Eye Diseases > Cornea
Corneal Pannus
Evidence-based assessment and management of corneal pannus. Comprehensive guide covering etiology, pathogenesis, classification, diagnosis, and treatment protocols for optometry practice.
Corneal pannus: fibrovascular membrane (red mesh) advancing subepithelially from the superior limbus over Bowman's layer. Herbert's pits (amber ovals) mark sites of regressed trachomatous limbal follicles — pathognomonic of trachoma. Ghost vessels (dashed grey) indicate areas of regressed pannus.
Corneal pannus is a fibrovascular membrane that grows from the limbus subepithelially over Bowman's layer onto the corneal surface. It is distinguished from pure corneal neovascularisation by the presence of both vascular and fibrous components — vessels alone do not constitute pannus.
The leading worldwide cause is trachoma (Chlamydia trachomatis) — the WHO's leading infectious cause of preventable blindness, affecting over 1.9 million people globally. In high-income settings, chronic contact lens hypoxia is the most common cause, alongside superior limbic keratoconjunctivitis (SLK), atopic keratoconjunctivitis (AKC), ocular rosacea, and chemical burns.
Pannus typically originates from the superior limbus (trachoma, SLK, contact lens), though inferior (rosacea, phlyctenular) and circumferential (chemical burns, SJS) forms occur. Progressive destruction of Bowman's layer leads to irreversible subepithelial scarring and, in advanced cases, visual loss.
- Trachoma (Chlamydia trachomatis): Most common worldwide; “pannus trachomatosus”; chronic conjunctival infection → superior limbal inflammation; endemic in sub-Saharan Africa, Middle East, Southeast Asia, Pacific islands
- Contact lens wear: Chronic corneal hypoxia from low-Dk lenses or overwear → limbal ischaemia → VEGF upregulation; superior or circumferential distribution
- Superior limbic keratoconjunctivitis (SLK): Mechanical friction between superior tarsal conjunctiva and bulbar conjunctiva/limbus → chronic superior limbal inflammation
- Atopic keratoconjunctivitis (AKC) / Vernal keratoconjunctivitis (VKC): Chronic IgE-mediated and T-cell-mediated limbal inflammation; severe forms cause progressive superior pannus
- Ocular rosacea: Sebaceous gland dysfunction and meibomian gland disease → lipid tear instability → inferior limbal inflammation; meibomian gland eyelid disease
- Phlyctenular keratoconjunctivitis: Type IV hypersensitivity reaction to tuberculin protein or Staphylococcus exotoxin; limbal nodule with vessel ingrowth
- Chemical / alkali burns: Limbal stem cell destruction → loss of corneo-conjunctival barrier → conjunctivalisation and pannus ingrowth
- Interstitial keratitis: Syphilitic; deep stromal vascularisation with surface pannus component; “ghost vessels” after treatment
- Radiation / UV exposure: Chronic actinic limbal damage; mechanism similar to pterygium formation
- Stevens-Johnson syndrome (SJS): Acute conjunctival necrosis → limbal stem cell failure → circumferential pannus
- Limbal hypoxia or chronic inflammation → upregulation of pro-angiogenic factors: VEGF-A, FGF-2, HIF-1α, PDGF at the limbus.
- Vascular sprouting from limbal capillaries → new vessels advance subepithelially over Bowman's layer toward the visual axis.
- Co-migration of activated fibroblasts → fibrous extracellular matrix deposited alongside the advancing vessels → fibrovascular pannus (vessels + fibrous stroma).
- In trachoma specifically: Chronic Chlamydia trachomatis infection → tarsal conjunctival follicles → scarring → trichiasis → repeated mechanical epithelial trauma → sustained superior limbal inflammation → progressive superior pannus. Bacterial lipopolysaccharide and cytokines (IL-1β, TNF-α) perpetuate the inflammatory cycle.
- Bowman's layer destruction: Advancing pannus disrupts and replaces Bowman's layer with fibrous tissue → subepithelial scarring → irreversible corneal opacification (leucoma).
- Regression / ghost vessels: With treatment (removal of hypoxic stimulus, antibiotic clearance of trachoma), active vessels lose blood flow but remain as optically empty channels — “ghost vessels” — visible on slit-lamp retroillumination. The fibrous stroma largely persists.
