Retinoblastoma is a rare form of eye cancer that primarily affects young children before the age of five. This malignancy originates in the retina, the light-sensitive tissue at the back of the eye. Examining the fundus holds significant importance for diagnosing this condition. This article clarifies what retinoblastoma looks like when viewed in the fundus and emphasizes the value of early detection.
Understanding Retinoblastoma
Retinoblastoma develops from uncontrolled growth of cells in the retina, the specialized tissue responsible for converting light into electrical signals sent to the brain. This cancer is caused by mutations in the RB1 gene, a tumor suppressor gene that normally regulates cell growth. When both copies of the RB1 gene are mutated or missing within a retinal cell, it can lead to unchecked cell division and tumor formation.
The disease can manifest in two main forms: hereditary and non-hereditary. Hereditary retinoblastoma involves an RB1 gene mutation present in all body cells, often leading to tumors in both eyes and an increased risk of other cancers. Non-hereditary retinoblastoma involves mutations only in the eye’s cells, affecting one eye and not being passed down to future generations.
Exploring the Eye’s Fundus
The fundus is the internal back surface of the eye, encompassing several structures such as the retina, optic disc, macula, and the network of blood vessels. It serves as a direct “window” into the eye’s health, allowing medical professionals to observe these components. The optic disc is where the optic nerve fibers exit the globe, and distinct blood vessels supply the retina.
A fundus examination is a routine part of comprehensive eye check-ups. This examination allows doctors to visually inspect these delicate structures for any abnormalities. Specialized cameras can also capture fundus photographs, aiding in the detection, monitoring, and treatment of various eye conditions.
Appearance of Retinoblastoma in the Fundus
During a fundus examination, retinoblastoma presents as one or multiple nodular, white, or cream-colored masses within the retina. These tumors exhibit increased vascularization, meaning they have prominent blood vessels feeding them. The appearance can vary depending on the tumor’s growth pattern.
Endophytic tumors grow from the retina into the vitreous cavity, the gel-like substance filling the eye, leading to vitreous seeding where viable tumor cells break off and float within the vitreous. Exophytic tumors grow towards the outer layers beneath the retina, causing a retinal detachment due to the accumulation of subretinal fluid. Calcification, appearing as bright, reflective spots within the tumor, is another common funduscopic sign and can indicate areas of dead tumor cells.
Observable Signs and Early Detection
Parents and caregivers are the first to notice signs of retinoblastoma, even before a professional fundus examination. The most common observable sign is leukocoria, also known as a “white pupil reflex” or “cat’s eye reflex”. This occurs when the tumor reflects light, causing the pupil to appear white or yellowish-white, especially noticeable in flash photographs or dim lighting. Normally, a flash photograph would produce a red reflex due to blood vessels at the back of the eye.
Another common sign is strabismus, where the eyes appear misaligned or “crossed”. While strabismus can have various causes, its presence warrants immediate medical evaluation to rule out retinoblastoma. Less common signs that might prompt concern include persistent redness of the eye, eye pain, poor vision, or an enlarged pupil. Prompt recognition of these signs and seeking a medical evaluation can significantly improve the child’s visual prognosis and overall survival rate.
Diagnosis and Treatment Approaches
Diagnosing retinoblastoma begins with a thorough eye examination, involving dilation of the pupil to allow for a detailed view of the retina. In young children who may find it difficult to remain still, the examination might be performed under anesthesia. This initial examination provides clues about the cause of the child’s symptoms.
Further diagnostic steps include imaging tests such as ultrasound and Magnetic Resonance Imaging (MRI). These tests provide detailed pictures of the eye and surrounding areas, helping to determine the tumor’s size, its exact location, and whether the cancer has spread beyond the eyeball. While Computed Tomography (CT) scans can also be used, MRI is preferred due to its ability to provide clear images without radiation exposure. Treatment plans are individualized, taking into account factors such as the tumor’s size, location, and whether it has spread. Common treatment approaches include chemotherapy, which uses strong medicines to kill cancer cells, and focal therapies like laser therapy or cryotherapy that directly target the tumor. Radiation therapy, either external beam or brachytherapy (placing a radioactive disk near the tumor), may also be considered. In some advanced cases, surgical removal of the eye, known as enucleation, might be necessary to prevent the cancer from spreading.