PanOph

Pterygium

Cornea

1. Clinical Analogy & Definition

Clinical Analogy
  • Think of pterygium as a "biological scar with ambitions" - like an aggressive contractor who was hired to repair a small crack (UV damage to the limbus) but then decides to knock down the entire wall (cornea). It has memory (recurrence), respects boundaries poorly, and carries its own blood supply like a tumour. The limbus is the "gate" - once breached, the vascularised fibrovascular tissue invades unchecked.

Definition

  • Pterygium (Greek: pterygion = little wing) is a
  • fibrovascular subepithelial proliferation of bulbar conjunctival tissue that encroaches upon the cornea.
  • It is characterised by elastotic degeneration of subepithelial collagen, vascularisation, and an abnormal epithelium–basement membrane interface.
  • Pterygium is generally regarded as a benign, non-cancerous ocular-surface disorder, but it can exhibit tumor-like proliferative and locally invasive behavior; its classification as purely degenerative versus neoplastic remains debated.
  • The key histological hallmark is elastotic degeneration (actinic elastosis) of the stroma.
  • Elastotic material in pterygium has been attributed to abnormal elastic-fiber formation and degeneration; earlier studies also proposed degeneration of collagen, so its origin should not be described categorically as collagen-derived or non-elastic.
  • The elastotic material can take up Verhoeff elastic stain, while ultrastructural studies demonstrate abnormal elastic fibers and elastogenesis rather than an absence of elastic fibers.
Exam pearl
  • VIVA PEARLS
  • Pterygium is not a true neoplasm but shares quasi-neoplastic features, including abnormal tumor protein 53 (p53), increased vascular endothelial growth factor (VEGF) expression, and increased matrix metalloproteinase (MMP) expression.
  • The elastotic tissue in pterygium is heterogeneous: it may include degenerated collagen, abnormal elastic-fiber precursors, and abnormal elastic fibers. It should not be equated simply with normal elastic tissue - a classic histology viva trap.
  • Pterygium usually arises in the interpalpebral zone, most often nasally. Ultraviolet (UV) exposure is an important risk factor; peripheral light focusing and other mechanisms have been proposed to contribute to this distribution.
  • Nasal pterygium is much more common than temporal pterygium. Peripheral light focusing of ultraviolet (UV) radiation toward the nasal limbus is a proposed contributor, but it may not fully explain the nasal predominance.

2. Epidemiology & Risk Factors

Epidemiology

  • Pterygium shows a classic "pterygium belt" distribution - approximately 37–40° north and south of the equator, with reported prevalence ranging from 0.3–33% globally.
  • It is highest in tropical/subtropical regions (South Asia, Africa, Pacific Islands).
  • Prevalence in India: approximately 9.5–13% in reported population studies; a South Indian population study reported 9.5%.
Risk FactorMechanism / NotesEvidence Level
UV radiation (major risk factor)• Limbal stem-cell injury and DNA damage • Stromal elastotic degeneration • p53 abnormalities or altered p53 expression reported • UV-induced p53 mutation remains unprovenWell established
Lower latitude / residence within the pterygium belt• Greater cumulative ultraviolet exposure • Association varies by population and exposureSupported
Outdoor occupation• Farmers, fishermen, construction workers • Cumulative ultraviolet exposureSupported
Dry eye / ocular-surface disease• Associated with pterygium in observational studies • Causal role remains uncertainUncertain
Dust and particulate exposure• Proposed ocular-surface irritant • Association with pterygium remains uncertainUncertain
Wind exposure• Proposed tear-film disruption and surface desiccation • Independent association with pterygium remains uncertainUncertain
Male sex• Greater outdoor exposure may contribute • Hormonal explanations remain uncertainSupported
Genetic predisposition• Family history reported • Rare familial inheritance described • Specific genetic associations remain emergingEmerging
Human papillomavirus (HPV) infection• Human papillomavirus (HPV) DNA detected in some pterygium specimens • Reported types vary among studies • Causal role and p53 degradation remain uncertainEmerging

3. PATHOGENESIS (Molecular & Cellular)

Exam pearl
  • Clinical Analogy: The limbal stem cell zone (LSCZ) helps maintain the boundary protecting the cornea from conjunctival invasion.
  • UV radiation can damage or alter these guards, contributing to limbal barrier disruption and allowing fibrovascular conjunctival tissue to extend onto the cornea.
  • Like a city wall being breached after the gatekeeper is impaired.

Key Molecular Mechanisms

A. UV-Induced Limbal Stem Cell Damage

  • Ultraviolet radiation, including UV-B (290–320 nm), is implicated in limbal epithelial and DNA injury relevant to pterygium pathogenesis.
  • Bowman’s layer is present as a stiff subepithelial layer in the central cornea and is absent in the limbus.
  • UV exposure has been associated with abnormal p53 expression in pterygium, but TP53 mutation has been reported inconsistently and is not established as a universal consequence of UV-B injury.
  • Abnormal p53 signaling and altered p53-dependent apoptosis are proposed contributors; p53 mutation should not be designated the most critical molecular event.
  • Focal limbal stem-cell insufficiency may permit conjunctivalization of the cornea and centripetal migration of conjunctival-like epithelium. The contribution of limbal stem-cell failure versus migration of altered limbal epithelial cells remains debated.

B. VEGF / Angiogenesis Pathway

  • Vascular endothelial growth factor A (VEGF-A) is overexpressed in pterygium tissue and contributes to angiogenesis and increased vascularity.
  • The role of vascular endothelial growth factor (VEGF) in promoting proliferation-related responses in cultured pterygium fibroblasts and contributing to fibrovascular stromal proliferation is uncertain.
  • Anti–vascular endothelial growth factor (anti-VEGF) agents (bevacizumab) have been trialled subconjunctivally to suppress recurrence; a randomized trial did not demonstrate a significant recurrence benefit.

C. Matrix Metalloproteinase Pathway

  • Matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-2 (MMP-2), and matrix metalloproteinase-9 (MMP-9) are overexpressed → contribute to Bowman’s-layer degradation.
  • Matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) degrade basement-membrane components → facilitate corneal invasion.
  • Doxycycline has been investigated as a potential medical treatment for pterygium because of its matrix metalloproteinase (MMP)-inhibitory activity; its role as an adjuvant therapy remains investigational.

