration
2. tenon+bulbar conj: edema & hyperaemia

CFs: red, gritty, [mild lacrimation & photophobia]

1. Diffuse: whole scleral inflmm but maximum confined to 1or2 quadrats
2. Nodular: firm, tender, pink-purple nodule 2-3mm form limbus with overlying mobile conjunctiva & surrounding injection

Rx:

• spontaneous regression after 10days-3wks
• protracted course of few days with topical steroids.
• recurrent disease- systemic NSAIDs

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Scleritis

seroius chronic inflmm of sclera proper.
Etiology:

• usually in elderly [40-70 female]
• Associated with:
  1. autoimmune collagen disorders- Rharthritis, PAN,SLE, ankylosing spondylitis, wegner’s granulomatis
  2. metabolic- gout, thyrotoxicosis
  3. scleral infections- Hzoster, staph, strep
  4. Granulomatous diseases- TB, syphilis, leprosy, sarcoidosis
  5. misc- rosacea, bechet’s, VHK syndrome, thermal/chemical burns

Pathogenesis: Granuloma-

1. fibrinoid necrosis
2. infiltration + collagen destruction
3. surrounded by epitheloid giant cells & bv

CFs:

• severe deep pain which radiates to jaw & temple
• local/diffuse redness
• mild to severe lacrimation & photophobia
• occasional visual impairment
• Types:
  

  Anterior non-necrotizing	DIFFUSE INFLMM [commonest]- pink/purple; ≥ 1quadrant NODULAR- 1or2 near limbus; hard elevated purple
  Anterior necrotizing	INFLAMM- localised acute severe; thin transparent ectatic vasculitic infarct; [associated uveitis] SCLEROMALACIA PERFORANS [non-inflmm due to obliteration of arterial supply]- initially yellow sequestrum → dead white → absorbed leaving a punched out sclearal peforation
  Posterior scleritis	CFs of inflmm of associated structures: exudative retinal detachment macular edema proptosis restricted ocular movts
  Complications	sclerosing keratitis, keratolysis complicated cataract secondary glaucoma

Diagnostic investigations:

• TLC, DLC, ESR
• immunological: C3, immune complexes, Rhfactor, LE cells, anti-nuclear antibodies
• syphilitic- VRDL
• gout- uric acid
• TB- mantoux test
• Xrays to rule out foreign body in chest, sacroiliac jt, PNS & orbit

Rx:

1. non-necritizing → topical steroids, systemic NSAIDs
2. necrotizing → oral+topical steroids [CI- subconj inj since scleral perforation], unresponsive cases – mtx,cyclophosphamide

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Blue sclera

Thinning due to

• osteogenesis imperfecta
• Marfan’s, Ehlers Danlos
• Buphthalmos
• high myopia
• healed scleritis

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Staphyloma

Types	localised bulge due to thinned outer fibrous coat	underneath shinning uvea is seen through
Anterior	pseudocornea [scar formed after total sloughing of cornea from organised exudate & eoithelial covering]	plastered prolapsed iris
Intercalary	limbal scar after perforating injury or peripheral corneal ulcer	iris root
Ciliary	thin sclera at 2-3mm from limbus due to perforating inj / scleritis / absolute glaucoma	ciliary body
Equatorial	at vortex vein perforations after scleritis / pathological myopia	choroid
Posterior	thinned sclera behind equatorial after perforating inj / pathological myopia / scleritis	excavation with dipping retinal bv

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