Optical coherence tomography in Best vitelliform macular dystrophy

Optical Coherence Tomography in Inherited Macular Dystrophies: A Review

Macular dystrophies (MDs) constitute a collection of hereditary retina disorders leading to notable visual impairment, primarily due to progressive macular atrophy. These conditions are distinguished by bilateral and relatively symmetrical abnormalities in the macula that significantly impair central visual function. Recent strides in fundus imaging, especially optical coherence tomography (OCT), have enhanced our comprehension and diagnostic capabilities for MD. OCT enables the identification of neurosensory retinal disorganization patterns and the extent of damage to retinal pigment epithelium (RPE) and photoreceptor cells in the dystrophies before visible macular pathology appears on fundus examinations. It not only helps us in diagnostic retinal and choroidal pathologies but also guides us in monitoring the progression of, staging of, and response to treatment. In this review, we summarize the key findings on OCT in some of the most common MD.

Multimodal imaging in Best Vitelliform Macular Dystrophy: Literature review and novel insights

Best Vitelliform Macular Dystrophy (BVMD) is a dominantly inherited retinal disease caused by dominant variants in the BEST1 gene. The original classification of BVMD is based on biomicroscopy and color fundus photography (CFP); however, advancements in retinal imaging provided unique structural, vascular, and functional data and novel insights on disease pathogenesis. Quantitative fundus autofluorescence studies informed us that lipofuscin accumulation, the hallmark of BVMD, is unlikely to be a primary effect of the genetic defect. It could be due to a lack of apposition between photoreceptors and retinal pigment epithelium in the macula with subsequent accumulation of shed outer segments over time. Optical Coherence Tomography (OCT) and adaptive optics imaging revealed that vitelliform lesions are characterized by progressive changes in the cone mosaic corresponding to a thinning of the outer nuclear layer and then disruption of the ellipsoid zone, which are associated with a decreased sensitivity and visual acuity. Therefore, an OCT staging system based on lesion composition, thus reflecting disease evolution, has been recently developed. Lastly, the emerging role of OCT Angiography proved a greater prevalence of macular neovascularization, the majority of which are non-exudative and develop in late disease stages. In conclusion, effective diagnosis, staging, and clinical management of BVMD will likely require a deep understanding of the multimodal imaging features of this disease.

HYPERREFLECTIVE FOCI AS A PATHOGENETIC BIOMARKER IN CHOROIDEREMIA

PURPOSE

To assess hyperreflective foci (HF) number and distribution in choroideremia (CHM) using spectral domain optical coherence tomography.

METHODS

Observational, cross-sectional case series. Consecutive patients and matched controls (20 eyes each) underwent best-corrected visual acuity measurement, fundoscopy, blue-light autofluorescence (BL-FAF) and spectral domain optical coherence tomography. Hyperreflective foci were assessed on a horizontal spectral domain optical coherence tomography scan, in the 500-µm area centered on the umbo, and in the 500-μm-wide areas internal (preserved border) and external (pathologic border) to the chorioretinal atrophy of CHM patients, and in the parafovea of controls. Hyperreflective foci were subclassified as retinal or choroidal. The spared central islet was measured on BL-FAF. Primary outcome was HF quantification in CHM. Secondary outcomes included their relationships with atrophy extent.

RESULTS

Choroideremia eyes disclosed a significantly higher HF number across the pathologic border and in the fovea when compared with controls; in particular, these HF were primarily located in the choroid (59-87%). Moreover, choroidal HF in the pathologic border inversely correlated with the area of the preserved central islet.

CONCLUSION

Hyperreflective foci might turn out to be a potential biomarker of CHM activity or severity. In this regard, we hypothesize that HF may be related to macrophages activation or progressive retinal pigment epithelium degeneration.

Hyperreflective foci as biomarkers for inflammation in diabetic macular edema: Retrospective analysis of treatment naïve eyes from south India

Purpose:

The aim of this study was to analyze the factors associated with hyperreflective foci (HRF) in diabetic macular edema (DME) in treatment naïve eyes.

Methods:

This retrospective observational study included 131 eyes of 91 treatment naïve patients with DME. Details of ophthalmological examination with duration of vision loss and systemic parameters were noted. The spectral-domain optical coherence tomography (SD-OCT) images were analyzed for number and location of HRF and the associated imaging biomarkers.

Results:

Inner retinal (IR) HRF were seen in 88 eyes (67%), outer retinal (OR) in 28 (21%), and subretinal (SR) in 12 (9%). The IR had (7.1 ± 7) HRF, the OR (6.5 ± 4.8), and SR (3.9 ± 2.9). A greater proportion of eyes with HRF also had subretinal fluid (SRF), significantly higher blood pressure and lower serum triglycerides. Univariate linear regression analysis showed women (3 HRF greater vs. men, P = 0.04), eyes with cystoid spaces (2.95 more HRF vs. no cystoid spaces, P = 0.02), and SRF (2.96 more HRF vs. no SRF, P = 0.007) had more HRF, whereas higher triglycerides (1 HRF lesser per 50 mg lower TGL, P = 0.03) had lesser.

Conclusion:

Our study highlights the importance of HRF as an imaging biomarker in DME suggesting an inflammatory origin. Long-term observations of large cohorts with automated analysis can give more insights.

Altered ellipsoid zone reflectivity and deep capillary plexus rarefaction correlate with progression in Best disease

AIMS

To evaluate the effects of neurovascular damage in patients with the typical vitelliform lesion of Best vitelliform macular dystrophy (BVMD) in the attempt to identify different progression patterns.