D. TGF-β / Fibroblast Activation

  • Transforming growth factor-beta 1 (TGF-β1) promotes fibroblast-to-myofibroblast transformation → myofibroblast activation, extracellular-matrix synthesis, and a contractile fibrotic phenotype.
  • Myofibroblast-rich fibrosis may contribute to postoperative scarring and contracture.
  • Recurrence is multifactorial and is also associated with residual fibrovascular tissue, postoperative inflammation, graft retraction, and surgical factors.
  • Mitomycin C (MMC) inhibits pterygium fibroblast proliferation and may reduce transforming growth factor-beta 1 (TGF-β1) expression; its antifibrotic mechanism is not definitively specific to the transforming growth factor-beta pathway.

E. Epithelial-Mesenchymal Transition

  • Pterygium epithelial cells undergo epithelial-mesenchymal transition-like changes, acquiring mesenchymal-associated and migratory properties.
  • Loss of E-cadherin with increased vimentin expression is associated with epithelial-mesenchymal transition-like changes and epithelial extension/invasion in pterygium.
  • May help explain how pterygium tissue acquires migratory and invasive behavior, allowing extension onto and into the cornea rather than remaining confined to the ocular surface.
MoleculeRole in PterygiumTherapeutic Target?
p53• p53 dysregulation • Altered apoptosis • Increased cellular proliferation• No established p53-directed therapy • Molecular marker under investigation
Vascular endothelial growth factor A (VEGF-A)• Angiogenesis/neovascularisation • Associated with pterygium growth • Direct evidence for fibroblast-survival effects is insufficient• Yes - bevacizumab trials have been conducted • Efficacy for recurrence benefit remains mixed
Matrix metalloproteinase 1 (MMP-1), matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9)• Bowman’s-layer degradation • Basement-membrane degradation • Corneal invasion• Candidate therapeutic targets • Doxycycline investigated in research • Benefit was not demonstrated across the entire study population
Transforming growth factor beta 1 (TGF-β1)• Implicated in fibroblast-to-myofibroblast differentiation • Associated with fibrosis/scarring • Precise causal contribution in vivo remains incompletely established• Investigational therapeutic target • Anti-transforming-growth-factor-beta strategies remain experimental
Cyclooxygenase-2 (COX-2)• Inflammation • Associated with fibroblast proliferation• Investigational therapeutic target • Topical nonsteroidal anti-inflammatory drugs (NSAIDs), such as pranoprofen, studied as perioperative or adjunctive therapy • Not established anti-recurrence treatment
Ki-67• Proliferation marker • Elevated in many pterygia• Prognostic value in pterygium is not established
Human papillomavirus (HPV) oncoproteins E6/E7• Human papillomavirus (HPV) 16/18 DNA and E6 oncoprotein detected in a subset of pterygia • E6 expression associated with p53 inactivation • Evidence that human papillomavirus (HPV) E7 promotes cell immortalisation in pterygium is insufficient• Possible aetiological cofactor, not an established sole aetiology • No established human papillomavirus (HPV)-directed therapy
E-cadherin (↓)• E-cadherin expression is altered and heterogeneous in pterygium epithelium • Reduced E-cadherin reported in experimental epithelial–mesenchymal-transition-like models • May contribute to migratory or invasive behaviour • Remains investigational• Research stage • No established E-cadherin-directed therapy
Exam pearl
  • The peripheral light-focusing effect is a proposed contributor to nasal > temporal predominance: obliquely incident ultraviolet light passing through the temporal cornea may be concentrated at the nasal limbus. However, a later optical analysis found peripheral light-focusing irradiation insufficient to explain the strong nasal preference of pterygium.
  • p53 accumulation or altered p53/apoptosis signaling has been reported in pterygium and may accompany abnormal proliferation; however, tumour protein p53 (TP53) mutation is not consistently demonstrated, and p53 expression has also been reported in Stage II pinguecula. It should therefore be regarded as a research/pathogenesis-related biomarker, not a definitive molecular discriminator or established diagnostic marker.
  • Transforming growth factor beta 1 (TGF-β1) is implicated in pterygium fibroblast activity, fibrosis, and recurrence-related biology. Mitomycin C reduces fibroblast proliferation and has been associated experimentally with reduced transforming growth factor beta 1 (TGF-β1) expression, but it should not be described as acting specifically or exclusively by blocking transforming growth factor beta-driven fibroblast proliferation.
  • Anti–vascular endothelial growth factor (VEGF) treatment primarily targets pterygium-associated neovascularisation. Bevacizumab has been studied mainly as an adjunct or investigational treatment, with inconsistent evidence for reducing recurrence; its effect on the invasive component is not sufficiently established.

4. Anatomy & Structural Components

Parts of a Pterygium

PartDescription & Clinical Significance
Head (Apex)• Advancing corneal edge. • Most active zone - rich in matrix metalloproteinases. • Fuchs' flecks are clusters of altered basal limbal epithelial cells. • An iron line anterior to the advancing edge is Stocker's line, especially when nasal.
Neck• Limbal crossing zone - narrowest part. • Contains fibrovascular stroma.
Body• Triangular conjunctival portion covering the sclera. • Contains tortuous dilated vessels. • Contains elastic tissue. • Contains goblet cells.
Cap (Halo)• Grey, glassy superficial corneal haze anterior to the head/apex. • Associated with subepithelial fibroblastic tissue beneath the migrating limbal epithelium.

