Aetiology

A winged-shaped fibrovascular growth progressing from the bulbar conjunctiva to involve the cornea
Possibly a tissue response to irritants rather than a true degeneration
Overall, the global prevalence of pterygium is 10%, but depending on demographic, environmental and lifestyle factors varies from 3% to 20%. Prevalence decreases with increasing distance from the equator.
Multifactorial aetiology, but generally attributed to chronic exposure to UV light, dust and wind.

Predisposing factors

Older age
Male gender (probably related to occupational exposure)
Long term exposure to ultraviolet radiation

• sunlight (residence at or near the equator, outdoor work, especially on reflective surfaces e.g. sand, concrete, water, snow)

Dryness, arid climate

Symptoms of pterygium

Mild irritation (redness, dryness, foreign body sensation)
May be exacerbated by incidents of acute inflammation

Effect on vision

• result of astigmatism (with the rule)
• in severe cases, pterygium may extend over visual axis

Cosmetic concern

Signs of pterygium

Usually bilateral; often asymmetrical. More common nasally
Starts with scarring, thickening and distortion of the bulbar conjunctiva
Small grey corneal opacities appear near the limbus
Conjunctiva overgrows these opacities
Slow insidious growth on to cornea (or may become stable)
Destroys Bowman’s membrane and superficial stroma lamellae
Epithelial iron deposit (Stocker’s line) ahead of advancing pterygium
Relatively rich surface vascularisation
Flattening of cornea in horizontal meridian

Differential diagnosis

Pinguecula (no corneal involvement) (See Clinical Management Guideline on Pinguecula)
Pannus
Pseudopterygium

• adhesion of a fold of conjunctiva to a peripheral corneal ulcer, which is fixed only at its apex to the cornea (pterygium is adherent to underlying structures throughout)

Carcinoma in situ of the cornea or conjunctiva (also known as Bowen’s disease and as intraepithelial squamous cell carcinoma)

Management by optometrist

Practitioners should recognise their limitations and where necessary seek further advice or refer the patient elsewhere

GRADE* Level of evidence and strength of recommendation always relates to the statement(s) immediately above

Advise on UV protection:

• brimmed hat, sunglasses (ideally wrap-around style for side protection)
• reduces risk of progression and of becoming inflamed and irritated

(GRADE*: Level of evidence=low, Strength of recommendation=strong)

Measure and draw diagram (photodocument if possible)
Cold compress when inflamed
(GRADE*: Level of evidence=low, Strength of recommendation=strong)

Ocular lubricants for symptomatic relief (drops for use during the day, unmedicated ointment for use at bedtime) NB Patients on long-term medication may develop sensitivity reactions which may be to active ingredients or to preservative systems (see Clinical Management Guideline on Conjunctivitis Medicamentosa). They should be switched to unpreserved preparations.
(GRADE*: Level of evidence=low, Strength of recommendation=strong)

Acute inflammation of a pterygium usually responds to a brief course of a ‘non-penetrating’ topical steroid (e.g. fluorometholone, loteprednol) or a topical non-steroidal drug (off-license use)
NB All patients on topical steroid drops or ointment should have their intraocular pressures checked initially, then measured again at 2 weeks and every 4 weeks for 2-3 months (see Clinical Management Guideline on Steroid Glaucoma)
(GRADE*: Level of evidence=low, Strength of recommendation=weak)

Management category

B2: alleviation/palliation; normally no referral
B1: refer to ophthalmologist if pterygium:

• threatens visual axis
• induces irregular astigmatism
• is associated with chronic inflammation
• is cosmetically unacceptable

Possible management by ophthalmologist

A variety of surgical techniques, including:

• surgical excision (bare sclera resection)
• surgical excision plus conjunctival closure, conjunctival flap closure or conjunctival autografting; or amniotic membrane grafting
• adjunctive treatment sometimes given; includes:
  • beta irradiation (post-op)
  • topical thiotepa (post-op)
  • intralesional injection of Bevacizumab (Avastin)
  • mitomycin C (intra- or post-op) or Fluorouracil (5FU)

A recent systematic literature review concluded that bare sclera resection was associated with high rates of recurrence. By contrast, conjunctival or limbal autograft was associated with lower rates of recurrence 
 

Evidence base

*GRADE: Grading of Recommendations Assessment, Development and Evaluation (www.gradeworkinggroup.org)
 

Sources of evidence

Clearfield E, Muthappan V, Wang X, Kuo IC. Conjunctival autograft for pterygium. Cochrane Database of Systematic Reviews 2016;2:CD011349

Fonseca EC, Rocha EM, Arruda GV. Comparison among adjuvant
treatments for primary pterygium: a network meta-analysis. Br J Ophthalmol. 2018;102(6):748-756

Frucht-Pery J, Siganos CS, Solomon A, Shvartzenberg T, Richard C, Trinquand C. Topical indomethacin solution versus dexamethasone solution for treatment of inflamed pterygium and pinguecula: a prospective randomized clinical study. Am J Ophthalmol. 1999;127(2):148-52

Liu L, Wu J, Geng J, Yuan Z, Huang D. Geographical prevalence and risk factors for pterygium: a systematic review and meta-analysis. BMJ Open. 2013 ;3(11)

Rezvan F, Khabazkhoob M, Hooshmand E, Yekta A, Saatchi M,
Hashemi H. Prevalence and risk factors of pterygium: a systematic
review and meta-analysis. Surv Ophthalmol. 2018;63(5):719-735

Viso E, Gude F, Rodríguez-Ares MT. Prevalence of pinguecula and pterygium in a general population in Spain. Eye (Lond). 2011;25(3):350-7

Zhang X, Jiang Y, Fu Q, Zhang X, Chen Y. Efficacy of bevacizumab in the treatment of pterygium: An updated meta-analysis of randomized controlled trials. Int Immunopharmacol. 2021;98:107921

Pterygium
Version 9
Date of search 24.01.22
Date of revision 28.01.22
Date of publication 22.11.22
Date for review 23.01.24
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