The experience of discovering a mass or cyst behind the eye can be unsettling, but many growths in this area are non-cancerous and treatable. The eye is housed within the orbit, a bony, pear-shaped socket that protects the globe, along with supporting muscles, nerves, blood vessels, and fat. Because this space is confined and rigid, any abnormal growth, even a benign one, can quickly cause noticeable symptoms.
Defining Orbital Cysts and Masses
The orbit is a small, pyramid-shaped bony cavity designed to protect the delicate structures of the visual system. Composed of seven bones, this structure is tightly packed with soft tissues. Any lesion that occupies space within this restrictive cavity is referred to as an orbital mass.
A true cyst is defined as a closed sac lined with epithelial tissue that contains fluid or semi-solid material. This differentiates a cyst from other orbital masses, such as solid tumors or inflammations. Cysts expand because the epithelial lining continuously secretes fluid or sheds cellular debris. Due to the fixed boundaries of the bony orbit, even slow-growing, benign cysts inevitably press upon surrounding tissues.
Common Types and Origins
The most common cysts behind the eye are developmental, meaning they form during embryonic growth. These lesions are classified as choristomas, which are growths composed of normal tissue found in an aberrant location. Dermoid cysts are the most frequent orbital masses seen in children.
Dermoid cysts originate from embryonic remnants trapped along the bony fusion lines of the skull and orbit during gestation. They are characterized by a wall of stratified squamous epithelium containing skin appendages, such as hair follicles and sebaceous glands. The cyst enlarges as the sebaceous glands secrete material and epithelial cells shed keratin into the center of the sac.
Epidermoid cysts are closely related but distinct, as they are lined by stratified squamous epithelium and contain only desquamated keratin. They lack the hair follicles and sebaceous glands found in dermoids. These cysts can be congenital, forming from displaced epithelial elements, or acquired, resulting from the traumatic implantation of surface cells. Both types are slow-growing and are usually diagnosed in childhood or early adulthood.
Recognizing the Signs
The symptoms of an orbital cyst arise from the “mass effect,” which is the pressure exerted by the growing lesion within the rigid orbital cavity. The most common sign is proptosis, or the forward bulging of the eyeball. This occurs because the cyst pushes the globe anteriorly, often causing noticeable asymmetry between the eyes.
As the cyst expands, it can displace the eye in other directions, leading to globe displacement. Pressure on the extraocular muscles, which control eye movement, can result in diplopia, or double vision. Rapid growth or acute inflammation may cause orbital pain due to nerve compression or swelling. Decreased visual acuity can occur if the mass compresses the optic nerve, a condition known as compressive optic neuropathy.
Medical Evaluation and Management
When an orbital mass is suspected, medical evaluation relies on advanced imaging to determine the lesion’s precise nature and location. Computed Tomography (CT) scans provide excellent detail of the bony orbit, helping identify bony erosion or calcifications. Magnetic Resonance Imaging (MRI) offers superior soft-tissue contrast, allowing clinicians to characterize the mass composition, such as the presence of fatty or fluid content.
Management strategies are tailored based on the cyst’s size, location, and symptoms. Small, asymptomatic cysts that are stable may be managed with a conservative approach involving regular monitoring. If the cyst is causing proptosis, affecting vision, or is rapidly growing, surgical intervention is recommended.
The goal of surgery is complete excision of the cyst, meaning removing the entire sac without rupture. This procedure is often curative for benign orbital cysts. Incomplete removal, especially leaving behind fragments of the epithelial wall, is a risk factor for recurrence, as remaining cells can continue to secrete material. Surgical techniques must be precise to avoid damaging the delicate nerves and muscles within the tightly packed orbital space.