ASSOCIATION BETWEEN CHOROIDAL CHARACTERISTICS AND SYSTEMIC SEVERITY IN AMYLOIDOSIS

OCT angiography indices and the choroidal vascularity index in wild-type transthyretin (TTR) amyloidosis (ATTRwt)

Purpose

Retinal angiopathy represents a well-known ocular manifestation of hereditary transthyretin amyloidosis (ATTRv). Until recently, there have been no reports on retinal changes in ATTRwt. In this retrospective observational clinical study, we aimed to determine whether vessel density (VD) indices and the choroidal vascularity index (CVI) could offer insights into retinal and choroidal vascular changes among patients affected by ATTRwt.

Methods

Eighteen patients with a confirmed diagnosis of ATTRwt underwent structural optical coherence tomography (OCT) and OCT angiography (OCTA). We established a control group consisting of 16 healthy subjects for statistical comparisons. The 3D OCT and OCTA datasets were analyzed to assess retinal and choroidal thickness and VD. For measuring CVI, we obtained measurements for the total choroid area (TCA), luminal area (LA), and stromal area (SA).

Results

The mean VD exhibited a statistically significant reduction in the superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC) among the ATTRwt group in comparison to the control group (p < 0.0001). Notably, ATTRwt patients displayed decreased choroidal thickness (p = 0.08). Additionally, the median CVI was lower in the ATTRwt group than in the control group (p = 0.04).

Conclusion

The indices from OCTA and CVI have the potential to serve as non-invasive biomarkers for the quantitative evaluation of retinal and choroidal vascular involvement in patients with ATTRwt.

Identification of Structures Labeled by Indocyanine Green in the Rat Choroid and Retina Can Guide Interpretation of Indocyanine Green Angiography

Purpose

Indocyanine green (ICG) is an albumin and lipoprotein binding dye absorbing in the far red used in angiography to visualize choroidal vessels (ICG angiography [ICGA]). To guide interpretation, ICG transport in the choroid, RPE, and retina of rats was studied.

Methods

Two conditions were used: RPE/choroid organoculture, incubated for 45 minutes in DMEM medium, 1% fetal bovine serum containing 0.25 mg/mL ICG and RPE/choroid and neural retina flat-mounts at 1 and 6 hours after intravenous ICG injection. Early and late sequences of ICGA were recorded until 6 hours. Ultra-deep red confocal microscope was used to localize ICG in flat-mounts and immunohistochemistry was performed for caveolin-1, tryptase (mast cell marker), and tubulin β3 (a nerve marker).

Results

In the organoculture, ICG penetrated homogeneously in the cytoplasm and stained the membranes of the RPE. At 1 hour after intravenous injection, ICG appeared in fine granules in RPE, partly labeled with caveolin-1 and decreasing at 6 hours. At 1 hour and 6 hours, ICG was found in the retinal vessels, faintly in the inner retina, and in the photoreceptor outer segments at 6 hours. In the choroid, ICG colocalized with mast cells, immunostained with tryptase, and accumulated along the large tubulin β3-labeled nerve bundles. The hypothesis was raised on the interpretation of late ICGA infrared photography in case of transthyretin amyloidosis with neuropathy.

Conclusions

Beside being a vascular dye, ICG is transported from the vessels to the RPE toward the outer retina. It stains mast cells and large choroidal nerves. These observations could help the analysis of ICGA images.

Ocular findings in patients with acquired ATTRv amyloidosis following domino liver transplantation

PURPOSE

To investigate the presence of amyloidosis-related ocular findings in patients who received domino liver transplantation from ATTRv amyloidosis donors.

METHODS

We reviewed the ocular findings in patients who had previously undergone domino liver transplantation and received ophthalmologic examinations between January 2009 and March 2023. The presence of amyloidosis-related ocular findings was retrospectively assessed by two ophthalmologists.

RESULTS

During the study period, a total of 7 patients with 14 eyes were examined. All patients were considered as acquired ATTRv amyloidosis. The mean age at the final visit was 64.6±8.4 years (52-75 years), and the mean time since domino liver transplantation was 167.6±76.2 months (69-257 months). The two evaluators' assessments for amyloidosis-related ocular findings were completely identical. No amyloid fibril deposition was observed in the pupil, lens, or vitreous. Five patients (10 eyes) had a Schirmer test result of 5mm or less than 5 mm, and four patients with a total of 8 eyes underwent fluorescein angiography and indocyanine green angiography, and no evidence of retinal amyloid angiopathy was found on fluorescein angiography. However, three patients with 6 eyes showed choroidal amyloid angiopathy on indocyanine green angiography.

CONCLUSION

While cases of choroidal amyloid angiopathy were observed, serious amyloidosis-related ocular complications such as vitreous opacity or secondary glaucoma did not occur even in the long term after domino liver transplantation.