Stocker’s Line vs Lots of Fuchs

FeatureStocker’s LineLots of Fuchs / Gray Subepithelial Extensions
Location• At the corneal side of the pterygium head• Round, gray, coin-like subepithelial extensions • May precede the cap or advancing apex
Composition• Iron deposition in the corneal epithelium• Gray subepithelial extensions • Not an iron-deposit finding
Significance• May indicate a stationary or slow-growing pterygium• May precede the cap or advancing apex
Visibility• Identified on slit-lamp examination • Appears as a golden-yellow or brown corneal epithelial iron line• Identified as gray subepithelial extensions preceding the cap or advancing apex
Exam trap• Associated with pterygium • Not restricted to nasal lesions• Hudson–Stähli line is a horizontal corneal epithelial iron line • Often seen in older people

5. Clinical Features

Symptoms

  • Foreign body sensation (most common presenting complaint)
  • Redness - due to inflammation
  • Epiphora - tear-film disturbance and localized inflammation
  • Blurred vision - due to irregular astigmatism (corneal distortion) or direct visual axis involvement
  • Cosmetic concern
  • Diplopia - rare; may occur after pterygium excision because of restrictive scarring

Signs - Slit-Lamp Examination

  1. Triangular fibrovascular membrane in interpalpebral zone (usually nasal)
  2. Stocker's line - brownish iron line in the corneal epithelium ahead of the pterygium head
  3. Corneal distortion - altered keratometry and corneal topography with induced astigmatism, most commonly with-the-rule but sometimes against-the-rule
  4. Dilated conjunctival vessels in the body - can look angry / inflamed
  5. Dellen formation adjacent to the pterygium - due to tear film disruption near the elevated margin
  6. Symblepharon - in recurrent/aggressive cases, with conjunctival fornix shortening or obliteration and possible ocular-motility restriction

Classification Systems

A. Based on Location
A. Based on Location
TypeFeatures
Nasal• More common than temporal; the exact ratio varies by population and study. • A proposed mechanism is the peripheral light-focusing effect (PLF), in which oblique ultraviolet light entering through the temporal cornea may concentrate at the nasal limbus. • The adequacy of the peripheral light-focusing effect as the sole explanation remains disputed.
Temporal• Less common than nasal. • Ultraviolet reflection from the nose is not established as its cause; mechanisms of temporal pterygium formation remain incompletely defined.
Double-headed• Simultaneous nasal and temporal pterygia in the same eye.
Bilateral• Pterygium involving both eyes.
Superior / Inferior• Atypical in location. • Should prompt consideration of pseudopterygium or an alternative diagnosis. • Specific attribution to trachoma, superior limbic keratoconjunctivitis (SLK), or rosacea-associated ocular surface disease (OSD) is not established as a general explanation.
B. Tan Grading System (Commonly Used)
B. Tan Grading System (Commonly Used)
GradeDescriptionVessel Visibility on Episcleral Vessels
Grade T1 (Atrophic)• Episcleral vessels are clearly visible or unobscured beneath the pterygium bodyClearly visible through pterygium
Grade T2 (Intermediate)• Partially obscures episcleral vesselsPartially visible
Grade T3 (Fleshy/Opaque)• Episcleral vessels are totally obscured beneath the pterygium bodyNot visible
Notes
  • Clinical significance: T3 (fleshy) pterygium is associated with increased recurrence risk after excision, particularly with bare-sclera excision.

C. Based on Corneal Involvement

GradeExtent of Corneal Invasion
• Grade 1• Reaching the limbus only
• Grade 2• Covering the cornea at about 2 mm
• Grade 3• Reaching the pupil margin
• Grade 4• Exceeding the pupil

Viva Pearls

  • Tan T3 (fleshy) morphology is associated with a higher risk of postoperative recurrence, especially after bare-sclera excision; recurrence risk also depends substantially on surgical technique and other clinical factors.
  • Stocker's line indicates chronicity. Its absence does not by itself establish active or progressive growth.
  • Dellen adjacent to pterygium can result from tear-film disruption and local corneal dehydration near an elevated or edematous edge; treat uncomplicated cases initially with lubricants.
  • Advanced or recurrent pterygium can restrict ocular motility, particularly abduction, through fibrosis or adhesions involving the nasal conjunctiva and medial rectus region.
  • Diplopia after pterygium excision can result from postoperative scar tissue and adhesions around the medial rectus region, causing restrictive strabismus.
Differential Diagnosis - Critical Comparisons
Differential Diagnosis - Critical Comparisons
FeaturePterygiumPseudopterygiumPinguecula
Nature• True fibrovascular growth• Conjunctival adhesion to cornea (post-injury/inflammation)• Degenerative conjunctival lesion
Adhesion to cornea• Yes - true invasion of Bowman's• Yes - but superficial adhesion only• No - stays at limbus
Probe test• Probe CANNOT pass under head• Probe CAN pass under body• N/A
Stocker's line• Present (nasal type)• Absent• Absent
Vascularity• Prominent• Variable• Less vascular
Relationship to limbus• Arises from limbus• Can arise from any conjunctival point• At limbus, does not cross
Histology• Elastotic degeneration with stromal fibroblasts and vessels• Fibrovascular tissue without foci of elastotic degeneration• Hyalinized subepithelial collagen with elastotic degeneration • No corneal invasion
p53 mutation• p53 abnormalities or expression have been reported• p53 status is not established here• p53 expression has been reported, but mutation status is not established
Cause• Ultraviolet exposure + multifactorial• Corneal–limbal injury or chronic inflammation (for example, chemical/thermal burns)• Ultraviolet exposure + environmental irritation/dryness
Treatment• Lubricants • Surgical excision when indicated• Treat the underlying cause • Consider surgery only after assessment• Conservative (lubricants)
  • Probe test: In PTERYGIUM - probe CANNOT be passed under the head. In PSEUDOPTERYGIUM - probe CAN be passed under the body at the limbus. This is the classic clinical differentiator.
  • Pinguecula does NOT cross or invade the cornea. Corneal extension is characteristic of pterygium; progression from pinguecula to pterygium is not established in every case.
  • Pseudopterygium can arise at any clock hour, whereas pterygium is typically interpalpebral, most often at the nasal or temporal 3 and 9 o’clock positions.
  • Pinguecula has elastotic degeneration histologically and does NOT invade the cornea. p53 abnormalities have been reported in pinguecula and pterygium; therefore, do not characterize pinguecula as having absolutely NO p53 mutation.

