Pterygium: A Practical Guide to Management Alfred L Anduze
Chapter Notes

Save Clear


2The hallmarks of pterygium formation are UV radiation exposure, altered tear film and inflammation. Duke-Elder defines a pterygium as a triangular shaped degenerative and hyperplastic process, occurring medially and laterally in the palpebral aperture, in which the bulbar conjunctiva encroaches onto the cornea.1 Since this description was made in 1954, much work has been done in identifying the cause and development of pterygium. The general consensus proposes that a pterygium arises in response to mechanical injury and/or chemical irritation which then results in the alteration of the eye's defenses, thus further perpetuating the growth of the lesion. The chief goal of pterygium management is to minimize the deleterious effect of the lesion by restoring the anatomy and physiology to normal or near normal conditions.
Several myths have circulated that a pterygium never crosses the midline and never crosses arcus senilis (Figures 1.1 and 1.2). Other speculations claim that a pterygium always occurs in the palpebral fissure, they are always preceded by a pingueculum, they do not occur in animals, they only occur in people who live in the tropics and they only occurs in people with outdoor occupations. The facts indicate that pterygia do occur outside the medial and lateral palpebral fissure and they can be located inferiorly when present in cases of incomplete blinking and subsequent changes in the inferior cornea or when due to focal trauma as shown in Figure 1.3.
zoom view
Figure 1.1: Pterygium crossing the midline
zoom view
Figure 1.2: Pterygium crossing arcus senilis
zoom view
Figure 1.3: Inferior pterygium due to chemical burn
A pterygium does occur de novo (Figure 1.4) in the absence of pingueculum and it does occur in sawmill workers and watch factory workers due to dryness, chronic irritation and abnormal blinking patterns. My personal observations have revealed the presence of pterygium in computer workers suffering from dry eyes and little exposure to outdoor influences. They do occur in the eyes of horses, cattle and dogs as a result of focal trauma. With respect to locations outside the Tropics, there are reports of pterygium cases in Newfoundland with an incidence of 30% and in the Eskimo population across Canada with a 9% incidence.2
The Pingueculum and the Pterygium
A pingueculum (Figure 1.5) is a mass of fatty degenerative deposits in the subconjunctival layers of the eye which raises it above the surface of the sclera. Though having a similar pathogenesis, histology and pathology as a degenerative pterygium, it consists only of a body. The limbal border (proximal, head) is usually wider than the canthal border (distal, body). It is usually avascular, stationary, and only becomes red when irritated. The symptoms are similar to those of dry eye and consist of fatigue and a gritty, foreign body sensation.
zoom view
Figure 1.4: Pterygium de novo
zoom view
Figure 1.5: Pingueculum
zoom view
Figure 1.6: Pterygium
A pterygium (Figure 1.6) has a morphology that is organized into head, neck and body. The canthal body is usually wider than the limbal head. It is usually vascularized and dynamic. The head grows onto and into the cornea with a definite horizontal pattern of radial vessels in fibrous tissue. This fibrovascular arrangement gives it the “wing-like” appearance characteristic of its name. The symptoms are similar to those of pingueculum with the addition of burning and pain when inflamed.
When the lesion becomes inflamed and red, acquires a fibrovascular architecture and moves toward or touches the cornea, in my opinion, it is a pterygium (Figure 1.7).
Visual Disturbances
With a pterygium the earliest and most common visual symptoms in eyes with pterygium begin as the result of anatomical and physiological changes in the tear film. These changes are subtle at first. In a clinical situation involving the observation of the tear film of a 10-year-old compared to that of an 18-year-old, both of which have been exposed to similar intensities and duration of UV radiation, there is a perceived difference in thickness and texture.
zoom view
Figure 1.7: Pingueculum in evolution to pterygium
The 18-year-old often reports a foreign body sensation and occasional blurred vision due to protein debris and threads in the oily layer and a decreased aqueous level and shows signs of early stage pterygium formation. The 10-year-old has a normal looking tear film and offers no complaints.
Once established, the lesion that rises above the surface limit of the tear film, is further exposed to the elements, loses its defenses and exhibits faster growth. At this point it may interfere with the eyelid coverage of the ocular surface leaving pockets of dryness (dry spots) as the result of reduced or incomplete blinking (Figure 1.8). The raised uneven surface initiates a decrease in immune defenses and an increase in irritation which leads to further inflammation.
Anatomical obstruction of the pupil by a large corneal mass is a late finding and indicates an advanced pterygium. A lesion in the papillary axis will also have passed deep enough to occupy the corneal stroma and cause mechanical contractions which will greatly affect the vision (Figure 1.9).
