Key Features

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  Common.

  
  
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  Bilateral usually.

  
  
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  Typically does not affect vision.

Associated Features

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  Increased prevalence with age.

  
  
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  Often associated with chronic light exposure.

  
  
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  May occur after past inflammation.

  
  
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  Not inherited.

Introduction

Degenerations of the conjunctiva are common conditions that, in most cases, have relatively little effect on ocular function and vision. They increase in prevalence with age as a result of past inflammation, long-term toxic effects of environmental exposure, or aging itself. Conjunctival degenerations may be associated with chronic irritation, dryness, or previous history of trauma. Progression to involve the cornea may occur, as in pterygium.

Pinguecula

Pingueculae are elevated, horizontally oriented areas of bulbar conjunctival thickening that are white to yellow in color and adjoin the limbus in the palpebral fissure area ( Fig. 4.9.1 ). They are less transparent than normal conjunctiva, often have a fatty appearance, are usually bilateral, and are located nasally much more often than temporally. When a pinguecula crosses the limbus onto the cornea, it is called a pterygium . Current information, however, suggests that pinguecula do not progress to pterygium and that the two are distinctly different disorders. Pingueculae are associated with a two- to threefold increased incidence of age-related macular degeneration, possibly through a common light exposure effect.

Nasal Pinguecula.

Elevated conjunctival lesion encroaches on nasal limbus.

The causes of pingueculae are not known with certainty. There is, however, good evidence of an association with increasing age and ultraviolet light exposure. Pingueculae are seen in most eyes by age 70 years and in almost all by age 80 years. Chronic sunlight exposure has been found to be a factor by association with outdoor work and equatorial residence. In some studies, the strength of this association is less than that for pterygium. It is thought that the predominantly nasal location is related to reflection of light from the nose onto the nasal conjunctiva. The effect of ultraviolet light may be mediated by mutations in the p53 gene.

Pingueculae rarely are associated with symptoms other than a minimal cosmetic defect. They may become red with surface keratinization. When inflamed, the diagnosis of pingueculitis is made.

Distinguishing pingueculae from other lesions usually is not a problem because of the typical appearance. Conjunctival intraepithelial neoplasia may be difficult to differentiate from keratinized pinguecula. Gaucher’s disease type I may be associated with tan pingueculae, but this is not a specific finding.

Histopathologically, pingueculae are characterized by elastotic degeneration of the collagen with hyalinization of the conjunctival stroma, collection of basophilic elastotic fibers, granular deposits, and noninvolvement of the cornea.

Pingueculitis responds to a brief course of topical corticosteroids or nonsteroidal anti-inflammatory agents. Chronically inflamed or cosmetically unsatisfactory pingueculae rarely warrant simple excision.

Pterygium

Pterygium is a growth of fibrovascular tissue on the cornea and conjunctiva. It occurs in the palpebral fissure, much more often nasally than temporally, although either or both (“double” pterygium) occur ( Fig. 4.9.2 ). Elevated whitish opacities (“islets of Vogt”) and an iron deposition line (“Stocker”) may delineate the head of the pterygium on the cornea. Like pinguecula, it is a degenerative lesion, although it may appear similar to pseudo-pterygium, which is a conjunctival adhesion to the cornea secondary to previous trauma or inflammation, such as peripheral corneal ulceration. A pseudo-pterygium often has an atypical position and is not adherent at all points, so a probe can be passed beneath it peripherally.

Double Pterygium.

(A) Note both nasal and temporal pterygia in a 57-year-old farmer. (B) It is the invasion of the cornea that distinguishes a pterygium from a pinguecula.

Like pinguecula, pterygium is associated with ultraviolet light exposure. It occurs at highest prevalence and most severely in tropical areas near the equator and to a lesser and milder degree in cooler climates. Outdoor work and both blue and ultraviolet light have been implicated in its causation. The use of hats and sunglasses is protective. Theories of pathogenesis of pterygia include the possibility of damage to limbal stem cells by ultraviolet light and by activation of matrix metalloproteinases. The histopathology of pterygium is similar to that of pinguecula except that Bowman’s membrane is destroyed within the corneal component and vascularization is seen. Evaluation using spectral domain optical coherence tomography reveals pterygium as an elevated, wedge-shaped mass of tissue separating the corneal epithelium from Bowman’s membrane, which appears abnormally wavy and interrupted and often destroyed, with satellite masses of subepithelial pterygium tissue beyond the clinically seen margins.

Pterygia warrant treatment when they cause discomfort (not responsive to conservative therapy), encroach upon the visual axis, induce significant astigmatism, or become cosmetically bothersome. Aggressive or recurrent pterygia may cause restrictive strabismus and distortion of the eyelids. A variety of surgical techniques have been developed. The goal of treatment is prevention of recurrence. The recurrence rates after simple excision are very high: Of recurrences, 50% reoccur within 4 months of excision and nearly all within 1 year. Beta-radiation applied postoperatively to the pterygium base was popular for many years but is associated with late scleral necrosis. Currently, the most widely used techniques are conjunctival autografting and amniotic membrane transplantation. Adjuvant use of mitomycin-C application—either pre-, intra-, or postoperatively—has been associated with scleral melt in some situations. Fibrin-based glues have been used to minimize operating time and discomfort associated with sutures, and to reduce the amount of suturing required.