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Summary Table

Category	Details
Risk Factors	History of ocular surface trauma, chemical/thermal burns, corneal ulceration, Stevens-Johnson syndrome, ocular cicatricial pemphigoid, prior ocular surgery
Etiology	Secondary adhesion of conjunctiva to a pre-existing corneal epithelial defect or ulcer during the healing process; NOT caused by chronic UV exposure
Patient Presentation	Fleshy tissue growing over the cornea in a patient with a clear history of preceding ocular injury or inflammation; may report foreign body sensation, tearing, or reduced vision if the visual axis is involved
Classic Physical Exam	Conjunctival fold adherent to cornea at any location (not limited to nasal side); positive probe test (a probe passes freely beneath the body of the lesion); absence of Stocker's line
Key Diagnostic Results	Clinical diagnosis on slit-lamp examination; probe test is the key discriminating maneuver; histopathology shows fibrosis and chronic inflammation without elastotic degeneration of collagen
Management	Address underlying etiology first; surgical excision with conjunctival or amniotic membrane graft if visually significant; lamellar keratoplasty for deep corneal scarring
Keywords	"History of chemical burn," "tissue adherent to cornea at unusual location," "probe passes beneath the lesion," "no Stocker's line," "corneal ulcer with overlying conjunctival growth"

1. Pathophysiology

Pseudopterygium develops through a fundamentally different mechanism than true pterygium, and understanding this distinction is the core concept being tested.

When the corneal epithelium is damaged or lost (from a chemical burn, peripheral ulcer, thermal injury, or inflammatory conditions like Stevens-Johnson syndrome), the adjacent conjunctival tissue responds by migrating onto the denuded corneal surface as part of the wound-healing response. The conjunctiva essentially "fills in" the epithelial defect, creating an adhesion between the conjunctival fold and the corneal stroma. This is a reparative, secondary process, driven by fibroblast proliferation and scar tissue formation at the site of prior injury.

Critically, this process does not involve elastotic degeneration of subconjunctival collagen, which is the hallmark histopathological finding of true pterygium. True pterygium arises from chronic ultraviolet radiation damage to limbal stem cells and subconjunctival connective tissue, leading to actinic elastosis. Pseudopterygium, by contrast, shows fibrosis, chronic inflammatory infiltrate, and neovascularization without elastotic changes.

Because the adhesion forms only at the original site of corneal damage, only the head (leading edge) of the pseudopterygium is adherent to the corneal surface. The body and the neck of the lesion are not fused to the underlying sclera or cornea. This explains the positive probe test: a glass rod or metal probe can be slid freely beneath the body of the pseudopterygium. In true pterygium, the entire structure is firmly adherent to the underlying tissue because it represents progressive subepithelial fibrovascular invasion through a destroyed Bowman's layer.

The location of pseudopterygium is dictated by the site of original corneal injury, which means it can occur anywhere on the corneal circumference. This contrasts sharply with true pterygium, which almost always originates from the nasal interpalpebral conjunctiva because this zone receives the highest UV exposure due to peripheral light focusing by the cornea (the "coroneo effect").

Stocker's line, a curvilinear iron deposition line (hemosiderin in the corneal epithelium) found at the advancing edge of a true pterygium, is characteristically absent in pseudopterygium. Stocker's line forms because of chronic, slow, progressive growth that allows tear film iron to deposit at the leading edge. Pseudopterygium does not exhibit this slow progressive march, so no iron line develops.

2. Classification and Clinical Manifestation

Classification	Category	Clinical Features
By Etiology	Post-traumatic	History of mechanical corneal trauma or foreign body; adhesion forms at the injury site
	Post-chemical/thermal burn	Often the most common cause; may be accompanied by extensive limbal stem cell deficiency, symblepharon, and lid abnormalities
	Post-inflammatory	Follows peripheral corneal ulcers (bacterial, marginal, Mooren's), or systemic conditions like Stevens-Johnson syndrome and ocular cicatricial pemphigoid
	Post-surgical	Develops after corneal or conjunctival surgery at the operative site
By Corneal Location	Nasal	Can mimic true pterygium; history and probe test differentiate
By Corneal Location	Temporal, superior, or inferior	Strongly suggests pseudopterygium, since true pterygium is overwhelmingly nasal
By Visual Significance	Non-axial	Does not encroach on the visual axis; may be observed
By Visual Significance	Axial	Crosses or threatens the pupillary axis; surgical intervention indicated
By Extent of Adhesion	Localized	Small area of conjunctival-corneal adhesion; probe test easily performed
By Extent of Adhesion	Extensive (with symblepharon)	Broad adhesion often associated with severe chemical burns; may involve fornix shortening and restricted motility

The clinical presentation varies depending on the underlying cause. A patient with a history of alkali burn may present with a broad, vascularized membrane extending from severely scarred conjunctiva onto an opacified cornea, often accompanied by symblepharon (adhesion of palpebral to bulbar conjunctiva) and fornix shortening. By contrast, a patient who had a small peripheral corneal ulcer may develop a localized, thin fold of conjunctiva bridging onto the healed ulcer site.

