Introduction

Unusual visual experiences are not rare in children, but are often difficult to interpret due to the difficulty for the child to express the peculiar sensation. Most complaints will be of a benign and usually transient nature requiring only reassurance. However, a visual complaint may have a more significant meaning, signifying a serious underlying disorder. It is important to take the child’s and parents’ complaint at face value and to approach its evaluation systematically.

I have made a short mnemonic which I find helpful when dealing with such cases. “OSCE” stands for:

This should ensure the approach to the evaluation of the problem is complete (Table 109.1). This can usually be achieved by appropriate history taking followed by a clinical examination, but may require ancillary investigations and referral to other specialists (Box 109.1). It has to be remembered that not all cases have a definitive diagnosis made (Fig. 109.1) and that even apparently bizarre symptoms can arise from organic disease (Fig. 109.2).

Table 109.1 Systematic approach to children who complain of seeing peculiar things

Fig. 109.1 This 9-year-old boy complained of constantly seeing a color grid in front of both eyes. Five months later, the color grid in one eye persisted, but changed to constant black and white vision in the other eye. He has no history of seizures or systemic illness or trauma. He is a well adjusted boy who likes school. All his investigations, including his ocular and pediatric examination, objective pupillary testing, his MRI brain, and electrodiagnostic testing (ERG, VEP, and EEG), have remained normal.

Fig. 109.2 A 14-year-old boy with known neurofibromatosis type 1 and a known glioma of the left optic nerve and chiasm (A) was complaining of seeing intermittently patches in his left and sometimes also in both eyes (B,C).

Typical peculiar visual complaints are broken up into individual visual symptoms and presented from common to rare. There are excellent reviews of this subject.^1–8

Entoptic phenomena

Entoptic phenomena are visual perceptions from sources within the eye rather than the outside world. Most are harmless curiosities which are usually not perceived or ignored, but may be noticed by a bright young child. They are noticed under special viewing or light conditions. Most people will have experienced some of them at some point in their life. Clinicians use them to assess the presence of gross retinal and optic nerve visual function when no direct fundal view is possible due to dense medial opacities. On the other hand, children with very poor sight will often rub and poke their eyes to stimulate entoptic phenomena (oculodigital sign; see Chapter 59).

Scheerer’s (or blue field entoptic) phenomenon consists of seeing tiny bright spots that rapidly move in squiggly lines, especially when looking into the bright clear blue sky or an open field of snow. They are due to the movements of white cells in the capillaries near the macula. Blue field entoptoscopy has been used to measure retinal capillary flow.

Most children with normal vision will notice Purkinje’s trees which are images of the own retinal circulation. This is best seen when a bright light is shone through the closed eye lids, resulting in the retinal vessels casting a shadow on the unadapted, underlying photoreceptors.

Other harmless entoptic phenomena include Purkinje’s blue arcs, Haidinger’s brushes, light diffraction through eye lashes, as well as floaters, photopsia,and phosphenes.

Floaters (myodesopsia, mouches volantes)

At birth, the tertiary vitreous is perfectly transparent. Myodesopsia is the perception of a floater and is caused by the development of imperfections or deposits within the vitreous body that cast a moving shadow on the retina. Floaters have been likened to “flying flies” (synonyms mouches volantes in French or muscae volitantes in Latin). The floater is most noticeable against a uniform, bright background and when it comes closest to the retina. Unlike a scotoma which is fixed in space, a floater comes and goes and moves position from second to second.

Most floaters are entirely harmless, albeit annoying, and require reassurance only. These are due to normal degenerative changes in the vitreous (vitreous syneresis, uncomplicated posterior vitreous detachment, Weiss ring) and are a ubiquitous visual complaint with growing age, affecting myopes earlier than emmetropes. Occasionally, asteroid hyalosis, synchysis scintillans, or a persistent primary vitreous remnant of the hyaloid artery in Cloquet’s canal is causative and is of no further consequence.

However, new floaters may point to a more concerning condition, especially if associated with photopsia, a sudden shower of black spots, a shadow, or reduced vision. This always warrants an ophthalmologic examination to exclude a retinal tear, retinal detachment, vitreous hemorrhage, or uveitis.

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