By Composition
- Progressive (active) pannus: Vascularised; active blood flow in vessels; fluorescein angiography shows leakage; associated with ongoing inflammation or hypoxia
- Degenerative (fibrous) pannus: Avascular; fibrosis and ghost vessels; stationary; seen after removal of causative stimulus
By Location
- Superior: Trachoma, SLK, contact lens-related — most common
- Inferior: Ocular rosacea, phlyctenular keratoconjunctivitis
- Circumferential (360°): Severe chemical burns, Stevens-Johnson syndrome, advanced atopic disease
By Extent — Herbert's Grading (trachoma)
| Grade | Description |
|---|---|
| Grade 1 | <2 mm from limbus; peripheral, asymptomatic |
| Grade 2 | 2–4 mm from limbus; mid-periphery |
| Grade 3 | >4 mm from limbus; approaching visual axis |
| Grade 4 | Central; visual axis involved; significant visual impairment |
Herbert's pits: Limbal depressions representing regressed follicles at the site of prior trachomatous pannus — pathognomonic of trachoma even in the absence of active disease.
- Trachoma: Endemic region residence; overcrowding; poor sanitation and water access; poverty; childhood exposure
- Contact lens wear: Extended / overnight wear; low oxygen-transmissibility (Dk/t) lenses; overwear; poor compliance; contaminated lens solutions
- Chronic ocular surface disease: AKC, VKC, SLK, ocular rosacea, phlyctenular keratoconjunctivitis; poorly controlled inflammation is the key driver
- Limbal stem cell deficiency (LSCD): Chemical or alkali burns; Stevens-Johnson syndrome / TEN; multiple ocular surgeries; aniridia
- Immunological: Systemic atopy (eczema, asthma, allergic rhinitis); autoimmune disease; graft-vs-host disease
- UV exposure: Outdoor workers in UV-intense environments (arid, high-altitude regions); pterygium co-morbidity
- Trichiasis: Inturned eyelashes causing chronic superior limbal mechanical trauma — particularly in trachoma sequelae
- Immunosuppression: Increased severity in organ transplant recipients; HIV; chemotherapy patients
- Grey-white fibrovascular membrane: Grows from the limbus (typically superior) over Bowman's layer; translucent to opaque depending on thickness
- Active vessels: Bright red vascular channels within the pannus; blood flow visible on slit-lamp (progressive type)
- Ghost vessels: Empty, bloodless vessel channels; seen by slit-lamp retroillumination or sclerotic scatter; indicate regressed or treated pannus
- Herbert's pits: Small limbal depressions at sites of resolved trachomatous limbal follicles; pathognomonic of trachoma even in quiescent disease
- Subepithelial fibrosis: Grey-white haze beneath the corneal epithelium; Bowman's layer disrupted or replaced
- Irregular corneal surface: Bowman's layer disruption → surface irregularity visible on retroillumination and topography
- Punctate epithelial staining: Fluorescein or rose bengal staining over the pannus surface
- Superior limbal vessel engorgement: Dilated limbal vasculature at the pannus leading edge
- Tarsal scarring and trichiasis (trachoma): Arlt's line — horizontal linear tarsal scar; entropion; trichiasis (inturned lashes)
- Papillary or follicular tarsal conjunctivitis: Signs of the underlying cause (trachoma follicles, AKC papillae, vernal shields)
- Asymptomatic (early): Peripheral pannus (Grade 1) commonly causes no visual symptoms
- Foreign body sensation / irritation: Epithelial disruption and surface irregularity over the pannus
- Photophobia: Active inflammatory pannus, particularly in VKC, AKC, phlyctenular disease
- Blurred vision: Visual axis involvement (Grade 3–4); irregular astigmatism from pannus-induced corneal distortion
- Chronic red eye: Superior limbic injection from active pannus or underlying conjunctivitis
- Epiphora: Ocular surface irritation and reflex tearing
- Contact lens intolerance: CL-related pannus; reduced comfortable wearing time; lens awareness; lens ejection
- Trichiasis symptoms (trachoma): Scratching sensation from inturned lashes; photophobia; lacrimation
Corneal
- Permanent corneal opacification / leucoma: Visual axis pannus (Grade 3–4) → irreversible scarring; leading complication of trachoma-related pannus
- Bowman's layer destruction: Irreversible; subepithelial fibrosis persists even after pannus regression
- Corneal thinning: Chronic epithelial disruption and stromal remodelling
- Irregular astigmatism: Bowman's layer disruption and surface irregularity; contact lens-correctable in mild cases
- Recurrent epithelial erosions: Disrupted epithelial adhesion over fibrous pannus
- Secondary bacterial keratitis: Disrupted ocular surface barrier; particularly post-trachoma with trichiasis
Ocular Surface
- Limbal stem cell deficiency (LSCD): Severe circumferential pannus → conjunctivalisation of corneal surface; goblet cells on cornea; vascularised, unstable epithelium
- Contact lens intolerance (permanent): Irreversible if significant fibrosis or LSCD develops
- Corneal graft rejection risk: Vascularised corneas have significantly higher graft rejection rates; neovascularisation provides immune effector cell access
Global burden: Trachoma remains the world's leading infectious cause of blindness. An estimated 1.9 million people are blind or visually impaired from trachoma sequelae (WHO, 2019). Corneal pannus with subsequent scarring is the primary mechanism of visual loss.