Corneal distortion due to changes in the stromal collagen will lead to an induced astigmatism.
zoom view
Figure 1.8: Raised degenerative lesion may cause blink interference
zoom view
Figure 1.9: Stage IV pterygium may cause blink interference with pupil interference
Astigmatism occurs when Bowman's membrane is destroyed by the advancing pterygium head and the stroma is contracted by the invading fibrous tissue which results in warping of the corneal curvature. The degree and direction of the astigmatism is dependent on the following factors: Size and invasiveness of the pterygium, the corneal elasticity, the inherent resistance to the mechanical forces and the duration of exertion of those forces. The force of the pterygium flattens the cornea in the horizontal meridian and the force of contracture steepens it in the vertical meridian at 90Ɔ away. This results in with the rule, plus (+) cylinder astigmatism on the side of the pterygium. More often the astigmatism occurs between 6Ɔ and 120Ɔ due natural distortion and variation in the forces of exertion. There is a significant correlation between the size and extension of the pterygium onto and into the cornea and the degree of astigmatism present. Surgical excision of the pterygium will reduce the amount of astigmatism in most cases but the outcome is dependent on the former mentioned factors concerning size, shape and age of the lesion.3
Figures 1.10A and B show the eye of a 30-year-old male with pterygium induced with-the-rule astigmatism which responds well after surgery.
zoom view
Figure 1.10A: Stage V pterygium with 3.5 D cylinder in a 30-year-old male
zoom view
Figure 1.10B: Corneal topography with induced astigmatism
zoom view
Figure 1.11A: Stage V pterygium with 3.0 D cylinder in a 60-year-old male
zoom view
Figure 1.11B: Corneal topography with irregular astigmatism
Figures 1.11A and B show the eye of a 60-year-old male with a more irregular with-the-rule pterygium induced astigmatism which is less responsive after surgical removal.
Differential Diagnosis
The size, shape and orientation usually distinguishes a pingueculum from a pterygium. Unless it is symptomatic or cosmetically displeasing, it can be left alone.
Results from a corneal injury or ulceration at or near the limbus.
A probe can usually be passed beneath the body. It is self-limited and may be easily removed for cosmetic reasons.8
Conjunctival Hemangioma
It is an irregular cluster of blood vessels in the subconjunctival layer (Figure 1.12). Caution is suggested when removing this lesion due to the likelihood of excessive bleeding.
Foreign Body
Foreign body in the conjunctiva and especially at the limbus elicits an inflammation response with the rapid proliferation of fibrovascular tissue which is pterygious in appearance and behavior (Figure 1.13).
It resembles a bunch of grapes but is hiding a very vascular core. It usually has a pedicle.
It is a raised, smooth lesion that arises rapidly following a history of recent surgery or injury.
zoom view
Figure 1.12: Conjunctival hemangioma
zoom view
Figure 1.13: Foreign body
It is a flat, fibrovascular, thin and is characterized by a history of infection. It usually appears in childhood or infancy and is associated with a hypersensitivity reaction.
Nodular Episcleritis
It is superficial, hyperemic, flat, rounded lesion consisting of irregular conjunctival and episcleral vessels which blanch with the application of decongestants. In the early stages it is often associated with localized pain.
Limbal Catarrh
It is known as vernal keratoconjunctivitis in temperate zones and is associated with allergy and atopy. The follicles are usually arranged around the limbus and are often in the palpebral fissure associated with exposure.
It has a history of congenital origin, is yellowish-red in color and has no abnormal blood vessels.
Squamous Cell Carcinoma
It is the most common neoplasm mistaken for pterygium. It often has irregular tiers and hard white calcifications. Definitive diagnosis by appearance only is difficult and must be made by histological examination. Bowen's epithelioma, malignant melanoma, malignant epithelioma, amelanotic melanoma and carcinoma in situ are all variants of serious lesions that occur on the ocular surface. Surgical removal and submission to pathology is mandatory with a suspected neoplasm4 (Figure 1.14).
zoom view
Figure 1.14: Squamous cell carcinoma
  1. Duke-Elder S.Textbook of Ophthalmology. Mosby  St Louis:  1954;7:57086.
  1. Peckar CO.The aetiology and histo-pathogenesis of pterygium. Documenta Ophthalmologica. Springer.  Netherlands.1972;31(1);141–57.
  1. Lindsay RG, Sullivan L.Pterygium-induced corneal astigmatism. Clin Exp Optom 2001 Jul;84(4):200–3.
  1. Buratto L, Phillips RL, Carito G. Pterygium Surgery. Thorofare NJ. Slack, inc  2000;10:33–4.