Dorsal pterygium, also known as nasal pterygium, is a common eye condition characterized by the growth of a triangular-shaped, fibrous tissue over the cornea (the clear, dome-shaped surface that covers the front of the eye). It typically starts from the conjunctiva, which is the clear, thin membrane that lines the inside of the eyelids and the white part of the eye (the sclera), and gradually advances over the cornea, leading to visual disturbance and discomfort.
The growth of a pterygium is often attributed to prolonged exposure to UV radiation, wind, dust, and other environmental factors. It is more prevalent in individuals living near the equator, where the UV index is high, and the climate is dry and windy. It can occur at any age, but it is more common in people aged 20 to 40 years and more frequent in men than women.
There are different types of pterygium, classified based on their location, shape, and severity. In this article, we will focus on dorsal pterygium, its main definitions, and types.
Main Definitions
- Dorsal pterygium: It is a fibrovascular growth that extends from the nasal conjunctiva towards the cornea, causing a gradual displacement of the cornea.
- Conjunctiva: It is a transparent, thin, and flexible membrane that covers the sclera (the white part of the eye) and the inside of the eyelids.
- Cornea: It is the clear, dome-shaped surface that covers the front of the eye, responsible for refracting light and allowing vision.
- Fibrous tissue: It is a connective tissue made of collagen and elastic fibers that provide support and structure to organs and tissues in the body.
Types of Dorsal Pterygium
- Simple Pterygium: It is the most common type of pterygium, characterized by a triangular-shaped, pinkish, fleshy tissue growing over the cornea. It may cause itching, burning, redness, and discomfort, and may lead to blurred vision and astigmatism (an eye condition that causes distorted vision due to an irregular shape of the cornea). It is typically treated with eye drops, lubricants, or surgery if it affects vision.
- Fatty Pterygium: It is a less common type of pterygium, characterized by a yellowish or whitish, raised, and thickened tissue. It may occur due to a combination of UV exposure and lipid accumulation in the conjunctiva. It may lead to irritation, redness, and discomfort and may require surgical removal if it affects vision.
- Vascularized Pterygium: It is a more severe type of pterygium, characterized by the invasion of blood vessels into the fibrous tissue, causing it to appear red and inflamed. It may cause vision loss and may require surgical removal.
- Inverted Pterygium: It is a rare type of pterygium, characterized by the growth of fibrous tissue under the conjunctiva, causing it to retract towards the cornea. It may lead to visual disturbance and discomfort and may require surgical intervention.
Causes
Dorsal pterygium is not a serious condition and is usually benign, but it can cause discomfort and affect vision in some cases. In this essay, we will explore the main causes of dorsal pterygium in detail.
- Exposure to UV Radiation – One of the primary causes of dorsal pterygium is exposure to ultraviolet (UV) radiation. This can occur when an individual spends prolonged periods of time outdoors without proper eye protection, such as sunglasses or a hat. UV radiation can damage the conjunctiva and cause it to thicken and form a pterygium. The prevalence of dorsal pterygium is higher in individuals who live in areas with high levels of UV radiation, such as tropical regions or high-altitude areas.
- Environmental Factors – Environmental factors can also play a role in the development of dorsal pterygium. Exposure to dust, wind, and other environmental irritants can cause the conjunctiva to become inflamed and irritated, which can lead to the formation of pterygium. This is especially true in individuals who work in industries that expose them to these irritants, such as construction workers, farmers, and those who work in dry and dusty environments.
- Genetics – Studies have shown that genetics may play a role in the development of dorsal pterygium. Individuals with a family history of the condition may be more likely to develop it themselves. This may be due to a genetic predisposition to the condition or shared environmental factors that increase the risk of developing it.
- Age – Age is another risk factor for dorsal pterygium. The condition is more common in individuals over the age of 50, although it can occur at any age. This may be due to cumulative exposure to environmental factors over time or changes in the immune system that occur with age.
- Gender – Dorsal pterygium is more common in men than in women. This may be due to differences in occupational and recreational exposure to UV radiation and other environmental factors. Men are also more likely to engage in activities such as outdoor sports and manual labor that increase the risk of developing dorsal pterygium.
- Smoking – Smoking is a risk factor for many health conditions, including dorsal pterygium. Studies have shown that individuals who smoke are more likely to develop the condition than non-smokers. This may be due to the harmful chemicals in cigarette smoke that can damage the conjunctiva and other tissues in the eye.
- Dry Eye Syndrome – Dry eye syndrome is another factor that can contribute to the development of dorsal pterygium. This condition occurs when the eyes do not produce enough tears, or when the tears evaporate too quickly. As a result, the surface of the eye becomes dry and irritated, which can lead to the growth of abnormal tissue. People who work in environments with low humidity or who spend a lot of time staring at computer screens are at increased risk of developing dry eye syndrome and, therefore, dorsal pterygium.
- Genetics – Genetics may also play a role in the development of dorsal pterygium. Some people may have a genetic predisposition to developing abnormal tissue growth on the surface of the eye. This may be related to a specific gene or set of genes that increase the risk of developing this condition. However, more research is needed to fully understand the genetic factors that contribute to dorsal pterygium.
