Application of optical coherence tomography angiography to assess systemic severity in patients with hereditary transthyretin amyloidosis

Abstract

Hereditary transthyretin amyloidosis is an autosomal dominant form of amyloidosis caused by an abnormality in transthyretin, with various ocular manifestations. Among these, ocular amyloid angiopathy has attracted attention because of its direct link to visual impairment and its correlation with systemic severity. We hypothesized that optical coherence tomography angiographic parameters would be useful biomarkers of amyloidosis systemic severity and investigated their correlation with the systemic severity score. The primary outcome was the correlation between the systemic severity score and choriocapillaris flow deficit percentage. Secondary outcomes were the correlations between the systemic severity score and retinal optical coherence tomography angiographic parameters, including foveal avascular zone size and circularity and superficial/deep/total retinal perfusion and vessel densities. The choroidal and retinal vasculature was quantified in 36 eyes from 36 patients (age, 51.8±12.1 years; disease duration, 13.4±6.2 years). Ten eyes had a history of vitrectomy for vitreous opacity. Choriocapillaris flow deficit percentage was not significantly correlated with the systemic severity score (Spearman's rank correlation: r = 2.96×10-2, p = 0.863). Similarly, foveal avascular zone size and circularity, and superficial/deep/total retinal perfusion and vessel densities were not significantly correlated with the systemic severity score. These results may indicate that optical coherence tomography angiographic parameters are not sufficient to predict amyloidosis severity.

Fig 1. En face swept-source OCTA choriocapillaris images before and after automatic local thresholding are shown.

(A) A choriocapillaris image obtained by a choriocapillaris slab with 20-μm thickness at 29–49 μm beneath the retinal pigment epithelium fit layer, with projection artifacts removal, is shown. (B) A choriocapillaris image thresholded with the Phansalkar method, using a radius of 6 pixels, is shown. OCTA, optical coherence tomography angiography.

Fig 2. Spearman’s rank correlation analysis showed no significant correlation between choriocapillaris flow deficit percentage (CC FD%) and the systemic severity score.

Fig 3. En face swept-source OCTA retinal images analyzed by Advanced Retina Imaging Network algorithms are shown.

(A) The total retinal slab is shown. (B) Automated identification of the foveal avascular zone in the superficial retina is shown. (C) Automated identification of the superficial en face perfusion trace is shown. (D) Automated identification of the superficial en face vessel trace is shown. OCTA, optical coherence tomography angiography.

Fig 4

Spearman’s rank correlation analysis showed no significant correlations between the foveal avascular zone (FAZ) parameters ((A) FAZ size; (B) FAZ circularity) and the systemic severity score.

Fig 5

Spearman’s rank correlation analysis showed no significant correlations between perfusion density in various slabs ((A) superficial slab; (B) deep slab; (C) total retinal slab) and the systemic severity score.

Fig 6

Spearman’s rank correlation analysis showed no significant correlations between the vessel density in various slabs ((A) superficial slab; (B) deep slab; (C) total retinal slab) and the systemic severity score.