6. Investigations

Essential Investigations

InvestigationPurposeFindings / Significance
Slit-lamp biomicroscopy• Primary assessment - grading, vascularity, extension• Grade (Tan/Johnston), Stocker's line, cap assessment
Corneal topography (Placido disc / Scheimpflug)• Quantify astigmatism and corneal distortion• Irregular astigmatism with "dragging" of mires toward pterygium • Usually asymmetric with-the-rule astigmatism • Oblique or against-the-rule patterns may also occur
Corneal topography• Preoperative assessment of pterygium-related corneal distortion and astigmatism• Baseline for postoperative astigmatic change monitoring
Keratometry• Measure central corneal astigmatism• Computerized corneal topography is preferred for assessing pterygium-related paracentral corneal distortion
Anterior-segment optical coherence tomography (AS-OCT)• Assess depth of invasion, including sub-Bowman's involvement• Can visualize the extent of Bowman's-layer involvement • Assess postoperative healing • May help predict recurrence after surgery
Confocal microscopy• Assess sub-basal nerve plexus alteration• Primarily used as an adjunctive or investigational imaging method • Demonstrates nerve disruption ahead of advancing head
Fluorescein/Rose Bengal staining• Assess ocular-surface health and tear film• Dellen staining • Corneal exposure • Dry eye assessment
Histopathology (excised specimen)• Particularly recommended for atypical or suspicious lesions to evaluate for ocular-surface squamous neoplasia (OSSN) or malignancy• Elastotic degeneration • Goblet-cell hyperplasia • Mild epithelial atypia or dysplasia can occur and should be assessed histologically
In-vivo confocal microscopy / conjunctival cytology• In atypical or suspicious lesions, provide adjunctive assessment for ocular-surface squamous neoplasia (OSSN) • Histopathology remains the diagnostic gold standard• Dysplastic epithelial cells support ocular-surface squamous neoplasia (OSSN) • Goblet-cell changes and fibrovascular tissue may be seen in pterygium but are not diagnostic in isolation

Corneal Topography in Pterygium - Key Concepts

  • Localized flattening central to the pterygium apex, often involving the horizontal meridian in a nasal pterygium.
  • Classic finding: With-the-rule astigmatism as a nasal pterygium flattens the horizontal meridian.
  • Topographic improvement after excision supports that the pterygium contributed to the astigmatism.
  • Irregular astigmatism on topography that does NOT fully resolve post-surgery → suspect subclinical corneal scarring.
  • Scheimpflug imaging (Pentacam) can assess the posterior corneal surface in post-pterygium corneas.

Viva Pearls

  • All excised pterygium specimens should be sent for histopathology; ocular surface squamous neoplasia (OSSN) can clinically mimic pterygium.
  • Anterior-segment optical coherence tomography (AS-OCT) can delineate pterygium anatomy and Bowman’s-layer and stromal involvement; useful for surgical planning.
  • Corneal topography can quantify astigmatism before and after surgery; improvement after excision supports pterygium-induced corneal distortion, but no universal greater-than-1-diopter threshold confirms causation.
  • Irregular astigmatism or corneal scarring that persists after pterygium surgery may warrant evaluation for phototherapeutic keratectomy (PTK) in selected cases, after corneal and ocular-surface stabilization.

7. Management

Conservative (Non-Surgical) Management

TreatmentAgent/MethodEvidence / Notes
Topical lubricants• Preservative-free artificial tears • Gels• Reduce surface irritation • May help limit inflammation and enlargement • First-line for mild symptomatic pterygium
Topical nonsteroidal anti-inflammatory drugs (NSAIDs)• Ketorolac 0.5% • Bromfenac 0.09%• Anti-inflammatory • Bromfenac 0.09% plus sodium hyaluronate 0.4% reduced inflammatory signs and symptoms in a 3-week trial
Topical steroids• Fluorometholone • Loteprednol• Short courses for active inflammation • Risk of increased intraocular pressure with prolonged use
Ultraviolet (UV) protection• Wraparound ultraviolet (UV)-blocking sunglasses • Wide-brimmed hat• Primary prevention • Reduces ultraviolet exposure
Subconjunctival bevacizumab• Anti-vascular endothelial growth factor (anti-VEGF) injection into the pterygium• Reduces vascularity before surgery • May reduce intraoperative bleeding • Effect on recurrence is inconsistent and not definitive
Topical cyclosporine A 0.05%• Immunosuppressive• Emerging adjunctive immunomodulatory therapy • Targets T-lymphocyte-mediated inflammation in pterygium • Clinical benefit in progressive pterygium remains insufficiently established
IndicationNotes
Visual compromise• Vision-impairing astigmatism induced by pterygium • Threat to the visual axis
Rapidly progressive growth• Documented growth on serial measurements
Restriction of ocular motility• Diplopia • Tethering of medial rectus
Severe ocular surface symptoms refractory to medical therapy• Persistent foreign-body sensation (FBS) • Redness • Epiphora
Contact lens intolerance• Pterygium distorts fitting
Corneal measurement distortion before ocular surgery• Excise before cataract or corneal refractive surgery when corneal measurements are affected • Proceed after corneal keratometric stability is confirmed
Pre-cataract/refractive surgery• Excise pterygium before cataract or corneal refractive surgery • Proceed after corneal keratometric stability is confirmed
Cosmetic (relative)• Patient preference • Informed consent about recurrence risk
Exam pearl
  • Active preoperative growth and concurrent ocular-surface inflammation are associated with higher postoperative recurrence risk.