3. Diagnostic Workup

Test	Role	Key Findings
Slit-lamp biomicroscopy	Best initial test	Conjunctival fold adherent to cornea; location of adhesion; assessment of corneal scarring and visual axis involvement
Probe test	Key discriminating maneuver	Probe passes freely beneath the body of pseudopterygium; cannot pass beneath true pterygium
Clinical history	Essential for diagnosis	Documented history of corneal ulceration, chemical burn, trauma, or inflammatory disease preceding the lesion
Histopathology	Confirmatory (post-excision)	Fibrosis, chronic inflammatory infiltrate, neovascularization; absence of elastotic degeneration (which would indicate true pterygium)
Corneal topography	Adjunctive	Quantifies induced astigmatism if the lesion is large; helps in surgical planning
Anterior segment OCT	Adjunctive	Demonstrates the plane of adhesion; may show a gap between the lesion body and the underlying cornea/sclera

The best initial test is a thorough slit-lamp examination combined with the patient's clinical history. The exam will reveal a conjunctival fold or flap adherent to the cornea. You should note the location of the lesion (non-nasal location is a strong clue) and look for associated findings such as corneal scarring at the adhesion site, symblepharon formation, or evidence of limbal stem cell deficiency.

The probe test is the single most important clinical maneuver for distinguishing pseudopterygium from true pterygium, and it is the detail most likely to appear in a vignette stem. You gently slide a probe (or glass rod) beneath the body of the lesion. If it passes freely, the lesion is a pseudopterygium. If the body is firmly adherent and the probe cannot be advanced, it is a true pterygium.

Histopathology serves as the gold standard for confirmation but is available only after surgical excision. The hallmark is the absence of elastotic degeneration. True pterygium specimens characteristically show Bowman's layer destruction, elastotic (actinic) degeneration of subepithelial collagen, and often a prominent fibrovascular core.

Anterior segment optical coherence tomography (OCT) has emerged as a helpful adjunctive tool. It can demonstrate a clear space beneath the body of a pseudopterygium, correlating with the clinical probe test, and can delineate the depth of corneal stromal involvement to guide surgical planning.

4. Management and Treatment

Scenario	Management	Details
Asymptomatic, non-axial	Observation	Lubricating eye drops (artificial tears, 4 to 6 times daily) for comfort; periodic follow-up
Visually significant or symptomatic	Surgical excision	Excision of the conjunctival adhesion from the cornea with reconstruction of the ocular surface
Post-excision surface reconstruction	Conjunctival autograft or amniotic membrane transplant (AMT)	Reduces recurrence and promotes epithelial healing
Significant corneal scarring	Lamellar or penetrating keratoplasty	Reserved for cases with dense central corneal opacity affecting vision after pterygium removal
Underlying limbal stem cell deficiency	Limbal stem cell transplantation	Necessary in severe chemical burn cases where limbal stem cells are depleted; without this, the epithelial surface cannot be restored
Post-operative medical therapy	Topical corticosteroids + topical antibiotics	Prednisolone acetate 1% QID, tapered over 4 to 6 weeks; moxifloxacin 0.5% or ofloxacin 0.3% QID for 7 to 14 days

Step 1: Address the underlying cause. Before any surgical intervention, the corneal and conjunctival surface must be stable. Active inflammation or ulceration should be treated. If the cause was a chemical burn, ensure adequate initial irrigation and control of ongoing inflammation.

Step 2: Determine visual significance. If the pseudopterygium does not threaten the visual axis and the patient has minimal symptoms, conservative management with artificial tears and monitoring is appropriate. Many pseudopterygia remain stable once the original insult has healed, unlike true pterygia which tend to progress.

Step 3: Surgical excision. For visually significant lesions, the pseudopterygium is dissected from the corneal surface. Because only the head is adherent, the dissection plane is generally straightforward. The bare scleral or corneal bed is then covered with either a conjunctival autograft (harvested from the superior bulbar conjunctiva) or an amniotic membrane transplant to reduce scarring and recurrence.

