Pterygium: Etiology, Degrees, Diagnosis, Treatment

Pterygium is a pathology of the anterior segment of the eye characterized by progressive growth of wing-shaped vascularized fibrovascular tissue on the bulbar conjunctiva side through the limbus over the adjacent cornea.

Etiology

Currently, it is believed that the most important provoking factors of pterygium are high levels of insolation, changes in the composition of tear fluid, imbalance of cytokines, growth factors, and mutations in the p53 gene.

Anatomy

Anatomically, pterygium is described as having three parts: head, neck, and body. The head, the invasive part of the triangular mass, is usually the progressive part. The neck is the communicating part between the body and head that covers the limbus, the narrowest part of the pterygium. The body is the widest conjunctival part of the pterygium with the base toward the medial corner of the eye. There may also be superficial corneal opacity in front of the tip of the pterygium (halo), both in the early and late stages of the disease.

The main feature of pterygium anatomy is dilated vessels compared to normal surrounding conjunctival vessels. Pterygium has a fairly translucent coloration.

Classification of pterygium

Depending on the length, pterygium is categorized into 3 degrees:

• Stage I – initial, the head of the pterygium is observed only at the limbal zone of the cornea, with no change in visual function or refraction;
• Stage II – the head of pterygium is located at the middle of the interval between the limbus and the projection of the outer edge of the pupil in the normal state (3 mm). There is irregular corneal astigmatism immediately anterior to the head of the pterygium, and in the central zone there is correct astigmatism of small values. Visual acuity is usually not reduced;
• Stage III – the head of pterygium is localized on the cornea in the projection of the pupil diameter in daylight (3 mm), astigmatism can reach up to 13 diopters due to thickening of the horizontal corneal meridian, visual functions are reduced.

There is also a classification that is based on an assessment of the propensity of pterygium to progressive growth:

• 1st degree – the membrane is translucent, atrophic, episcleral vessels are clearly visible through it. The risks of progression are low;
• The 2nd degree is active. Pterygium is translucent, located above the cornea, episcleral vessels are partially visible;
• Grade 3 – highly active, fleshy consistency, opaque, scarlet in color. The episcleral vessels cannot be evaluated.

Classification of pterygium by length and propensity to grow

3D models of pterygium of different stages:

Pterygium stage I

Pterygium stage II

Pterygium stage III

Diagnosis

Clinical history:

• Dryness of the ocular surface;
• Irritation that does not go away for a long period of time;
• Foreign body sensation, rubbing, burning;
• Hyperemia of the eyeball;
• Increased photophobia;
• Reduced contrast sensitivity due to loss of corneal transparency.

Instrumental methods of research:

• Visual acuity testing with current correction;
• Autorefractometry;
• Keratometry;
• Tonometry;
• Optical coherence tomography of the anterior segment of the eye.

Physical examination: biomicroscopy of the anterior segment with slit lamp.

Clinical picture

The diagnosis of pterygium is based on clinical manifestations such as:

• Fibrovascular overgrowth of the conjunctiva within the open eye slit;
• Spread to the corneal surface;
• The membrane is triangular or trapezoidal in shape;
• It grows on the nasal and temporal side of the eyeball;
• The formation is white to pink in color depending on the presence of blood vessels;
• Pigmented epithelial line of iron accumulation (Stoker) adjacent to the pterygium, indicative of a chronic course.

Treatment of pterygium

There are a number of therapeutic options for pterygium, ranging from conservative treatment to surgical removal.

Because of the potential for recurrence as well as other complications, surgical removal of pterygium should not be performed casually. Surgical removal of a pterygium is indicated if it causes persistent discomfort, is resistant to conservative therapy, obscures the visual axis or causes decreased visual function due to induced astigmatism, increases in size, or limits ocular mobility.

Medical treatment

Inflamed pterygium can cause irritation, foreign body sensation, and tearing, which in many cases can be relieved with over-the-counter drops high in Dexpanthenol or Hyaluronic Acid. To reduce inflammation, short courses of topical corticosteroids can be used: eye drops Dexamethasone 0.1%, ointment eye Hydrocortisone 0.5%, but long-term use of these drugs is not recommended.

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Surgical treatment

Complete excision using conjunctival autograft is considered the gold standard at present because of the low recurrence rate.

Excision using an amniotic membrane graft can be considered as an alternative to conjunctival autografting, although the recurrence rate is still higher than with conjunctival autografting.

Simple excision with exposure of the sclera or closure of the conjunctiva results in a recurrence rate as high as 80% and is now considered unacceptable.

Peripheral layer-by-layer keratoplasty, due to corneal opacity.