Bare sclera excision
- Recurrence Rate
- 30–80%
- Advantages
- Simple, fast, no donor site
- Disadvantages
- Unacceptably high recurrence — obsolete as primary technique
- Best Indication
- Very elderly/debilitated patients only
Pterygium
Cornea
Key Points
- •Conjunctival autograft (CAG) with fibrin glue is the current gold standard for pterygium excision — recurrence rate 5–10% vs 30–80% with bare sclera
- •Nasal predilection of pterygium is explained by the coroneo effect — peripheral light focusing concentrates UV damage at the nasal limbus
- •Stocker line (iron deposition at the leading edge) indicates a slow-growing pterygium — analogous to other corneal iron lines (Fleischer ring, Hudson-Stahli line)
- •Always send excised pterygium for histopathology — OSSN can masquerade as pterygium and must not be missed
- •Surgery is indicated when the visual axis is threatened (Grade 3–4), significant astigmatism exists, or before refractive surgery (LASIK/PRK)
A pterygium is a wing-shaped, fibrovascular, degenerative and hyperplastic growth of bulbar conjunctiva that encroaches onto the cornea. It is a common ocular surface disorder related to chronic ultraviolet (UV) light exposure, characterised by elastotic degeneration of subconjunctival connective tissue with overlying epithelial changes. The name is derived from the Greek pteron (wing).
Prevalence: highly variable; 0.7–33% worldwide; highest in the 'pterygium belt' (latitudes 37°N to 37°S of the equator).
Higher prevalence in tropical and subtropical regions: Southeast Asia, Middle East, Africa, Central America, Australia.
Male predominance (2–3:1) — reflects occupational outdoor UV exposure.
Peak incidence in 3rd–4th decades of life; uncommon before age 20.
More common in rural/outdoor workers, fishermen, farmers.
Nasal pterygium far more common than temporal (~3:1 ratio) — nasal cornea receives more peripheral light focusing (coroneo effect).
Bilateral pterygia in 30–40% of affected individuals.
Recurrence after excision: 30–80% with bare sclera technique; 5–10% with conjunctival autograft.
Primary aetiological factor: chronic ultraviolet (UV) light exposure (UV-B, 280–315 nm).
UV-related mechanisms:
- Direct UV damage to limbal stem cells and basal epithelium
- Coroneo effect: peripheral light focusing by anterior corneal surface concentrates UV rays at nasal limbus (explains nasal predilection)
- UV-induced mutations in tumour suppressor gene p53 → abnormal cell proliferation
Contributing factors:
- Chronic environmental irritation: wind, dust, dryness, heat
- Genetic predisposition (familial clustering observed)
- HPV infection (possible cofactor — viral DNA found in some pterygia specimens)
- Chronic inflammation: pro-inflammatory cytokines (IL-1, IL-6, IL-8, TNF-alpha)
- Oxidative stress: reduced antioxidant capacity in pterygium tissue
Histopathological features:
- Elastotic degeneration of stromal collagen (basophilic degeneration on H&E)
- Squamous metaplasia and goblet cell loss in overlying epithelium
- Neovascularisation and chronic inflammatory infiltrate
- Destruction of Bowman layer at leading edge
- Stocker line — iron deposition line (ferritin) at leading edge of pterygium from tear pooling
- Chronic UV-B exposure damages limbal stem cells at the nasal limbus (coroneo effect — peripheral light focusing).
- UV-induced p53 mutations and upregulation of growth factors (VEGF, bFGF, PDGF, TGF-beta) → loss of normal growth regulation.
- Altered limbal stem cells produce abnormal epithelial cells that proliferate and migrate centripetally onto the cornea.
- UV-induced production of matrix metalloproteinases (MMP-1, MMP-2, MMP-9) → dissolution of Bowman layer → allows fibrovascular tissue invasion of corneal stroma.
- Elastotic degeneration of subconjunctival collagen (Elastodysplasia → Elastodystrophy → Elastodysgenesis — Hogan and Alvarado classification).
- Upregulation of VEGF and bFGF → neovascularisation and fibrovascular proliferation.
- Chronic inflammation with lymphocytic and plasma cell infiltration perpetuates growth.
- Advancing edge (head/cap) actively destroys Bowman layer and invades corneal stroma.