- Irritants – Exposure to certain irritants can also increase the risk of developing dorsal pterygium. For example, people who work in jobs that require them to handle chemicals or other irritants may be at increased risk of developing this condition. Irritants can cause damage to the cells on the surface of the eye, leading to the growth of abnormal tissue.
Symptoms
The main symptoms of dorsal pterygium include:
- Eye redness: Pterygium can cause redness in the affected eye due to irritation of the conjunctiva.
- Eye irritation: Pterygium can cause a feeling of grittiness or foreign body sensation in the eye. This may be due to the presence of the pterygium itself or the associated inflammation.
- Blurred vision: Pterygium can cause blurred vision if it grows over the cornea and affects the refractive power of the eye.
- Dryness: Pterygium can disrupt the normal tear film of the eye and cause dryness, which can further contribute to eye irritation.
- Astigmatism: Pterygium can cause astigmatism, which is an uneven curvature of the cornea that affects vision.
- Corneal scarring: In severe cases, pterygium can cause scarring of the cornea, which can affect vision permanently.
- Conjunctival injection: Pterygium can cause dilation of the blood vessels in the conjunctiva, leading to a “red eye” appearance.
- Itching: Pterygium can cause itching of the eye due to irritation of the conjunctiva.
- Tearing: Pterygium can cause tearing of the eye due to irritation of the conjunctiva.
- Sensitivity to light: Pterygium can cause sensitivity to light, also known as photophobia, due to inflammation of the conjunctiva.
In addition to these symptoms, dorsal pterygium can also cause cosmetic concerns, as it can appear as a raised, fleshy growth on the eye that can be unsightly.
Diagnosis
Diagnosis:
Dorsal pterygium is usually diagnosed by a comprehensive eye examination conducted by an ophthalmologist or an optometrist. The examination typically includes a review of the patient’s medical history, symptoms, and risk factors, such as exposure to UV radiation, dry and dusty environments, and frequent eye irritation. The doctor will also perform a thorough inspection of the eyes using specialized instruments and techniques, including:
- Slit-lamp biomicroscopy: This is a powerful microscope that allows the doctor to examine the front and back of the eye under high magnification and illumination. The slit-lamp biomicroscopy is used to assess the size, shape, color, and texture of the pterygium, as well as its impact on the cornea and the conjunctiva. The doctor may also use special dyes, such as fluorescein or rose bengal, to highlight the affected areas and evaluate the degree of inflammation, dryness, or damage.
- Visual acuity testing: This is a standard eye chart test that measures the patient’s ability to see objects at various distances. The visual acuity testing is used to assess the impact of the pterygium on the patient’s vision and to monitor any changes over time.
- Refraction testing: This is a test that measures the patient’s refractive error, which is the degree of nearsightedness, farsightedness, or astigmatism. The refraction testing is used to determine the correct prescription for glasses or contact lenses, if needed, and to rule out any other underlying eye conditions that may affect the visual acuity.
- Intraocular pressure (IOP) testing: This is a test that measures the pressure inside the eye using a special instrument called a tonometer. The IOP testing is used to screen for glaucoma, a serious eye condition that can cause irreversible vision loss if left untreated. Pterygium can cause an elevated IOP due to the growth obstructing the eye’s drainage system.
- Fundus examination: This is a test that examines the back of the eye, including the retina, optic nerve, and blood vessels, using a specialized instrument called an ophthalmoscope. The fundus examination is used to evaluate the health of the eye and to rule out any other underlying eye conditions that may affect the visual acuity.
Laboratory tests:
Laboratory tests are usually not required for the diagnosis of dorsal pterygium. However, in certain cases, additional tests may be recommended to confirm the diagnosis, monitor the progression of the condition, or evaluate the effectiveness of the treatment. These tests may include:
- Histopathology: This is a laboratory test that analyzes a small tissue sample taken from the pterygium under a microscope. The histopathology is used to confirm the diagnosis of pterygium and to rule out any other underlying conditions, such as conjunctival tumors or cysts. It can also identify the type of cells and proteins present in the pterygium, which can help in determining the most appropriate treatment approach.
- Eye pressure test: This test, also known as tonometry, measures the pressure inside the eye. High eye pressure can be a sign of glaucoma, a condition that can cause vision loss if left untreated.
- Visual field test: This test measures the patient’s peripheral vision. It can be useful in detecting any vision loss that may be associated with the pterygium.
- Corneal topography: This test uses a special machine to create a detailed map of the surface of the cornea. It can help the doctor to identify any irregularities or distortions in the cornea, which can be a sign of other conditions.
- Biopsy: In some cases, a biopsy of the pterygium may be recommended to rule out other conditions, such as cancer. During the biopsy, a small sample of the tissue will be removed and sent to a laboratory for analysis.
Treatment
It is often associated with long-term exposure to UV light, wind, and dust, and can cause symptoms such as irritation, redness, and blurred vision. In this article, we will discuss the main treatment options for dorsal pterygium and their details.
