Role of red free imaging, retinal reflectance and fundus autofluorescence in Bietti crystalline dystrophy: case report

Bietti crystalline dystrophy (BCD), a rare autosomal recessive hereditary disorder, is identified by its clinical features. It is characterised by crystalline deposits and hence called crystalline retinopathy. The retinopathy progresses with age, showing a decrease in the number of crystalline deposits and increase in the area of chorioretinal degeneration, which spreads in a centrifugal pattern. Thus, BCD can be confused with other disorders with crystalline-like deposits and chorioretinal degenerations. The red-free and near-infrared reflectance allows prominent visualisation of crystalline deposits that may be missed. The non-inferiority of red-free imaging and its wider availability could allow its use as a screening tool. The enhanced depth imaging optical coherence tomography shows crystalline deposits throughout the retina and outer retinal tubulation. Thus, multimodality imaging can act as an adjunct in diagnosis, monitoring and follow up in these cases, acting not only as a teaching tool but also giving an insight into the underlying pathophysiology of the disorder. PLAIN LANGUAGE SUMMARY: Use of imaging in diagnosis of Bietti crystalline dystrophy Bietti crystalline dystrophy is a rare familial disorder but is not shown in all family members and may skip generations, as it has an autosomal recessive pattern of inheritance. It shows refractile yellow-white crystalline deposits and degenerative changes in the retina. These crystalline deposits disappear with age while degenerative changes increase and spread from centre to the periphery. This may cause difficulty in early detection, and confusion with similar degenerative diseases of the retina. The use of various imaging modalities can help in diagnosis and follow up of these cases. These modalities also provide understanding of the basic disease process.