Case 2: A three-year-old boy with photographic leukocoria

A three-year-old Caucasian boy was referred by his paediatrician with concerns of leukocoria in the left eye, which was visible in all his photographs (Figure 1). His medical history was unremarkable, and the patient was meeting all developmental milestones. Two photographs (A) and (B) displaying a white crescent in the inferior pupil margin of left eye. The corneal reflections from the camera flash are imaged symmetrically within the pupil of each eye with a slight nasal bias. The red background in (B) arises from greater diffuse scatter being captured by the camera On examination, the patient’s visual acuity in the right eye was 20/30. Left eye acuity was attempted; however, unable to be assessed due to severe agitation on occlusion (of the right eye). The Hirschberg test revealed symmetrically imaged corneal reflexes within the pupils, indicating no sign of strabismus. The Bruckner reflex revealed asymmetrical reflexes with the whiter, brighter reflex in the left eye. Significant hyperopia (+6.50D) was revealed in the left eye; however, normal levels (+1.50D) were displayed in the right eye. Pupils were equal, round and reactive to light, with no relative afferent pupil defect. Both the anterior and posterior segments revealed no abnormalities including negative signs for cataract, intraretinal tumour and retinal exudates. The diagnosis of photographically induced leukocoria in the left eye was confirmed by the consistent presence of leukocoria in photographs, anisometropia and normal retinal fundus. The leukocoria in the present case arose from an optical effect of flash photography, in which the image of the flash source appears as a white crescent formed in the pupil. Flash sources are typically offset from the aperture of a camera lens. Normally, when the subject views a camera, scattered light is observed in the pupil, giving rise to the so-called ‘red eye’ effect. (Figure 1B, right eye). However, if the eye is not focused on the camera, but rather in front or behind it, then an actual crescent of white light is formed in the pupil (1). This crescent will be formed regardless of whether the background scatter is present (Figure 1A and 1B). The size of the crescent will vary directly according to the degree to which the eye is defocused from the camera. Because for most digital cameras the flash source is set above the camera aperture, hyperopic eyes exhibit the crescent in the inferior pupil margin, and significantly myopic eyes exhibit the crescent in the superior pupil margin (1). In the present case, the patient was only focused on the camera with the right eye. The left eye was highly hyperopic, which led to a crescent of light that was formed in the lower margin of the pupil (1). If another photograph was taken with the right eye covered, thereby forcing the left eye to focus on the camera, the crescent would be expected to disappear. Typically, the eye in focus is the least hyperopic. The constant out-of-focus imagery of the left eye leads to amblyopia, which was evident in the present case. Another source of photographically induced leukocoria can arise when the eyes are misaligned (strabismus) (1). This can be accentuated in esotropia, in which reflection becomes very bright when it originates from the optic nerve. Photographic causes of leukocoria are less repeatable compared with anatomical causes, such as retinoblastoma or cataracts, because focus and alignment behaviours will be variable. Furthermore, when present, the crescent will be most intense at one pupil margin and will become more diffuse toward the line of sight. This pattern would not be consistently found in other pathological causes of leukocoria, such as Coates disease, cataract or retinopathy of prematurity. Careful attention should, therefore, be devoted to the location and appearance of the leukocoria. Education regarding the origin of the leukocoria is important for both patient and parent. Evidence from large-scale studies of pre-school anisometropes stress the importance of wearing spectacle correction full time when amblyopia from anisometropia is discovered (2). Should amblyopia persist, patching can be considered. Parents may identify photographic leukocoria. When this is found, professional eyecare advice needs to be sought. In our case, the patient was prescribed glasses with trivex lenses for full-time wear. At the 10-week follow-up, visual acuity was measured at 20/100. At this appointment, amblyopia treatment was initiated, consisting of patching the right eye for 6 h per day with an emphasis on hand-eye coordinated activities. Evidence-based studies suggest visual acuity will improve in the left eye by at least 4.8 lines at the four-month follow-up appointment (3). Leukocoria is a major presenting sign that can be representative of various sight-threatening ocular diseases in children that demand immediate medical attention. It is important to recognize the optical origin of leukocoria due to the presence of anisometropia. Photographic evidence of a white pupil in infants and children should be cause for immediate referral for a comprehensive eye examination.

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