Predicting visual acuity in Bietti crystalline dystrophy: evaluation of image parameters

Natural history of progressive vision loss in Bietti crystalline dystrophy: a model-based meta-analysis

PURPOSE

Bietti crystalline corneoretinal dystrophy (BCD) is an autosomal recessive progressive retinal degenerative disease due to mutations in the CYP4V2 gene. Best-corrected visual acuity (BCVA) is a common primary endpoint in clinical trials for retinal diseases, but the natural history of BCVA loss remains unclear because of the heterogeneity of manifestations in BCD patients.

METHODS

Based on the individual data of untreated BCD patients, a disease progression model was established using the change in BCVA from baseline as an index, and covariates including age of onset, age, duration of disease, baseline BCVA, gender, race (East Asian/non-East Asian), genotype, and family history. Then, based on the final model, the natural disease progression characteristics of BCD were simulated.

RESULT

A total of 14 studies met the inclusion criteria, with a total sample size of 117 cases, including 6 studies (N=80) with East Asian populations and 9 studies (N=37) with non-East Asian populations. The change of BCVA from baseline increased linearly with time, and the disease progression model of BCD was successfully established. BCVA increased by 0.06 logarithm of the minimum angle of resolution (LogMAR) per year in BCD patients. BCVA increased by 0.09 LogMAR per year in patients with BCVA≥0.5LogMAR and disease duration more than 10 years.

CONCLUSIONS

For the first time, we successfully established a BCD disease progression model based on the change in BCVA from baseline. The mean visual acuity loss increased linearly with the progression of the disease. A sharper loss of BCVA may be expected in patients with BCVA≥0.5LogMAR and disease duration ≥10 years.

Quantitative swept-source optical coherence tomography angiography (SS-OCTA) analysis of macular microvascular alterations in Bietti crystalline dystrophy

PURPOSE

Bietti crystalline dystrophy (BCD) is a rare retinal dystrophy characterized by progressive visual impairment. This study aimed to evaluate changes in retinal and choroidal vessels and blood flow in BCD patients using swept-source optical coherence tomography angiography (SS-OCTA) and to investigate potential parameters associated with visual function.

METHODS

This cross-sectional study included 166 eyes from 86 clinically diagnosed BCD patients, classified into three disease stages based on Yuzawa's classification. OCTA imaging (VG200S; SVision Imaging, Henan, China) covered a 12 mm × 12 mm area of the macula, measuring thickness, vessel density (VD), perfusion area (PA), choroidal vascularity index (CVI), choroidal vascularity volume (CVV), and foveal avascular zone (FAZ) metrics. Associations between OCTA parameters and visual function metrics, including best-corrected visual acuity (BCVA), mean deviation (MD) and visual field index (VFI) of the Humphrey visual field test, were analyzed.

RESULTS

By stage 3, 92 % of eyes exhibited an undetectable ellipsoid zone (EZ). From stage 1 to stage 2, VD in all retinal layers decreased significantly (P < 0.05), whereas differences between stages 2 and 3 were not statistically significant (P > 0.05). The FAZ area and perimeter showed no significant difference across the three stages (P > 0.05). Choroidal parameters, including PA, CVI, and CVV, progressively decreased across all stages (P < 0.001). Multivariate regression analysis revealed that SVC-VD (P < 0.001), SVC-PA (P < 0.001) and choroid-PA (P = 0.030) were significantly associated with BCVA, while DVC-VD (P = 0.014), outer retinal thickness (P = 0.011), and CVI (P = 0.004) were significantly associated with visual field damage.

CONCLUSIONS

SS-OCTA effectively quantifies the progressive microvascular changes in the retina and choroid associated with BCD. Retinal vascular alterations are prominent in the early stages of the disease, whereas choroidal damage persists throughout its progression. OCTA parameters of the retina and choroid demonstrate varying degrees of correlation with visual function, underscoring their potential as biomarkers for monitoring disease progression and evaluating therapeutic efficacy.

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.