Surgical Techniques - Comparison

TechniqueRecurrence RateKey Feature / Indication
Bare sclera excisionUp to approximately 80%; substantial variation across studies• Historically used. • Substantially higher recurrence than conjunctival autograft and other adjuvant techniques. • ABANDONED as a stand-alone technique.
Primary closure (conjunctival advancement)Approximately 14–45% in reported observational and comparative series; substantial variation by study and follow-up.• Simple technique. • Inferior to conjunctival autograft in comparative recurrence outcomes. • Used for primary pterygium; a specific indication for small primary pterygium is not established by the reviewed evidence.
Conjunctival autograftApproximately 5–15% in study-dependent reports• GOLD STANDARD. • Free conjunctival graft from healthy superior or superotemporal bulbar conjunctiva placed on the post-excision bare scleral recipient bed. • Conventional conjunctival autograft does not necessarily include limbal tissue or transfer limbal stem cells.
Limbal conjunctival autograftApproximately 0–15% in published series; study- and disease-dependent• Includes a strip of limbal tissue intended to provide limbal stem cells. • Any advantage over conventional conjunctival autograft is biologically plausible but comparative superiority is not definitively established. • Used for primary or recurrent cases.
Amniotic membrane transplantApproximately 6–42% across randomized trials; substantial study-dependent variation• Considered when the conjunctival defect is large or a conjunctival autograft is unavailable or should be preserved, including conjunctival scarring, glaucoma devices or surgery, or double-headed/bilateral pterygium. • Less recurrence than bare sclera excision in comparative evidence, although the magnitude varies by technique and study. • Does not transfer limbal tissue or limbal stem cells.
Conjunctival autograft + intraoperative mitomycin C0–15.6% across studies; no reliable universal estimate of 1–5%• Can achieve low recurrence, but should not be described categorically as the lowest among all listed techniques. • Mitomycin C is applied intraoperatively before graft placement. • Reported exposure times vary, including 1–3 minutes in conjunctival autograft protocols; no optimal universal dose or duration has been established.
Conjunctival autograft + postoperative bevacizumabInconsistent recurrence effect; no consistent advantage over conjunctival autograft alone• May reduce pterygium vascularity in some studies. • Evidence that postoperative bevacizumab reduces recurrence is inconsistent and remains technique- and follow-up-dependent.
Notes
  • Conjunctival autograft is the current GOLD STANDARD for primary pterygium excision.

Graft Fixation Methods - Conjunctival Autograft

MethodAdvantagesDisadvantages
10-0 Nylon sutures• Reliable fixation • Strong fixation• Postoperative discomfort or foreign-body symptoms
Fibrin glue (Tisseel)• Shorter operating time • Less early postoperative discomfort • Less postoperative inflammation• Possible graft dehiscence, loss, or displacement
Autologous serum• Avoids the additional cost of suture or fibrin glue • Graft infection was not observed in one cohort• Graft retraction or displacement may occur • Comparative evidence is limited
Notes
  • Fibrin glue (Tisseel) is an established fixation option for conjunctival autografts, associated with shorter operating time, less postoperative inflammation, and greater patient comfort.
  • Comparative studies report recurrence rates that are similar to or lower than those reported with sutures; the evidence is low-certainty and variable across studies.
  • There is no clear evidence indicating whether fibrin glue or sutures should be preferred for conjunctival-autograft fixation.

Mitomycin C (MMC) - Pharmacology & Use

  • Mechanism: Alkylating agent → DNA cross-linking → inhibits fibroblast proliferation (primarily through DNA damage/alkylation; experimental studies also report reduced transforming growth factor beta-1 expression).
  • Concentration used: 0.02% (0.2 mg/mL) or 0.04% (0.4 mg/mL).
  • Duration of application: 2–5 minutes on bare sclera after pterygium excision, before graft placement.
  • Application method: Cellulose sponge soaked in mitomycin C (MMC) applied to bare sclera.
  • Confine mitomycin C (MMC) to the intended treatment area.
  • Avoid unintended exposure of the cornea and adjacent non-target conjunctiva or graft tissue.
  • Complications: Scleral necrosis (especially with higher concentrations/longer duration).
  • Scleral melt.
  • Infectious scleritis.
  • Reported cataract, iritis/anterior uveitis, and endophthalmitis.
  • Risk reduction: Thorough irrigation with balanced salt solution (BSS) after mitomycin C (MMC).
  • Use the lowest effective concentration and shortest effective exposure time.
  • Consider reserving intraoperative mitomycin C (MMC) for recurrent or otherwise high-risk pterygium rather than using it indiscriminately.
  • The optimal concentration and duration are not definitively established.

Viva Pearls

  • Mitomycin C (MMC) can cause scleral thinning, avascularization, necrosis, and melt; avoid applying it over areas of pre-existing scleral thinning as a safety precaution.
  • Rare delayed scleral or corneoscleral melt can occur years after mitomycin C (MMC) use, particularly after postoperative topical therapy; counsel patients about this rare late complication and the need to report persistent redness, pain, or visual change.
  • Mitomycin C (MMC) combined with conjunctival autograft (CAG) may reduce recurrence in selected cases, but reported rates vary and an approximately 1–5% rate is not universal.
  • Mitomycin C (MMC) applied to bare sclera carries rare but potentially vision-threatening complications, including scleral necrosis, melt, perforation, and infectious scleritis.
  • When mitomycin C (MMC) is selected as an adjuvant, a single controlled intraoperative application is generally favored because exposure can be monitored and postoperative dosing errors are avoided; postoperative drops have also been studied but are less commonly used because of safety and adherence concerns.
  • Postoperative topical mitomycin C (MMC) drops and intraoperative mitomycin C (MMC)–soaked sponges have both been used and may have similar recurrence rates; mitomycin C (MMC) in either form carries rare but severe long-term complications, so intraoperative application is often favored when controlled exposure is preferred.

8. Surgical Anatomy & Operative Pearls

Key Anatomical Considerations

StructureSurgical Relevance
Tenon's capsule• Dissect and remove the pterygium with associated Tenon's and fibrovascular tissue as completely as safely possible. • Retained fibrovascular or Tenon's tissue may increase recurrence risk.
Bowman's layer• The pterygium head may be adherent to or involve Bowman's layer. • Carefully dissect it from the cornea with a crescent or No. 15 blade. • A diamond burr may be used for residual fibrotic tissue when needed. • Avoid excessive depth because corneal thinning or globe perforation are surgical complications and may contribute to postoperative scarring.
Medial rectus• Traction during surgery can cause medial rectus avulsion or damage. • Beware with recurrent pterygium with deep sub-Tenon's adhesion.
Conjunctival defect / limbus• Size the conjunctival autograft approximately 1 mm larger than the measured conjunctival defect. • The graft should lie without tension and adequately cover the defect.
Superior bulbar conjunctiva (donor site)• Avoid superior limbus area to preserve stem cells for future glaucoma surgery (trabeculectomy site).
Anterior ciliary vessels• Medial anterior ciliary vessel runs close to medial rectus. • Can be damaged during deep Tenon's dissection.