METHODS

Prospective, observational case series. Patients in the vitelliform stage of BVMD and healthy controls underwent complete ophthalmological examination on a yearly basis, including best-corrected visual acuity (BCVA), biomicroscopy, optical coherence tomography (OCT) and OCT angiography (OCT-A). 4.5×4.5 mm OCT-A slabs were imported into ImageJ software and their vessel density (VD) was calculated. Similarly, the ellipsoid zone (EZ) was manually outlined and the reflectivity was measured above the vitelliform lesion and in the 500 µm external to it. Retinal pigment epithelium-Bruch's membrane complex was taken as internal reference.

RESULTS

34 eyes (24 patients) and 34 matched controls were included in the study. Mean follow-up was of 28.4±5.8 months, with 12 eyes showing signs of stage progression at the end follow-up. The EZ overlying the vitelliform lesion and in the peri-lesional area disclosed a significant reduction in reflectivity when compared with the foveal and para-foveal EZ of controls, respectively. VD resulted meaningfully decreased only at the deep capillary plexus. Of notice, more extensive EZ (reflectivity <0.7) and vascular alterations (VD <0.4) at baseline strongly correlated with worse BCVA and were associated with a more rapid progression at follow-up.

CONCLUSIONS

Both EZ reflectivity and VD at deep capillary plexus may prove valuable biomarkers to assess BVMD severity and detect progression. In this view, 'rapid progressors' might benefit the most from timely genetic therapies in the future.

[Foveal avascular zone and OCT angiography. An overview of current knowledge]

BACKGROUND

The foveal avascular zone (FAZ) has often been analyzed under different aspects in the last decades, mainly by fluorescence angiography (FA); however, the novel technology of optical coherence tomography angiography (OCTA) enables a non-invasive examination, visualization and quantitative analysis of the FAZ, which has recently led to many new findings, especially in a multidisciplinary manner. This article provides an overview of the investigation of the FAZ using OCTA and the new findings that have been obtained using OCTA in recent years.

METHODS

This article is based on a comprehensive literature review.

RESULTS

In many studies a good reproducibility and repeatability of the FAZ measurements by OCTA could be proven, also by comparing different OCTA devices. In patients with ocular pathologies and systemic diseases, e. g. after retinal vein occlusion or retinal surgery and in patients with diabetes mellitus without diabetic retinopathy, differences to healthy control groups and correlations to visual function could be shown. Moreover, in patients with neurological diseases, such as Alzheimer's dementia, changes of the FAZ could be identified.

CONCLUSION

The OCTA is a non-invasive technology, which enables a reliable visualization and reproducible quantification of the FAZ. The size of the FAZ seems to be altered in different retinal and systemic diseases, which also may correlate with visual function; however, long-term studies evaluating the diagnostic value of these changes in the course of the disease are currently lacking.

Identification of hyperreflective foci in angioid streaks

AIMS

To assess hyperreflective foci (HF) number in angioid streaks (AS) by means of spectral-domain optical coherence tomography (SD-OCT).

METHODS

Observational and cross-sectional study. Sixty-two eyes with AS and 62 controls underwent best-corrected visual acuity (BCVA), fundoscopy, and SD-OCT. HF were assessed on the horizontal scan of a six-line radial OCT, in the fovea (1500-μm diameter) and parafovea (500 μm external to the fovea), and sub-classified as retinal or choroidal, small or large. Eyes were distributed in one of four groups, as carrying foveal AS without choroidal neovascularization (CNV) (14 eyes), extra-foveal AS without CNV (14), active CNV (20), and inactive CNV (14). Primary outcome was HF assessment in AS. Secondary outcomes included their correlations with BCVA.

RESULTS

AS-affected eyes had higher HF numbers. Our sub-analysis revealed that patients with active CNV had a larger number of retinal and choroidal HF than all the other groups, whereas retinal and choroidal foci were significantly increased in inactive CNV only with respect to controls. Interestingly, patients with foveal AS showed HF number increase in the choroid and fovea. BCVA deterioration positively correlated with the total HF number found in the fovea and the choroid.

CONCLUSION

HF are significantly increased in patients with AS. Despite being especially evident in active CNV, the increasing number in eyes without CNV might suggest new pathogenetic aspects of the disease.

Hyperreflective Foci Number Correlates with Choroidal Neovascularization Activity in Angioid Streaks

Purpose

To assess the changes in hyperreflective foci (HF) by means of spectral-domain optical coherence tomography (SD-OCT) in patients undergoing anti-VEGF treatment for subfoveal choroidal neovascularization (CNV) secondary to angioid streaks (AS).

Methods

Fifteen eyes with diagnosis of AS-related CNV (8 males) and 15 control eyes with uncomplicated AS were consecutively recruited. Patients and controls underwent complete ophthalmologic examination and SD-OCT. Patients were subjected to a pro re nata treatment regimen, including monthly examinations and intravitreal aflibercept injection in case of fluid detection on SD-OCT. HF were measured on horizontal scans of the six-line radial SD-OCT, in the fovea and parafovea and the subdivided as retinal or choroidal. Specifically, HF were analyzed at the following time points: baseline, dry on SD-OCT, 1 month before its reactivation, and the time of CNV reactivation.

Results

HF numbers resulted higher in all CNV phases with respect to controls, except during inactive phase. Moreover, foveal and parafoveal HF were found significantly increased in active, prereactive, and reactive phases when compared with inactive phase (P < 0.05). A similar trend was detected for choroidal HF. Interestingly, a subanalysis revealed that only foveal choroidal HF are significantly higher in a prereactive phase if compared with an inactive phase (P = 0.03). Our correlational analysis unveiled negative associations between intraretinal HF numbers and logMAR best-corrected visual acuity.

Conclusions

Our findings suggest that HF represent useful markers to monitor CNV activity. Choroidal HF appear already increased in the fovea 1 month before CNV reactivation. Validation of our results might lead to earlier anti-VEGF reinjection and possibly better visual outcomes.