- Trachoma (Chlamydia trachomatis): WHO neglected tropical disease; SAFE strategy (Surgery for trichiasis, Antibiotic mass drug administration, Facial cleanliness, Environmental improvement) is the global elimination programme. Systemic Chlamydia infection (genital, respiratory) may co-exist.
- Ocular rosacea: Associated with facial rosacea (papulopustular, phymatous, erythematotelangiectatic); sebaceous gland dysfunction; systemic oral doxycycline reduces meibomian gland inflammation and pannus activity; gut microbiome associations under investigation.
- Atopic keratoconjunctivitis (AKC): Associated with systemic atopy — atopic eczema, asthma, allergic rhinitis; IgE-mediated and Th2-driven; severe corneal pannus in AKC may require systemic immunosuppression (ciclosporin, mycophenolate).
- Stevens-Johnson syndrome (SJS) / Toxic epidermal necrolysis (TEN): Severe circumferential pannus and limbal stem cell failure from acute conjunctival necrosis; long-term management may require KLAL (keratolimbal allograft) or keratoprosthesis; systemic cause (drug reaction, mycoplasma) requires separate management.
- Graft-vs-host disease (GvHD): Chronic GvHD causes progressive ocular surface disease including pannus; haematology-directed systemic immunosuppression; topical ciclosporin may reduce ocular GvHD severity.
- Congenital / acquired syphilis (interstitial keratitis): VZV, HSV, or treponeme-mediated stromal vascularisation and pannus historically common; rare now due to congenital syphilis screening; ghost vessel pattern diagnostic; parenteral penicillin for active syphilis.
- Vernal keratoconjunctivitis (VKC): Prevalent in young males in tropical/subtropical climates (including Singapore); severe superior pannus possible; associated with systemic atopy; long-term topical ciclosporin reduces corneal complications.
- Slit-lamp biomicroscopy: Location (superior, inferior, circumferential); extent in mm from limbus; vessel activity; fibrosis depth; Herbert's pits; surface irregularity
- Eyelid eversion (essential in trachoma): Assess tarsal conjunctiva for follicles, Arlt's line (linear scar), papillae, trichiasis, entropion
- Fluorescein staining: Epithelial disruption over pannus; Rose Bengal / lissamine green for conjunctival health and pannus surface staining
- AS-OCT (anterior segment OCT): Pannus depth (subepithelial vs stromal); Bowman's layer integrity; pannus thickness measurement; monitor progression
- Corneal topography / tomography: Irregular astigmatism from pannus; quantify surface distortion; guide contact lens fitting post-pannus
- IVCM (in vivo confocal microscopy): Sub-basal nerve plexus; inflammatory cell infiltration; vessel density at limbus; corneal nerve damage in severe cases
- Conjunctival swab + PCR: For Chlamydia trachomatis in suspected trachoma; gold standard microbiological diagnosis
- Serology: Chlamydia IgG / IgM; syphilis VDRL / TPHA in suspected interstitial keratitis
- Contact lens assessment: Lens Dk/t; wearing schedule; fit; tear film with lens in-situ; compliance history — critical in CL-related pannus
- IgE and allergy workup: Total IgE, specific allergen testing (RAST) in suspected AKC / VKC
1. Treat Underlying Cause (most important — pannus does not resolve without cause removal)