- Iron deposition at the advancing edge (Stocker line) from tear film pooling.
- Centripetal growth can reach the visual axis → induced astigmatism and visual obstruction.
- After surgical excision, residual activated fibroblasts and inflammatory mediators drive recurrence.
By morphology (Tan classification — Duke-Elder modified):
- Atrophic (Grade T1): thin, flat, translucent; underlying episcleral vessels clearly visible through body. Low recurrence risk.
- Intermediate (Grade T2): moderately thick; vessels partially obscured.
- Fleshy/thick (Grade T3): thick, opaque, fleshy; vessels completely obscured. High recurrence risk.
By extent of corneal involvement:
- Grade 1: crosses limbus but <2 mm onto cornea
- Grade 2: 2–4 mm onto cornea (approaching but not at pupillary margin)
- Grade 3: >4 mm onto cornea or involving pupillary area
- Grade 4: crosses visual axis
Anatomical parts:
- Cap (leading edge): thin, avascular zone just ahead of the head; actively destroys Bowman layer
- Head: apex of pterygium on cornea; elevated, vascular
- Neck: at the limbus; transitional zone
- Body: portion on the bulbar conjunctiva; fleshy, vascular
By location:
- Nasal (most common — ~75% of unilateral cases)
- Temporal
- Double-headed (nasal and temporal — bilateral in same eye)
- UV light exposure — strongest and most consistent risk factor; cumulative lifetime exposure.
- Geographic location within the pterygium belt (37°N–37°S latitude).
- Outdoor occupation: farmers, fishermen, construction workers, military personnel.
- Male sex (occupational exposure bias).
- Older age (cumulative UV damage; peak in 3rd–4th decade).
- Family history (genetic susceptibility, possible HPV cofactor).
- Dry, dusty, windy climates.
- Lack of UV-protective eyewear (sunglasses, hats).
- Rural residence (more outdoor exposure).
- Coexisting dry eye disease (shares risk factors and may perpetuate growth).
Symptoms:
- Often asymptomatic in early stages
- Foreign body sensation, irritation, dryness
- Redness (cosmetic concern)
- Blurred vision — from induced with-the-rule astigmatism (flattening of cornea in meridian of pterygium) or visual axis obstruction
- Tearing
- Diplopia (rare — if restricts motility in advanced cases)
Signs:
- Wing-shaped fibrovascular growth — typically nasal, extending from conjunctiva across limbus onto cornea
- Stocker line — iron deposition line (ferritin) at leading edge of pterygium on cornea; indicates slow/long-standing growth
- Destruction of Bowman layer at advancing edge
- Fuchs patches — grey subepithelial opacities at advancing edge (rare)
- Induced astigmatism — with-the-rule (flattening of cornea in meridian of pterygium), measurable on topography/keratometry
- Tear film disruption over and around pterygium
- Conjunctival injection of the body
Advanced/complicated:
- Visual axis involvement → significant visual impairment
- Restricted ocular motility (rare, large pterygia)
- Symblepharon (rare)
- Corneal dellen formation adjacent to pterygium
- OSSN (ocular surface squamous neoplasia) arising within a pterygium — rare but important; always send excised tissue for histopathology
Clinical diagnosis — no investigations routinely needed.
Slit-lamp biomicroscopy: confirms diagnosis, assesses grade/extent, identifies complications.
Corneal topography: quantifies induced astigmatism; useful pre- and post-operatively.
- Shows flattening in the meridian of pterygium (with-the-rule astigmatism)
- Asymmetric bowties
Keratometry: documents pre-operative corneal curvature.
Anterior segment OCT: pterygium thickness, depth of corneal involvement, Bowman layer integrity.
Dry eye workup: TBUT, Schirmer test — pterygium often coexists with dry eye disease.
Histopathology (of excised specimen):
- Elastotic degeneration (basophilic degeneration on H&E, Verhoeff-van Gieson stain)
- Squamous metaplasia
- Chronic inflammation
- Neovascularisation
- IMPORTANT: always send excised pterygium for histopathology to rule out OSSN (ocular surface squamous neoplasia), which can masquerade as pterygium
Refraction: document pre-operative refraction and astigmatism.
