Using two smartphones to look for corneal cystine crystals.

Cystinosis, a rare autosomal recessive lysosomal storage disease, can be difficult to detect. The most common form of the disease is infantile or nephropathic cystinosis. Crystals can accumulate in the eye as early as 1 year of age. Early recognition and prompt investigations prevent further accumulation of cystine and resultant end-organ injury. The disease is usually confirmed through biochemical and genetic testing, which can be time consuming. Looking for cystine corneal deposits remains an important diagnostic criterion and is the least invasive test to perform. It is recommended that ophthalmic manifestations of cystinosis be confirmed by an ophthalmologist. We describe the case of a 3-year-old girl who presented with worsening emesis, pyrexia, and lethargy, and was diagnosed with infantile cystinosis. This case is used to present a technique that can facilitate the preliminary search for corneal cystine crystals by using equipment as readily available as two smartphones. The technique may be easily used in a variety of settings, including hospitals, clinics, and primary care centers where there is delayed or difficult access to ophthalmologists.