- Trachoma: Azithromycin 1g single dose (adults) — WHO SAFE strategy mass drug administration; trichiasis surgery (bilamellar tarsal rotation); community-level intervention for facial cleanliness and environmental improvement
- CL-related: Cease contact lens wear or significantly reduce wearing time; switch to highest available Dk silicone hydrogel; ensure daily disposable or compliant replacement schedule; assess and correct fit
- Ocular rosacea: Oral doxycycline 50–100 mg once daily (anti-inflammatory dose); lid hygiene; warm compresses; omega-3 supplementation; meibomian gland expression
- SLK: N-acetylcysteine 10% drops; bandage soft contact lens; 0.5% silver nitrate application to superior palpebral conjunctiva; superior bulbar conjunctival recession (ophthalmology)
- VKC / AKC: Topical ciclosporin 0.05–1%; tacrolimus 0.03%; mast cell stabilisers (sodium cromoglicate, lodoxamide); short-course topical steroid; systemic immunosuppression for severe / sight-threatening disease
2. Anti-VEGF Therapy (adjunctive — ophthalmology)
- Bevacizumab (Avastin): Subconjunctival 2.5 mg/0.1 mL or topical 1%; reduces active vessel density; adjunctive to cause treatment; may require repeat dosing; not curative alone
- Ranibizumab: Similar mechanism; comparable efficacy profile in limited series
3. Topical Steroids
- Prednisolone acetate 1% — reduce inflammation and slow pannus progression; slow taper; IOP monitoring required
- Caution in trachoma — steroids may exacerbate active infection; ensure antibiotic cover
- Topical ciclosporin as steroid-sparing agent for chronic inflammatory pannus
4. Lubrication
- Preservative-free lubricating drops for surface protection, symptom relief, and epithelial support over pannus
5. Surgical (ophthalmology — vision-threatening disease)
- Superficial keratectomy + amniotic membrane transplantation (AMT): Mechanical pannus removal; AMT reduces re-epithelialisation time and pannus recurrence; first-line surgical option
- PTK (phototherapeutic keratectomy): Post-pannus subepithelial fibrosis; smooths Bowman's layer; may improve vision and reduce recurrence
- Limbal stem cell transplantation (CLET / KLAL): Severe LSCD from burns, SJS, aniridia; restores limbal barrier function
- Penetrating keratoplasty (PK) / DALK: End-stage scarring with visual loss; significantly higher rejection risk in vascularised/pannus cornea; pre-operative vessel regression with bevacizumab recommended
- Trichiasis management (trachoma): Epilation; bilamellar tarsal rotation (WHO-recommended); posterior lamellar grafting for severe cases
Singapore Optometry Scope Note: Optometrists in Singapore may identify and document corneal pannus at slit-lamp, assess extent and vessel activity, and determine likely aetiology (e.g., contact lens hypoxia, SLK, chronic ocular surface inflammation). Therapeutic-endorsed optometrists may prescribe preservative-free lubricants and manage contact lens-related pannus by modifying lens material (Dk), wearing schedule, and replacement frequency. Anti-VEGF therapy, topical steroids for inflammatory pannus, and all surgical interventions require referral to ophthalmology. Refer urgently for rapidly progressive or visually significant pannus involving or approaching the visual axis.