Pinguecula — yellow-white subconjunctival deposit; does NOT cross the limbus onto the cornea (unlike pterygium); same UV-related elastotic degeneration.
Pseudopterygium — conjunctival adhesion to cornea secondary to prior inflammation, trauma, or chemical burn; can be distinguished by passing a probe under the body (pseudopterygium is not adherent to limbus — probe passes freely under it at the limbus, unlike true pterygium).
OSSN (ocular surface squamous neoplasia) — papillomatous or gelatinous limbal/conjunctival mass; may have feeder vessels; leukoplakia; may arise within or resemble a pterygium; biopsy is definitive.
Conjunctival papilloma — pedunculated or sessile, papillomatous surface; HPV-related.
Pannus — corneal vascularisation with fibrovascular tissue growing into cornea from limbus superiorly (trachoma) or 360° (contact lens); no conjunctival wing-shaped growth.
Dermoid — solid, white-yellow limbal mass; congenital; may have hair follicles; choristoma (unlike pterygium which is a degeneration).
Induced corneal astigmatism — with-the-rule; may be significant enough to impair vision even before reaching visual axis.
Visual axis obstruction — direct visual impairment.
Recurrence after surgery — the most significant surgical complication; 30–80% with bare sclera, 5–10% with CAG, further reduced with MMC.
Motility restriction — large pterygia can restrict adduction or abduction (rare).
Corneal scarring — residual scarring at site after excision, especially if deep stromal involvement.
Dry eye — pterygium disrupts tear film; may worsen post-operatively.
OSSN transformation — rare malignant degeneration.
Dellen formation — corneal thinning adjacent to elevated pterygium.
Symblepharon — with very large pterygia.
Mitomycin C complications (if used): scleral necrosis/calcification, delayed epithelial healing, secondary infection, scleral melting, rarely endophthalmitis.
Conservative (for mild, asymptomatic pterygium):
- UV protection: sunglasses (wrap-around), wide-brimmed hat — essential preventive measure
- Lubricating drops for irritation and associated dry eye
- Topical vasoconstrictors for cosmetic redness (short-term only)
- Observation with periodic monitoring
Indications for surgery:
- Visual axis threatened or involved (Grade 3–4)
- Significant induced astigmatism impairing vision
- Restriction of ocular motility
- Recurrent inflammation not controlled by lubricants
- Cosmetic concern (patient request)
- Pre-refractive surgery: must be removed before LASIK/PRK
- Suspicion of OSSN (excisional biopsy)
Surgical techniques:
- Pterygium excision with conjunctival autograft (CAG) — gold standard:
- Excise pterygium head and body
- Harvest free conjunctival graft from superotemporal bulbar conjunctiva (same eye)
- Secure with fibrin glue (preferred — faster, less discomfort) or sutures (e.g., 10-0 nylon or 8-0 Vicryl)
- Recurrence rate: 5–10%
- Maintain correct orientation (epithelial side up, limbal edge toward limbus)
- Pterygium excision with conjunctival-limbal autograft (CLAU):
- Includes limbal tissue in the graft — provides limbal stem cells
- Lower recurrence than CAG alone (~2–5%)
- Indicated for recurrent pterygia
- Pterygium excision with mitomycin C (MMC):
- Intraoperative MMC 0.02–0.04% applied to bare sclera for 1–3 minutes, then copious irrigation
- Reduces recurrence to 5–15%
- Risk: scleral necrosis, delayed healing, calcification, rarely endophthalmitis
- Can be combined with conjunctival autograft for very high recurrence risk
- Bare sclera technique (obsolete as primary technique):
- Simple excision without graft or anti-metabolite
- Recurrence rate 30–80% — unacceptably high
- Only used in very elderly or debilitated patients
- Amniotic membrane graft:
- Alternative when conjunctival autograft not feasible (double-headed pterygium, insufficient conjunctiva)
- Recurrence intermediate between bare sclera and CAG
Post-operative:
- Topical steroid (prednisolone 1% or dexamethasone 0.1%) QID, taper over 4–6 weeks
- Topical antibiotic (moxifloxacin) QID for 1–2 weeks
- Lubricating drops
- UV protection advice — lifelong
- Follow-up at 1 day, 1 week, 1 month, then 3-monthly for 1 year (recurrence monitoring)
Non-operated pterygium: slow growth over years; many remain stable; may never require surgery.
