Author: Lorenzo Bianco (Italy)
Co-authors: Lorenzo Bianco, Alessandro Arrigo, Alessio Antropoli, Andrea Attilio Rosolia, Maurizio Battaglia Parodi, Francesco Bandello
Purpose
Best Vitelliform Macular Dystrophy (BVMD) is an extremely heterogeneous genetic retinal dystrophy characterized by the presence of different pathologic alterations, including lipofuscin deposition, fluid accumulation, atrophy, and neovascular complications. Although progression through Gass’ stages is generally associated with a worse visual prognosis, scant data are available regarding the impact of each pathologic alteration on retinal functional deterioration, in terms of sensitivity and fixation stability. The main aim of the present study is to investigate the influence of clinical and imaging parameters on retinal sensitivity by means of microperimetry, structural optical coherence tomography (OCT), blue-light fundus autofluorescence (BAF), and OCT-Angiography (OCTA).
Setting/Venue
Observational and cross-sectional study on a consecutive series of patients affected by genetically confirmed BVMD, enrolled in the Retinal Heredodystrophies Unit of San Raffaele Hospital in Milan, Italy.
Methods
Enrolled patients underwent a complete ophthalmologic examination including macular integrity assessment (MAIA) microperimetry, OCT, BAF, and OCTA. Eyes that satisfied the inclusion criteria were classified into five subtypes, according to the tomographic aspect of the lesion: subclinical, solid vitelliform deposition, mixed (combination of solid and fluid accumulation), subretinal fluid (vitelliform material entirely reabsorbed and replaced by fluid), atrophic. Eyes were also categorized as having a hyper-autofluorescent, patchy or hypo-autofluorescent pattern on BAF. The mean threshold of testing points within the area of the lesion was calculated in order to assess the sensitivity of the affected retina. 63% and 95% Bivariate Contour Ellipse Area (BCEA) were used as outcome variables for fixation stability. We calculated area of ellipsoid zone (EZ) integrity, thickness of the outer nuclear layer (ONL), and central macular thickness (CMT) using structural OCT. Presence of non-exudative MNVs and values of vessel density (VD), and tortuosity (VT) were assessed using OCTA. The primary outcome was the analysis of retinal sensitivity among lesion subtypes and BAF patterns. The secondary outcome was to analyze the influence of ONL thickness, CMT, area of EZ integrity, presence of non-exudative MNV, vessel density, and tortuosity on retinal sensitivity, fixation stability, and visual acuity.
Results
57 eyes of 30 patients were included in the analysis. The subclinical stage displayed the highest retinal sensitivity (24.44 dB; p <0.01) while eyes characterized by atrophic areas the lowest one (11.85 dB; p <0.01). Lesions showing solid vitelliform deposition had higher retinal sensitivity (21.97 dB) than subtypes with partial or total substitution with fluid (17.27 dB; p <0.01). Lesions totally composed of subretinal fluid had a lower retinal sensitivity (15.68 dB) than mixed ones (18.73 dB; p <0.05). The hyper-autofluorescent pattern was associated with a better sensitivity (21.96 dB) than patchy (16.24 dB; p <0.01) and hypo-autofluorescent patterns (14.53 dB; p <0.01). The presence of a non-exudative MNV marked a worse functional outcome (14.96 dB; p <0.01). A larger area of preserved EZ (p <0.01) was associated with a more stable fixation and a higher visual acuity. A thicker ONL and a larger area of EZ integrity were associated with better retinal sensitivity (both p <0.01). Vessel tortuosity correlated positively with retinal sensitivity (p <0.01) while vessel density correlated negatively with 63% BCEA and 95% BCEA (p <0.05).
Conlusions
The present study expands the knowledge on retinal sensitivity variation in different subtypes of BVMD lesions. In particular, we assessed the contribution of different pathological features in determining retinal function deterioration, as assessed by microperimetry. We found that the morphological composition had a remarkable influence on the sensitivity of BVMD lesions. In detail, our results suggest that retinal sensitivity deteriorates in a linear fashion as lipofuscin reabsorbs progressively and an area of subretinal fluid takes its place until atrophy ensues. On the other hand, fixation stability and visual acuity showed a relationship with ellipsoid zone status, rather than with lesion subtype or autofluorescence pattern. Lastly, we found that thickness of ONL, integrity status of EZ, and vascular perfusion at superficial and deep retinal capillary plexuses are valuable imaging markers of good retinal sensitivity in BVMD.
Financial Disclosure
None
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