H12.041-043 Pterygium

Corneal edema is a clinical sign of corneal disease.  The condition is characterized by an increase in corneal thickness secondary to an abnormal accumulation of fluid.  The excess fluid produces a swelling of the corneal tisssue and can result in a loss of stromal transparency that produces blurred vision or visual impairment. 

A pterygium presents as an elevated, superficial, external ocular mass on the perilimbal conjunctiva that grows into and onto the cornea.  Pterygia can vary in size, height, and rate of growth. 

The typical triangular-shaped lesion is comprised of three different anatomic segments.

• Body
• Hood
• Head

A pterygium is a mass characterized by collagen degeneration in the bulbar conjunctiva, fibrovascular proliferation, and an overylying covering of epithelium.

A pterygium evolves through a sequence of three milestones:

1.  Small opacity appears of the surface of the conjunctiva
2.  Focal limbal failure occurs as the pterygium enlarges- (conjunctivalization of the cornea)
3.  Conjunctivalization of the cornea damages corneal structure and decreases function

3rd Milestone – Conjunctivalization of the cornea continues

Cornea becomes more abnormal.

• Cellular proliferation
• Connective tissue remodeling
• Abnormal blood vessel formation
• Irregular astigmatism

Functional Damage to the Eye

• Irregular astigmatism may be created by pterygium encroachment onto the corneal surface and produce visual impairment
• An elevated pterygium may produce disturbances in the precorneal tear film that disrupt vision
• Large, aggressive, rapidly growing pterygia can obscure the visual axis of the cornea

Progressive Pterygium Large, elevated pterygium Severe fibrovascular proliferation High risk of vision loss if the pterygium grows across the visual axis

The main goal of the diagnostic evaluation is to accomplish the following:

• Identify the lesion
• Evaluate the cornea for structural damage or functional loss
• Identify risk factors for pterygium development
• Prescribe a treatment program

Patient History

Patients with pterygium present with a variety of complaints, ranging from no symptoms to any or all of the following:

• Persistent ocular redness
• Foreign body sensation
• Dry eyes
• Itchy eyes
• Swelling
• Decreased vision

Clinical Appearance of the Conjunctiva

• Pterygium encroachment onto and into the cornea

DIAGNOSTIC TESTS

		External Ocular Photography Document the size and shape of the pterygium Document the amount of pterygium encroachment towards the visual axis To help plan a treatment program Document the delivery of medical treatment Document the response to treatment
		Corneal Topography Document the shape and physical features of the anterior surface of the cornea Identification and follow-up for irregular astigmatism secondary to pterygium encroachment onto the cornea Most importantly, help quantify the effect the pterygia may be having on vision To help plan a treatment program Document the delivery of medical treatment Document the response to treatment

The clinical presentation of pterygia can be divided into two general categories – Stationary and Progressive.

		Stationary Pterygium Monocular pterygium in an 82-year-old black woman Mildly-elevated fibrovascular body Slightly atrophic appearance The presence of a pigment line in front of the pterygium is called Stocker’s line and is commonly found in long-standing lesions Pterygium is unchanged in clinical presentation for at least ten years
		Progressive Pterygium Significantly-elevated fibrovascular body Tend to be fast-growing High amount of irregular surface corneal astigmatism Permanent visual loss may occur as the pterygium encroaches upon the visual axis

This would include any other disease that presents as an interpalpebral conjunctival mass or elevation.  Lesions with this clinical appearance mayalso be a clinical sign of the following diseases or conditions.

Conjunctival Tumors

• Conjunctival intraepithelial neoplasia
• Papilloma
• Malignant neoplasms
• Nevus 

Conjunctival intraepithelial neoplasia (CIN) is the most common mis-diagnosis of a pterygium that can have significant consequences.  CINs are the most common primary conjunctival tumor, more commonly seen in those with lighter skin and/or higher degrees of UV exposure.  They have a hallmark presentation of blister-like appearances on the conjunctiva, a “frosted” appearance onto the cornea, suspicious vascularization, and in the later stages actual ulceration of the tissue near the limbus.  CIN are precursors to squamous cell carcinoma.  

Any lesions with findings suspicious for CIN should be referred for an incisional biopsy and likely surgical removal.

Pseudopterygium

A pseudopterygium occurs when a fold of conjunctiva becomes attached to the peripheral cornea.  It is caused by corneal inflammation secondary to any of the following conditions:

• Chemical burns
• Peripheral corneal ulcer
• Corneal perforation
• Contact lens wear
• Cicatrizing conjunctivitis

		Pseudopterygium vs. Pterygium History of prior inflammation Monocular clinical presentation Sometimes located other than the horizontal meridian Tend to be non-progressive
		Pseudopterygium secondary to contact lens wear History of current or previous hard contact lens wear Associated with mechanical irritation of the corneal surface Associated with inadequate lubrication of the corneal surface
		Phlyctenulosis Corneal phlycten could be misdiagnosed as the head of a progressive pterygium
		Corneal Neovascularization with Lipid Deposition Neovascularizaton combined with loss of stromal transparency is similar in appearance to a pterygium This can also mimic the appearance of scarring from a prior pterygium surgery

Patients with a normal pterygium can be observed.  If the pterygium is small and stable, it is an option.  The best way to document and monitor a pterygium is by corneal topography.  This will not only document the extent of encroachment but will more importantly document the effect the distortion is having on the visual axis.

Preventative Treatment

• Decrease excessive exposure to wind and sunlight (UVA and UVB)
• Aggressively treat any coexisting ocular surface disease
• Discontinue contact lens wear
• Prescribe contact lenses that do not irritate a pre-existing pterygium

Medical Treatment

• Aggressive lubrication treatment
• Topical steroids if moderate to significant inflammation exists

Surgical Treatment

The only effective treatment for aggressive pterygium growth or pterygia encroaching on the visual axis is surgical removal.

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3.  Skorin L.  Become familiar wih advances in pterygium surgery.  Primary Care Optometry News.  2009 January:  14.
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