Post-operative: excellent cosmetic and functional outcomes with modern techniques.
Recurrence rates:
- Bare sclera: 30–80% (unacceptable — obsolete)
- CAG with fibrin glue: 5–10%
- CLAU: 2–5%
- MMC adjunct: 5–15%
- CAG + MMC: >5%
Recurrence is most common in the first 6–12 months post-surgery.
Fleshy (Grade T3) pterygia have higher recurrence than atrophic (Grade T1).
Younger patients have higher recurrence rates.
Corneal astigmatism often partially resolves after excision but may not fully normalise.
Corneal scarring at the excision site may cause residual visual impairment if the visual axis was involved.
OSSN risk: very low but always send excised tissue for histopathology.
Clinical Pearls
1
Conjunctival autograft with fibrin glue is the current gold standard for pterygium surgery — it has replaced bare sclera technique and suturing due to lower recurrence and better patient comfort.
2
Always pass a probe under a conjunctival growth at the limbus to distinguish true pterygium (adherent at limbus — probe does NOT pass) from pseudopterygium (probe passes freely under it at the limbus).
3
Always send excised pterygium tissue for histopathology — OSSN (ocular surface squamous neoplasia) can masquerade as a pterygium and would be missed without biopsy.
4
The coroneo effect explains why pterygia are predominantly nasal: peripheral light entering from the temporal side is refracted and focused by the anterior corneal surface onto the nasal limbus, concentrating UV damage there.
5
Stocker line (iron deposition at the leading edge) indicates a slow-growing, long-standing pterygium — analogous to other corneal iron lines (Fleischer ring in keratoconus, Hudson-Stahli line at the junction of upper and lower tear menisci).
6
Exam Trap: Distinguishing pterygium from pseudopterygium is a classic exam question — the probe test is the key differentiating manoeuvre. In a true pterygium, the growth is adherent at the limbus and a probe does NOT pass under it. In a pseudopterygium (which forms after prior inflammation, trauma, or chemical burn), the probe passes freely under the body at the limbus because the adhesion is only at the corneal scar site.
7
Exam Trap: Stocker's line is an iron deposition line (ferritin) at the head (leading edge) of a pterygium, indicating chronicity and slow growth. It is frequently tested alongside other corneal iron lines: Fleischer ring (keratoconus), Hudson-Stahli line (junction of upper and lower tear menisci), Ferry's line (filtering bleb), and coat's white ring (old metallic foreign body site). The presence of Stocker's line suggests a long-standing, slowly progressive lesion.
8
Exam Trap: Pterygium recurrence rate varies enormously by surgical technique and this is heavily tested: bare sclera excision has an unacceptable recurrence of 30–80% (now obsolete as primary technique); conjunctival autograft (CAG) achieves 5–15% recurrence; conjunctival-limbal autograft (CLAU) achieves 2–5%. The dramatic difference between bare sclera and autograft is a favourite exam question — always choose CAG as the gold standard.
Oral-exam questions
- What is the coroneo effect? — Peripheral light rays entering the eye from the temporal side are refracted and concentrated by the anterior corneal curvature onto the nasal limbus, explaining why pterygia are predominantly nasal (Krachmer, Cornea 4th Ed).
- What is the gold standard surgical technique for pterygium? — Conjunctival autograft (CAG) with fibrin glue, achieving 5–10% recurrence vs 30–80% with bare sclera. Fibrin glue is preferred over sutures for better patient comfort and faster healing.
- What is the Stocker line and what does it indicate? — Stocker line is a brown iron deposition line (ferritin from tear stasis) at the leading edge of pterygium on the cornea. It indicates a slow-growing, long-standing pterygium and is analogous to other corneal iron lines (Fleischer ring in keratoconus).
- Why must you always send excised pterygium for histopathology? — OSSN (ocular surface squamous neoplasia) can masquerade as a pterygium clinically. Without histopathology, a dysplastic or malignant lesion would be missed — leading to inadequate treatment and potential metastatic risk.
- How do you distinguish a pterygium from a pseudopterygium? — Probe test at the limbus: pass a blunt probe (e.g., a muscle hook or probe) under the growth at the limbus. In a true pterygium, the probe does NOT pass (adherent to limbus); in a pseudopterygium, the probe passes freely (only adheres at the corneal scar site from prior injury).