Step-by-Step Surgical Approach (Conjunctival autograft (CAG))

StepDetail
1. Anesthesia• Commonly local anaesthesia, including subconjunctival infiltration. • General anaesthesia may be used for children or patients unable to cooperate.
2. Head dissection• At the limbus, dissect the pterygium head from the cornea with a crescent blade. • Remove residual pterygium tissue or corneal opacity with a diamond burr when required.
3. Body + Tenon's excision• Dissect and excise the pterygium body with associated Tenon's and fibrovascular tissue to leave a clean scleral bed.
4. Haemostasis• Bipolar or low-temperature cautery may be used for haemostasis. • Avoid excessive cautery because it may increase scarring and rare scleral ectasia or necrosis. • Mitomycin C can cause scleral thinning, ulceration, necrosis, or melt.
5. Mitomycin C (MMC) application (if indicated)• Apply mitomycin C (MMC) at 0.2 mg/mL (0.02%) on sponges to the bare sclera for approximately 2 minutes. • Irrigate vigorously or copiously with balanced salt solution. • The regimen remains technique- and risk-dependent.
6. Graft harvesting• Measure the bare scleral or conjunctival defect. • Harvest a thin superior bulbar conjunctival autograft sized to cover the defect, often with a small margin. • Dissect the graft free of excess Tenon's tissue rather than routinely harvesting it with Tenon's.
7. Graft placement• Mark the graft for orientation before harvesting. • Orient the limbal edge toward the recipient limbus. • Keep the epithelial side facing up.
8. Fixation• Fix the conjunctival graft with fibrin glue or sutures, such as interrupted 10-0 nylon, according to the selected technique. • Fibrin glue may reduce operative time and postoperative discomfort but is not universally established as the preferred method.
9. Postoperative care• Use topical corticosteroid therapy and lubricants. • Topical antibiotics or nonsteroidal anti-inflammatory drugs may be used when clinically indicated. • Select the steroid, dose, frequency, and taper according to the surgeon's protocol and the degree of postoperative inflammation.
  • INVERTED GRAFT: Incorrect graft orientation can compromise graft survival. Keep the epithelial surface facing UP and preserve correct limbal orientation. Mark the graft or limbal edge before harvesting.
  • TENON’S TISSUE: Retained Tenon’s tissue under the graft may promote fibroblast proliferation and recurrence. Dissect the graft free of excess Tenon’s tissue.
  • LIMBAL CONJUNCTIVAL AUTOGRAFT: Harvest a thin, appropriately sized graft and avoid unnecessary excess limbal tissue or conjunctival sacrifice. A limbal conjunctival autograft may intentionally include a small limbal component. Preserve conjunctiva when future glaucoma surgery is anticipated.
  • DONOR SITE: The donor site is commonly left bare to heal by secondary epithelialization. Primary closure is not universally prohibited and may be considered when clinically indicated.
  • HAEMOSTASIS: Over-aggressive cautery can contribute to scleral thinning or necrosis. Use judicious bipolar cautery. Mitomycin C (MMC) can cause scleral stromalysis and should be used with extreme caution.

9. Recurrence - Pathology, Prediction & Management

Exam pearl
  • Clinical Analogy: Recurrent pterygium is like a fire that was incompletely extinguished.
  • Incomplete removal of fibrovascular tissue and retained Tenon’s tissue may contribute to recurrence, with aggressive fibrovascular growth and scarring complicating further management.
  • Recurrent pterygium can exhibit aggressive fibrovascular growth associated with corneal and conjunctival scarring and limbal stem-cell deficiency, requiring extensive dissection during repeat surgery.

Risk Factors for Recurrence

FactorEffect on Recurrence
Tan T3 (Fleshy) type• Higher recurrence risk, particularly after bare-sclera excision • Specific attribution to high transforming growth factor beta (TGF-β) or vascular endothelial growth factor (VEGF) activity is not established
Young age (<40 years)• Younger age is associated with increased recurrence • The exact under-40-year cutoff and a more aggressive fibroblast response are not established
Male sex• Male sex was associated with higher reoperation risk in a large multivariable registry study • The contribution of occupational or outdoor ultraviolet (UV) exposure to this association is not established
Pterygium size/extent• May be associated with higher recurrence risk, but the relationship is inconsistent • The explanation that this is simply due to more tissue available to recur is not established
Bare sclera technique• High recurrence risk when used alone • One controlled trial reported 61% recurrence after bare-sclera excision versus 2% after conjunctival autografting • Generally avoid as the sole technique when graft or adjunctive options are available
Tropical latitude / high ultraviolet (UV) exposure postoperatively• High ultraviolet (UV) exposure is associated with pterygium development and has been reported in association with recurrence • The independent effect of continued postoperative ultraviolet (UV) exposure is not consistently established
Inadequate Tenon's excision• Incomplete removal or inadequate control of fibrovascular or Tenon's tissue may contribute to recurrence • Not established as the single most important preventable surgical factor
Short duration between surgeries• Not an established independent risk factor for recurrence • In one series, 91.6% of recurrences appeared by postoperative day 360 • A 12-month follow-up period was concluded to be optimal in that series before judging the result
Absence of adjuvant mitomycin C (MMC)• Higher recurrence than with adjunctive mitomycin C (MMC) has been reported • The supplied evidence does not specifically establish the comparison with mitomycin C (MMC)-augmented conjunctival autografting

Recurrence Classification (Prabhasawat)

GradeDescription
Grade 1• Normal appearance of operated site
Grade 2• Fine episcleral vessels extending to, but not beyond, the limbus • No fibrous tissue
Grade 3• Fibrous/fibrovascular tissue reaching the limbus but not invading the cornea
Grade 4• True corneal recurrence - fibrovascular tissue invading the cornea

