retroequatorial zone and posterior pole. From this point, known as the “threshold disease”, the risk of blindness is 50% and cryotherapy is indicated (Early Treatment for Retinopathy of Prematurity Cooperative 2001, 2003; Palmer et al 2005). Medulloepithelioma Medulloepithelioma is a non hereditary tumor, usually unilat- eral, deriving from the immature embryonic non-pigmented ciliary body (Andersen 1962; Broughton and Zimmerman 1978) or, more rarely, from the optic nerve or retina. First manifestations usually occur in early childhood, occasionally in the adult, with leukocoria, poor vision and typically a vas- cularized iris mass, this greyish or salmon-colored, in some cases pigmented. The tumor may be polycystic and cystic fragments may be found liberated into the aqueous humor or vitreous body. Tumor growth is slow, developing in the surrounding structures of the anterior segment or towards the optic nerve. It is difﬁcult to assess the benign or malignant nature of the tumor, even on histopathological examination (Broughton and Zimmerman 1978). Optic nerve glioma Optic nerve glioma is the most frequent intrinsic tumor of the anterior portion of the optic nerve (65%), followed by menin- gioma (35%, Dutton, 1994). Preschool or school-age children are most often affected and the ﬁrst manifestations are usually exophthalmia and loss of vision (Dutton, 1994, Hamelin et al 2000). The tumor is associated with neuroﬁbromatosis in over 30% of cases. A true neoplasm, optic nerve glioma presents phases of rapid growth followed by stagnation, sometimes even spontaneous regression (Parsa et al 2001). The tumor may remain dormant for long periods of time then suddenly resume growth in a wholly unpredictable manner. Papillary and intraocular involvement is possible but very rare. The mortality rate is low (5%) as long as the tumor is restricted to the optic nerve. However, invasion of surround- ing tissues may lead to involvement of the chiasma and inﬁltration of adjacent cerebral structures. Involvement of the hypothalamus and third ventricule considerably increases the mortality rate, this reaching 50% after 15 years follow-up (Dutton 1994). In the adult, optic nerve glioma is malignant and invari- ably fatal due to involvement of the chiasma and cerebral structures. Methods of diagnosis In difﬁcult cases, where fundus examination alone does not enable diagnosis to be made with certainty (around 10% of Clinical Ophthalmology 2007:1(4) Differential diagnosis of leukocoria and strabismus cases), ultrasonography is the next method of choice, this being an inexpensive, inoffensive and highly speciﬁc means of detecting the calciﬁcations distinctive of retinoblastoma (Figures 4a and 4b). OCT (optical coherence tomography) is used more and more frequently to evaluate macular tumors or simulating lesions. Non invasive and well tolerated, it provides invaluable information on the presence of ﬁbro- sis, edema or subretinal ﬂuid in the foveal area (Shields et al 2004). A CT scan is useful in detecting calciﬁcations that may have escaped ultrasonography but does involve X-rays and is thus potentially dangerous with cumulative examinations (Apushkin et al 2005). Magnetic resonance imaging (MRI) is ideal for detecting any budding asymptomatic tumor of the pineal gland or optic chiasma in hereditary bilateral multifocal cases (trilateral retinoblastoma). It also enables differentiation between solid tumors (over 2 mm diameter) and lesions surrounded with subretinal ﬂuid, as is the case with advanced Coats’ disease or PFV (Apushkin et al 2005). The role of the primary care physician Whether the family doctor or pediatrician, the primary care physician is usually the ﬁrst to be confronted with the prob- lem and thus plays an essential role, as the evolution and ultimate outcome of the disease will depend on the speed of reaction at this initial stage. Any report of a white pupil, whatever the context, should be taken seriously and, until proved otherwise, considered to be at best the result of a benign malformation, at worst the ﬁrst sign of cancer of the retina, retinoblastoma. A full family anamnesis is essential, with particular attention to any history of enucleation in infancy. The age of the child should be taken into account and a full description of the anomaly noted. An assessment of the child’s vision (ﬁxation and ability to follow objects), iris color and eye position (strabismus) will be recorded. Most importantly, any leukocoria must be sought out with the use of a pen torch under subdued lighting (McLaughlin and Levin 2006). All positions of gaze should be elicited, ﬁrst of all in miosis then repeated with the pupil fully dilated, taking advantage of mydriasis to detect any anomaly of the macular or papillary region on ophthalmoscopy. Whether the leukocoria or any retinal lesion be conﬁrmed at this stage or not, there should be no delay in referring the child to a specialist. Depending on the outcome of this 437