- The prevalence of pterygium was found to be 10.2% in the world, with highest prevalence in low altitude regions (Liu et al, 2013).
- Increased incidence of pterygium is noted in the tropics and in an equatorial zone between 30° north and south latitudes (Liu et al, 2013).
- Higher incidence is associated with chronic sun exposure (ultraviolet light), older age, male sex, and outdoor activity (Liu et al, 2013).
Regional Information (LATIN AMERICA)
- One study among a Latino population in Tucson Arizona, United States found the prevalence of pterygium to be 16% (West et al, 2009).
- A hospital-based study in Lima, Peru, reported the prevalence of pterygium to be 31%, with a significant increase in prevalence with increasing age (Rojas et al, 1986).
- In a population-based sample in Botucatu City, Sao Paulo State, Brazil, the reported prevalence was 8.12%, affecting primarily 40–50 year-old males (Shiratori et al, 2010).
PATHOPHYSIOLOGY / DEFINITION
Chart 1. Pterygium pathophysiology. See Image Library for figure.
- Pterygium comes from the Greek word meaning wing, pterygos.
- Pterygium is a triangular fibrovascular growth that extends from the conjunctiva toward the cornea.
- It is more common in the interpalpebral fissure area and may occur nasally or temporally or both. The nasal location is more common.
- Although the pathophysiology is not clearly understood, ultraviolet (UV) light is identified as the most important risk factor.
- UV light forms free radicals that induce damage in DNA, RNA, and the extracelluar matrix of cells.
- Ultraviolet-B (UVB) induces expression of cytokines and growth factors in pterygial epithelial cells.
- Polymorphisms of the DNA break repair gene Ku70 have been associated with genetic predisposition to pterygia development.
- Increased levels of T-cells and inflammatory markers have also been noted in pterygial tissue compared to normal conjunctival tissue.
- Ultraviolet exposure (single most significant risk factor)
- Exposure to irritants (dust, sand, wind)
- Dry ocular surface
- Wedge-shaped, translucent membrane with apex extending onto cornea (Figure 6)
- White to pink in color, depending on vascularity
- Vascular straightening in the direction of the advancing head of the pterygium
- Stocker line: iron line on cornea at leading edge of pterygium (Figure 7)
- Regular or irregular astigmatism
- Degenerative changes such as cystic changes
- May be asymptomatic
- Decreased vision
- Diagnosis is made clinically based on slit-lamp examination and typical appearance of the lesion (Figure 1).
- Wearing eye protection, sunglasses, goggles, and/or a brimmed hat is recommended when one is exposed to sunlight or dust.
- Sunglasses that block 99%–100% of both UVA and UVB rays are preferred.
- Small pterygia without visual impairment can be treated symptomatically with artificial tears and ocular lubricants.
- Medical treatment (artificial tears and lubricants) does not decrease progression or cause regression of pterygia.
- In patients with irritative symptoms, preservative-free artificial tears are recommended for mild inflammation and topical steroids are recommended for moderate inflammation.
- Monitoring pterygia at 6–12 months is reasonable.
Surgical removal is considered for the following conditions:
- Decrease in visual acuity due to astigmatism or encroachment onto visual axis
- A cosmetically significant pterygium
- When it interferes with contact lens wear
- Symptomatic degenerative changes like cystic changes
- Restriction of extraocular movements
Surgical techniques include the following:
- Simple excision (without transplantation, aka bare sclera) is associated with a higher recurrence rate and hence it has been supplemented with conjunctival transplantation.
- Adjuvant therapies including mitomycin C (MMC), 5-fluorouracil (5-FU), ethanol, irradiation, and anti-angiogenic agents, among others, are used to reduce recurrence rate, but there is insufficient evidence that one is superior (Kaufman et al, 2013).
- The ideal treatment recommended involves excision of pterygium with conjunctival autograft (CAG) supplementation. Alternatively, if there is not enough conjunctiva, then amniotic membrane transplant (AMT) may be glued or sutured into place (Figure 8).
