Name

Corrélation entre l'atteinte de la rétine externe et l'acuité visuelle dans la maladie de Best

To describe outer retinal structure in patients with Best vitelliform macular dystrophy (BVMD) using Spectral-domain optical coherence tomography (SD-OCT) and correlate these results with visual acuity and patient age.

In this case-control retrospective observational study, patients with molecularly confirmed BVMD were compared to normal control subjects (NC). For all subjects, a complete clinical evaluation was performed including best corrected visual acuity (BCVA), fundus photography, SD-OCT and fundus auto fluorescence (FAF). For BVMD patients with an available follow-up, data from the first and the last visits were compared. FAF and SD-OCT images were analyzed to determine the stage of the lesion, the presence of vitelliform material (VM) and subretinal fluid (SRF), the photoreceptor outer segment (PROS) length inside the subretinal detachment (SRD), the central macular thickness (CMT), the foveal outer nuclear layer (ONL) thickness, the disruption of the external limiting membrane (ELM) and the ellipsoid zone (EZ). Staging was based on the Gass clinical classification. Correlations between age, tomographic measurements and visual acuity were assessed.

Forty-two BVMD patients (83 eyes) with a molecular diagnosis and 42 NC (42 eyes) were included. Clinical stages were distributed as follow: 7.2% for stage 1, 20.4% for stage 2, 18.1% for stage 3, 41.2% for stage 4 and 12.1% for stage 5. The presence of SRF and VM was noted in 72% and 78% of the BVMD eyes examined, and was not associated with BCVA modification (P = 0.096 and P = 0.458, respectively). The average (standard deviation) ONL thickness was 43 (± 27) µm and significantly lower compared to the control group (P< 0.001). BCVA was significantly correlated with stage (R = 0.634; P < 0.001), age of patients (R = 0.375; P = 0.001), CMT (R = -0.271; P = 0.014), ONL thickness (R = -0.644; P <0.001). The disruption of the ELM and the EZ was associated with a decreased BCVA (P < 0.001 for both). Among the 62 eyes with SRD, the PROS length was significantly correlated with BCVA (R = -0.505; P <0.01) and ONL thickness (R = 0.416; P = 0.004).

Our results indicate that regardless of the clinical stage, ONL thickness measured by SD-OCT was significantly lower in BVMD patients compared to control subjects and was well correlated with BCVA. Despite a short follow-up, measurement of foveolar ONL thickness was found to be a relevant quantitative criterion for documenting an anatomical difference concomitantly with a decreased visual acuity. The ONL is essentially composed of the photoreceptor nuclei, which explains the consistent relationship between photoreceptor loss and thinning of the ONL measured in SD-OCT, as initially observed by Mullins et al. in histological samples.

This study demonstrates the correlation between visual acuity, age and OCT features in BVMD patients. The ONL thickness as well as PROS length are relevant functional correlates and outcome measures to follow photoreceptor impairments and could be used to monitor effects of future therapeutic approaches.