Management of Recurrent Pterygium

ScenarioManagement
Prabhasawat Grade 1–2• Observation may be considered for selected Grade 1–2 recurrent pterygium that is clinically non-progressive and not vision-threatening. • Artificial tears and lubricating ointment may be used for pterygium-related irritation. • Ultraviolet-protective sunglasses may be used as supportive environmental protection. • The available evidence does not establish this as a validated grade-based management protocol. • Subconjunctival bevacizumab has been studied for selected early or impending recurrent pterygium to reduce vascularity, but it is not an established Grade 1–2 management protocol.
Prabhasawat Grade 3–4• Surgical re-excision may be considered for clinically significant recurrent pterygium. • Re-excision is not automatic solely because of Grade 3–4 classification. • Recurrent disease may involve scarring or altered anatomy, increasing surgical complexity. • This association is not established as specific to Prabhasawat Grade 3–4 recurrence. • Escalation should be guided by clinical progression, threat to the visual axis, or inflammation that cannot be controlled.
First recurrence• Excision plus conjunctival autograft or limbal-conjunctival autograft may be considered when suitable healthy donor conjunctiva is available. • The evidence does not establish a distinct algorithm limited to a first recurrence. • Intraoperative mitomycin C may be considered selectively as an adjunct in selected higher-risk recurrent pterygium. • Intraoperative mitomycin C is not established as a routine requirement for every first recurrence.
Bilateral/multiple recurrences• Amniotic membrane transplantation may be considered for selected recurrent pterygium when conjunctival donor tissue is limited or should be preserved, including some advanced or bilateral-head cases. • Mitomycin C may be added selectively. • Amniotic membrane transplantation plus mitomycin C is not established as mandatory for all bilateral or multiple recurrences. • Limbal-conjunctival autograft may be considered for selected recurrent pterygium when adequate healthy donor tissue is available. • Limbal-conjunctival autograft is not a separately validated indication for bilateral or multiple recurrences.
Aggressive recurrence (multiple)• Postoperative strontium-90 beta-irradiation may have been used as an adjunct after excision in primary and recurrent pterygium. • The available findings do not establish a specific indication for selected difficult recurrent disease. • The evidence does not establish a universal indication limited to aggressive, multiple recurrence. • One 10-year study used 2000–3000 centigray (cGy) total in three fractions. • This is a study-specific regimen, not a universal safety-established protocol. • Reported serious adverse effects include scleral necrosis, cataract, and ocular infection.

Viva Pearls

  • Postoperative strontium-90 beta irradiation has been used as an adjuvant to reduce recurrence in selected recurrent pterygia, but dose and fractionation vary; recurrent-pterygium series report substantial recurrence and risks including cataract, symblepharon, corneal thinning or ulceration, and late scleral injury. Its use requires careful selection and is not routine first-line management.
  • Subconjunctival bevacizumab has been studied at varying doses, including 2.5 mg/0.1 mL. Effects on vascularity and recurrence are inconsistent, and meta-analysis has not demonstrated a statistically significant recurrence-prevention benefit; it should not be considered established first-line recurrence prophylaxis.
  • Amniotic membrane transplantation provides a biological scaffold but does not itself provide a limbal stem-cell autograft. Conjunctival or limbal-conjunctival autografting generally has lower recurrence in recurrent pterygium, although comparative evidence is heterogeneous. Amniotic membrane transplantation is a useful alternative when suitable conjunctival autograft tissue is unavailable or should be preserved.
  • Re-excision of recurrent pterygium is technically more complex because subconjunctival scar tissue may increase bleeding and the risk of extraocular-muscle injury. Scleral thinning or perforation can occur during difficult dissection; other complications, including symblepharon, are possible but are not established as inevitable or solely attributable to re-excision.

10. Complications of Pterygium & Its Surgery

ComplicationMechanismManagement
Irregular astigmatismCorneal distortion by pterygium• Resolves partially post-surgery • Residual → rigid contact lens (CL) / phototherapeutic keratectomy (PTK) / photorefractive keratectomy (PRK)
Recurrence• Incomplete Tenon's excision • T3 type • Young ageRe-excision + conjunctival autograft (CAG) + mitomycin C (MMC)
Dellen formationTear-film disruption at an elevated edge• Lubricants • Ointment • Patching • Consider punctal occlusion or corneal protection if refractory
DiplopiaRestrictive scar tissue and adhesions near the medial rectusScar-tissue release with ocular-surface reconstruction
Ocular surface squamous neoplasia (OSSN) (missed)Ocular surface squamous neoplasia misdiagnosed as pterygium• Histopathologic assessment of suspicious excised lesions • Excision ± topical mitomycin C or interferon alfa-2b
Scleral melt / necrosisPost-mitomycin C ischaemia• Treatment according to cause and severity • Tenon's membrane covering with amniotic membrane transplantation (AMT) • Corneoscleral patch grafting • Systemic immunosuppression for surgically induced necrotizing scleritis
Graft dehiscence• Poor fixation • Haematoma • Inverted graftRe-fixation with sutures
Pyogenic granulomaInflammatory granulation tissue around the free conjunctival flapSurgical excision + topical corticosteroid drops
Symblepharon• Inadequate conjunctival closure • Fornix involvementAmniotic membrane transplantation (AMT) for lysis and reconstruction
Infectious scleritisPost-mitomycin C devascularisation + infection• Aggressive topical antibiotics • Systemic antibiotics • Scleral debridement
Cataract / uveitisRare reported mitomycin C–associated iritis or cataractManagement according to complication and severity