- CL-related (early, peripheral): Excellent — active vessels may partially regress with lens cessation and high-Dk refitting; established subepithelial fibrosis persists but does not progress
- Trachoma-related: Guarded — permanent scarring common in advanced cases (Grade 3–4); blindness preventable with early community-level SAFE strategy intervention
- Rosacea / SLK: Good with systemic and topical treatment; recurrence common if underlying disease remains uncontrolled; long-term follow-up required
- VKC / AKC: Variable; severe atopic pannus can progress despite maximal treatment; systemic immunosuppression may stabilise but not reverse established fibrosis
- Advanced central pannus (Grade 3–4) with Bowman's destruction: Poor visual prognosis without surgery; surgical outcomes (keratoplasty) compromised by ongoing LSCD and neovascularisation; vessel regression before transplant improves outcomes
- Key favourable prognostic factors: Peripheral location; early diagnosis; identified and controlled aetiology; absence of LSCD
- Key poor prognostic factors: Central location; delayed presentation; Bowman's layer destruction; LSCD; circumferential (360°) pannus
| Condition | Key Differentiator from Corneal Pannus |
|---|---|
| Corneal Neovascularisation | Vessels only — no fibrous component; subepithelial fibrosis absent; typically CL-related hypoxia; no grey fibrous membrane |
| Pterygium | Triangular fleshy growth; nasal (occasionally temporal) location; older UV-exposed patients; Stocker's iron line; can be lifted at limbus |
| Pseudopterygium | Any corneal quadrant (not just nasal); history of chemical burn or trauma; can be lifted off limbus at base (distinguishing from true pterygium) |
| Interstitial Keratitis | Deep stromal vascularisation (not subepithelial); associated with syphilis, HSV, VZV; "salmon patches" → ghost vessels; no surface fibrovascular membrane |
| Limbal Dermoid | Congenital solid white/yellow mass; typically inferotemporal; may contain hair follicles; Goldenhar syndrome association; present from birth |
| Subepithelial Corneal Fibrosis | Post-adenoviral (EKC) or post-traumatic grey haze; no active vessels; no limbal origin; localised; does not advance from limbus |
| SLK (active, early) | Superior redness and filaments; no fibrovascular membrane initially; responds to silver nitrate or bandage CL; no advancing pannus |
| Corneal Keloid | Rare; raised white fibrotic tissue post-trauma or surgery; no limbal origin; no active vessels; elevated above corneal surface |
- Resnikoff S, Pascolini D, Etya'ale D, et al. Global data on visual impairment in the year 2002. Bull World Health Organ. 2004;82(11):844-851.
- West S. Trachoma: new assault on an ancient disease. Prog Retin Eye Res. 2004;23(2):179-199.
- Hu VH, Massae P, Weiss HA, et al. In vivo confocal microscopy in active trachoma: a cross-sectional study. Ophthalmology. 2011;118(5):872-879.
- Liesegang TJ. Physiologic changes of the cornea with contact lens wear. CLAO J. 2002;28(1):12-27.
- Papas EB. The significance of oxygen during contact lens wear. Cont Lens Anterior Eye. 2014;37(6):394-404.
- Saini JS, Sharma A, Grewal SP. Chronic superior limbic keratoconjunctivitis. CLAO J. 1995;21(2):105-107.
- Iyer G, Srinivasan B, Agarwal S, et al. Treatment modalities and clinical outcomes in ocular rosacea: a 26-year experience. Cornea. 2012;31(10):1117-1122.
- Kim SW, Kim EK, Cho BJ, et al. Use of digital image analysis to quantify changes in the vascularity of pannus. Cornea. 2008;27(4):438-443.
- Bachmann B, Taylor RS, Cursiefen C. Corneal neovascularization as a risk factor for graft failure and rejection after keratoplasty. Ophthalmology. 2010;117(7):1300-1305.
- Cursiefen C, Chen L, Borges LP, et al. VEGF-A stimulates lymphangiogenesis and hemangiogenesis in inflammatory neovascularization via macrophage recruitment. J Clin Invest. 2004;113(7):1040-1050.
- You IC, Shin YJ, Yoon KC. Treatment of superficial corneal pannus in vernal keratoconjunctivitis with subconjunctival bevacizumab. Cornea. 2011;30(10):1141-1142.
- Doan S, Gabison EE, Gatinel D, et al. Topical cyclosporine A in severe steroid-dependent childhood phlyctenular keratoconjunctivitis. Am J Ophthalmol. 2006;141(1):62-66.
- Reinhard T, Böhringer D, Sundmacher R. Histological studies on the subepithelial fibrous pannus in extended contact lens wear. Ger J Ophthalmol. 1996;5(2):82-86.
- Dua HS, Azuara-Blanco A. Limbal stem cells of the corneal epithelium. Surv Ophthalmol. 2000;44(5):415-425.
- Solomon A, Ellies P, Anderson DF, et al. Long-term versus short-term conjunctival and amniotic membrane transplantation for the treatment of corneal surface disorders. Ophthalmology. 2002;109(5):883-892.