Large, flat peripheral pterygium

ICD-10 Diagnosis Codes:

H11.041–Peripheral pterygium, stationary,right eye
H12.042–Peripheral pterygium, stationary, left eye
H12.043–Peripheral pterygium, stationary,bilateral




Disorders Of The Conjunctiva


A pterygium is a type of conjunctival degeneration. 

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
DG37241AB Stationary Peripheral Pterygium

  • No apparent inflammation
  • 3-4 mm of corneal encroachment
  • Relatively flat lesion
DG37241Pic01 Stationary Peripheral Pterygium

  • The body of the pterygium is the segment composed of collagenous degenerative tissue and a vascularized subepithelial stroma
DG37241Pic03 Stationary Peripheral Pterygium

  • The hood of the pterygium is the segment that is fibrous and nonvascular
DG37241Pic05 Stationary Peripheral Pterygium

  • The apex of the pterygium is known as the head and it is typically elevated and vascularized

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

1st Milestone — Opacification of the conjuctiva

  • In its early stages, a pterygium usually appears as a small opacity of the surface of the conjunctiva at the nasal limbus
  • As it develops, the lesion spreads to become a fleshy, raised area

2nd Milestone — Focal limbal failure occurs

Corneal Invasion

  • As the pterygium continues to grow, the conjunctivalization of the cornea begins
  • The pterygium crosses the limbus as the apex invades the subepithelial cornea
  • Continued pterygium growth is marked by a trail of degenerative hyaline and pseudoelastic tissue on the corneal surface

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
DG37241Pic16 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
Stationary Peripheral Pterygium

  • Minimal fibrovascular proliferation
  • Relatively flat lesion
  • Tend to be slow-growing
  • Lower incidence of recurrence following surgical removal


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
PterygiumPic30 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.

DG37241Pic14 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
DG37241Pic25 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.

Malignant Conjunctival Neoplasm

  • Lesion could be misdiagnosed as a pterygium
CT_ICD9_190-3_Pic03_041209 Malignant Conjunctival Neoplasm

  • Lesion could be misdiagnosed as an inflamed pterygium

  • Conjunctival hyperemia is similar to an pterygium
  • No corneal involvement
  • Nodular-shaped pinguecula vs. triangular-shaped pterygium


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
DG37241Pic36 Pseudopterygium vs. Pterygium

  • History of prior inflammation
  • Monocular clinical presentation
  • Sometimes located other than the horizontal meridian
  • Tend to be non-progressive
DG37241Pic32 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
DG37241Pic38 Phlyctenulosis

  • Corneal phlycten could be misdiagnosed as the head of a progressive pterygium
DG37241Pic37 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.

1.  Rao SK.  Pterygium:  a review.  eJournal of Ophthalmology.  Last accessed April 2, 2014.
2.  Fisher JP.  Pterygium.  Medscape.  Last accessed April 2, 2014.
3.  Skorin L.  Become familiar wih advances in pterygium surgery.  Primary Care Optometry News.  2009 January:  14.
4.  Aminlari A.  Singh R.  Liang D.  Management of pterygium.  American Academy of Ophthalmology.  Last accessed April 2, 2014.