Relationship between outer retinal tubulation, retinal volume, and visual field in Bietti crystalline dystrophy.

Purpose: To investigate the presence of tubulation in the outer nuclear layer of patients with Bietti crystalline dystrophy (BCD) using optical coherence tomography (OCT) and evaluate its relationship with visual field, visual field progression, and retinal volume.

Methods: This retrospective cross-sectional study included 37 patients diagnosed with BCD who underwent spectral-domain OCT examination. OCT examinations and Humphrey visual field tests (10-2 program) were conducted. We performed correlation analyses to assess the correlation of the number of tubulations with the visual field parameters and retinal volume. We also compared the number and prevalence of tubulations in groups based on median values of the parameters. The primary outcome measure was the number and prevalence of tubulations.

Results: The average age of the participants was 58.7 ± 9.6 years. The mean deviation (MD) value was -25.0 ± 9.0 decibels (dB). The MD slope value during an average follow-up period of 5.9 ± 3.8 years was -0.91 ± 1.02 dB/year. The number of tubulations tended to increase as the MD values worsened (P = 0.055, r = -0.33). Moreover, the number (P = 0.48) and prevalence (P = 0.42) of tubulations tended to be higher in the group with lower MD values. The number of tubulations decreased with worsening logarithmic minimum angle of resolution (logMAR) (P = 0.68, r = -0.07). The prevalence of tubulations was higher in the group with poorer logMAR (P = 0.068). We observed no significant correlations between the number of tubulations and the retinal outer, inner, or center volume (P = 0.46, r = -0.13; P = 0.76, r = 0.05; P = 0.47, r = 0.12, respectively). However, the prevalence of tubulations in the group with smaller retinal center volume was lower (P = 0.054).

Conclusion: The number of tubulations correlated with the severity of visual field loss in patients with BCD; however, it did not correlate with visual field progression or retinal volume measurements. Further studies are needed to understand the development of tubulations and their implications for retinal atrophy in BCD.