Pterygium is a triangular-shaped ingrowth that forms with the medial (internal) the sides of the conjunctival membrane of the eyeball, and has a length up to the surface layers of the cornea. It occurs more often asymptomatically, with the aggravation of the disease, there may be complaints of a cosmetic defect, dry eyes, decreased visual acuity. Pathology is diagnosed using the method of biomicroscopy, ophthalmoscopy, analysis of lacrimal fluid, histological examination, fluorescent angiography. Surgical treatment, however, if pterygium does not cause subjective complaints and discomfort, then treatment is not carried out.
Pterygium (pterygoid hymen) is a disease, more often bilateral, which is a subepithelial ingrowth of a degeneratively altered bulbar conjunctiva in the form of a triangle from the limb to the cornea. In the pterygium, the head, neck and body are isolated. The head is the tip of a triangular formation, its progressive part. Next comes the neck – a slight narrowing. The widest part is called the pterygium body. Most often, disease is detected in residents of countries with hot climates. The geographical zone, called the “periequatorial belt of pterygium”, is located up to 37° north and south of the equator. The disease is more common in men than in women. The age of occurrence is from 40 years and older.
For the development of pterygium, prolonged exposure to any irritating factors on the conjunctiva of the eye is necessary. For example, increased levels of ultraviolet and/or infrared radiation cause dry eye syndrome. Staying outdoors for more than 5 hours a day (agricultural workers, hunting and fishing enthusiasts) or staying in a room with a high level of dust for a long time (people employed in the construction industry – carpenters, painters, plasterers) is a risk factor for the development of conjunctival inflammation, which turns into a chronic process. Dry eyes and chronic conjunctivitis are the main mechanisms leading to the development of this disease. In recent years, people who spend a lot of time at the computer have been singled out as a risk group, as a result of which, due to insufficient hydration of the conjunctiva, dry eye syndrome occurs, which also leads to the formation of pterygium.
Prolonged exposure to adverse external factors leads to damage to the cells of the integumentary epithelium, an inflammatory reaction occurs, and the natural protection of the conjunctiva decreases. There is a violation of the structure of goblet cells, the development of “dry eye” syndrome begins. Microcirculation is disrupted, which leads to the intensive formation of new vessels. The continued impact of adverse factors contributes to the further development of pathological processes and the formation of pterygium.
Histological examination of the pterygium reveals hypertrophied and structurally altered subconjunctival connective tissue containing a large number of fibroblasts and newly formed blood vessels that grow into the cornea. In all cases, inflammatory infiltration and abnormal deposition of elastin and collagen in the intercellular space are determined.
According to the degree of progression in ophthalmology, stationary and progressive pterygium are distinguished. The progressive form of the pterygium is distinguished by the following signs: a thickened head protrudes above the surface of the cornea; full-blooded convoluted vessels form a developed network in the pterygium. Depending on the condition of the vessels of the episclera, the ability of the pterygium to progress can be determined:
- 1 degree – the pterygium is transparent, atrophic, the vessels of the episclera are clearly visible through it; the probability of progression is minimal.
- Grade 2 – the pterygium is protruding, translucent, the vessels of the episclera are partially visible.
- Grade 3 – pterygium is highly active, opaque; vessels are not visible.
Based on the prevalence of ingrowth, the magnitude of astigmatism and decreased visual acuity, five clinical stages of pterygium are distinguished: from initial to pronounced, leading to a significant decrease in vision:
- I art. – education is observed only in the limb, patients do not make any complaints.
- II art. – the head of the pterygium is located in the middle of the distance between the limb and the edge of the pupil. The appearance of abnormal corneal astigmatism in the area immediately in front of the pterygium head is characteristic, and in the optical zone, correct astigmatism of a small degree is revealed. Visual acuity can be reduced to 0.9–0.7.
- III art. – the head of the pterygium is located on the cornea at the edge of the pupil, astigmatism due to thickening of the horizontal meridian of the cornea increases, visual acuity can decrease to 0.5.
- IV art. – the head reaches the center of the cornea (projection of the center of the pupil). Significantly pronounced incorrect or correct astigmatism prevails (2.5–7.5 diopters). Visual acuity decreases to 0.3–0.2.
- V art. – the head of the pterygium goes beyond the center of the cornea and can spread further along the cornea. Refraction cannot be determined, visual acuity is below 0.1; corneal thorn may develop, fusion of the altered conjunctiva with the eyelids or lacrimal organs.
Pterygium can be detected on one eye from the nasal side, but it may grow on the cornea from both sides at once. At the initial stages, the patient does not experience any discomfort, the only thing that can bother him is a small seal in the limb area or a visible cosmetic defect in the form of a grayish triangular-shaped film with a vertex facing the pupil. With the progressive growth of the pterygium, sensations of a foreign body, dryness and irritation of the eyes appear. Inflammation of the altered conjunctiva is accompanied by swelling, redness, itching, lacrimation.
With further growth of the pterygium, astigmatism and decreased vision of varying degrees of severity develop. Of the complications, scarring of the conjunctiva and cornea, restriction of the mobility of the eyeball, the occurrence of strabismus, malignant degeneration of the pterygium are noted.
Pterygium is easily diagnosed by an ophthalmologist. The leading diagnostic method is biomicroscopy using a slit lamp. This technique allows the ophthalmologist to visually assess the size of the pterygium and the degree of its overgrowth. To clarify the stage of pterygium, ophthalmoscopy, visometry and refractometry are performed.
Of the additional examination methods, high-precision procedures are used for a detailed study of the pterygium, such as a study of lacrimal function with crystallography of lacrimal fluid (necessary to predict the degree of further proliferation and possible recurrence of pterygium after surgical treatment), keratotopography (to determine the degree and shape of pterygium), morphological examination of pterygium tissue (to detect and assess the activity of proliferation of the vascular component), a method of fluorescent angiography (to detect changes in microangioarchitectonics, characteristic of pterygium).
Treatment is carried out either for cosmetic purposes at the request of the patient, or when the pterygium reaches the optical part of the cornea. The operation to remove the pterygium is based on the method of separating the altered conjunctiva from the surface of the cornea, limb, sclera, its resection and plasty of the defect with displaced flaps. There are methods of treatment with the use of an amniotic membrane and alloplastic materials, the use of cytostatics (mitomycin C, 5-fluorouracil) and metered exposure to beta radiation, as well as photodynamic therapy, laser coagulation of vessels of pterygium tissues. Disease is characterized by frequent relapses after excision.
Due to numerous surgical interventions, complications may occur in the form of fusion of the conjunctiva of the eyeball with the conjunctiva of the eyelids (simblefaron) and lacrimal organs, fusion of the edges of the eyelids or corneal cataract. As a result of impaired eye movement, convergent strabismus may occur.
To prevent pterygium, it is necessary to reduce the time spent in rooms with various irritating factors. It is mandatory to use eye protection products from dust, dry air, chemicals. In the event of inflammatory diseases, timely and adequate treatment and observation by an ophthalmologist is necessary. People over 40 years of age are recommended to wear glasses with high UV protection when in the sun. While working at the computer, be sure to take breaks every 30-40 minutes and instill moisturizing drops at the first signs of discomfort in the eyes.