11. PTERYGIUM vs OSSN - CRITICAL DIFFERENTIATION

Exam pearl
  • Clinical Analogy: If pterygium is an overzealous contractor, OSSN (Ocular Surface Squamous Neoplasia) is a malignant architect with no rules - it infiltrates deeper planes, metastasises, and can invade the globe. Missing OSSN under the disguise of pterygium is a catastrophic clinical error.
FeaturePterygiumOcular surface squamous neoplasia (OSSN)
Location• Interpalpebral • Nasal more common than temporal• Usually interpalpebral and near the limbus • Rare lesions may occur at other conjunctival or ocular-surface locations
Surface• Smooth or well-delineated • Triangular fibrovascular lesion• May be papillomatous • May be leukoplakic • May be gelatinous • May be nodular
Vascularity• Vessels commonly straighten toward the advancing corneal head• Prominent tortuous or dilated feeder vessels may occur • “Corkscrew” vessels are not universal
Borders• Usually well-defined and triangular• May have irregular margins • Some nodular or gelatinous lesions may be relatively well-demarcated
Mobility• Typically remains continuous with and mobile with the conjunctiva• Invasive squamous cell carcinoma may become immobile or fixed to underlying sclera • Mobility alone is not diagnostic
Growth pattern• Usually enlarges progressively from interpalpebral conjunctiva onto the cornea • May progress toward the visual axis • Growth may be variable or stationary• Growth rate and direction are variable • Lesions may be slow-growing • Lesions may be diffuse • Lesions may be locally invasive
Fluorescein• An adjacent dellen or epithelial defect may stain • Staining is a complication, not a universal feature• Surface epithelial irregularity or defects may stain • Fluorescein staining is nonspecific and should not be used alone for distinction
Rose Bengal / Lissamine green• Staining may occur over exposed, damaged, devitalized, or mucin-deficient epithelium • A normal staining pattern should not be assumed• May highlight abnormal or devitalized epithelial areas and help delineate lesion borders • Staining is nonspecific and does not specifically identify dysplastic cells
Anterior-segment optical coherence tomography (AS-OCT)• Usually normal-thickness epithelium overlying subepithelial fibrosis• Thickened, hyper-reflective epithelium with an abrupt transition from normal to abnormal epithelium • May help identify ocular surface squamous neoplasia (OSSN) • Does not reliably assess deep invasion
Histopathology• Elastotic degeneration with fibrovascular subepithelial tissue • Overlying epithelium is usually preserved • May show goblet-cell hyperplasia • May show acanthosis • May show hyperkeratosis • May show dysplasia• Epithelial dysplasia or conjunctival intraepithelial neoplasia (CIN) • Basement-membrane invasion defines invasive squamous cell carcinoma
Tumor protein 53 (p53)• Tumor protein 53 (p53) expression or tumor protein 53 gene (TP53) pathway alteration has been reported • Tumor protein 53 gene (TP53) mutation is inconsistent and is not universal• Tumor protein 53 gene (TP53) abnormalities, including mutations, are reported in a substantial subset • Tumor protein 53 (p53) status alone does not define aggressiveness
Treatment• Excision with conjunctival autograft is a commonly used recurrence-reducing approach • Technique is selected according to lesion and recurrence risk• Lesion-dependent management • No-touch excision with adequate margins and cryotherapy for suitable focal lesions • Topical mitomycin C, interferon-alpha 2b, or 5-fluorouracil may be used as primary or adjuvant therapy

Exam Traps & MCQ Traps

  • Corkscrew or meandering vessels may occur in ocular surface squamous neoplasia (OSSN). Straight superficial vessels may occur in pterygium. Vascular morphology alone is not diagnostic; investigate lesions suspicious for ocular surface squamous neoplasia (OSSN).
  • An atypical conjunctival lesion suspicious for ocular surface squamous neoplasia (OSSN) requires appropriate assessment. Incisional or excisional biopsy with histopathologic evaluation provides the definitive diagnosis. Ocular surface squamous neoplasia (OSSN) can mimic pterygium.
  • Leukoplakia on a conjunctival mass is suspicious for ocular surface squamous neoplasia (OSSN), but is not diagnostic on its own.
  • Topical interferon alfa-2b, 1 million international units/mL four times daily, is a commonly used regimen for ocular surface squamous neoplasia (OSSN). Interferon alfa-2b has also been studied as a postoperative adjunct for pterygium recurrence prevention.

12. Emerging Therapies & Evolving Concepts

TherapyMechanismCurrent Status
Limbal stem cell transplant (LSCT)• Restore ocular-surface epithelial barrier function with autologous or allogeneic limbal stem-cell transplantation• Studied as an adjunct to excision for primary and recurrent pterygium • Selected case series describe use in aggressive recurrent pterygium associated with limbal stem-cell deficiency
Photodynamic therapy (PDT)• Use a photosensitizer and light exposure to modulate postoperative wound healing and fibrovascular recurrence• Limited evidence • Not in standard practice
Extracorporeal irradiation graft (ECG)• Irradiated autograft to reduce antigenicity• Experimental
Topical anti-sense oligonucleotides• Modulate expression of a complementary ribonucleic acid (RNA) target • A pterygium-specific topical antisense treatment has not been established• Not established

Key Landmark Considerations:

  • There is no single landmark randomized controlled trial for pterygium surgery akin to the Beaver Dam Eye Study (BDES) or branch retinal vein occlusion (BRVO) studies.
  • Evidence includes randomized controlled trials, prospective comparative series, and systematic reviews and meta-analyses.
  • A 2016 Cochrane review found low-certainty evidence that fibrin glue may reduce recurrence and operating time compared with sutures for conjunctival autografting, with possible postoperative comfort advantages but more graft-related complications.
  • The role of adjuvant bevacizumab remains unresolved in high-quality randomized controlled trial data.

13. High-Yield Questions

HIGH-YIELD MCQ-STYLE QUESTIONS WITH TRAPS
Q1

A 35-year-old farmer presents with a nasal fibrovascular conjunctival growth with an avascular grey zone ahead of the leading edge. Stocker's line is absent. What does this indicate?

Oral-exam Q&A
Q1

During pterygium excision, the surgeon places the conjunctival autograft and the patient returns post-op Day 7 with a white, avascular graft.

HIGH-YIELD MCQ-STYLE QUESTIONS WITH TRAPS
Q1

Which grading parameter best predicts recurrence after pterygium excision?

Oral-exam Q&A
Q1

A patient underwent pterygium excision with bare sclera technique 2 months ago. She now presents with a whitish, avascular, painful scleral plaque at the site. No prior MMC was used. What is the diagnosis?

Oral-exam Q&A
Q1

A probe passed at the limbus can go BENEATH the conjunctival mass freely. What is the diagnosis?

Oral-exam Q&A
Q1

Bevacizumab is injected subconjunctivally into a pterygium before surgery. What is the PRIMARY mechanism of action?

14. Consultant-Level Extension Question

Consultant-level oral-exam question

A 28-year-old fisherman from coastal Tamil Nadu presents with a Tan T3, Johnston Grade 3 nasal pterygium in his only functional eye (the other eye was enucleated after trauma). He has had two previous excisions at another centre - the last one with bare sclera technique. Slit-lamp shows an irregular, papillomatous surface with corkscrew vessels at the leading edge. Anterior-segment optical coherence tomography (AS-OCT) shows abrupt epithelial thickening with a hyperreflective signal. What is your diagnostic approach, surgical plan, and how would you counsel this patient regarding prognosis and long-term management?

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