Cross-Sectional Analysis of Outer Retinal Tubulation in Inherited Retinal Diseases: A Multicenter Study

PURPOSE

This study aims to explore genetic variants that potentially lead to outer retinal tubulation (ORT), estimate the prevalence of ORT in these candidate genes, and investigate the clinical etiology of ORT in patients with inherited retinal diseases (IRDs), with respect to each gene.

DESIGN

Retrospective cohort study.

METHODS

A retrospective cross-sectional review was conducted on 565 patients with molecular diagnoses of IRD, confirming the presence of ORT as noted in each patient's respective spectral-domain optical coherence tomography (SD-OCT) imaging. Using SD-OCT imaging, the presence of ORT was analyzed in relation to specific genetic variants and phenotypic characteristics. Outcomes included the observed ORT frequencies across 2 gene-specific cohorts: non-retinal pigment epithelium (RPE)-specific genes, and RPE-specific genes; and to investigate the analogous characteristics caused by variants in these genes.

RESULTS

Among the 565 patients included in this study, 104 exhibited ORT on SD-OCT. We observed ORT frequencies among the following genes from our patient cohort: 100% (23/23) for CHM, 100% (2/2) for PNPLA6, 100% (4/4) for RCBTB1, 100% for mtDNA [100% (4/4) for MT-TL1 and 100% (1/1) for mtDNA deletion], 100% (1/1) for OAT, 95.2% (20/21) for CYP4V2, 72.7% (8/11) for CHM female carriers, 66.7% (2/3) for C1QTNF5, 57.1% (8/14) for PROM1, 53.8% (7/13) for PRPH2, 42.9% (3/7) for CERKL, 28.6% (2/7) for CDHR1, 20% (1/5) for RPE65, 4% (18/445) for ABCA4. In contrast, ORT was not observed in any patients with photoreceptor-specific gene variants, such as RHO (n = 13), USH2A (n = 118), EYS (n = 70), PDE6B (n = 10), PDE6A (n = 4), and others.

CONCLUSIONS

These results illustrate a compelling association between the presence of ORT and IRDs caused by variants in RPE-specific genes, as well as non-RPE-specific genes. In contrast, IRDs caused by photoreceptor-specific genes are typically not associated with ORT occurrence. Further analysis revealed that ORT tends to manifest in IRDs with milder intraretinal pigment migration (IPM), a finding that is typically associated with RPE-specific genes. These findings regarding ORT, genetic factors, atrophic patterns in the fundus, and IPM provide valuable insight into the complex etiology of IRDs. Future prospective studies are needed to further explore the association and underlying mechanisms of ORT in these contexts.

Investigating Microperimetric Features in Bietti Crystalline Dystrophy Patients: A Cross-Sectional Longitudinal Study in a Large Cohort

Purpose

To assess the clinical and genetic characteristics of patients with Bietti crystalline dystrophy (BCD) with a focus on potential of microperimetry in monitoring macular function.

Methods

A total of 208 genetically-confirmed BCD patients were enrolled in this retrospective study. The patients were categorized into subgroups based on their fundus characteristics (fovea sparing and fovea involved), optical coherence tomography (OCT) findings (presence/absence of retinal pigment epithelium [RPE] or ellipsoid zone [EZ] line at the fovea/parafovea), and genetic profiles (Mis/Mis, Tru/Mis, Tru/Tru). Fixation patterns were analyzed, and macular sensitivity (MS) parameters were compared among different groups. Longitudinal analysis was performed to calculate the annual changes in MS parameters. Correlation between genotype and phenotype were further investigated by analyzing cumulative incidence of vision impairment among different genotypic groups.

Results

Patients with well-preserved RPE or EZ at the foveal/parafoveal region exhibited higher MS. Notably, there was a decline in sensitivity parameters, with a decrease of -2.193 dB/year (95% confidence interval [CI] -4.292 to -0.095, P = 0.041) at the fovea and -1.353 dB/year (95% CI -2.047 to -0.659, P < 0.001) in average sensitivity. An age-adjusted comparison of sensitivity among genotypic groups and cumulative incidence analyses showed no association between genotypic groups and vision loss.