Step 4: Manage corneal opacity. If the cornea beneath the excised pseudopterygium has significant stromal scarring that limits visual recovery, lamellar keratoplasty (partial thickness corneal transplant) may be needed as a secondary procedure.

Step 5: Post-operative care. Topical prednisolone acetate 1% is initiated four times daily and tapered gradually over 4 to 6 weeks to control inflammation and reduce fibrosis. A topical fluoroquinolone antibiotic (moxifloxacin 0.5% or ofloxacin 0.3%) is used four times daily for 7 to 14 days for infection prophylaxis. Preservative-free artificial tears are continued for comfort and surface lubrication.

Contraindications and special considerations: In patients with severe limbal stem cell deficiency (common after extensive chemical burns), simple excision will fail because the corneal epithelium cannot regenerate. These patients require limbal stem cell transplantation before or concurrent with pterygium excision. Without restoring the stem cell population, the conjunctival tissue will simply re-invade the corneal surface.

Recurrence of pseudopterygium after surgery is less common than recurrence of true pterygium, provided the underlying cause has been adequately treated and the ocular surface is stable.

5. Differential Diagnosis and Distractors

Differential	Why It Is Similar	Key Discriminator
True pterygium	Both present as a wing-shaped conjunctival tissue extending onto the cornea; both can cause astigmatism and visual axis obstruction	True pterygium is nasal, progressive, UV-related, has a negative probe test (body adherent), and shows Stocker's line; pseudopterygium can be at any location, has a positive probe test, and has a history of preceding corneal injury
Pannus	Vascularized tissue on the corneal surface; can cause corneal opacification	Pannus is a superficial corneal vascularization (often superior, as in trachoma, or circumferential, as in contact lens overuse) without a raised conjunctival fold; no probe test applicable; associated with chronic hypoxia or infection, not a focal adhesion
Limbal dermoid	A fleshy, elevated lesion at the limbus that may extend onto the cornea	Dermoid is congenital, well-circumscribed, may contain hair follicles or fat; it is a choristoma, not an adhesion; typically presents in childhood
Conjunctival intraepithelial neoplasia (CIN)	A vascularized, gelatinous conjunctival lesion that can extend onto the cornea	CIN is typically a papillomatous or leukoplakic lesion with feeder vessels; it does not form a fold or adhesion; biopsy shows dysplastic epithelial cells; associated with UV and HPV
Symblepharon	Adhesion of conjunctival surfaces, often in the same clinical setting (chemical burns, SJS)	Symblepharon is adhesion of palpebral to bulbar conjunctiva (lid to globe), not specifically conjunctiva to cornea; may coexist with pseudopterygium in the same patient
Pingueculum	Yellowish conjunctival lesion near the limbus; UV-related	Pingueculum is a degenerative lesion confined to the conjunctiva and does not cross the limbus onto the cornea; elastotic degeneration histologically

6. Traps and High-Yield Pearls

The most common way students get questions on pseudopterygium wrong is by confusing it with true pterygium and selecting UV-related or nasal-location-based answers when the vignette clearly describes a different mechanism. The vignette will typically plant a history of ocular trauma or chemical burn earlier in the stem, and the student who does not connect that history to the conjunctival-corneal adhesion will default to "pterygium" and choose the wrong diagnosis.

The second major trap involves the probe test. A well-constructed question may describe a pterygium-like lesion and then ask for the best clinical maneuver to differentiate true from pseudo. Students who are unfamiliar with the probe test may choose biopsy or imaging, both of which are less practical and not the expected answer. The probe test is the key bedside differentiator.

Another pitfall is location. If the vignette describes a wing-shaped conjunctival growth at the temporal or inferior limbus, this should immediately raise suspicion for pseudopterygium over true pterygium. True pterygium in the temporal position is uncommon; a non-nasal location combined with a relevant history essentially clinches the diagnosis.

Finally, be aware of the management trap: students sometimes select "mitomycin-C application" or "conjunctival autograft to prevent recurrence" as if managing a true pterygium. While surface reconstruction techniques overlap, the more important management principle for pseudopterygium is treating the underlying cause and ensuring ocular surface stability. Without addressing limbal stem cell deficiency or ongoing inflammation, no graft will hold.

The core competency being tested is the ability to integrate clinical history (preceding trauma or inflammation) with examination findings (location, probe test, absence of Stocker's line) to distinguish a secondary, reparative process from a primary degenerative one.

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