Description: My attention is drawn to the lack of red reflex in the left eye, which in itself is more alarming in the setting of strabismus. The eye does not particularly appear hyperopic in this photo, but I do suspect some type of sensory strabismus to be present in this eye with leukocoria shown in Figure 9.1.

Differential Diagnosis: My differential diagnosis for unilateral leukocoria in this girl includes ocular pathologies (retinoblastoma, cataract, Norrie disease, retinopathy of prematurity, coloboma); congenital conditions (persistent anterior fetal vasculature); infectious causes (chronic toxocara endophthalmitis); and vascular etiologies (Coats disease, persistent fetal vasculature). Given the age of presentation, the most concerning and most likely diagnosis is a unilateral retinoblastoma. Retinoblastoma is well known to present as strabismus, and in all cases of pediatric strabismus, we need to rule out retinoblastoma.

History: It is important for me to know the timing of onset of the change. Has it been present since birth? Did the patient have prenatal complications or a complicated birth? Does the patient have any family members with similar problems? Is there exposure to pets, specifically dogs? Is there any family history of childhood cancers?

Exam: On exam, a complete examination including ocular examination, examination of the iris, and inspection of the lens is required. Dilated fundus examination and anterior vitreous examination are also necessary. Retinoblastoma may be diagnosed by a dilated indirect ophthalmoscopy, so a thorough physical examination such as this is critical. Visualization of a chalky, white mass with friable consistency is consistent for retinoblastoma.

Workup: Early detection of intraocular disease and genetic analysis are important for establishing long-term prognosis. The favorability of prognosis is based on the Reese-Ellsworth classification. Visualization of calcification on the lesion with B-scan ultrasonography and computed tomography (CT) scan can confirm the diagnosis of retinoblastoma. Magnetic resonance (MR) imaging is useful to determine extension into the optic nerves.

Treatment: Treatment priorities are to preserve life, preserve the globe, and preserve vision. Chemoreduction is the mainstay treatment with systemic chemotherapy administered to shrink the tumors. Surgical enucleation is reserved for significant tumor burden not amenable to more conservative treatment. On pathologic examination of the tumor, H&E staining will reveal fleurettes.

Advice: Sixty percent of retinoblastoma cases are unilateral and are nonhereditary following the two-hit hypothesis of the RB1 gene. I would explain to family members the importance of genetic testing for understanding the risk of this disease for other family members and future siblings.

Follow-up: I would follow the patient for complete ocular examination under general anesthesia every 6-8 weeks after initial treatment to monitor for tumor regression. I would document with photography the tumor regression over this period of time until the tumor becomes more quiescent at which point the interval between examinations may be extended.