Conclusions

Microperimetry proves to be one of a credible tool for detecting macular functional changes in BCD patients. BCD patients with different genotypes may have similar disease progression.

Diagnostic and Management Strategies of Bietti Crystalline Dystrophy: Current Perspectives

Bietti crystalline dystrophy (BCD) is a rare, genetically determined chorioretinal dystrophy presenting with intraretinal crystalline deposits and varying degrees of progressive chorioretinal atrophy commencing at the posterior pole. In some cases, there can be concomitant corneal crystals noted first in the superior or inferior limbus. CYP4V2 gene, a member of the cytochrome P450 family is responsible for the disease and more than 100 mutations have been defined thus far. However, a genotype-phenotype correlation has not been established yet. Visual impairment commonly occurs between the second and third decades of life. By the fifth or sixth decade of life, vision loss can become so severe that the patient may potentially become legally blind. Multitudes of multimodal imaging modalities can be utilized to demonstrate the clinical features, course, and complications of the disease. This present review aims to reiterate the clinical features of BCD, update the clinical perspectives with the help of multimodal imaging techniques, and overview its genetic background with future therapeutic approaches.

The role of near-infrared reflectance imaging in retinal disease: A systematic review

Near-infrared reflectance (NIR) retinal imaging aids in a better visualization of structures at the level of outer retina, retinal pigment epithelium, and choroid. It has multiple advantages, including easy acquisition in association with structural spectral domain optical coherence tomography, more comfort for patients, and enhanced contrast and spatial resolution. It helps in the diagnosis of chorioretinal diseases that present with minimal funduscopic findings and can be used to follow up many chorioretinal conditions. We describe the chorioretinal NIR imaging appearance and the clinical role of NIR imaging in ocular inflammatory disease, vascular and acquired disease, degenerative disease, tumors, associated systemic condition, toxic and traumatic disease, optic nerve head conditions, and physiological findings.

Presumed Bietti crystalline dystrophy with optic nerve head drusen: a case report

Background

Bietti crystalline dystrophy is primarily a retinal dystrophy caused by a CYP4V2 mutation and typically presents with crystalline retinal deposits in the posterior fundus.

Case presentation

We present the case of an otherwise healthy 39-year-old Iranian woman with no family history of ocular disease who suffered with progressive vision loss that had started 2 years prior to presentation. Ocular examination revealed blurry optic nerve head margin and diffuse retinal crystalline deposit in both eyes. Spectral domain optical coherence tomography images showed retinal crystals, located mostly in outer retinal layers, with some areas of outer retinal tubulation and attenuation of outer retinal layers. Crystalline deposits were better visualized on near-infrared images as hyperreflective spots. Fundus autofluorescence images showed hyperautofluorescence areas on optic nerve head consistent with optic nerve head drusen and large hypoautofluorescence areas in posterior retina consistent with retinal pigment epithelium atrophy. Cystinosis was ruled out by blood testing.

Conclusion

Bietti crystalline dystrophy may be associated with optic nerve head drusen.

Foveolar thickness as potential standardized structural outcome measurement in studies of Bietti crystalline dystrophy

Bietti crystalline dystrophy (BCD) is an ultra-rare orphan disorder that can lead to blindness. Because of the variable rates of progression of the disease, it is necessary to identify suitable outcome measurements for tracking progression in BCD. A retrospective analysis of patients with a clinical and genetic diagnosis of BCD was conducted. Four measurements of spectral domain-optical coherence tomography were compared to patients’ best corrected visual acuity. We observed that patients with higher measurements of foveolar thickness, choroidal thickness in the foveolar region, ellipsoid zone band length and the outer nuclear layer + area, had on average better visual acuity. Future studies are needed to validate the structural–functional correlations we observed in BCD and to propose a sensitive and clinically meaningful outcome measurement for tracking this rare, variable disease.