- What is the role of mitomycin C (MMC) in pterygium surgery? — Intraoperative MMC 0.02–0.04% applied to bare sclera for 1–3 minutes inhibits fibroblast proliferation and reduces recurrence. Used as an adjunct with CAG for high-risk cases (young patients, Grade T3, recurrence). Risk of scleral necrosis and calcification with excess use.
Mnemonics
CANSS
C — Coroneo effect (nasal predilection from UV focusing)
A — Always histopathology (rule out OSSN)
N — Never bare sclera alone (30–80% recurrence)
S — Stocker line (iron at leading edge — slow growth)
S — Surgery: CAG gold standard (fibrin glue, 5–10% recurrence)
Probe test
True pterygium — probe does NOT pass under the body at the limbus (adherent at limbus).
Pseudopterygium — probe PASSES freely under the body at the limbus (adherent only at the corneal site of injury, not at the limbus).
Comparison Tables
Surgical Techniques for Pterygium Excision: Recurrence and Outcomes
| Technique | Recurrence Rate | Advantages | Disadvantages | Best Indication |
|---|---|---|---|---|
| Bare sclera excision | 30–80% | Simple, fast, no donor site | Unacceptably high recurrence — obsolete as primary technique | Very elderly/debilitated patients only |
| Conjunctival autograft (CAG) + fibrin glue | 5–10% | Gold standard, no compounding, faster healing, less discomfort vs sutures | Requires superotemporal donor site; fibrin glue cost | Primary pterygium (all ages) |
| Conjunctival-limbal autograft (CLAU) | 2–5% | Provides limbal stem cells, lowest recurrence | Larger donor site, technically demanding | Recurrent pterygium |
| CAG + intraoperative MMC | <5% | Lowest recurrence combined approach | MMC risk of scleral necrosis/calcification | High recurrence risk (young, fleshy T3, bilateral) |
| Bare sclera + MMC | 5–15% | Simpler than CAG | No graft; MMC side effects | When CAG not feasible |
| Amniotic membrane graft | 10–20% | Useful when conjunctiva insufficient (double-headed) | Higher recurrence than CAG; requires amniotic membrane | Double-headed pterygium; insufficient conjunctiva |
Conjunctival autograft (CAG) + fibrin glue
- Recurrence Rate
- 5–10%
- Advantages
- Gold standard, no compounding, faster healing, less discomfort vs sutures
- Disadvantages
- Requires superotemporal donor site; fibrin glue cost
- Best Indication
- Primary pterygium (all ages)
Conjunctival-limbal autograft (CLAU)
- Recurrence Rate
- 2–5%
- Advantages
- Provides limbal stem cells, lowest recurrence
- Disadvantages
- Larger donor site, technically demanding
- Best Indication
- Recurrent pterygium
CAG + intraoperative MMC
- Recurrence Rate
- <5%
- Advantages
- Lowest recurrence combined approach
- Disadvantages
- MMC risk of scleral necrosis/calcification
- Best Indication
- High recurrence risk (young, fleshy T3, bilateral)
Bare sclera + MMC
- Recurrence Rate
- 5–15%
- Advantages
- Simpler than CAG
- Disadvantages
- No graft; MMC side effects
- Best Indication
- When CAG not feasible
Amniotic membrane graft
- Recurrence Rate
- 10–20%
- Advantages
- Useful when conjunctiva insufficient (double-headed)
- Disadvantages
- Higher recurrence than CAG; requires amniotic membrane
- Best Indication
- Double-headed pterygium; insufficient conjunctiva
Pterygium vs Pinguecula vs Pseudopterygium
| Feature | Pterygium | Pinguecula | Pseudopterygium |
|---|---|---|---|
| Crosses limbus | YES — grows onto cornea | NO — confined to conjunctiva | YES — adheres to cornea at site of prior injury |
| Probe test at limbus | Probe does NOT pass under it | N/A (doesn't reach limbus) | Probe passes freely at the limbus |
| Stocker line | PRESENT at leading edge | Absent | Absent |
| Aetiology | UV degeneration + limbal stem cell alteration | UV degeneration only | Prior inflammation/trauma/chemical burn |
