Introduction
Leiomyoma of the iris is a benign intraocular smooth muscle tumor. It originates more commonly from the sphincter muscles. Iris is the colored part of the eye seen in the front part containing the pupil. It comprises two layers; the anterior stroma and the pigment epithelium in the posterior region. The stroma of the iris is a highly vascular connective tissue and fibroblasts. It consists of only a bare strip of epithelium. Leiomyoma of the iris enjoys an excellent prognosis. Iris leiomyoma is a slow-growing benign tumor that does not spread to other body parts.
What Is a Leiomyoma?
Leiomyoma is a benign tumor of smooth muscles. In middle-aged women, leiomyomas are more commonly seen involving the smooth muscles of the uterus, gastrointestinal tract, and skin. Leiomyomas are thought to be hormone-mediated. Leiomyomas are made of smooth muscle cells and varying amounts of connective tissue fibers. The reason behind the iris leiomyoma of the iris is not known. Leiomyoma of the iris is the rarest condition. It occurs even more rarely than previously thought. It most frequently affects females compared to males, especially in the age group of ten to 77 years. In addition, whites are more likely to get affected by the condition.
What Are the Most Common Sites of Eye Leiomyoma?
Leiomyomas are most commonly present inside the eye. The most common site of intraocular leiomyoma presentation are:
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Iris (colored part of the eye).
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The ciliary body (the circular extension of the iris).
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Uvea (it is the middle part of the eye made up of the iris, ciliary body, and choroid).
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Choroid (it is a part of the eye's middle layer, present between the sclera and the retina).
How Does Leiomyoma of the Iris Occurs?
The actual cause for the development of leiomyoma is unclear. Iris is composed of both ectodermal and mesenchymal tissue. They are formed due to the growth of the smooth muscles and fibers present in the eye. The muscles of the iris involved in the originating of the tumor include:
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Sphincter muscle.
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Dilator muscle.
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Iris leiomyomas can also originate from the vasculature and are more commonly found in the ciliary body region.
What Are the Clinical Features of Iris Leiomyoma?
Leiomyomas are localized destructive tumors and may cause thinning of the sclera (white part of the eye) and extensions. It is a localized flat or elevated mass, lightly pigmented with a grayish coloring. It is most commonly seen in the sphincter muscle of the iris.
The other presenting symptoms of iris leiomyoma are:
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Lenticular astigmatism (mismatch in the curvature of both surfaces of the lens). It is indicative of a tumor of the anterior segment of the eyes.
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The tumor remains static without any growth.
What Are the Complications of Iris Leiomyoma?
The complication of the tumor are:
What Are the Conditions That Appear Similar to Iris Leiomyoma?
The conditions which share similarities with leiomyoma of the iris are:
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Melanoma of the ciliary body.
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Melanoma of the iris.
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Juvenile xanthogranuloma.
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Iris cysts.
How Is Iris Leiomyoma Diagnosed?
Diagnosis of iris leiomyoma is difficult as patients with leiomyoma are mostly asymptomatic, also because leiomyoma of the iris can easily masquerade itself as a melanoma. Leiomyoma of the iris is diagnosed by the following with the help of obtaining a complete history, clinical examination, and investigations. The imaging used for diagnosing leiomyoma are:
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Optical coherence tomography (OCT) is used to evaluate the changes occurring in the tumor.
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Ultrasound biomicroscopy.
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Electron microscopy is used for diagnosing the histological features of the tumor.
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Fluorescence angiography shows hyper-fluorescence in the peripheral part of the tumor.
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Immunohistochemistry shows consistency with characteristics of myogenic tumors. They show positivity for smooth muscle actin and desmin. Immunohistochemistry staining of the smooth muscle remains the gold standard for diagnosing leiomyoma and differentiating it from melanoma.
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Fine-needle aspiration biopsy is used for diagnosing the disease.
How Is Iris Leiomyoma Treated?
Before the initiation of the surgery, documentation for the condition with photos is necessary to help keep a follow-up.
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Conservative treatment is recommended for iris tumors occupying the iris's centermost part.
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In case of compromise to the visual field, it is necessary to go for surgical excision of the tumor within the pupillary zone.
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Phacoemulsification (the process of utilizing ultrasound energy to emulsify the nucleus, irrigate, and aspirate the nucleus of the cataract).
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Damage caused to the pupil can be managed with pupillary repair and reconstruction of the pupil.
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Sclerouvectomy (a surgical procedure used to remove melanomas in the outer portion of the sclera) is performed if the ciliary body leiomyoma extends towards the iris.
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Post-operatively, patients are prescribed oral painkillers, steroids, and topical antibiotics.
There is no need to manage the lesion in the long run. However, regular follow-up and monitoring of the ocular structures for any leakage or worsening of the vision is necessary.
Conclusion
Iris leiomyoma is the rarest of all benign tumors affecting the eye. The tumor arises either from the smooth muscles or the vasculature of the eyes. It is a localized, slow-growing tumor that might show grayish pigmentation. The diagnosis of the entity is difficult as the patients are asymptomatic in the initial stages, and the lesion is most often confused with melanoma of the uvea. Immunohistochemistry remains the standard gold method for diagnosing and differentiating the condition from other tumors affecting the eye. The treatment of the lesion is excision if it interferes with the normal functioning of the eye. Patients with iris leiomyomas are kept under long-term follow-up to check for any deterioration or spread.