Morphological and Morphometric Analysis of Canine Choroidal Layers Using Spectral Domain Optical Coherence Tomography

The choroid, a multifunctional tissue, has been the focus of research interest for many scientists. Its morphology and morphometry facilitate an understanding of pathological processes within both the choroid and retina. This study aimed to determine the choroidal layer thicknesses in healthy, mixed-breed mesocephalic dogs, both male (M) and female (F), using spectral domain optical coherence tomography (SD-OCT) with radial, cross-sectional, and linear scans. The dogs were divided into two groups based on age: middle-aged (MA) and senior (SN). Thicknesses of choroidal layers, namely RPE-Bruch's membrane-choriocapillaris complex (RPE-BmCc) with tapetum lucidum in the tapetal fundus, the medium-sized vessel layer (MSVL), and the large vessel layer with lamina suprachoroidea (LVLS), as well as whole choroidal thickness (WCT), were measured manually using the caliper function integrated into the OCT software. Measurement was performed dorsally and ventrally at a distance of 5000-6000 μm temporally and nasally at a distance of 4000-7000 μm to the optic disc on enhanced depth scans. The measurements were conducted temporally and nasally in both the tapetal (temporal tapetal: TempT, nasal tapetal: NasT) and nontapetal (temporal nontapetal: TempNT, nasal nontapetal: NasNT) fundus. The ratio of the MSVL thickness to the LVLS thickness for each region was calculated. In all examined dogs, the RPE-BmCc in the dorsal (D) region and MSVL in the Tt region were significantly thicker than those in the other regions. The MSVL was thinner in the ventral (V) region than in the D, TempT, TempNT and NasT regions. The MSVL was significantly thinner in the NasNT region than in the D region. LVLS thickness and WCT were significantly greater in the D and TempT regions than those in the other regions and significantly lesser in the V region than those in the other regions. The MSVL-to-LVLS thickness ratio did not differ between the age groups. Our results reveal that the choroidal thickness profile does not depend on age. Our findings can be used to document the emergence and development of various choroidal diseases in dogs in the future.

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

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.

OCULAR MANIFESTATIONS OF ASP38ALA AND THR59LYS FAMILIAL TRANSTHYRETIN AMYLOIDOSIS

PURPOSE

To describe the ophthalmic manifestations of familial transthyretin amyloidosis (FTA) mutations, including Asp38Ala and Thr59Lys, which have not been previously reported to have ocular involvement.

METHODS

This is an observational case series of prospectively collected data of 16 patients with FTA who were taking tafamidis for mild peripheral neuropathy and underwent a comprehensive ophthalmic examination at a single tertiary center, between January 2013 and March 2020. The ocular involvement of each FTA mutation type and the specific manifestations were the main outcome measures.

RESULTS

Six of 16 patients with FTA manifested ocular involvement. Ocular involvement was noted in two of three patients with Glu89Lys mutations having retinal deposits, retinal hemorrhages, and corneal opacity. Three of nine patients with Asp38Ala mutations and one of two patients with Thr59Lys mutations showed ocular involvement that had not been previously described. The ophthalmic findings included glaucoma, anterior lens capsule opacity, vitreous opacity, and retinal deposits. The decrease in vascular flow due to perivascular cuffing of the amyloid deposits was detected by optical coherence tomography angiography.

CONCLUSION

The current study newly described that two transthyretin mutation types of FTA, Asp38Ala and Thr59Lys, may manifest with ocular findings such as anterior lens capsule opacity and retinal deposits.

Ocular Involvement in Hereditary Amyloidosis

The term amyloidosis describes a group of rare diseases caused by protein conformation abnormalities resulting in extracellular deposition and accumulation of insoluble fibrillar aggregates. So far, 36 amyloid precursor proteins have been identified, and each one is responsible for a specific disease entity. Transthyretin amyloidosis (ATTRv) is one of the most common forms of systemic and ocular amyloidosis, due to the deposition of transthyretin (TTR), which is a transport protein mainly synthesized in the liver but also in the retinal pigment epithelial cells. ATTRv amyloidosis may be misdiagnosed with several other conditions, resulting in a significant diagnostic delay. Gelsolin and keratoepithelin are other proteins that, when mutated, are responsible for a systemic amyloid disease with significant ocular manifestations that not infrequently appear before systemic involvement. The main signs of ocular amyloid deposition are in the cornea, irido-corneal angle and vitreous, causing complications related to vasculopathy and neuropathy at the local level. This review aims at describing the main biochemical, histopathological and clinical features of systemic amyloidosis associated with eye involvement, with particular emphasis on the inherited forms. We discuss currently available treatments, focusing on ocular involvement and specific ophthalmologic management and highlighting the importance of a prompt treatment for the potential sight-threatening complications derived from amyloid deposition in ocular tissues.