- Procedures using fibrin glue take about half the time as surgeries using sutures and patients often report less postoperative surgical pain and discomfort (Marticorena, Joaquin et al, 2006).
- However, fibrin glue is more expensive and can be difficult to obtain in some countries.
- The glue is a blood-derived product and carries the risk (however minimal) of viral and prion disease.
- Another approach is autoblood graft fixation, a technique also known as suture- and glue-free autologous graft. This approach affixes the graft into place with the patient’s own blood, eliminating the concern of disease transmission.
- Patch/shield overnight
- Drops: Steroid antibiotic combination 4 times a day for 1 month
Complications of Pterygium Surgery
- Buttonhole of the conjunctival autograft
- Injury to extraocular muscles
- Graft slippage
- Graft retraction
- Donor site granuloma formation
- The most common complication is recurrence after removal.
- The recurrence rate is as high as 50% within 4 months and 97% recurrence rate within 12 months without autograft or amniotic membrane transplant (Hirst LW, 2003).
- The recurrence rate is higher with fleshy, nontranslucent pterygia and increased postoperative inflammation. It is often dependent on the surgical procedure.
- The recurrence rate is decreased to 5%–10% with conjunctival flap/graft supplementation.
- Other complications include corneal scarring, corneal perforation, strabismus, nonhealing defect (especially with mitomycin C), scleral melt (especially with mitomycin C), and scleral dellen (Figure 9) (Kaufman, SC et al, 2013).
- If scleral dellen are present, aggressive lubrication with artificial tear ointment every 2 hours.
- Scleral graft patch is placed in severe cases of scleral thinning. (Tsai et al, 2002)
History of Present Illness
A 45-year-old patient presented with hyperemia, foreign body sensation, and itchiness in her right eye without improvement after artificial tears. Her family history is significant for diabetes. Eyelids of the right eye were within normal limits. The right eye had mild conjunctival hyperemia and a 2–3 mm temporal pterygium without involvement of the papillary area (Figure 10). Ocular examination of the left eye was normal.
Resection of pterygium plus conjunctival autograft in right eye. One week after surgery, there is mild conjunctival hyperemia and chemosis with complete resection of the pterygium (Figure 11).
Figure 1. Pseudopterygium. (Courtesy Dr. N. Nenkatesh Prajna.)
Figure 2. Pinguecula. (© 2015 American Academy of Ophthalmology, www.aao.org.)
Figure 3. Pannus. (© 2015 American Academy of Ophthalmology, www.aao.org.)
Figure 4. Conjunctival intraepithelial neoplasia. A. Papilliform. B. Gelatinous. C. Leukoplakic. (© 2015 American Academy of Ophthalmology, www.aao.org.)
Figure 5. Limbal dermoid. (© 2015 American Academy of Ophthalmology, www.aao.org.)
Figure 6. Slit-lamp image of a pterygium. (Reproduced, with permission, from Reidy, JJ, Basic and Clinical Science Course, Section 8: External Disease and Cornea. American Academy of Ophthalmology, 2010–2011).
Figure 7. Stocker line (arrow). (Courtesy Dr. N. Nenkatesh Prajna.)
Figure 8. Immediate postoperative photograph showing a suture conjunctival autograft after pterygium excision. (Reproduced from Ward M. Pterygium excision with conjunctival autograft. EyeRounds Online Atlas of Ophthalmology.)
Figure 9. Scleral dellen. (Reproduced from Garcia-Medina JJ et al. Severe scleral dellen as an early complication of pterygium excision with simple conjunctival closure and review of the literature. Arq Bras Oftalmol. 2014;77.)
Figure 10. A 2–3 mm temporal pterygium without involvement of the papillary.
Figure 11. One week after resection of the pterygium and placement of temporal conjunctival autograft.
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