| Astigmatism | YES — with-the-rule | No | Possible |
| Histology | Elastotic degeneration + VEGF + MMP | Elastotic degeneration | Fibrous scar tissue + neo-vessels |
Crosses limbus
- Pterygium
- YES — grows onto cornea
- Pinguecula
- NO — confined to conjunctiva
- Pseudopterygium
- YES — adheres to cornea at site of prior injury
Probe test at limbus
- Pterygium
- Probe does NOT pass under it
- Pinguecula
- N/A (doesn't reach limbus)
- Pseudopterygium
- Probe passes freely at the limbus
Stocker line
- Pterygium
- PRESENT at leading edge
- Pinguecula
- Absent
- Pseudopterygium
- Absent
Aetiology
- Pterygium
- UV degeneration + limbal stem cell alteration
- Pinguecula
- UV degeneration only
- Pseudopterygium
- Prior inflammation/trauma/chemical burn
Astigmatism
- Pterygium
- YES — with-the-rule
- Pinguecula
- No
- Pseudopterygium
- Possible
Histology
- Pterygium
- Elastotic degeneration + VEGF + MMP
- Pinguecula
- Elastotic degeneration
- Pseudopterygium
- Fibrous scar tissue + neo-vessels
Morphological Grading of Pterygium (Tan Classification)
| Grade | Appearance | Vessels Visible? | Recurrence Risk | Management Implication |
|---|---|---|---|---|
| T1 (Atrophic) | Thin, flat, translucent | Clearly visible through body | LOW | Conservative or simple CAG |
| T2 (Intermediate) | Moderately thick | Partially obscured | MODERATE | CAG ± MMC consideration |
| T3 (Fleshy) | Thick, opaque, fleshy | Completely obscured | HIGH | CLAU or CAG + MMC; highest recurrence risk |
T1 (Atrophic)
- Appearance
- Thin, flat, translucent
- Vessels Visible?
- Clearly visible through body
- Recurrence Risk
- LOW
- Management Implication
- Conservative or simple CAG
T2 (Intermediate)
- Appearance
- Moderately thick
- Vessels Visible?
- Partially obscured
- Recurrence Risk
- MODERATE
- Management Implication
- CAG ± MMC consideration
T3 (Fleshy)
- Appearance
- Thick, opaque, fleshy
- Vessels Visible?
- Completely obscured
- Recurrence Risk
- HIGH
- Management Implication
- CLAU or CAG + MMC; highest recurrence risk
Self-Assessment (5)
MCQ
A 35-year-old male farmer from Tamil Nadu presents with a nasal wing-shaped fibrovascular growth encroaching 3 mm onto the cornea, causing 1.5 D of with-the-rule astigmatism. The overlying vessels are partially visible. He requests surgery. What is the gold standard surgical technique?
MCQ
Which investigation is MANDATORY after surgical excision of a pterygium?
MCQ
A patient undergoes pterygium excision. To distinguish a recurrent pterygium from a pseudopterygium at the limbus, the clinician passes a probe. What finding is expected for a TRUE pterygium?
MCQ
The coroneo effect explains the nasal predilection of pterygia. What is the mechanism?
MCQ
A fleshy (Grade T3) pterygium in a 28-year-old patient is excised using conjunctival autograft. Which additional intraoperative intervention most effectively reduces the risk of recurrence in this high-risk scenario?
References
- AAO Preferred Practice Pattern: Conjunctival and Corneal Neoplasms (2016)
- Krachmer JH, Mannis MJ, Holland EJ. Cornea and External Disease: Clinical Diagnosis and Management, 4th Edition
- Ehlers JP, Shah CP. The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease, 8th Edition
- Tan DT, Chee SP, Dear KB, Lim AS. Effect of pterygium morphology on pterygium recurrence in a controlled trial comparing conjunctival autografting with bare sclera excision. Arch Ophthalmol. 1997;115(10):1235-1240.
- Coroneo MT. Pterygium as an early indicator of ultraviolet insolation: a hypothesis. Br J Ophthalmol. 1993;77(11):734-739.
- Kanski JJ, Bowling B. Clinical Ophthalmology: A Systematic Approach, 9th Edition
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