- Observation and conservative management
In many cases, dorsal pterygium does not cause significant symptoms or affect vision, and therefore, observation and conservative management may be recommended. This involves regular monitoring of the condition and avoiding any factors that may exacerbate the growth, such as exposure to UV light and dry environments. Lubricating eye drops or ointments may be prescribed to relieve any symptoms of dryness or irritation. However, it is important to note that this approach does not address the underlying cause of the pterygium and may not prevent it from growing larger or causing more significant symptoms in the future.
- Surgical excision
Surgical excision is the most common treatment option for dorsal pterygium, especially when it causes significant symptoms or impairs vision. The procedure involves removing the abnormal tissue and repairing the affected area with conjunctival tissue grafts to prevent regrowth. There are several techniques for pterygium excision, including bare sclera excision, conjunctival autograft, and amniotic membrane transplantation.
a) Bare sclera excision
Bare sclera excision involves removing the pterygium tissue without any conjunctival grafts. This technique is simple and quick, but it has a high recurrence rate, as the exposed sclera may encourage regrowth. It is therefore recommended only for small, uncomplicated pterygia that are not likely to recur.
b) Conjunctival autograft
Conjunctival autograft involves harvesting healthy conjunctival tissue from another area of the same eye or the other eye and using it to cover the area where the pterygium was removed. The harvested tissue is carefully sutured in place and acts as a barrier to prevent regrowth of the pterygium. This technique has a lower recurrence rate than bare sclera excision and can be used for larger or more complex pterygia.
c) Amniotic membrane transplantation
Amniotic membrane transplantation involves using a membrane derived from the inner lining of the human placenta to cover the affected area after pterygium removal. The membrane contains growth factors and anti-inflammatory proteins that promote healing and reduce scarring. This technique is particularly useful for patients with recurrent or aggressive pterygium, as it has a lower recurrence rate than bare sclera excision and a similar recurrence rate to conjunctival autograft.
- Radiation therapy
Radiation therapy is a relatively new treatment option for dorsal pterygium, but it has shown promising results in preventing recurrence after surgical excision. The procedure involves delivering a targeted dose of radiation to the affected area immediately after pterygium excision. The radiation damages the remaining tissue and blood vessels, which can help prevent regrowth of the pterygium. Radiation therapy is generally reserved for patients with a high risk of recurrence, such as those with a history of multiple recurrences or large, aggressive pterygia.
Medications
- Topical medication – Topical medication is not typically used as a primary treatment for dorsal pterygium, but it may be prescribed in combination with other therapies to reduce inflammation and prevent regrowth. Steroid eye drops, for example, can help reduce inflammation and scarring after pterygium excision, while mitomycin C eye drops can be used to inhibit the growth of abnormal cells in the affected area.
- Artificial Tears: Artificial tears are the first line of treatment for mild cases of dorsal pterygium. They are used to lubricate the eyes and relieve the symptoms of dry eyes caused by the pterygium. Artificial tears contain a variety of ingredients, such as sodium hyaluronate, polyethylene glycol, and hydroxypropyl guar, which help to maintain the moisture balance of the ocular surface.
- Topical Steroids: Topical steroids are a common treatment for moderate to severe cases of dorsal pterygium. They are effective in reducing inflammation and suppressing the growth of the pterygium. The most commonly used topical steroids for the treatment of dorsal pterygium are dexamethasone, prednisolone, and fluorometholone. Topical steroids should be used under the supervision of an ophthalmologist, as prolonged use can lead to adverse side effects such as cataract formation and increased intraocular pressure.
- Topical Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): Topical NSAIDs such as ketorolac and diclofenac are another class of drugs that can be used in the treatment of dorsal pterygium. They work by inhibiting the production of prostaglandins, which are involved in the inflammatory process. Topical NSAIDs are effective in reducing inflammation and relieving the symptoms of pain and redness associated with dorsal pterygium.
- Mitomycin C: Mitomycin C is a chemotherapeutic agent that has been used in the treatment of dorsal pterygium. It works by inhibiting the growth of fibrovascular tissue and preventing the recurrence of the pterygium. Mitomycin C is usually applied topically during the surgical removal of the pterygium.
- Interferon Alpha-2b: Interferon alpha-2b is a cytokine that has been shown to be effective in the treatment of dorsal pterygium. It works by inhibiting the proliferation of fibroblasts and reducing the production of extracellular matrix proteins. Interferon alpha-2b is usually applied topically after the surgical removal of the pterygium.
- Bevacizumab: Bevacizumab is a monoclonal antibody that inhibits the activity of vascular endothelial growth factor (VEGF), which is involved in the angiogenesis and growth of the pterygium. Bevacizumab has been used in the treatment of dorsal pterygium, either as a single agent or in combination with surgical removal of the pterygium. However, the use of bevacizumab in the treatment of dorsal pterygium is still controversial, and more studies are needed to establish its efficacy and safety.
In conclusion, the main drugs used in the treatment of dorsal pterygium include artificial tears, topical steroids, topical NSAIDs, mitomycin C, interferon alpha-2b, and bevacizumab. The choice of treatment depends on the severity of the pterygium and the individual needs of the patient. It is important to consult with an ophthalmologist before starting any treatment for dorsal pterygium.
