Purpose: To study the functional and clinical characteristics in Bietti’s crystalline dystrophy (BCD) and to evaluate the sensitivity of functional and morphological examinations in assessing BCD in fifteen Chinese patients.

Methods: The clinical characteristics of BCD were studied in fifteen Chinese patients with BCD, using fundoscopy, fundus fluorescein angiography (FFA), and autofluorescence (AF). The functional features were evaluated by full-field electroretinography (fERG), 85-degree and 30-degree perimetry, multifocal ERG (mERG), and chromatic pupillometry.

Results: The fifteen patients were separated into three clinical stages according to their fundus defects. fERG- and mERG-decreased waves appeared in the early stage. Various fERG disorders and 85-degree visual field defects were observed in intermediate stage patients. The substages were defined by the fERG stage. The blind visual field and extinguished fERG and mERG waves were observed in all patients in the advanced stage. Decreased blue and white light-induced pupillary light reflex (PLR) waves were elicited in the patients in all three stages. The relative pupillary constriction (RPC) was lower in BCD patients than in normal controls (p<0.01). Furthermore, the RPC in the advanced-stage patients was lower than in the early- to intermediate-stage patients (p<0.01).

Conclusions: Functional examinations are more sensitive than fundus morphological examinations in the early and intermediate stages of BCD. The substages can be defined by fERG results. PLR is an effective objective assessment of photoreceptor dysfunction in all three stages, but it is particularly sensitive in advanced-stage patients. This study provides a direction for further therapeutic study of BCD.